The 1.6 m off-axis New Solar Telescope (NST) in Big Bear
Author(s):
Philip R. Goode;
Wenda Cao
Show Abstract
The 1.6-m New Solar Telescope (NST) has been used to observe the Sun for more than three years with ever
increasing capabilities as its commissioning phase winds down. The NST is the first facility-class solar telescope
built in the U.S. in a generation, and it has an off-axis design as is planned for the 4 m Advanced Technology
Solar Telescope. Lessons learned will be discussed. Current NST post-focus instrumentation includes adaptive
optics (AO) feeding photometric and near-IR polarimetric sytems, as well as an imaging spectrograph. On-going
instrumentation projects will be sketched, including Multi-Conjugate AO (MCAO), next generation (dual Fabry-
Perot) visible light and near-IR polarimeters and a fully cryogenic spectrograph. Finally, recent observational
results illustrating the high resolution capabilities of the NST will be shown.
Applications of infrared techniques in solar telescopes NVST
Author(s):
Yinzhu Li;
Fangyu Xu;
Shanjie Huang;
Guangqian Liu
Show Abstract
This paper presents the applications of infrared techniques in National Vacuum Solar Telescope(NVST) .We give a brief
introduction to infrared thermography for nondestructive evaluation, especially for the measurement of mirror
temperature gradient and the dome temperature distribution. The results give us more reference for the Mirror Seeing and
Dome Seeing improvement.
Introduction to the Chinese Giant Solar Telescope
Author(s):
Zhong Liu;
Yuanyong Deng;
Zhenyu Jin;
Haisheng Ji
Show Abstract
In order to detect the fine structures of solar magnetic field and dynamic field, an 8 meter solar telescope has been
proposed by Chinese solar community. Due to the advantages of ring structure in polarization detection and thermal
control, the current design of CGST (Chinese Giant Solar Telescope) is an 8 meter ring solar telescope. The spatial
resolution of CGST is equivalent to an 8 meter diameter telescope, and the light-gathering power equivalent to a 5 meter
full aperture telescope. The integrated simulation of optical system and imaging ability such as optical design, MCAO,
active maintenance of primary mirror were carried out in this paper. Mechanical system was analyzed by finite element
method too. The results of simulation and analysis showed that the current design could meet the demand of most science
cases not only in infrared band but also in near infrared band and even in visible band. CGST was proposed by all solar
observatories in Chinese Academy of Sciences and several overseas scientists. It is supported by CAS and NSFC
(National Natural Science Foundation of China) as a long term astronomical project.
Large-field high-resolution mosaic movies
Author(s):
Robert H. Hammerschlag;
Guus Sliepen;
Felix C. M. Bettonvil;
Aswin P. L. Jägers;
Peter Sütterlin;
Sara F. Martin
Show Abstract
Movies with fields-of-view larger than normal for high-resolution telescopes will give a better understanding of
processes on the Sun, such as filament and active region developments and their possible interactions. New active
regions can influence, by their emergence, their environment to the extent of possibly serving as an igniter of the
eruption of a nearby filament. A method to create a large field-of-view is to join several fields-of-view into a mosaic.
Fields are imaged quickly one after another using fast telescope-pointing. Such a pointing cycle has been automated at
the Dutch Open Telescope (DOT), a high-resolution solar telescope located on the Canary Island La Palma. The observer
can draw with the computer mouse the desired total field in the guider-telescope image of the whole Sun. The guider
telescope is equipped with an H-alpha filter and electronic enhancement of contrast in the image for good visibility of
filaments and prominences. The number and positions of the subfields are calculated automatically and represented by an
array of bright points indicating the subfield centers inside the drawn rectangle of the total field on the computer screen
with the whole-sun image. When the exposures start the telescope repeats automatically the sequence of subfields.
Automatic production of flats is also programmed including defocusing and fast motion over the solar disk of the image
field. For the first time mosaic movies were programmed from stored information on automated telescope motions from
one field to the next. The mosaic movies fill the gap between whole-sun images with limited resolution of synoptic
telescopes including space instruments and small-field high-cadence movies of high-resolution solar telescopes.
The Advanced Technology Solar Telescope: design and early construction
Author(s):
Joseph P. McMullin;
Thomas R. Rimmele;
Stephen L. Keil;
Mark Warner;
Samuel Barden;
Scott Bulau;
Simon Craig;
Bret Goodrich;
Eric Hansen;
Steve Hegwer;
Robert Hubbard;
William McBride;
Steve Shimko;
Friedrich Wöger;
Jennifer Ditsler
Show Abstract
The National Solar Observatory’s (NSO) Advanced Technology Solar Telescope (ATST) is the first large U.S. solar telescope accessible to the worldwide solar physics community to be constructed in more than 30 years. The 4-meter diameter facility will operate over a broad wavelength range (0.35 to 28 μm ), employing adaptive optics systems to achieve diffraction limited imaging and resolve features approximately 20 km on the Sun; the key observational parameters (collecting area, spatial resolution, spectral coverage, polarization accuracy, low scattered light) enable resolution of the theoretically-predicted, fine-scale magnetic features and their dynamics which modulate the radiative output of the sun and drive the release of magnetic energy from the Sun’s atmosphere in the form of flares and coronal mass ejections. In 2010, the ATST received a significant fraction of its funding for construction. In the subsequent two years, the project has hired staff and opened an office on Maui. A number of large industrial contracts have been placed throughout the world to complete the detailed designs and begin constructing the major telescope subsystems. These contracts have included the site development, AandE designs, mirrors, polishing, optic support assemblies, telescope mount and coudé rotator structures, enclosure, thermal and mechanical systems, and high-level software and controls. In addition, design development work on the instrument suite has undergone significant progress; this has included the completion of preliminary design reviews (PDR) for all five facility instruments. Permitting required for physically starting construction on the mountaintop of Haleakalā, Maui has also progressed. This paper will review the ATST goals and specifications, describe each of the major subsystems under construction, and review the contracts and lessons learned during the contracting and early construction phases. Schedules for site construction, key factory testing of major subsystems, and integration, test and commissioning activities will also be discussed.
ATST Enclosure final design and construction plans
Author(s):
Gaizka Murga;
Heather Marshall;
Javier Ariño;
Tom Lorentz
Show Abstract
The Advanced Technology Solar Telescope (ATST) is a 4-m class solar telescope to be built at the Haleakalā High
Altitude Observatory Site in Maui, Hawai'i. It will be the largest solar telescope in the world, with unprecedented
abilities to view details of the Sun. Using adaptive optics technology, ATST will be able to provide the sharpest views
ever taken of the solar surface. It is expected that the 4-meter class telescope will have a significant impact on the study
of stellar magnetic fields, plasma physics and astronomy, allowing scientists to learn even more about the Sun and solarterrestrial
interactions.
The ATST enclosure is unique in its functionality, as not only it provides protection from adverse weather conditions
when not in operation, but it also positions the telescope Aperture Stop which must be accurately aligned so that the
primary mirror is fully illuminated, while insolation in other telescope equipment is prevented. The proposed design is
based on a multi-sector shutter system arrangement with an innovative crawler drive system (patent pending) assembled
on two steel fabricated arch girders. These arch girders are stiffened by a secondary structure and supported on a steel
fabricated base ring. The base ring rests on an azimuth mechanism composed of several driven/idling bogies. The outer
shape of the enclosure is configured by the secondary structure which supports the cladding and has been selected so as
to minimize the solar irradiated surface and reduce shell seeing in early morning hours when the seeing is the best.
This paper describes the work performed by AEC IDOM and ATST team to define both the final design of the Enclosure
and the construction plan to erect it at the Observatory Site.
Progress making the top end optical assembly (TEOA) for the 4-meter Advanced Technology Solar Telescope
Author(s):
Blaise Canzian;
J. Barentine;
J. Arendt;
S. Bader;
G. Danyo;
C. Heller
Show Abstract
L-3 Integrated Optical Systems (IOS) Division has been selected by the National Solar Observatory (NSO) to design and
produce the Top End Optical Assembly (TEOA) for the 4-meter Advanced Technology Solar Telescope (ATST) to
operate at Haleakalā, Maui. ATST will perform to a very high optical performance level in a difficult thermal
environment. The TEOA, containing the 0.65-meter silicon carbide secondary mirror and support, mirror thermal
management system, mirror positioning and fast tip-tilt system, field stop with thermally managed heat dump, thermally
managed Lyot stop, safety interlock and control system, and support frame, operates in the "hot spot" at the prime focus
of the ATST and so presents special challenges. In this paper, we describe progress in the L-3 technical approach to
meeting these challenges, including silicon carbide off-axis mirror design, fabrication, and high accuracy figuring and
polishing all within L-3; mirror support design; the design for stray light control; subsystems for opto-mechanical
positioning and high accuracy absolute mirror orientation sensing; Lyot stop design; and thermal management of all
design elements to remain close to ambient temperature despite the imposed solar irradiance load.
The azimuth axes mechanisms for the ATST telescope mount assembly
Author(s):
Hans J. Kärcher;
Ulrich Weis;
Oliver Dreyer;
Paul F. Jeffers;
Giovanni Bonomi
Show Abstract
The ATST Telescope Mount Assembly uses for the Azimuth axes mechanisms bearing and drive technologies as
developed for the machine tool industry. An overview on the ATST mount project and design and its verification by
analysis, simulation and tests are given in two separate papers of this conference. This paper describes the main design
and accuracy features of the bearing and drive subsystems, their adaption to the ATST mount and their influence on the
telescope structural design, and gives a hint to the challenges in the upcoming manufacturing, installation and
commissioning phases.
Manufacturing and testing of the large lenses for Dark Energy Survey (DES) at THALES SESO
Author(s):
Denis Fappani;
Julien Fourez;
Peter Doel;
David Brooks;
Brenna Flaugher
Show Abstract
After a brief introduction of what is the Dark Energy Survey (DES) project and which optical instrumentation will be
used, the presentation will be mainly focused onto the optical production of the large lenses (up to 1m diameter)
constituting the DES Camera (DECAM) located at the focal plane of the main observing telescope. Special emphasis
will be made onto the optical manufacturing issues and interferometric testing solutions, including compensation of
index inhomogeneities, which have been carried out by THALES SESO especially for the biggest entrance lens (very
challenging CV/CX meniscus named C1). Through several examples of typical past realizations or future possible
ones for different astronomical projects requiring 1m-class optics, the presentation will conclude by a brief over
review of the corresponding existing "state of the art" at THALES SESO for these technologies.
NGTS: a robotic transit survey to detect Neptune and super-Earth mass planets
Author(s):
Bruno Chazelas;
Don Pollacco;
Didier Queloz;
Heike Rauer;
Peter J. Wheatley;
Richard West;
Joao Da Silva Bento;
Matthew Burleigh;
James McCormac;
Philipp Eigmüller;
Anders Erikson;
Ludovic Genolet;
Mike Goad;
Andrés Jordán;
Marion Neveu;
Simon Walker
Show Abstract
NGTS is a new ground-based transit survey aimed at detecting sub-Neptune sized exoplanets around bright stars. The
instrument will be installed at the ESO Paranal observatory in order to benefit from the excellent observing conditions and
follow-up synergy with the VLT and E-ELT. It will be a robotic facility composed of 12, 200 mm telescopes equipped with
2Kx2K NIR sensitive detectors. It is built on the legacy of the WASP experience.
Design of a compact wide field telescope for space situational awareness
Author(s):
David Lee;
Andrew Born;
Philip Parr-Burman;
Peter Hastings;
Brian Stobie;
Naidu Bezawada
Show Abstract
The European Space Agency, in the framework of its Space Situational Awareness (SSA) Preparatory Programme, has
commissioned a study for a global network of surveillance telescopes to monitor the ever increasing number of objects in
Earth orbit. A possible scenario identified by the study is a network of 20 SSA Telescopes located at various observatory
sites. This paper presents the conceptual design of a telescope system optimised for wide field, short exposures and fast
tracking – all requirements of SSA.
The requirements of the SSA telescope will be presented followed by a brief review of potential telescope technologies.
Following a trade study analysis a 1 m compact Schmidt telescope design was chosen. This design provides a field of
view of 3.4 degrees diameter. The design is achromatic and covers the wavelength range 380 – 900 nm. The sensitivity
of the telescope is such that it can monitor the orbital parameters of objects as small as 1 cm in low Earth orbit. This is
equivalent to 17th magnitude in 0.07 seconds at a signal to noise ratio of 5. The telescope is mounted on an Altitude-
Azimuth type mount that enables wide coverage of the sky and fast tracking speeds. The entire telescope is contained
within a Calotte type enclosure. The camera, detector control, and telescope control system design will also be presented.
Systems engineering aspects will be addressed, with particular attention given to the analysis and flow-down of
requirements and a practical and pragmatic process of system-level design trade-offs.
OAJ: 2.6m wide field survey telescope
Author(s):
Olivier Pirnay;
Vincent Moreau;
Grégory Lousberg
Show Abstract
AMOS S.A. is in charge of the development of the telescopes for the "Observatorio Astrofisico de Javalambre" in Spain
where a 2.6 m wide field telescope is complemented by an 80 cm telescope. This paper focuses on the 2.6 m telescope
Javalambre Survey Telescope (JST): it is combining a large collecting surface with a wide field of view for reaching a
vast portion of the sky, which is the most relevant parameter for surveys, while ensuring an optical image quality
compatible with the site seeing and a suitable depth in the sky sighting.
The major difficulty consists in maintaining the image quality over a 500 mm focal plane. A good design is the result of
a thorough multidisciplinary optimization process where the fabrication constraints are a major driving parameter. The
complexity of the system led to elaborate innovative solutions for the closed loop control of both image quality and
tracking features.
The design and the methodology of working are presented in details. The optics fabrication, the integration and
acceptance tests are also reviewed.
Design differences between the Pan-STARRS PS1 and PS2 telescopes
Author(s):
Jeffrey S. Morgan;
Nicholas Kaiser;
Vincent Moreau;
David Anderson;
William Burgett
Show Abstract
The PS2 telescope is the second in an array of wide-field telescopes that is being built for the Panoramic-Survey
Telescope and Rapid Response System (Pan-STARRS) on Haleakala. The PS2 design has evolved incrementally based
on lessons learned from PS1, but these changes should result in significant improvements in image quality, tracking
performance in windy conditions, and reductions in scattered light. The optics for this telescope are finished save for
their coatings and the fabrication for the telescope structure itself is well on the way towards completion and installation
on-site late this year (2012). The most significant differences between the two telescopes include the following:
secondary mirror support changes, improvements in the optical polishing, changes in the optical coatings to improve
throughput and decrease ghosting, removal of heat sources inside the mirror cell, expansion of the primary mirror figure
control system, changes in the baffle designs, and an improved cable wrap design. This paper gives a description of each
of these design changes and discusses the motivations for making them.
Ground-based search for the brightest transiting planets with the Multi-site All-Sky CAmeRA: MASCARA
Author(s):
Ignas A. G. Snellen;
Remko Stuik;
Ramon Navarro;
Felix Bettonvil;
Matthew Kenworthy;
Ernst de Mooij;
Gilles Otten;
Rik ter Horst;
Rudolf le Poole
Show Abstract
The Multi-site All-sky CAmeRA MASCARA is an instrument concept consisting of several stations across the globe,
with each station containing a battery of low-cost cameras to monitor the near-entire sky at each location. Once all
stations have been installed, MASCARA will be able to provide a nearly 24-hr coverage of the complete dark sky, down
to magnitude 8, at sub-minute cadence. Its purpose is to find the brightest transiting exoplanet systems, expected in the
V=4-8 magnitude range - currently not probed by space- or ground-based surveys. The bright/nearby transiting planet
systems, which MASCARA will discover, will be the key targets for detailed planet atmosphere observations. We
present studies on the initial design of a MASCARA station, including the camera housing, domes, and computer
equipment, and on the photometric stability of low-cost cameras showing that a precision of 0.3-1% per hour can be
readily achieved. We plan to roll out the first MASCARA station before the end of 2013. A 5-station MASCARA can
within two years discover up to a dozen of the brightest transiting planet systems in the sky.
LSST secondary mirror assembly baseline design
Author(s):
Douglas R. Neill;
William J. Gressler;
Jacques Sebag;
Oliver Wiecha;
Mike Warner;
Bill Schoening;
Joe DeVries;
John Andrew;
German Schumacher;
Edward Hileman
Show Abstract
The 3.5-meter diameter Large Synoptic Survey Telescope (LSST) secondary (M2) mirror utilizes a 100mm thick
meniscus ULE™ blank completed by Corning Incorporated in 2009. Sub-aperture interferometry will guide the
polishing process to meet mirror structure function requirements. The convex asphere is actively supported by 72
axial actuators and 6 tangential links. These tangent links utilize an embedded lever system to meet the
requirements. The axial actuators have force limiting devices. The control system utilizes a higher level "outer loop
controller" for monitoring and commanding the tangent links and axial actuators. Numerous sensors determine the
assembly status. To prevent thermally induced image degradation, the interior air of the M2 cell is conditioned.
Current status of the Hobby-Eberly Telescope wide field upgrade
Author(s):
Gary J. Hill;
John A. Booth;
Mark E. Cornell;
John M. Good;
Karl Gebhardt;
Herman J. Kriel;
Hanshin Lee;
Ron Leck;
Walter Moreira;
Phillip J. MacQueen;
Dave M. Perry;
Marc D. Rafal;
Tom H. Rafferty;
Chuck Ramiller;
Richard D. Savage;
Charles A. Taylor III;
Brian L. Vattiat;
Lawrence W. Ramsey;
Joseph H. Beno;
Timothy A. Beets;
Jorge D. Esguerra;
Marco Häuser;
Richard J. Hayes;
James T. Heisler;
Ian M. Soukup;
Joseph J. Zierer;
Michael S. Worthington;
Nicholas T. Mollison;
Douglas R. Wardell;
Gregory A. Wedeking
Show Abstract
The Hobby-Eberly Telescope (HET) is an innovative large telescope of 9.2 meter aperture, located in West Texas at the
McDonald Observatory (MDO). The HET operates with a fixed segmented primary and has a tracker which moves the
four-mirror corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. A
major upgrade of the HET is in progress that will increase the pupil size to 10 meters and the field of view to 22′ by
replacing the corrector, tracker and prime focus instrument package. In addition to supporting the existing suite of
instruments, this wide field upgrade will feed a revolutionary new integral field spectrograph called VIRUS, in support
of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEXχ). This paper discusses the current status of this
upgrade.
ATST telescope pier
Author(s):
Paul Jeffers;
Eric Manuel;
Oliver Dreyer;
Hans Kärcher
Show Abstract
The Advanced Technology Solar Telescope (ATST) will be the largest solar telescope in the world with a 4m aperture primary mirror. The off axis nature of the telescope optical layout, has the proportions of an 8 metre class telescope. Accordingly the instrumentation for solar observations a 16m diameter co-rotating laboratory (Coude Rotator) is also located within the telescope pier. The pier has a lower cylindrical profile with an upper conical section to support both the telescope mount with a 9m bearing diameter and contain the 16m diameter Coudé rotator. The performance of this pier cannot be considered in isolation but must account for ancillary equipment, access and initial installation. The Coude rotator structure and bearing system are of similar size to the telescope base structure and therefore this is the proverbial 'ship in a bottle' problem. This paper documents the competing requirements on the pier design and the balancing of these as the design progresses. Also summarized is the evolution of the design from a conceptual traditional reinforced concrete pier to a composite concrete and steel framed design. The stiffness requirements of the steel frame was a unique challenge for both the theoretical performance and overall design strategy considering constructability. The development of design acceptance criteria for the pier is discussed along with interfacing of the AandE firm responsible for the pier design and the telescope designer responsible for the telescope performance.
Design concepts for the EST mount
Author(s):
Hans J. Kärcher;
Martin Süss;
David Fischer
Show Abstract
The EST has unique an optical layout, with an on-axis Gregorian tube system and the altitude axis behind the M1 mirror
unit - a great challenge for the mount designer in regard of balancing. Three different structural design concepts and
various alternatives for the bearing and drive systems were investigated. Hydrostatic bearings with direct drives are
compared with roller bearings and geared drives. The influence of available bearing and drive technology were
investigated by FE calculations, dynamic analysis and end-to-end simulations. The finally recommended design concept
is based on large-diameter segmented roller bearings and so-called pinion motors in both axes.
Progress on the structural and mechanical design of the Giant Magellan Telescope
Author(s):
Michael Sheehan;
Steve Gunnels;
Charles Hull;
Jonathan Kern;
Carey Smith;
Matt Johns;
Stephen Shectman
Show Abstract
The Giant Magellan Telescope (GMT), one of several next generation Extremely Large Telescopes (ELTs), is a 25.4
meter diameter altitude over azimuth design set to be built at the summit of Cerro Campanas at the Las Campanas
Observatory in Chile. The primary mirror consists of 7 individual 8.4 meter diameter segments resulting in an equivalent
collecting area of a 21.5 meter diameter single mirror. The telescope structure, optics and instrumentation has a rotating
mass of approximately 1250 metric tons and stands approximately 40 meters tall. This paper reports the results of our
ongoing preliminary design and development of the GMT structure and its major mechanical and opto-mechanical
components. A major recent redesign of the Gregorian Instrument Rotator (GIR) resulted in significant changes to the
telescope structure and several mechanisms. Design trade studies of various aspects of the main structure, hydrostatic
bearing system, main axes drives, M2 positioner, M3 subsystem and the corrector-ADC subsystem have refined the
preliminary design in these areas.
The E-ELT project: the telescope main structure detailed design study
Author(s):
Gianpietro Marchiori;
Andrea Busatta;
Leonardo Ghedin;
Simone De Lorenzi
Show Abstract
The European Extremely Large Telescope (E-ELT) is the biggest telescope in the world. Within the Detailed Design
activities, ESO has awarded EIE GROUP (European Industrial Engineering) a contract for the Design of the Main
Structure to the point where the concept of the telescope has been consolidated, from a construction point of view.
All the Design activities have been developed in order to create an integrated system in terms of functionality and
performance, while the engineering activities have been performed with the aim of obtaining a telescope that can be
built, transported, integrated, with a reduced maintainability.
E-ELT dome for modified baseline design
Author(s):
Armando Bilbao;
Gaizka Murga;
Celia Gómez
Show Abstract
During the last two years a modified baseline design for the E-ELT was developed. The aim of this revision was both to
achieve a significant cost saving and to reduce risk on major items. The primary mirror diameter was slightly reduced to
39 m and the total height of the telescope also decreased accordingly. This paper describes the work performed by IDOM
under contract with ESO to review the EELT dome and foundations design to match the modified baseline. Detailed
design and construction planning, as well as detailed cost estimates were updated for the 39-metre baseline design. In
June 2011, ESO Council formally endorsed this modified design as the E-ELT revised baseline.
Key redesign drivers are explained and final redesign details of all major subsystems are outlined. In general, the original
compact dome design philosophy is maintained and adapted to the new dimensions. Cost optimisation strategies are
applied throughout the detailed design update process. Special attention is also given to some specific new items now
included in the modified baseline, such as the special ad-hoc seismic base isolation system for the telescope foundation.
The E-ELT project: the dome design study
Author(s):
G. Marchiori;
S. De Lorenzi;
A. Busatta
Show Abstract
Further to the re-dimensioning of the E-ELT (European Extremely Large Telescope) telescope to 37 metres, the project
of the dome has been completely reviewed, together with the Auxiliary Building and the Foundations. The Dome is
now constituted by a structure with a steel hemispherical architecture, 79m.-high, with a 101m.-external pier diameter
and a 42m-wide observing slit. These dimensions require the application of technologies for big structures (like
stadiums, hangars, etc.) in order to comply with the manufacturing, transport and assembly constrains.
The dome is characterized by an agglomerate of mechathronic technologies originated by the long experience matured
by EIE in the industrial and astronomical fields.
The solutions adopted for the NTT, the VLT, the LBT, the VST and the VISTA have demonstrated, along the years of
service, their functionality, as well as their reliability and maintainability.
Moreover, innovative technologies have been introduced, especially for what concerns the rotation systems of the
Dome, the louvers, the windscreen, etc. The architecture of the control systems has been completed re-formulated, and
they are now able to manage in real time all the exigencies of the E-ELT Observatory.
All Project phases have been properly analysed and simulated, guaranteeing the completeness of the constructability
and the maintainability.
The entire work has been developed in close cooperation with ESO Project Team, further to a specific contract.
Seismic design accelerations for the LSST telescope
Author(s):
Douglas R. Neill;
Mike Warner;
Jacques Sebag
Show Abstract
The Large Synoptic Survey Telescope will be located on a seismically active Chilean mountain. Seismic ground
accelerations produce the telescope's most demanding load cases. Consequently, accurate prediction of these
accelerations is required. These seismic accelerations, in the form of Peak Spectral Acceleration (PSA), were compared
for site specific surveys, the Chilean building codes and measured seismic accelerations. Methods were also investigated
for adjusting for variations in damping level and return period. The return period is the average interval of time between
occurrences of a specific intensity.
Seismic analysis of the LSST telescope
Author(s):
Douglas R. Neill
Show Abstract
The Large Synoptic Survey Telescope (LSST) will be located on the seismically active Chilean mountain of Cerro
Pachón. The accelerations resulting from seismic events produce the most demanding load cases the telescope and its
components must withstand. Seismic ground accelerations were applied to a comprehensive finite element analysis
(FEA) model which included the telescope, its pier and the mountain top. Response accelerations for specific critical
components (camera and secondary mirror assembly) on the telescope were determined by applying seismic
accelerations in the form of Power Spectral Densities (PSD) to the FEA model. The PSDs were chosen based on the
components design lives. Survival level accelerations were determined utilizing PSDs for seismic events with return
periods 10 times the telescope's design life which is equivalent to a 10% chance of occurring over the lifetime. Since the
telescope has a design life of 30 years it was analyzed for a return period of 300 years. Operational level seismic
accelerations were determined using return periods of 5 times the lifetimes. Since the seismic accelerations provided by
the Chilean design codes were provided in the form of Peak Spectral Accelerations (PSA), a method to convert between
the two forms was developed. The accelerations are also affected by damping level. The LSST incorporates added
damping to meets its rapid slew and settle requirements. This added damping also reduces the components' seismic
accelerations. The analysis was repeated for the telescope horizon and zenith pointing. Closed form solutions were
utilized to verify the results.
GMT enclosure wind and thermal study
Author(s):
Arash Farahani;
Alexy Kolesnikov;
Leighton Cochran;
Charles Hull;
Matt Johns
Show Abstract
The GMT (Giant Magellan Telescope) is a large ground-based telescope for astronomical research at optical and infrared
wavelengths. The telescope is enclosed inside an Enclosure that rotates to follow the tracking of the telescope. The
Enclosure is equipped with adjustable shutters and vents to provide maximum ventilation for thermal control while
protecting the telescope from high wind loads, stray light, and severe weather conditions. The project will be built at Las
Campanas Observatory in Chile on Cerro Las Campanas. The first part of this paper presents the wind tunnel test data as
well as CFD (Computational Fluid Dynamics) study results for the GMT Enclosure. The wind tunnel tests include
simulations for: a) Topography, b) Open Enclosure (all the shutters and vents open), and c) Closed Enclosure (all the
vents and shutters closed). The CFD modeling was carried out for a wide range of conditions such as low and high wind
speeds at various wind directions, and for the fully open and partially open Enclosure. The second part of this paper
concerns the thermal effects of the Enclosure steel members. The wind speed and member sizes have been studied in
relation to the required time to reach a defined temperature inside the Enclosure. This is one of the key performance
characteristics of the Enclosure that can affect "Dome Seeing" significantly. The experimental data and theoretical
predications have been used to identify the areas inside the Enclosure that need to be ventilated. The Enclosure thermal
control strategy has been determined and an optimized system has been designed based on the final results.
Vibration mitigation for wind-induced jitter for the Giant Magellan Telescope
Author(s):
Roger M. Glaese;
Michael Sheehan
Show Abstract
The Giant Magellan Telescope (GMT) is a planned large terrestrial telescope with a segmented primary mirror with a
24.5 meter overall diameter. Like most terrestrial telescopes, the GMT resides within an enclosure designed to protect
the telescope from the elements and to reduce the effects of wind on the optical performance of the telescope. Wind
impingement on the telescope causes static deformation and vibration in the telescope structure that affects the alignment
and image jitter performance of the telescope. Actively controlled primary mirror segments and a secondary mirror can
correct for the static and low frequency portions of the wind effects, but typically the actuators do not have the
bandwidth to address higher frequency components of the wind environment. Preliminary analyses on the GMT indicate
that the image jitter associated with wind effects meets budgeted allowances but without much margin. Preliminary
models show that the bulk of the residual jitter arises from excitation of a small number of modes in the 9 to 12 Hz
range. Therefore, as a risk mitigation effort to increase the margin on the wind induced jitter, passive and active
vibration mitigation approaches have been examined for the GMT, which will be the focus of this paper. Using a finite
element model of the GMT along with wind loading load cases, several passive and active vibration mitigation
approaches were analyzed. These approaches include passive approaches such as tuned mass dampers targeting the
worst offending modes, and constrained layer damping targeting all of the modes within the troublesome frequency
range. Active approaches evaluated include two active damping approaches, one using several reaction mass actuators
and the other using active strut type actuators. The results of the study show that although all approaches are successful
in reducing the jitter, the active damping approach using reaction mass actuators offers the lightest weight, least
implementation impact, and most adaptability of any of the approaches.
Feasibility studies to upgrade the Canada-France-Hawaii Telescope site for the next generation Canada-France-Hawaii Telescope
Author(s):
Kei Szeto;
Mathieu Angers;
Craig Breckenridge;
Steven Bauman;
Nathan Loewen;
David Loop;
Alan McConnachie;
Jonh Pazder;
Derrick Salmon;
Paolo Spano;
Siegfried Stiemer;
Christian Veillet
Show Abstract
The Next Generation Canada-France-Hawaii Telescope is a dedicated, 10m aperture, wide-field, fiber-fed multiobject
spectroscopic facility proposed as an upgrade to the existing Canada-France-Hawaii Telescope on the summit
of Mauna Kea. The Next Generation Canada-France-Hawaii Telescope baseline concept assumes the new facility is
built on the existing Canada-France-Hawaii Telescope telescope pier and enclosure pier and occupies the same three
dimensional exterior “footprint”. Three technical studies have been planned to examine the validity of these
assumptions. The technical studies are executed in series as they represent technical decision points in a logical
sequence. The three technical studies in succession are: 1. Telescope Pier Study – Load Capacity and Structural
Interface, 2. Enclosure Fixed Base Study – Telescope and Enclosure Configuration and Load Capacity and 3. Aero-
Thermal Study – Dome Thermal Seeing and Air Flow Attenuation over the Enclosure Aperture Opening. The paper
outlines the baseline facility (telescope, spectrograph and enclosure) concept and the status of these studies, and
discusses the proposed telescope and enclosure configuration in terms of the redevelopment assumptions. A
consolidated feasibility study report will be submitted to the CFHT Board and Science Advisory Committee in the
Fall of 2012, with first light for the facility aiming to be in the early 2020s.
The Astronomical Telescope of New York: a new 12-meter astronomical telescope
Author(s):
T. Sebring;
R. Junquist;
C. Stutzki;
P. Sebring;
S. Baum
Show Abstract
The Astronomical Corporation of New York has commissioned a study of a 12-meter class telescope to be
developed by a group of NY universities. The telescope concept builds on the basic principles established by the
Keck telescopes; segmented primary mirror, Ritchey Chretien Nasmyth instrument layout, and light weight
structures. New, lightweight, and low cost approaches are proposed for the primary mirror architecture, dome
structure and mechanisms, telescope mount approach, and adaptive optics. Work on the design is supported by
several NY based corporations and universities. The design offers a substantially larger aperture than any existing
Visible/IR wavelength telescope at historically low cost. The concept employs an adaptive secondary mirror and
laser guide star adaptive optics. Two First Light instruments are proposed; A High resolution near infrared
spectrograph and a near infrared Integral field spectrograph/imager.
Reviewing off-axis telescope concepts: a quest for highest possible dynamic range for photometry and angular resolution
Author(s):
Gil Moretto;
Jeff R. Kuhn;
Phil R. Goode
Show Abstract
We review off-axis telescope concepts that use unobstructed pupils. Built and prospective telescopes
for ground and space astronomy will be presented and discussed. Such concepts offer great
advantages in terms of emissivity, throughput, diffraction- limited energy concentration and higher
dynamic range. The coronagraphic performance of off-axis telescopes will enable instruments,
which are starving for higher dynamic range, for example, those devoted to faint companion
detection and solar studies. Smaller telescopes like SOLAR-C (IfA/Haleakala Observatory), and the
New Solar Telescope (NST/NJIT/ Big Bear Observatory) are operational and are test beds for the
Advanced Technology Solar Telescope (ATST Project) for which site construction is beginning on
Haleakala.
Early science results from SOFIA
Author(s):
Erick T. Young;
Terry L. Herter;
Rolf Güsten;
Edward W. Dunham;
Eric E. Becklin;
Pamela M. Marcum;
Alfred Krabbe;
B.-G. Andersson;
William T. Reach;
Hans Zinnecker
Show Abstract
SOFIA, the Stratospheric Observatory for Infrared Astronomy, is an airborne observatory with a 2.7-m telescope that is
under development by NASA and the German Aerospace Center DLR. From late 2010 and through the end of 2011,
SOFIA conducted a series of science demonstration flights, Early Science, using FORCAST (the Faint Object InfraRed
Camera for the SOFIA Telescope), HIPO (the High-speed Imaging Photometer for Occultations), and GREAT (the
German REceiver for Astronomy at Terahertz frequencies). Flying at altitudes as high as 13.7 km (45,000 ft), SOFIA
operates above more than 99.8% of the water vapor in the Earth’s atmosphere, opening up most of the far-infrared and
sub-millimeter parts of the spectrum. During Early Science, 30 science missions were flown with results in solar system
astronomy, star formation, the interstellar medium, the Galactic Center, and extragalactic studies. Many of these
investigations were conducted by the first group of SOFIA General Investigators, demonstrating the operation of SOFIA
as a facility for the astronomical community. This paper presents some recent highlights from Early Science.
Active damping of the SOFIA Telescope assembly
Author(s):
Paul J. Keas;
Edward Dunham;
Ulrich Lampater;
Enrico Pfüller;
Stefan Teufel;
Hans-Peter Roeser;
Manuel Wiedemann;
Jürgen Wolf
Show Abstract
The NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA) employs a 2.5-meter reflector telescope in
a Boeing 747SP. The telescope is housed in an open cavity and is subjected to aeroacoustic and inertial disturbances in
flight. To meet pointing requirements, SOFIA must achieve a pointing stability of approximately 0.5 arcseconds RMS.
An active damping control system is being developed for SOFIA to reduce image jitter and image degradation due to
resonance of the telescope assembly. Our paper discusses the history of the active damping design for SOFIA, from
early concepts to the current implementation which has recently completed a ground and flight testing for proof-of-concept.
We describe some milestones in the analysis and testing of the telescope assembly which guided the
development of the vibration control system. The control synthesis approach and current implementation of the active
damping control system is presented. Finally, we summarize the performance observed in early flight tests and the steps
that are currently foreseen to completing the development of this system.
Evaluation of the aero-optical properties of the SOFIA cavity by means of computional fluid dynamics and a super fast diagnostic camera
Author(s):
Christian Engfer;
Enrico Pfüller;
Manuel Wiedemann;
Jürgen Wolf;
Thorsten Lutz;
Ewald Krämer;
Hans-Peter Röser
Show Abstract
The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a 2.5 m reflecting telescope housed in an open cavity
on board of a Boeing 747SP. During observations, the cavity is exposed to transonic flow conditions. The oncoming
boundary layer evolves into a free shear layer being responsible for optical aberrations and for aerodynamic and aeroacoustic
disturbances within the cavity. While the aero-acoustical excitation of an airborne telescope can be minimized
by using passive flow control devices, the aero-optical properties of the flow are difficult to improve. Hence it is
important to know how much the image seen through the SOFIA telescope is perturbed by so called seeing effects. Prior
to the SOFIA science fights Computational Fluid Dynamics (CFD) simulations using URANS and DES methods were
carried out to determine the flow field within and above the cavity and hence in the optical path in order to provide an
assessment of the aero-optical properties under baseline conditions. In addition and for validation purposes, out of focus
images have been taken during flight with a Super Fast Diagnostic Camera (SFDC). Depending on the binning factor and
the sub-array size, the SFDC is able to take and to read out images at very high frame rates.
The paper explains the numerical approach based on CFD to evaluate the aero-optical properties of SOFIA. The CFD
data is then compared to the high speed images taken by the SFDC during flight.
Optical characterization of the SOFIA telescope using fast EM-CCD cameras
Author(s):
Enrico Pfüller;
Jürgen Wolf;
Helen Hall;
Hans-Peter Röser
Show Abstract
The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently demonstrated its scientific capabilities in a
first series of astronomical observing flights. In parallel, special measurements and engineering flights were conducted
aiming at the characterization and the commissioning of the telescope and the complete airborne observatory. To support
the characterization measurements, two commercial Andor iXon EM-CCD cameras have been used, a DU-888 dubbed
Fast Diagnostic Camera (FDC) running at frame rates up to about 400 fps, and a DU-860 as a Super Fast Diagnostic
Camera (SFDC) providing 2000 fps. Both cameras have been mounted to the telescope’s Focal Plane Imager (FPI)
flange in lieu of the standard FPI tracking camera. Their fast image sequences have been used to analyze and to improve
the telescope’s pointing stability, especially to help tuning active mass dampers that suppress eigenfrequencies in the
telescope system, to characterize and to optimize the chopping secondary mirror and to investigate the structure and
behavior of the shear layer that forms over the open telescope cavity in flight. In June 2011, a collaboration between the
HIPO science instrument team, the MIT’s stellar occultation group and the FDC team, led to the first SOFIA observation
of a stellar occultation by the dwarf planet Pluto over the Pacific.
SOFIA observatory performance and characterization
Author(s):
Pasquale Temi;
Pamela M. Marcum;
Walter E. Miller;
Edward W. Dunham;
Ian S. McLean;
Jurgen Wolf;
Eric E. Becklin;
Thomas A. Bida;
Rick Brewster;
Sean C. Casey;
Peter L. Collins;
Scott D. Horner;
Holger Jakob;
Stephen C. Jensen;
Jana L. Killebrew;
Ulrich Lampater;
Georgi I. Mandushev;
Allen W. Meyer;
Enrico Pfueller;
Andreas Reinacher;
Jeonghee Rho;
Thomas L. Roellig;
Maureen L. Savage;
Erin C. Smith;
Stefan Teufel;
Manuel Wiedemann
Show Abstract
The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities have been viewed as a first comprehensive assessment of the Observatory's performance and will be used to address the development activity that
is planned for 2012, as well as to identify additional Observatory upgrades. A series of 8 SOFIA Characterization
And Integration
flights have been conducted from June to December 2011. The HIPO science instrument in
conjunction with the DSI Super Fast Diagnostic Camera (SFDC) have been used to evaluate pointing stability,
including the image motion due to rigid-body and
flexible-body telescope modes as well as possible aero-optical
image motion. We report on recent improvements in pointing stability by using an Active Mass Damper system
installed on Telescope Assembly. Measurements and characterization of the shear layer and cavity seeing, as
well as image quality evaluation as a function of wavelength have been performed using the HIPO+FLITECAM
Science Instrument conguration (FLIPO). A number of additional tests and measurements have targeted basic
Observatory capabilities and requirements including, but not limited to, pointing accuracy, chopper evaluation
and imager sensitivity. This paper reports on the data collected during these
flights and presents current SOFIA
Observatory performance and characterization.
Optical design and calibration of a medium size telescope prototype for the CTA
Author(s):
Bagmeet Behera;
Jürgen Bähr;
Sandra Grünewald;
Gareth Hughes;
Igor Oya;
David Melkumyan;
Stefan Schlenstedt;
Ullrich Schwanke
Show Abstract
The Cherenkov Telescope Array (CTA) is designed to make a major improvement in the sensitivity of ground based
VHE (Very High Energy, defined as > 20GeV to 100s of TeV) gamma-ray telescopes. Not only will the differential-flux
sensitivity be an order of magnitude better than those of the currently operating Cherenkov telescopes, but there will also be
significant improvements in the energy, spectral and angular resolution. Delivering these features cost-effectively requires
several telescope sizes and designs - a few large size telescopes (23m diameter) are designed for the lowest energies, a
large number of small size telescopes (4-7m diameter) to increase the overall collection area which helps at the highest
energies and a number of Medium Size Telescopes (MST, 9.5m or 12m diameter, depending on the mirror design) to
provide the greatest sensitivity at ∼ 1 TeV. To provide complete sky coverage, CTA will have both a Northern Hemisphere
and a Southern Hemisphere site.
A prototype for an MST design (currently under development) will be build in Berlin by 2012. This MST prototype
has a modified Davies-Cotton design with a tessellated mirror, with individual facets of ∼ 1.2m in diameter. The facets are
three-point mounted on the optical support structure, having two powered actuators for alignment adjustments. In addition
a number of CCD cameras will be mounted at various positions on the dis and will be used for calibration. Here we present
the various optical calibration tasks - optimization of the optical point-spread-function (PSF) and the pointing of this MST
prototype, along with initial results.
Development of a mid-sized Schwarzschild-Couder Telescope for the Cherenkov Telescope Array
Author(s):
Robert A. Cameron
Show Abstract
The Cherenkov Telescope Array (CTA) is a ground-based observatory for very high-energy (10 GeV to 100 TeV)
gamma rays, planned for operation starting in 2018. It will be an array of dozens of optical telescopes, known as
Atmospheric Cherenkov Telescopes (ACTs), of 8 m to 24 m diameter, deployed over an area of more than 1 square km,
to detect flashes of Cherenkov light from showers initiated in the Earth's atmosphere by gamma rays. CTA will have
improved angular resolution, a wider energy range, larger fields of view and an order of magnitude improvement in
sensitivity over current ACT arrays such as H.E.S.S., MAGIC and VERITAS.
Several institutions have proposed a research and development program to eventually contribute 36 medium-sized
telescopes (9 m to 12 m diameter) to CTA to enhance and optimize its science performance. The program aims to
construct a prototype of an innovative, Schwarzschild-Couder telescope (SCT) design that will allow much smaller and
less expensive cameras and much larger fields of view than conventional Davies-Cotton designs, and will also include
design and testing of camera electronics for the necessary advances in performance, reliability and cost. We report on the
progress of the mid-sized SCT development program.
Status and performance of the Discovery Channel Telescope during commissioning
Author(s):
Stephen E. Levine;
Thomas A. Bida;
Tomas Chylek;
Peter L. Collins;
William T. DeGroff;
Edward W. Dunham;
Paul J. Lotz;
Alexander J. Venetiou;
Saeid Zoonemat Kermani
Show Abstract
Lowell Observatory's Discovery Channel Telescope is a 4.3m telescope designed for optical and near infrared astronomical observation. At first light, the telescope will have a cube capable of carrying five instruments and the wave front sensing and guider system at the f/6.1 RC focus. The corrected RC focus field of view is 30’ in diameter. Nasmyth and prime focus can be instrumented subsequently. Early commissioning work with the installed primary mirror and its support system started out using one of the wave front sensing probes mounted at prime focus, and has continued at RC with the recent installation of the secondary mirror. We will report on the on-sky pointing and tracking performance of the telescope, initial assessment of the functionality of the active optics support system, and tests of the early image quality of the telescope and optics. We will also describe the suite of first light instruments, and early science operations.
The Large Binocular Telescope
Author(s):
J. M. Hill;
R. F. Green;
D. S. Ashby;
J. G. Brynnel;
N. J. Cushing;
J. K. Little;
J. H. Slagle;
R. M. Wagner
Show Abstract
The Large Binocular Telescope (LBT) Observatory is a collaboration between institutions in Arizona, Germany,
Italy, Indiana, Minnesota, Ohio and Virginia. The telescope on Mt. Graham in southeastern Arizona uses two
8.4-meter diameter borosilicate honeycomb primary mirrors mounted side-by-side to produce a collecting area
equivalent to an 11.8-meter circular aperture. A unique feature of LBT is that the light from the two primary
mirrors can be combined to produce phased-array imaging of an extended field. This coherent imaging along with
adaptive optics gives the telescope the diffraction-limited resolution of a 22.65-meter telescope. The first on-sky
phasing of the two telescopes in the mid-infrared occurred in October 2010 with the LBTI instrument in Fizeau
mode. The telescope control system has been upgraded to allow binocular (2-sided) observations with pairs of
instruments. The prime focus cameras (LBC) routinely operate in this mode. Improved collimation and pointing
models have been deployed to keep both sides collimated and pointed at the same target. The control system
has also been upgraded to allow observations of solar system objects at non-sidereal tracking rates. Science
observations are scheduled for 60% of the nights including a significant fraction of adaptive optics imaging with
the first adaptive secondary mirror and the FLAO system with natural guide stars. MODS1, a nearUV-optical
spectrometer, has been added to the suite of science instruments along with LBC (visible imagers) and LUCI1
(near infrared spectrometer). LMIRcam (2-5 microns) and PISCES (1-2.5 microns) have been used for adaptive
optics imaging. The remaining nights are scheduled for telescope and instrument commissioning activities as new
instruments arrive. The second of the two F/15 adaptive secondary mirrors has been installed on the telescope
in Fall 2011 and has been commissioned on-sky in Spring 2012.
New Fraunhofer Telescope Wendelstein: assembly, installation, and current status
Author(s):
Hans Thiele;
Nancy Ageorges;
Dirk Kampf;
Mike Hartl;
Sebastian Egner;
Peter Aniol;
Micheal Ruder;
Christian Abfalter;
Ulrich Hopp;
Ralf Bender;
Claus Gössl;
Frank Grupp;
Florian Lang-Bardl;
Wolfgang Mitsch
Show Abstract
Due to the exposed location of the Wendelstein observatory on the steep summit of mount Wendelstein no road exists to
transport telescope components and heavy equipment to the observatory in order to install the new 2m Fraunhofer
Telescope Wendelstein (FTW) in its new dome. A two step installation concept was therefore followed to mitigate any
risks that essential hardware would not work once installed on the mountain.
This paper reports on the telescope factory assembly and tests, including on-sky tests, which were performed in early
summer 2011 at the factory site to make sure, that the telescope and all essential subsystems are working properly before
the telescope would be installed on the mountain. The telescope was disassembled again to be transported to the
mountain in summer. Lifting of all structural subsystems and the optics up to the mountain observatory with the help of a
heavy lift helicopter will be presented in detail, also looking at specific design drivers, logistic aspects and special tools
for installation of the telescope and its mirrors in its new dome. Handling and transport concept for the M1 mirror
installation, which also will have to be used when the mirror is disassembled for recoating, are presented. Up to end of
2011 the telescope installation and pre-alignment could be completed including first on-sky tests. The system will
undergo a detailed performance test campaign in the first halve of 2012. Current performance results of these
commissioning activities will be reported.
VST: from commissioning to science
Author(s):
Pietro Schipani;
Massimo Capaccioli;
Carmelo Arcidiacono;
Javier Argomedo;
Massimo Dall'Ora;
Sergio D'Orsi;
Jacopo Farinato;
Demetrio Magrin;
Laurent Marty;
Roberto Ragazzoni;
Gabriele Umbriaco
Show Abstract
The VLT Survey Telescope (VST) has started the scientific operations on the ESO Paranal observatory after a successful
commissioning period. It is currently the largest telescope in the world specially designed for surveying the sky in visible
light. The VST is dedicated to survey programmes, supporting the VLT with wide-angle imaging by detecting and pre-characterising
sources, which the VLT Unit Telescopes can then observe further.
Commissioning results from the Large Binocular Telescope
Author(s):
Joar G. Brynnel;
Norman J. Cushing;
Richard F. Green;
John M. Hill;
Douglas L. Miller;
Andrew Rakich;
Konstantina Boutsia
Show Abstract
Commissioning of a telescope facility such as the Large Binocular Telescope presents us with unprecedented challenges.
The logistical and managerial balance act of scheduling commissioning of telescope, adaptive optics and twelve focal
stations with subsequent commissioning of the instruments that populate the focal stations, while still providing for
adequate science opportunity with already operational instruments is an equation that is problematic to solve in a way
that meets the interests of all stakeholders. This paper presents strategies and priorities applied at the LBTO, and status
of telescope commissioning programs. We provide a summary of telescope commissioning results, including a
discussion about specific efforts to improve performance of the LBT.
Discovery Channel Telescope active optics system early integration and test
Author(s):
Alexander J. Venetiou;
Thomas A. Bida
Show Abstract
The Discovery Channel Telescope (DCT) is a 4.3-meter telescope with a thin meniscus primary mirror (M1) and a
honeycomb secondary mirror (M2). The optical design is an f/6.1 Ritchey-Chrétien (RC) with an unvignetted 0.5°
Field of View (FoV) at the Cassegrain focus. We describe the design, implementation and performance of the DCT
active optics system (AOS). The DCT AOS maintains collimation and controls the figure of the mirror to provide
seeing-limited images across the focal plane. To minimize observing overhead, rapid settling times are achieved
using a combination of feed-forward and low-bandwidth feedback control using a wavefront sensing system.
In 2011, we mounted a Shack-Hartmann wavefront sensor at the prime focus of M1, the Prime Focus Test Assembly
(PFTA), to test the AOS with the wavefront sensor, and the feedback loop. The incoming wavefront is decomposed
using Zernike polynomials, and the mirror figure is corrected with a set of bending modes. Components of the
system that we tested and tuned included the Zernike to Bending Mode transformations. We also started open-loop
feed-forward coefficients determination.
In early 2012, the PFTA was replaced by M2, and the wavefront sensor moved to its normal location on the
Cassegrain instrument assembly. We present early open loop wavefront test results with the full optical system and
instrument cube, along with refinements to the overall control loop operating at RC Cassegrain focus.
E-ELT update of project and effect of change to 39m design
Author(s):
Alistair McPherson;
Jason Spyromilio;
Markus Kissler-Patig;
Suzanne Ramsay;
Enzo Brunetto;
Philippe Dierickx;
Mark Cassali
Show Abstract
During the last year a modified baseline design for the E-ELT has been developed. The aim of this revision was both to
achieve a significant cost saving and to reduce risk on major items. The primary mirror diameter was slightly reduced to
39 m and the total height of the telescope also decreased accordingly. This paper describes the work performed by ESO
and a variety of contractors to review the EELT design to match the modified baseline. Detailed design and construction
planning, as well as detailed cost estimates were updated for the 39-metre baseline design. In June 2011, ESO Council
formally endorsed this modified design as the E-ELT revised baseline.
The design drivers and balancing cost factors will be described along with the risk reduction measures taken during this
phase. This will culminate in the design which has been agreed as being ready to move forward to construction once
approval from ESO Council has been achieved.
Thirty Meter Telescope project update
Author(s):
Larry Stepp
Show Abstract
The Thirty Meter Telescope (TMT) is a public-private-international partnership to build an extremely large optical-infrared telescope on the summit of Mauna Kea on the island of Hawai'i. This paper summarizes the design and predicted performance of TMT, and provides updates on the status of the development and prototype testing activities. TMT is currently in its preconstruction phase. The roles of the partner institutions for developing and delivering observatory subsystems are now well defined, the design work is maturing and plans for construction are in place. Current plans are for start of construction in April 2014, with first light including all 492 segments installed by the end of 2021.
Giant Magellan Telescope: overview
Author(s):
Matt Johns;
Patrick McCarthy;
Keith Raybould;
Antonin Bouchez;
Arash Farahani;
Jose Filgueira;
George Jacoby;
Steve Shectman;
Michael Sheehan
Show Abstract
The Giant Magellan Telescope (GMT) is a 25-meter optical/infrared extremely large telescope that is being built by an
international consortium of universities and research institutions. It will be located at the Las Campanas Observatory,
Chile. The GMT primary mirror consists of seven 8.4-m borosilicate honeycomb mirror segments made at the Steward
Observatory Mirror Lab (SOML). Six identical off-axis segments and one on-axis segment are arranged on a single
nearly-paraboloidal parent surface having an overall focal ratio of f/0.7. The fabrication, testing and verification
procedures required to produce the closely-matched off-axis mirror segments were developed during the production of
the first mirror. Production of the second and third off-axis segments is underway.
GMT incorporates a seven-segment Gregorian adaptive secondary to implement three modes of adaptive-optics
operation: natural-guide star AO, laser-tomography AO, and ground-layer AO. A wide-field corrector/ADC is available
for use in seeing-limited mode over a 20-arcmin diameter field of view. Up to seven instruments can be mounted
simultaneously on the telescope in a large Gregorian Instrument Rotator. Conceptual design studies were completed for
six AO and seeing-limited instruments, plus a multi-object fiber feed, and a roadmap for phased deployment of the GMT
instrument suite is being developed.
The partner institutions have made firm commitments for approximately 45% of the funds required to build the
telescope. Project Office efforts are currently focused on advancing the telescope and enclosure design in preparation for
subsystem- and system-level preliminary design reviews which are scheduled to be completed in the first half of 2013.
Science with the re-baselined European Extremely Large Telescope
Author(s):
J. Liske;
P. Padovani;
M. Kissler-Patig
Show Abstract
The modifications to the European Extremely Large Telescope (E-ELT) baseline design were accompanied by an evaluation of their impact on science. We will present the conclusions of this evaluation. The Design Reference Mission served as the benchmark for the evaluation. None of the modifications critically affect the Science Case. In particular, the full instrumentation suite can still be implemented allowing for the full foreseen suite of science cases. The largest impact is induced by the reduced diameter. For a large fraction of the science cases this can be offset by increasing the exposure times by ~20% to 34%. Where spatial resolution is the limiting factor, the limits have to be reduced by 9%. The exoplanet case deserves a special mention: two of the three components of this case (detection of Earth twins by the radial velocity method, and characterisation of the atmospheres of transiting planets) are unaffected; for the third component (direct imaging of Earth-like planets) the same results as for the original baseline can be achieved, but only at 20% smaller distances. Overall, all of the major science cases of the E-ELT can essentially be maintained.
Opacity measurements at Summit Camp on Greenland and PEARL in northern Canada with a 225 GHz tipping radiometer
Author(s):
Keiichi Asada;
Pierre L. Martin-Cocher;
Chien-Ping Chen;
Satoki Matsushita;
Ming-Tang Chen;
Yau-De Huang;
Makoto Inoue;
Paul T. P. Ho;
Scott N. Paine;
Eric Steinbring
Show Abstract
We report the first measurements of 225 GHz atmospheric opacity at Summit Camp (Latitude 72°.57 N; Longitude
38°.46 W; Altitude 3250 m) in Greenland and the Polar Environment Atmospheric Research Laboratory
(PEARL: Latitude 80°.05 N; Longitude 86°.42 W; Altitude 600 m) in Northern Canada with a tipping radiometer.
Summit Camp and PEARL are research stations mostly interested in meteorology and geophysics, and
they are potentially excellent sites for astronomical observations at sub-millimeter wavelength. We purchased
a tipping radiometer from Radiometer Physics GmbH. After a test run at the summit of Mauna Kea, Hawaii,
the radiometer was deployed to PEARL in February 2011, and relocated to Summit Camp in August 2011. The
atmospheric opacity has been monitored from February 14th to May 10th, 2011 at PEARL and since August
2011 at Summit Camp. The median values of the measured opacity at PEARL ranged from 0.11 in February to 0.19 in May; Summit Camp varied in the range from 0.04 to 0.18 between August 2011 and May 2012. Summit
Camp in Greenland is expected to be an excellent site for sub-millimeter and Terahertz astronomy, and we plan
to set up there a 12-m telescope for VLBI and single-dish observations.
Site characterization studies in high plateau of Tibet
Author(s):
Yongqiang Yao;
Hongshuai Wang;
Liyong Liu;
Yiping Wang;
Xuan Qian;
Jia Yin
Show Abstract
The site survey in western China has been carried out since 2003. Remote studies and local surveys are performed,
and Oma site, Ali area in southwest Tibet, has been selected in 2005 to make site testing measurements. The
monitoring results show that Ali area can be the best choice for astronomical observations over the East Asian
regions. A new site in Ali has been identified and begun construction in 2010 for small telescopes and detailed
site characterization. This paper reviews the long term site survey, presents site characteristics in Tibet, and
introduces current status of the new Ali observatory.
New instruments to calibrate atmospheric transmission
Author(s):
Peter Zimmer;
John T. McGraw;
Daniel C. Zirzow;
Claire Cramer;
Keith Lykke;
John T. Woodward IV
Show Abstract
Changing atmospheric transmission accounts for the largest systematic errors limiting photometric measurement
precision and accuracy for ground-based telescopes. While considerable resources have been devoted to correcting the
effects of the atmosphere on image resolution, the effects on precision photometry have largely been ignored. To correct
for the transmission of the atmosphere requires direct measurements of the wavelength-dependent transmission in the
same direction and time that the supported photometric telescope is acquiring its data.
We describe a multi-wavelength lidar, the Facility Lidar for Astronomical Measurement of Extinction (FLAME) that
observes the stable upper stratosphere, and the Astronomical Extinction Spectrophotometer (AESoP), a
spectrophotometer that creates and maintains NIST absolute standard stars. The combination of these two instruments
enables high photometric precision of both the stellar spectra and atmospheric transmission. The throughput of both
FLAME and AESoP are calibrated to NIST radiometric standards.
This inexpensive and replicable instrument suite provides the lidar-determined monochromatic transmission of Earth’s
atmosphere at visible and near-infrared wavelengths to better than 0.25% per airmass and the wavelength-dependent
transparency to better than 1% uncertainty per minute. These atmospheric data are merged to create a metadata stream
that allows throughput corrections from data acquired at the time of the scientific observations to be applied to
broadband and spectrophotometric scientific data. This new technique replaces the classical use of nightly mean
atmospheric extinction coefficients, which invoke a stationary and plane-parallel atmosphere and ultimately limit
ground-based all-sky photometry to 1% - 2% precision.
The Greenland Telescope
Author(s):
Paul Grimes;
Raymond Blundell
Show Abstract
In the spring of 2010, the Academia Sinica Institute of Astronomy and Astrophysics, and the Smithsonian Astrophysical
Observatory, acquired the ALMA North America prototype antenna – a state-of-the-art 12-m diameter dish designed for
submillimeter astronomy. Together with the MIT-Haystack Observatory and the National Radio Astronomy
Observatory, the plan is to retrofit this antenna for cold-weather operation and equip it with a suite of instruments
designed for a variety of scientific experiments and observations. The primary scientific goal is to image the shadow of
the Super-Massive Black Hole in M87 in order to test Einstein’s theory of relativity under extreme gravity. This requires
the highest angular resolution, which can only be achieved by linking this antenna with others already in place to form a
telescope almost the size of the Earth. We are therefore developing plans to install this antenna at the peak of the
Greenland ice-sheet. This location will produce an equivalent North-South separation of almost 9,000 km when linked
to the ALMA telescope in Northern Chile, and an East-West separation of about 6,000 km when linked to SAO and
ASIAA’s Submillimeter Array on Mauna Kea, Hawaii, and will provide an angular resolution almost 1000 times higher
than that of the most powerful optical telescopes. Given the quality of the atmosphere at the proposed telescope location,
we also plan to make observations in the atmospheric windows at 1.3 and 1.5 THz. We will present plans to retrofit the
telescope for cold-weather operation, and discuss potential instrumentation and projected time-line.
Status of the first Antarctic survey telescopes for Dome A
Author(s):
Zhengyang Li;
Xiangyan Yuan;
Xiangqun Cui;
Daxing Wang;
Xuefei Gong;
Fujia Du;
Yi Zhang;
Yi Hu;
Haikun Wen;
Xiaoyan Li;
Lingzhe Xu;
Zhaohui Shang;
Lifan Wang
Show Abstract
The preliminary site testing carried out since the beginning of 2008 shows the Antarctic Dome A is very likely to be the
best astronomical site on earth even better than Dome C and suitable for observations ranging from optical wavelength to
infrared and sub-millimeter. After the Chinese Small Telescope Array (CSTAR) which is composed of four small fixed
telescopes with diameter of 145mm and mounted on Dome A in 2008 for site testing and variable star monitor, three
Antarctic Survey Telescopes (AST3) were proposed for observations of supernovas and extrasolar planets searching.
AST3 is composed of 3 large field of view catadioptric telescopes with 500mm entrance diameter and G, R, I filter for
each. The telescopes can point and track autonomously along with a light and foldable dome to keep the snow and icing
build up. A precise auto-focusing mechanism is designed to make the telescope work at the right focus under large
temperature difference. The control and tracking components and assembly were successfully tested at from normal
temperature down to -80 Celsius degree. Testing observations of the first AST3 showed it can deliver good and uniform
images over the field of 8 square degrees. The first telescope was successfully mounted on Dome A in Jan. 2012 and the
automatic observations were started from Mar. 2012.
Ukpik: testbed for a miniaturized robotic astronomical observatory on a high Arctic mountain
Author(s):
Eric Steinbring;
Brian Leckie;
Tim Hardy;
Kris Caputa;
Murray Fletcher
Show Abstract
Mountains along the northwestern coast of Ellesmere Island, Canada, possess the highest peaks nearest the Pole. This
geography, combined with an atmospheric thermal inversion restricted to below ~1000 m during much of the long arctic
night, provides excellent opportunities for uninterrupted cloud-free astronomy - provided the challenges of these
incredibly remote locations can be overcome. We present a miniaturized robotic observatory for deployment on a High
Arctic mountaintop. This system tested the operability of precise optical instruments during winter, and the logistics of
installation and maintenance during summer. It is called Ukpik after the Inuktitut name for the snowy owl, and was
deployed at two sites accessible only by helicopter, each north of 82 degrees latitude; one on rock at 1100 m elevation
and another on a glacier at 1600 m. The instrument suite included at first an all-sky-viewing camera, with the later
addition of a small telescope to monitor Polaris, both protected by a retractable weather-proof enclosure. Expanding this
to include a narrow-field drift-scanning camera for studying extra-solar planet transits was also investigated, but not
implemented. An unique restriction was that all had to be run on batteries recharged primarily by a wind turbine.
Supplementary power came from a methanol fuel-cell electrical generator. Communications were via the Iridium
satellite network. The system design, and lessons learned from three years of operation are discussed, along with
prospects for time-domain astronomy from isolated, high-elevation polar mountaintops.
The Gattini South Pole UV experiment
Author(s):
Anna M. Moore;
Sara Ahmed;
Michael C. B. Ashley;
Ernest Croner;
Alex Delacroix;
Yusuke Ebihara;
Jason Fucik;
D. Christopher Martin;
Viswa Velur;
Allan Weatherwax
Show Abstract
The Gattini South Pole UV experiment (Gattini SPUV) was deployed to the South Pole dark sector in February 2010 and
has recently completed a highly successful first season of winter time observations. The experiment has, for the first time
ever, measured and categorized the optical night sky brightness at the very blue wavelengths. The experiment consists of
a remotely operated 6” aperture custom designed telescope. The telescope feeds a blue sensitive imager with 4 degree
field of view that contains a bank of 3 filters: SDSS g’, Bessel U and a custom “super U” filter specifically designed to
probe the sky emission at wavelengths approaching the atmospheric cut-off. The filters are continually cycled with
exposure times ranging from 30 to 300 seconds throughout the winter period. The telescope, in addition, feeds a 2 degree
long slit VPH grating spectrograph with R~1000. The bandwidth is 350-450nm. The spectra are recorded simultaneously
with the imager exposures. The experiment is designed for low temperature Antarctic operation and resides on the roof
of the MAPO building in the South Pole Antarctic sector. The primary science goals are to categorize the Antarctic
winter-time sky background at the very bluest of wavelengths as a pathfinder for the Antarctic Cosmic Web Imager. We
present a technical overview of the experiment and results from the first winter season.
PLATO-R: a new concept for Antarctic science
Author(s):
Michael C. B. Ashley;
Yael Augarten;
Colin S. Bonner;
Michael G. Burton;
Luke Bycroft;
Jon S. Lawrence;
Daniel M. Luong-Van;
Scott McDaid;
Campbell McLaren;
Geoff Sims;
John W. V. Storey
Show Abstract
PLATO-R is an autonomous, robotic observatory that can be deployed anywhere on the Antarctic plateau by Twin Otter
aircraft. It provides heat, data acquisition, communications, and up to 1kW of electric power to support astronomical and
other experiments throughout the year. PLATO-R was deployed in 2012 January to Ridge A, believed to be the site with
the lowest precipitable water vapour (and hence the best atmospheric transmission at terahertz frequencies) on earth.1-4
PLATO-R improves upon previous PLATO designs that were built into ten-foot shipping containers by being much smaller
and lighter, allowing it to be field-deployable within 2-3 days by a crew of four.
Canada-France-Hawaii Telescope image quality improvement initiative: thermal assay of the observing environment
Author(s):
Karun Thanjavur;
Kevin Ho;
Sarah Gajadhar;
Marc Baril;
Tom Benedict;
Steve Bauman;
Derrick Salmon
Show Abstract
As part of the image quality (IQ) assessment and improvement initiative being carried out at the 3.6m Canada
France Hawaii Telescope (CFHT) on Mauna Kea, Hawaii, our objective in the work reported here is to obtain
a systematic assay of thermal sources within the dome and in the summit environment around the observatory,
and therefore mitigate their contributions to convective instability leading to 'dome seeing'. Toward this, we
undertook a nighttime overflight to capture thermal images with a calibrated infrared camera of the outer
structures of CFHT and the neighboring observatories on the summit ridge, as well as of a significant area
of the surrounding terrain. The same thermal camera was then used to image heat sources within the dome.
Using a convective heat transfer model, all these measured surface temperatures were converted to heat fluxes,
and thus used to build a thermal assay of the dome. In addition, using button type temperature loggers, we
simultaneously recorded the nighttime dome skin temperatures of CFHT and two other observatories over a
weeklong period to evaluate nighttime supercooling of the dome skin due to radiation to the cold night sky. As a
complementary goal we compared the efficacy of different paints and coatings used in observatories to minimize
this effect. Though similar studies have been carried out at other observatories, the results are rarely available
in published literature. Therefore, here we explain our methodologies, along with a detailed discussion of our
results and inferences to serve as a useful resource to the larger observing community.
New optical telescope projects at Devasthal Observatory
Author(s):
Ram Sagar;
Brijesh Kumar;
Amitesh Omar;
A. K. Pandey
Show Abstract
Devasthal, located in the Kumaun region of Himalayas is emerging as one of the best optical astronomy site in the
continent. The minimum recorded ground level atmospheric seeing at the site is 0.006 with median value at 1.001.
Currently, a 1.3-m fast (f/4) wide field-of-view (660) optical telescope is operating at the site. In near future, a 4-m
liquid mirror telescope in collaboration with Belgium and Canada, and a 3.6-m optical telescope in collaboration
with Belgium are expected to be installed in 2013. The telescopes will be operated by Aryabhatta Research
Institute of Observational Sciences. The first instruments on the 3.6-m telescope will be in-house designed and
assembled faint object spectrograph and camera. The second generation instruments will be including a large
field-of-view optical imager, high resolution optical spectrograph, integral field unit and an optical near-infrared
spectrograph. The 1.3-m telescope is primarily used for wide field photometry imaging while the liquid mirror
telescope will see a time bound operation to image half a degree wide strip in the galactic plane. There will
be an aluminizing plant at the site to coat mirrors of sizes up to 3.7 m. The Devasthal Observatory and
its geographical importance in between major astronomical observatories makes it important for time critical
observations requiring continuous monitoring of variable and transient objects from ground based observatories.
The site characteristics, its expansions plans and first results from the existing telescope are presented.
Towards a national astronomy observatory for the United Arab Emirates
Author(s):
S. Els;
J. Maree;
S. Al Marri;
Y. Al Muqbel;
A. Yousif;
H. Al Naimiy
Show Abstract
The Emirates Institute for Advanced Science and Technology (EIAST) investigated the possibility to setup an astronomical research and outreach center within the United Arab Emirates. The main goals of such a new institution are to raise interest in space research and to ultimately develop a significant research community within the UAE. Such an astronomy center will also require appropriate observatory facilities. In this paper current concepts of such a possible national UAE astronomy observatory will be outlined, and the findings of an initial survey for suitable locations to host the telescopic facilities within the UAE are presented.
The 3,6 m Indo-Belgian Devasthal Optical Telescope: general description
Author(s):
Nathalie Ninane;
Carlo Flebus;
Brijesh Kumar
Show Abstract
AMOS SA has been awarded of the contract for the design, manufacturing, assembly, tests and on site installation
(Devasthal, Nainital in central Himalayan region) of the 3.6 m Indo-Belgian Devasthal Optical Telescope (IDOT).
The telescope has Ritchey-Chrétien optical configuration with one axial and two side Cassegrain ports. The meniscus
primary mirror is active and it is supported by pneumatic actuators. The azimuth axis system is equipped with hydrostatic
bearing.
The telescope was completely assembled and tested in AMOS workshop. This step is completed and successful. The
telescope is now ready for shipment to Nainital.
This paper describes the telescope and summarizes the test results performed at AMOS to demonstrate that the telescope
satisfies the main system requirements.
Manufacturing optics of a 2.5m telescope
Author(s):
F. Poutriquet;
P. Plainchamp;
J. Billet;
B. Pernet;
T. Lagrange;
C. Cavadore;
JL Carel;
H. Leplan;
E. Ruch;
R. Geyl;
JC Jouve
Show Abstract
Over the past few years, Sagem REOSC has designed, manufactured and tested a 2.5m ALT/AZ telescope and
its complete observatory. The next stage - integration - should occur in 2012. The aim of this paper is to develop
the different stages of the project from technical and management's point of view.
The telescope is a 2.5m-class telescope with an aperture of F/8. It is composed of a 2.5m primary mirror made of
Zerodur©, a silica secondary mirror and a rotating tertiary mirror that allows pointing at Nasmyth foci. In
addition, a wide field corrector can be adapted either at Cassegrain focus or at Nasmyth focus. Results achieved
on the realization of such optics will be presented. An emphasis on the concurrent engineering and the problem
solving approach will also be presented.
E-ELT optomechanics: overview
Author(s):
M. Cayrel
Show Abstract
The E-ELT is a project led by the European Southern Observatory (ESO) for a 40-m class optical, near- and midinfrared,
ground-based telescope. When it will enter into operation, the E-ELT will be the largest and most powerful
optical telescope ever built. It will not only offer unrivalled light collecting power, but also exceedingly sharp images,
thanks to its ability to compensate for the adverse effect of atmospheric turbulence on image sharpness.
The basic optical solution for the EELT is a folded three-mirror anastigmat, using a 39-m segmented primary mirror
(M1), a 4-m convex secondary mirror (M2), and a 4-m concave tertiary mirror (M3), all active. Folding is provided by
two additional flat mirrors sending the beams to either Nasmyth foci along the elevation axis of the telescope. The
folding arrangement (flat M4 and M5 mirrors) is conceived to provide conveniently located flat surfaces for an adaptive
shell (M4) and field stabilization (M5).
That paper provides an overview of the specifications, design, and expected performance of the E-ELT optical systems.
E-ELT M1 test facility
Author(s):
M. Dimmler;
J. Marrero;
S. Leveque;
P. Barriga;
B. Sedghi;
M. Mueller
Show Abstract
During the advanced design phase of the European Extremely Large Telescope (E-ELT) several critical components
have been prototyped. During the last year some of them have been tested in dedicated test stands. In particular, a
representative section of the E-ELT primary mirror has been assembled with 2 active and 2 passive segments. This test
stand is equipped with complete prototype segment subunits, i.e. including support mechanisms, glass segments, edge sensors, position actuators as well as additional metrology for monitoring. The purpose is to test various procedures such as calibration, alignment and handling and to study control strategies. In addition the achievable component and subsystem performances are evaluated, and interface issues are identified. In this paper an overview of the activities related to the E-ELT M1 Test Facility will be given. Experiences and test results are presented.
Active damping strategies for control of the E-ELT field stabilization mirror
Author(s):
B. Sedghi;
M. Dimmler;
M. Mueller
Show Abstract
The fifth mirror unit (M5) of the E-ELT is a field stabilization unit responsible to correct for the dynamical tip
and tilt caused mainly due to the wind load on the telescope. The unit is composed of: i) an electromechanical
subunit, and ii) an elliptical mirror with a size of approximately 2.4 by 3-m. The M5 unit has been designed
and prototyped using a three point support for the mirror actuated by piezo actuators without the need of a
counter weight system. To be able to meet the requirements of the telescope, i.e. sufficient wavefront rejection
capability, the unit shall exhibit a sufficient bandwidth for tip/tilt reference commands. In the presence of the
low damped mechanical resonant modes, such a bandwidth can be guaranteed thanks to an active damping loop.
In this paper, different active damping strategies for the M5 unit are presented. The efficiency of the approaches
are analyzed using a detailed model of the unit. On a scale-one prototype active damping was implemented and
the efficiency was demonstrated.
Development of a fast steering secondary mirror prototype for the Giant Magellan Telescope
Author(s):
Myung K. Cho;
Andrew Corredor;
Christoph Dribusch;
Kwijong Park;
Young-Soo Kim;
Il-Kweon Moon;
Won Hyun Park
Show Abstract
The Giant Magellan Telescope (GMT) will be a 25m class telescope currently in the design and development phase. The
GMT will be a Gregorian telescope and equipped with a fast-steering secondary mirror (FSM). This secondary mirror is
3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the
primary. The prototype of FSM (FSMP) development effort is led by the Korea Astronomy and Space Science Institute
(KASI) with several collaborators in Korea, and the National Optical Astronomy Observatory (NOAO) in USA. The
FSM has a tip-tilt feature to compensate image motions from the telescope structure jitters and the wind buffeting. For
its dynamic performance, each of the FSM segments is designed in a lightweight mirror. Support system of the
lightweight mirror consists of three axial actuators, one lateral support at the center, and a vacuum system. A parametric
design study to optimize the FSM mirror configuration was performed. In this trade study, the optical image qualities
and structure functions for the axial and lateral gravity print-through cases, thermal gradient effects, and dynamic
performances will be discussed.
Repairing stress induced cracks in the Keck primary mirror segments
Author(s):
Dennis McBride;
John S. Hudek;
Sergey Panteleev
Show Abstract
Stress induced cracks have developed in the Zerodur glass at bonded supports for the primary mirror segments of the
W.M. Keck Observatory telescopes. This has been a slow process that has advanced over the 20 year life of the
telescopes. All mirror segments exhibit cracks to varying degrees. The number and severity of cracks has now reached a
stage at which repairs are mandatory. A project is under way to determine the root causes of the cracks, and to develop a
repair strategy. New supports and bonding methods are being designed and tested that will replace all of the original
supports.
Alignment algorithms for the Thirty Meter Telescope
Author(s):
Gary Chanan
Show Abstract
A variety of algorithms utilized in the alignment of segmented telescopes were developed for and implemented
on the Keck telescopes in the 1990s. The algorithms associated with the Keck segmented primary mirrors are
very similar to those that will be used for the Thirty Meter Telescope (TMT). However, there are alignment
or related wavefront measurement tasks associated with the TMT secondary and tertiary mirrors for which the
corresponding Keck algorithms either did not exist or are not adequate for TMT. We discuss two particular
algorithms associated with the TMT secondary and tertiary mirrors.
Phasing metrology system for the GMT
Author(s):
D. Scott Acton;
Antonin Bouchez
Show Abstract
The Giant Magellan Telescope (GMT) is a 25.4 m diameter ground-based segmented Gregorian telescope, composed of
7 8.4 meter diameter primary mirror segments, and 7 1 meter diameter adaptive secondary mirror segments. Co-phasing
of the integrated optical system will be partially achieved by making real-time measurements of the wavefront of an offaxis
guide star. However, slowly varying aberrations due to thermal and gravitational effects, as well as wind buffeting,
will make it difficult to maintain alignment using real-time optical measurements alone. Consequently, we are proposing
internal metrology systems to maintain the relative alignment of the optical elements. In this paper we describe a
differential capacitive edge sensing system to maintain the relative alignment of the adaptive secondary mirror reference
bodies. We also propose an interferometric system for sensing of the relative displacements of primary mirror segments.
Performance prediction of the fast steering secondary mirror for the Giant Magellan Telescope
Author(s):
Myung Cho;
Andrew Corredor;
Christoph Dribusch;
Won-Hyun Park;
Michael Sheehan;
Matt Johns;
Stephen Shectman;
Jonathan Kern;
Charlie Hull;
Young-Soo Kim;
John Bagnasco
Show Abstract
The Giant Magellan Telescope (GMT) Fast-steering secondary mirror (FSM) is one of the GMT two Gregorian
secondary mirrors. The FSM is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to
the seven 8.4m segments of the primary. A parametric study and optimization of the FSM mirror blank and central
lateral flexure design were performed. For the optimized FSM configuration, the optical image qualities and structure
functions for the axial and lateral gravity print-through cases, thermal gradient effects, and dynamic performances will be
discussed. This paper reports performance predictions of the optimized FSM. To validate our lateral flexure design
concept, mechanical and optical tests were conducted on test mirrors installed with two different lateral flexures.
Dynamics, active optics, and scale effects in future extremely large telescopes
Author(s):
Renaud Bastaits;
Bilal Mokrani;
Goncalo Rodrigues;
André Preumont
Show Abstract
This paper examines the active optics of future large segmented telescopes from the point of view of dynamic simulation and control. The first part of the paper is devoted to the modelling of the mirror. The model has a moderate size and separates the quasi-static behavior of the mirror (primary response) from the dynamic response (secondary or residual response). The second part of the paper is devoted to control. The control strategy considers explicitly the primary response of the telescope through a singular value controller. The control-structure interaction is addressed with the general robustness theory of multivariable feedback systems, where the secondary response is considered as uncertainty. This approach is very fast and allows extensive parametric studies. The study is illustrated with an example involving 90 segments, 270 inputs, and 654 outputs.
The development of the actuator prototypes for the active reflector of FAST
Author(s):
QiMing Wang;
MingChang Wu;
Ming Zhu;
JianXing Xue;
Qing Zhao;
XueDong Gu
Show Abstract
Upon its completion, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) will be the largest single dish
radio telescope ever in the world. The construction has been initiated in March 2011 in Guizhou province of China. The
whole construction process is expected to be completed in September 2016, with duration of 5.5 years.
With an aperture of 500 meters and an illumination aperture of 300 meters, the active reflector is one of the most
important parts of FAST. The reflector is composed of a ring beam, a cable net and thousands of panels, tie-down cables,
actuators and anchors. For the observation process of source switching and source tracking, the parabola shape of the
reflector is achieved by drawing back of the tie-down cables by the actuators. The motion performance and the reliability
of the actuators are of great importance to the telescope.
In this paper, the motion models of the actuators are analyzed for the observation process of source switching and source
tracking. Several design schemes are proposed, including mechanical and hydraulic design. The electric, mechanical and
hydraulic characteristics of these designs are discussed. Related experimental studies are performed to investigate the
electric and mechanical performances of these actuator prototypes. Based on the analysis and test results, a final type of
actuator will be optimally concluded to meet the requirements of the reflector of FAST.
Design, development, and manufacturing of highly advanced and cost effective aluminium sputtering plant for large area telescopic mirrors.
Author(s):
Rajeev R. Pillai;
Sanjith K. K.;
K. Mohanachandran;
Nagarjun Sakhamuri;
Vishal Shukla;
Alok Gupta
Show Abstract
The design, development and manufacturing of a fully automated and cost effective aluminum sputtering unit for the
deposition of aluminum on large area telescopic mirrors (maximum diameter of 3600mm) is presented here. The unit
employs DC planar magnetron sputtering for the deposition process. A large area glow discharge unit is also designed
for the pre-cleaning of the mirrors prior to aluminum coating. A special kinematic support structure with rotation is
designed to support heavy mirrors of large area to minimize the deflection of the mirrors during deposition process. A
custom designed 'mask' is employed in the magnetron system to improve the thickness uniformity within <±3%. The
adhesion, thickness uniformity and reflectivity properties are studied in detail to validate the sputtering plant. Special
fixtures have been designed for the system to accommodate smaller mirrors and studies have been conducted for the
coatings and reported in the paper. The unit was successfully tested at HHV facility in Bangalore and will be installed at
the ARIES Facility, Nainital.
The Australian SKA Pathfinder
Author(s):
Antony E. Schinckel;
John D. Bunton;
Tim J. Cornwell;
Ilana Feain;
Stuart G. Hay
Show Abstract
The Australian Square Kilometre Array Pathfinder (ASKAP) will be the fastest cm-wave survey radio-telescope and is
under construction on the new Murchison Radio-astronomy Observatory (MRO) in Western Australia. ASKAP consists
of 36 12-meter 3-axis antennas, each with a large chequerboard phased array feed (PAF) operating from 0.7 to 1.8 GHz,
and digital beamformer preceding the correlator. The PAF has 94 dual-polarization elements (188 receivers) and the
beamformer will provide about 36 beams (at 1.4 GHz) to produce a 30 square degree field of view, allowing rapid, deep
surveys of the entire visible sky. As well as a large field of view ASKAP has high spectral resolution across the 304
MHz of bandwidth processed at any one time generating a large data-rate (30Gb/sec in to the imaging system) that
requires real-time processing of the data. To minimise this processing and maximise the field of view for long
observations the antenna incorporates a third axis, which keeps the PAF field of view and sidelobes fixed relative to the
sky. This largely eliminates time varying artefact in the data that is processed.
The MRO is 315 kilometres north-east of Geraldton, in Western Australia’s Mid West region. The primary
infrastructure construction for ASKAP and other telescopes hosted at the Murchison Radio-astronomy Observatory has
now been completed by CSIRO, the MRO manager, including installation of the fibre connection from the MRO site to
Perth via Geraldton. The radio-quietness of the region is protected by the Mid West Radio Quiet Zone, implemented by
the Australian Federal Government, out to a radius of 260km surrounding the MRO.
LOFAR, the low frequency array
Author(s):
R. C. Vermeulen
Show Abstract
LOFAR, the Low Frequency Array, is a next-generation radio telescope designed by ASTRON, with antenna stations
concentrated in the north of the Netherlands and currently spread into Germany, France, Sweden and the United
Kingdom; plans for more LOFAR stations exist in several other countries. Utilizing a novel, phased-array design,
LOFAR is optimized for the largely unexplored low frequency range between 30 and 240 MHz. Digital beam-forming
techniques make the LOFAR system agile and allow for rapid re-pointing of the telescopes as well as the potential for
multiple simultaneous observations. Processing (e.g. cross-correlation) takes place in the LOFAR BlueGene/P
supercomputer, and associated post-processing facilities. With its dense core (inner few km) array and long (more than
1000 km) interferometric baselines, LOFAR reaches unparalleled sensitivity and resolution in the low frequency radio
regime.
The International LOFAR Telescope (ILT) is now issuing its first call for observing projects that will be peer reviewed
and selected for observing starting in December. Part of the allocations will be made on the basis of a fully Open Skies
policy; there are also reserved fractions assigned by national consortia in return for contributions from their country to
the ILT. In this invited talk, the gradually expanding complement of operationally verified observing modes and
capabilities are reviewed, and some of the exciting first astronomical results are presented.
The RAEGE VLBI 2010 radiotelescope design
Author(s):
Eberhard Sust;
José Antonio López Fernández
Show Abstract
The goal of the RAEGE (Red Atlantica Estaciones Geodinamicas Espaciales) project is the establishment of a Spanish-Portuguese network of geodynamical and spatial geodesy stations by the installation and operation of four fundamental geodetic / astronomical stations provided with radio telescopes located at
- Yebes, close to Madrid / Spain
- Tenerife, Canary Islands / Spain
- Santa Maria, Azores Islands / Portugal.
VLBI 2010 radiotelescopes are belonging to a new generation of radiotelescopes suitable for high precision geodetical earth observation and measurements, that shall allow to built up a high precision global reference system. The design of the radiotelescopes has been finished by MT Mechatronics in summer 2011 and currently three radiotelescopes are being manufactured. The first one is scheduled for installation in summer 2012 at Yebes Observatory close to Madrid.
Architecture of the metrology for the SRT
Author(s):
Tonino Pisanu;
Franco Buffa;
Gian Luigi Deiana;
Pasqualino Marongiu;
Marco Morsiani;
Claudio Pernechele;
Sergio Poppi;
Giampaolo Serra;
Giampaolo Vargiu
Show Abstract
The Sardinia Radio Telescope (SRT) Metrology team is planning to install an initial group of devices on the new 64
meters radio-telescope. These devices will be devoted for the realization of the antenna deformation control system: an
electronic inclinometer able to monitor the alidade deformations and a Position Sensing Device (PSD) able to map the
antenna secondary mirror (M2) displacements and tilts. The inclinometer will be used to map the rail conditions, the
azimuthal axis inclination and the thermal effects on the alidade structure. The PSD will be used to measure the
secondary mirror displacements induced by the gravity and by the thermal deformations that produce shifts and tilts with
respect to its ideal optical alignment. The PSD will be traced by diode laser installed on a mechanically stable position
inside the elevation equipment room. The inclinometer has been tested in laboratory with the aim to compare its
performances with a reference measurement system. The PSD and the laser have been characterized by a long-term tests
to assess their stability and accuracy, thus simulating the open air conditions that will be experienced by the device
during its operative life. M2 may move freely in space thanks to a six axis actuator system (hexapod). The PSD
measurements are processed by a hexapod kinematic model (HKM) to evaluate the correct actuator elongations, thus
closing the control loop. The sensors will be acquired and recorded by a dedicated PC installed in the Alidade equipment
room and connected to the sensors via the Ethernet network.
Requirements and considerations of the surface error control for the active reflector of FAST
Author(s):
MingChang Wu;
QiMing Wang;
XueDong Gu;
BaoQing Zhao
Show Abstract
The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is currently under construction at a Karst
depression in the Guizhou province of China. The active reflector of the telescope is composed of 4395 triangular panels
laid on a cable-net structure. The aperture of the spherical surface is 500 meters, with open angle of about 110~120
degrees. Acting as the nodes of the reflector, the joint of these panels are adjusted by 2235 down-tie cables drawn by
actuators. The RMS error of the parabola reflector is expected to be 5mm.
To form the parabola shape of the reflector, for each of the actuators, a minimal working stroke of 950mm is required,
with maximal speed of 1.6mm/s at the load of 50kN. Considering the elastic deformation of the down-tie cable and other
factors, a positioning error within 0.25mm is required for the actuators.
In this paper, the base formula for the motion of a general actuator at a typical observation time is studied analytically.
The results are used to estimate the control error of the actuators and the pointing error of the whole reflector. Based on
the designed error budgets, a statistical method is employed to estimate the overall surface error of the parabola reflector.
The overall surface error is a comprehensive result of the panel design error, panel fabrication error, thermal deformation
error, panel wind load induced error, cable-net error, installation error, measurement and control error etc. The results
may be used as a reference in the measurement and control of the active reflector when in operation.
The Sardinia Radio Telescope (SRT) optical alignment
Author(s):
Martin Süss;
Dietmar Koch;
Heiko Paluszek
Show Abstract
The Sardinia Radio Telescope (SRT) is the largest radio telescope recently built in Europe – a 64m
Radio Telescope designed to operate in a wavelength regime down to 1mm.
The SRT is designed in a classical Gregorian configuration, allowing access to the primary mirror focus
(F1), the Gregorian focus (F2) as well as a further translation to different F3 using a beam waveguide
system and an automated change between different F3 receiver positions.
The primary mirror M1, 64m in diameter, is composed by 1008 individual panels. The surface can be
actively controlled. It’s surface, as well as the one of the 8 m Gregorian subreflector, needed to be adjusted
after panel mounting at the Sardinia site. The measurement technique used is photogrammetry. In
case of the large scale M1 a dedicated combination of a large scale and a small scale approach was
developed to achieve extremely high accuracy on the large scale dimension. The measurement/
alignment efforts were carried out in 2010 and 2011, with a final completion in spring 2012. The
results obtained are presented and discussed.
The overall alignment approach also included the absolute adjustments of M2 to M1 and the alignments
of M3, M4 and M5. M3 is a rotating mirror guiding the RF beam to M4 or M5, depending on the operational
scenario. These adjustments are based on Lasertracker measurements and have been carried out in
an integrated approach.
Final tests and performances verification of the European ALMA Antennas
Author(s):
Gianpietro Marchiori;
Francesco Rampini
Show Abstract
The Atacama Large Millimeter Array (ALMA) is under erection in Northern Chile. The array
consists of a large number (up to 64) of 12 m diameter antennas and a number of smaller antennas,
to be operated on the Chajnantor plateau at 5000 m altitude. The antennas will operate up to 950
GHz so that their mechanical performances, in terms of surface accuracy, pointing precision and
dimensional stability, are very tight.
The AEM consortium constituted by Thales Alenia Space France, Thales Alenia Space Italy,
European Industrial Engineering (EIE GROUP), and MT Mechatronics is assembling and testing the
25 antennas. As of today, the first set of antennas have been delivered to ALMA for science.
During the test phase with ESO and ALMA, the European antennas have shown excellent
performances ensuring the specification requirements widely.
The purpose of this paper is to present the different results obtained during the test campaign:
surface accuracy, pointing error, fast motion capability and residual delay. Very important was also
the test phases that led to the validation of the FE model showing that the antenna is working with a
good margin than predicted at design level thanks also to the assembly and integration techniques.
ALMA system verification
Author(s):
Richard Sramek;
Koh-Ichiro Morita;
Masahiro Sugimoto;
Peter Napier;
Maurizio Miccolis;
Pavel Yagoubov;
Denis Barkats;
William Dent;
Satoki Matsushita;
Nicholas Whyborn;
Shin'ichiro Asayama;
Javier Marti Canales;
Ravinder Bhatia;
Eugene DuVall;
Samantha Blair
Show Abstract
The ALMA aperture synthesis radio telescope is under construction in northern Chile. This paper presents the
organization and process of ALMA System Verification. The purpose of System Verification is to measure the
performance of the integrated instrument with respect to the ALMA System Technical Requirements. The System
Technical Requirements flow down from the Science Requirements of the telescope and are intended to guide the design
of the array and set the standards for technical performance. The process of System Verification will help determine
how well the ALMA telescope meets its science goals. Some verification results are discussed.
The CCAT 25m diameter submillimeter-wave telescope
Author(s):
David Woody;
Steve Padin;
Eric Chauvin;
Bruno Clavel;
German Cortes;
Andy Kissil;
John Lou;
Paul Rasmussen;
David Redding;
Jeff Zolkower
Show Abstract
CCAT will be a 25 m diameter telescope operating in the 2 to 0.2 mm wavelength range. It will be located at an altitude
of 5600 m on Cerro Chajnantor in Northern Chile. The telescope will be equipped with wide-field, multi-color cameras
for surveys and multi-object spectrometers for spectroscopic follow up. Several innovations have been developed to
meet the <0.5 arcsec pointing error and 10 μm surface error requirements while keeping within the modest budget
appropriate for radio telescopes.
High performance holography mapping with the LMT
Author(s):
David R. Smith;
Kamal Souccar
Show Abstract
When making holography measurements on a large telescope, there are many factors that make it difficult to
obtain a consistent map. Two of these factors are variations of the satellite and temperature-induced deformations
of the reflecting surface. The former requires frequent returns to the center of the map to check the satellite and
the latter requires that the map be completed rapidly and at night. While holography mapping has traditionally
been performed using point-by-point or raster scanning, these methods involve substantial overhead in the
frequent movements back to the center of the map.
In performing holography maps of the Large Millimeter Telescope (LMT) for the first light campaign, the
observing team proposed a radial scanning approach. This strategy has the advantage that every scan passes
through the center of the map. However, such a scan results in a disproportionate amount of telescope time
near the center region. To achieve more uniform coverage, the team proposed a velocity profile that is inversely
proportional to the distance from the center of the map. Because the velocity profile is defined with respect
to position rather than time, this new approach required an extension of the existing parametric scanning
capabilities at the LMT. The high axis rates resulting from this velocity profile present additional challenges.
This paper describes the implementation and performance results for holography maps that use a radial
scan pattern with a position-dependent velocity profile at the LMT. Both theoretical and experimental results
are presented.
Photonic local oscillator technics for large-scale interferometers
Author(s):
H. Kiuchi;
M. Saito;
S. Iguchi
Show Abstract
In signal transmission through optical fiber, cable length delay fluctuation accompanied by chromatic and
polarization-mode dispersion affects the coherence of distributed signals. To maintain signal coherence, it is
very important to generate very-high-frequency signals with minimum phase noise and transmission loss. In a
photonic local signal generation/distribution system with a microwave-photonic signal generator and a real-time
microwave-photonic signal phase stabilizer that we developed as an alternative photonic LO system for ALMA
(Atacama Large Millimeter/sub-millimeter Array), signals are transmitted in the form of frequency difference
between two coherent light waves, effectively maintaining the coherence of distributed reference signals. Through
the development of the real-time phase stabilizer, we discovered that the system would be further improved with
the introduction of a post-processing scheme phase stabilizer and confirmed its effectiveness by experiments.
Precision attitude control for the BETTII balloon-borne interferometer
Author(s):
Dominic J. Benford;
Dale J. Fixsen;
Stephen A. Rinehart;
Maxime Rizzo;
Stephen F. Maher;
Richard K. Barry
Show Abstract
The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-meter baseline far-infrared
interferometer to fly on a high altitude balloon. Operating at wavelengths of 30-90 microns, BETTII will obtain spatial
and spectral information on science targets at angular resolutions down to less than half an arcsecond, a capability
unmatched by other far-infrared facilities. This requires attitude control of the gondola at the several arcsecond level,
and phase correction of the gondola attitude at a level of less than a tenth of an arcsecond, great challenges for a
lightweight balloon-borne system. We have designed a precision attitude determination system to provide gondola
attitude knowledge at a level of 2 milliarcseconds at rates up to 100Hz, with accurate absolute attitude determination at the half arcsecond level at rates of up to 10Hz. A multi-stage control system involving rigid body motion and tip-tiltpiston correction provides precision pointing stability to the level required for the far-infrared instrument to perform its spatial/spectral interferometry in an open-loop control. We present key aspects of the design of the attitude determination and control and its development status.
First technological steps toward opening a near-IR window at stratospheric altitudes
Author(s):
Fernando Pedichini;
Mauro Centrone;
Dario Lorenzetti;
Massimiliano Mattioli;
Masimo Ricci;
Fabrizio Vitali
Show Abstract
The possibility to open a near-IR window at stratospheric altitude is crucial for a large variety of astronomical issues,
from cosmology to the star formation processes. Up to now, one of the main issue is the role of the OH and thermal sky
emission that are rising the sky background level when such observations are performed through ground based
telescopes. We present the results of our technological activity aimed at affording some critical aspects typical of balloon
flights. In particular, the obtained performances of prototype systems for rough and fine tracking will be illustrated. Both
these systems constitute a high precision device (≤ 1 arcsec) for pointing and tracking light telescopes on board
stratospheric balloons. We give the details concerning the optical and mechanical layout, as well as the detector and the
control system. We demonstrate how such devices, when used at the focal plane of enough large telescopes(2-4m, F/10),
may be capable to provide diffraction limited images in the near infrared bands. We have also developed a prototypal
single channel photometer NISBA (Near Infrared Sky Background at Arctic pole), working in the H band (1.65 μm), able
to evaluate, during a high-latitude balloon flight, how OH emission affects the sky background during the arctic night.
The laboratory tests and performance on sky are presented and analyzed.
SOFIA in operation: telescope performance during the basic science flights
Author(s):
Hans J. Kärcher;
Jörg Wagner;
Alfred Krabbe;
Ulrich Lampater;
Thomas Keilig;
Jürgen Wolf
Show Abstract
The Stratospheric Observatory for Infrared Astronomy SOFIA started in December 2010 with the first series of science
flights, and has successfully completed about 38 science missions until fall 2011. The science instruments flown included
HIPO, FORCAST, GREAT and FLITECAM. Beside their scientific results (see related papers in these proceedings)
the flights delivered an extensive data base which is now used for the telescope performance characterization and the
operational optimization of the telescope in its unique environment. In this progress report we summarize recent
achievements of the observatory as well as the status of the telescope and give an update of the SOFIA pointing system
completed by intended future pointing optimization activities.
A new backup secondary mirror for SOFIA
Author(s):
Michael Lachenmann;
Martin J. Burgdorf;
Jürgen Wolf;
Rick Brewster
Show Abstract
The telescope of the Stratospheric Observatory for Infrared Astronomy (SOFIA) is a Cassegrain design with a convex, hyperbolic secondary mirror. It is 352 mm in diameter, was made from silicon carbide and weighs
only 1.9 kg. As this material is brittle, and the secondary mirror is indispensable to observations with SOFIA, a backup with the same mass and moments of inertia was made of aluminium in 2004. This mirror, however, allows diffraction-limited observations only above 20 μm and it produces double peaked images. In this paper we discuss
the requirements for a new backup secondary mirror that can be employed also at near-infrared and even visible wavelengths and describe the most important aspects of the manufacturing process. The starting point of our
analysis was a high-precision measurement of the surface properties of the existing aluminium secondary mirror, using the NANOMEFOS technique, which was recently developed by TNO in Delft, the Netherlands. With the
exact shape of the mirror as input for a Zemax model we could reproduce the results of actual measurements of its optical performance that had been carried out on SOFIA in 2004. Based on these findings we determined
then the specifications to be fulfilled by a new backup secondary mirror in order to meet the requirements on improved optical performance. Finally, we discuss the dynamic deformation of the aluminium mirror during
chopping motions.
Upgrade of the SOFIA target acquisition and tracking cameras
Author(s):
Manuel Wiedemann;
Jürgen Wolf;
Hans-Peter Roeser
Show Abstract
The Stratospheric Observatory for Infrared Astronomy (SOFIA) uses three CCD cameras with different optics for target acquisition and tracking. The Wide Field Imager (WFI with 68 mm optics) and the Fine Field Imager (FFI with 254 mm optics) are mounted on the telescope front ring and are therefore exposed to stratospheric conditions in flight. The Focal Plane Imager (FPI) receives the visible light from the 2.5 meter telescope and is mounted inside the pressurized aircraft cabin at ca. 20°C. It is planned to replace all three imagers' CCD sensors with commercial Andor iXon cameras to significantly increase the sensitivity allowing for tracking on fainter stars. Andor cameras were temporarily mounted on the FPI flange as stand-alone systems to optically measure the telescope's pointing stability and the performance of various telescope sub-systems during engineering flights. Three DU-888 cameras will now be integrated in SOFIA's telescope system, so their image data can be used for target acquisition and tracking. To replace the WFI and FFI, the cameras will also need to be tested under stratospheric conditions, to ensure that they can be operated safely and without degradation of performance. In this paper we will report about the results of the environmental tests with the cameras, the integration of the camera in the SOFIA tracker and the current status of the upgrade project.
The 3,6 m Indo-Belgian Devasthal Optical Telescope: assembly, integration and tests at AMOS
Author(s):
Nathalie Ninane;
Christian Bastin;
Jonathan de Ville;
Fabrice Michel;
Maxime Pierard;
Eric Gabriel;
Carlo Flebus;
Amitesh Omar
Show Abstract
AMOS SA has been awarded of the contract for the design, manufacturing, assembly, tests and on site installation
(Devasthal, Nainital in central Himalayan region) of the 3.6 m Indo-Belgian Devasthal Optical Telescope (IDOT).
The telescope has a Ritchey-Chrétien optical configuration with a Cassegrain focus equipped with one axial port and two
side ports. The meniscus primary mirror is active and is supported by pneumatic actuators. The mount is an Alt-Az type
with for the azimuth axis a 5 m diameter hydrostatic track.
The telescope was completely assembled and tested in AMOS workshop. This step is completed and successful. The
telescope is now ready for shipment to Nainital.
This paper describes the test campaign at sub-system and system level that has taken place to demonstrate that the
telescope satisfies the main system requirements. Besides of the functionality of the telescope, the units interacting with
the image quality or the tracking performance were plenty tested. Some selected tests directly connected to the
performance of the telescope are also looked specifically in this paper.
First tests of the compact low scattered-light 2m-Wendelstein Fraunhofer Telescope
Author(s):
Ulrich Hopp;
Ralf Bender;
Frank Grupp;
Hans Thiele;
Nancy Ageorges;
Peter Aniol;
Heinz Barwig;
Claus Gössl;
Florian Lang-Bardl;
Wolfgang Mitsch;
Michael Ruder
Show Abstract
The integration of the 2m Fraunhofer telescope started in August 2011 at the Mt. Wendelstein observatory. The
logistics of the project are a key problem of the integration as the observatory has no road access. All large
or heavy components inlcuding the primary mirror were successfully delivered by helicopter. Meanwhile, they
are integrated in the telescope. The special design features of this alt-az telescope are its compactness and the
low-ghost wide field optics (0.7 deg. f.o.v. diameter).
We will briefly report on tests of the building and of the telescope system before the telescope moved to the
mountain. The integration at the observatory and the first astronomical performances tests of the telescopes are
discussed, and a brief update on the status of its instruments is presented. We comment on the cleaning and
recoating strategy for the primary mirror based on sample tests.
SALT's transition to science operations
Author(s):
David A. H. Buckley;
J. C. Coetzee;
Steven M. Crawford;
Kenneth H. Nordsieck;
Darragh O'Donoghue;
Theodore B. Williams
Show Abstract
The Southern African Large Telescope (SALT) began its re-commissioning phase in April 2011 following the
completion of remedial engineering work on the telescope and the major science instrument, the Robert Stobie
Spectrograph (RSS). The engineering work required modifications to the spherical aberration corrector, in order to
improve the telescope’s image quality, and RSS, to improve its throughput. Positive test results included delivery of
sub-arcsecond images, essentially meeting the original telescope image quality specifications and exhibiting none of
the previous field-dependent aberrations, while the RSS has shown greatly improved efficiency performance. SALT
has since transitioned to science operations, as from 1 September 2011, following the first open call for charged
science proposals from the SALT partners. This paper discusses the current performance of SALT and it First
Generation instruments, some initial science results, the proposal process and the operational model for the
telescope.
The QUIJOTE-CMB experiment: studying the polarisation of the galactic and cosmological microwave emissions
Author(s):
J. A. Rubiño-Martín;
R. Rebolo;
M. Aguiar;
R. Génova-Santos;
F. Gómez-Reñasco;
J. M. Herreros;
R. J. Hoyland;
C. López-Caraballo;
A. E. Pelaez Santos;
V. Sanchez de la Rosa;
A. Vega-Moreno;
T. Viera-Curbelo;
E. Martínez-Gonzalez;
R. B. Barreiro;
F. J. Casas;
J. M. Diego;
R. Fernández-Cobos;
D. Herranz;
M. López-Caniego;
D. Ortiz;
P. Vielva;
E. Artal;
B. Aja;
J. Cagigas;
J. L. Cano;
L. de la Fuente;
A. Mediavilla;
J. V. Terán;
E. Villa;
L. Piccirillo;
R. Battye;
E. Blackhurst;
M. Brown;
R. D. Davies;
R. J. Davis;
C. Dickinson;
S. Harper;
B. Maffei;
M. McCulloch;
S. Melhuish;
G. Pisano;
R. A. Watson;
M. Hobson;
K. Grainge;
A. Lasenby;
R. Saunders;
P. Scott
Show Abstract
The QUIJOTE (Q-U-I JOint Tenerife) CMB Experiment will operate at the Teide Observatory with the aim
of characterizing the polarisation of the CMB and other processes of Galactic and extragalactic emission in the
frequency range of 10-40GHz and at large and medium angular scales. The first of the two QUIJOTE telescopes
and the first multi-frequency (10-30GHz) instrument are already built and have been tested in the laboratory.
QUIJOTE-CMB will be a valuable complement at low frequencies for the Planck mission, and will have the
required sensitivity to detect a primordial gravitational-wave component if the tensor-to-scalar ratio is larger
than r = 0.05.
The next generation of the Canada-France-Hawaii Telescope: science requirements and survey strategies
Author(s):
Alan McConnachie;
Patrick Côté;
David Crampton;
Daniel Devost;
Doug Simons;
Kei Szeto
Show Abstract
A concept study is underway to upgrade the existing 3.6 meter Canada-France-Hawaii Telescope (CFHT) to a
10 meter class, wide-field, dedicated, spectroscopic facility, which will be the sole astronomical resource capable
of obtaining deep, spectroscopic follow-up data to the wealth of photometric and astrometric surveys planned
for the next decade, and which is designed to tackle driving science questions on the formation of the Milky Way
galaxy and the characterization and nature of dark energy. This unique facility will operate at low (R ∼ 2000),
intermediate (R ∼ 6000) and high (R ∼ 20000) resolutions over the wavelength range 370 ≤ λ≤ 1300nm,
and will obtain up to 3200 simultaneous spectra per pointing over a 1.5 square degree field. Unlike all other
proposed or planned wide field spectroscopic facilities, this “Next Generation CFHT” will combine the power
of a 10m aperture with exquisite observing conditions and a mandate for dedicated spectroscopic studies to
enable transformative science programs in fields as diverse as exoplanetary host characterization, the interstellar
medium, stars and stellar astrophysics, the Milky Way galaxy, the Local Group, nearby galaxies and
clusters, galaxy evolution, the inter-galactic medium, dark energy and cosmology. A new collaboration must
be formed to make this necessary facility into a reality, and currently nearly 60 scientists from 11 different
communities - Australia, Brazil, Canada, China, France, Hawaii, India, Japan, South Korea, Taiwan, USA - are
involved in defining the science requirements and survey strategies. Here, we discuss the origins of this project,
its motivations, the key science and its flow-down requirements. An accompanying article describes the technical
studies completed to date. The final concept study will be submitted to the CFHT Board and Science Advisory
Committee in Fall 2012, with first light for the facility aiming to be in the early 2020s.
The optics and detector-simulation of the air fluorescence telescope FAMOUS for the detection of cosmic rays
Author(s):
Tim Niggemann;
Thomas Hebbeker;
Markus Lauscher;
Christine Meurer;
Lukas Middendorf;
Johannes Schumacher;
Maurice Stephan
Show Abstract
A sophisticated method for the observation of ultra-high-energy cosmic rays (UHECRs) is the
fluorescence
detection technique of extensive air showers (EAS).
FAMOUS will be a small
fluorescence telescope, instrumented with silicon photomultipliers (SiPMs) as highly-sensitive
light detectors. In comparison to photomultiplier tubes, SiPMs promise to have a higher photon-detection-efficiency. An increase in sensitivity allows to detect more distant and lower energy showers which
will contribute to an enrichment of the current understanding of the development of EAS and the chemical
composition of UHECRs.
Experimental characterization of the turbulence inside the dome and in the surface layer
Author(s):
Aziz Ziad;
Dali-Ali Wassila;
Julien Borgnino;
Marc Sarazin
Show Abstract
We present the concept of a new instrument dedicated to modeling turbulence inside the dome and in the surface
layer. It consists of using parallel laser beams separated by non redundant baselines between 0.1 and 2-3m and
measuring Angle-of-Arrival (AA) fluctuations from spots displacements on a CCD. We use weighted least-square
method to fit the measured AA longitudinal and transverse covariances with theoretical forms deduced from
the usual models of turbulence. Then, the whole parameters characterizing this turbulence are provided from a
complete spatio-temporal analysis of AA fluctuations. Thus, the surface layer turbulence energy in terms of C2N
constant is provided from the AA structure function as in the DIMM instrument.
Seeing trends from deployable Shack-Hartmann wavefront sensors, MMT Observatory, Arizona, USA
Author(s):
J. Duane Gibson;
G. Grant Williams;
Thomas Trebisky
Show Abstract
Deployable Shack-Hartmann wavefront sensors (WFS) for the f/5 and f/9 secondary configurations have been used at
the 6.5-meter MMT Observatory (MMTO) since 2003. Probe mirrors for these WFS's are moved into the optical path of
the telescope between scientific observations multiple times each night. Results from the wavefront measurements are
then used to bend the primary mirror (M1) and to reposition the secondary mirror (M2) to correct for wavefront errors.
In addition to measuring the optical wavefront error, the Shack-Hartmann data are used to determine the delivered seeing
using the measured spot sizes. This study attempts to analyze the more than 75,000 WFS measurements and associated
seeing values obtained at the MMTO since 2003. The overall WFS data reduction and analysis procedure is discussed.
This data analysis includes: 1) finding the spots in each image, 2) centroiding the spots, 3) measuring a point-spread
function, 4) determining an average spot width and a derived seeing value, and 5) computing the best-fit Zernike
polynomial coefficients. Wavefront slopes are calculated from spot displacements and wavefront aberrations are fit with
a 19-term Zernike polynomial. As part of this study, the WFS-derived seeing values are correlated with other observing
parameters, such as mirror-air temperature contrasts. Finally, seasonal climate and local weather (e.g., prevailing wind
direction) effects on astronomical seeing are evaluated.
An updated T-series thermocouple measurement system for high-accuracy temperature measurements of the MMT primary mirror
Author(s):
D. Clark;
J. D. Gibson
Show Abstract
Starting in 2009, MMTO began design and installation of a new set of electronics to measure a set of radiallydistributed
type T thermocouples installed after the primary mirror polishing was completed. These thermocouples
are arranged in both single measurement points and as thermopiles for differential temperature sensing. Since the
goal of the primary mirror temperature control system is to minimize mirror seeing and mirror figure errors induced
by temperature variation across the primary mirror, it depends on excellent accuracy from the temperature sensing
system. The new electronics encompass on-board cold-junction compensation, real-time ITS-90 curve fitting, and
Ethernet connectivity to the data servers running in the MMTO software infrastructure. We describe the hardware
design, system wiring, and software used in this system.
A spectropolarimetric focal station for the ESO E-ELT
Author(s):
Klaus G. Strassmeier;
Igor DiVarano;
Ilya Ilyin;
Manfred Woche;
Uwe Laux
Show Abstract
We present a conceptual design for a spectropolarimetric focal station for ESO's European Extremely Large Telescope
(E-ELT). It uses the intermediate f/4.4 focus, the only symmetric focus of the telescope. A dual channel, full Stokesvector
polarimeter provides on-axis light for the wavelength range 380-1600nm to up to two spectrographs
simultaneously via two pairs of fibers. With such spectropolarimetric capability and a proper spectrograph for the optical
and the near infrared wavelengths, the E-ELT would be able to provide the full parameter space of an incoming
wavefront. Because of the on-axis entrance location of the polarimeter collimator and an entrance aperture of just 1.3
arcsec, the expected poor image quality of the intermediate telescope focus is not directly relevant.
Performance of industrial scale production of ZERODUR mirrors with diameter of 1.5 m proves readiness for the ELT M1 segments
Author(s):
Thomas Westerhoff;
Peter Hartmann;
Ralf Jedamzik;
Alexander Werz
Show Abstract
The two Extremely Large Telescopes under discussion, the Thirty Meter Telescope and the European Extremely Large Telescope, will use a multitude of hexagonal shaped mirror segments to achieve the large aperture of 30 m and 39 m, respectively. The proper functionality of both telescopes will strongly depend upon the variation of material properties between individual segments.
SCHOTT has a well proven experience in production of mirror substrates for segmented telescopes. Today five of the world's six segmented telescopes are using ZERODUR® as mirror substrate material. Since 2003 SCHOTT delivered more than 260 mirrors of 1.5 m in diameter for industrial application not related to astronomy. In this paper the achievements during the serial production of those are presented for specified material properties and dimensional parameters. The presentation includes data on the fulfillment of the CTE specification, the achieved tolerances on surface figure and flatness and other geometrical quality parameters. The data to be presented will demonstrate the excellent reproducibility of ZERODUR®'s material properties and its manufacturing process. The production capabilities at SCHOTT for the successful delivery in time of the multitude of ZERODUR® segments are presented and discussed. They will demonstrate that ZERODUR® is well prepared for the demands of industrial scale production for the two large segmented ELT's in quality, quantity, and in the requested time period.
E-ELT project: geotechnical investigation at Cerro Armazones
Author(s):
Paolo Ghiretti;
Volker Heinz;
Daniela Pollak;
Jose Lagos
Show Abstract
The design and construction of large telescopes include significant geotechnical challenges. In order to guarantee
reliable and stable operations, a giant telescope like the European - Extremely Large Telescope (E-ELT) requires a
foundation performance according to the level of accuracy of the other telescope's components. This paper describes
the main geological and geotechnical activities conducted on site along with the studies completed in specialized
geotechnical laboratories with the objective to achieve a thorough characterization of the ground conditions. This
study shows that, the properties of the foundation materials are appropriate to guarantee a good performance of the
E-ELT.
Technological developments toward the small size telescopes of the Cherenkov Telescope Array
Author(s):
R. Canestrari;
T. Greenshaw;
G. Pareschi;
R. White
Show Abstract
In the last two decades a new window for ground-based high energy astrophysics has been opened. This explores the
energy band from about 100 GeV to 10 TeV by making use of Imaging Atmospheric Cherenkov Telescopes (IACTs).
Research in Very High Energy (VHE) gamma-ray astronomy is progressing rapidly and, thanks to the newest facilities
such as MAGIC, HESS and VERITAS, astronomers and particle physicists are obtaining data with far-reaching
implications for theoretical models.
The Cherenkov Telescope Array (CTA) is the ambitious international next-generation facility for gamma-ray astronomy
and astrophysics that aims to provide a sensitivity of a factor of 10 higher than current instruments, extend the energy
band coverage from below 50 GeV to above 100 TeV, and improve significantly the energy and angular resolution to
allow precise imaging, photometry and spectroscopy of sources. To achieve this, an extended array composed of nearly
100 telescopes of large, medium and small dimensions is under development. Those telescopes will be optimized to
cover the low, intermediate and high energy regimes, respectively.
In this paper, we focus our attention on the Small Size Telescopes (SSTs): these will be installed on the CTA southern
hemisphere site and will cover an area of up to 10 km2. The energy range over which the SSTs will be sensitive is from
around 1 TeV to several hundreds of TeV. The status of the optical and mechanical designs of these telescopes is
presented and discussed. Comments are also made on the focal surface instruments under development for the SSTs.
SST-GATE: an innovative telescope for very high energy astronomy
Author(s):
Philippe Laporte;
Jean-Laurent Dournaux;
Hélène Sol;
Simon Blake;
Catherine Boisson;
Paula Chadwick;
Delphine Dumas;
Gilles Fasola;
Fatima de Frondat;
Tim Greenshaw;
Olivier Hervet;
James Hinton;
David Horville;
Jean-Michel Huet;
Isabelle Jégouzo;
Jürgen Schmoll;
Richard White;
Andreas Zech
Show Abstract
The Cherenkov Telescope Array (CTA) is an international collaboration that aims to create the world's
largest (ever) Very High Energy gamma-ray telescope array, consisting of more than 100 telescopes
covering an area of several square kilometers to observe the electromagnetic showers generated by
incoming cosmic gamma-rays with very high energies (from a few tens of GeV up to over 100 TeV).
Observing such sources requires - amongst many other things - a large FoV (Field of View). In the
framework of CTA, SST-GATE (Small Size Telescope - GAmma-ray Telescope Elements) aims to
investigate and to build one of the two first CTA prototypes based on the Schwarzschild-Couder (SC)
optical design that delivers a FoV close to 10 degrees in diameter. To achieve the required
performance per unit cost, many improvements in mirror manufacturing and in other technologies are
required. We present in this paper the current status of our project. After a brief introduction of the
very high energy context, we present the opto-mechanical design, discuss the technological tradeoffs
and explain the electronics philosophy that will ensure the telescopes cost is minimised without
limiting its capabilities. We then describe the software nedeed to operate the telescope and conclude
by presenting the expected telescope performance and some management considerations.
A new era for the 2-4 meters class observatories: an innovative integrated system telescope-dome
Author(s):
G. Marchiori;
A. Busatta;
S. De Lorenzi;
F. Rampini;
C. Perna;
G. Vettolani
Show Abstract
The experience and the lessons learned gained in two decades of activity in astronomical industry in projects like NTT,
VLT, LBT, VST VISTA and finally E-ELT brought to study a flexible fully integrated system which could address every
astronomic institute to approach astronomy with a complete self standing facility including a dome, a telescope with 2 to
4 meters class optics and relative instruments with which it is possible to match the desired science cases and objectives.
This paper describes the aspects of the flexibility which is so important to adapt the design to the specifications in order
to fulfil the institutes science goals in the least time possible through the latest design tools such as CAD CAE FEM etc
and the best and more cost effective technology experienced along the projects mentioned before.
Low-frequency high-sensitivity horizontal monolithic folded-pendulum as sensor in the automatic control of ground-based and space telescopes
Author(s):
F. Acernese;
R. De Rosa;
G. Giordano;
R. Romano;
F. Barone
Show Abstract
This paper describes a new mechanical implementation of a monolithic folded pendulum based inertial sensor, configurable as seismometer and as accelerometer. The sensor is a compact, light, fully scalable, tunable in
frequency (< 100mHz), with large measurement band (10−6 Hz ÷ 10Hz) and high quality factor (Q > 1500 in air) instrument, with immunity to environmental noises guaranteed by an integrated laser optical readout.
The measured sensitivity curve is in very good agreement with the theoretical one (10−12m/√Hz) in the band (0.1 ÷ 10Hz). Although its natural application is in the fields of earthquake engineering and geophysics, its
performances make it suitable also for applications as sensor in the control of inertial platforms for interferometric detectors of gravitational waves, where a residual horizontal motion better than 10−15m/√Hz in the band
0.01 ÷ 100Hz is a requirement, and in the control of the mechanical support systems of ground-based or space telescopes.
ALMA temporal phase stability and the effectiveness of water vapor radiometer
Author(s):
Satoki Matsushita;
Koh-Ichiro Morita;
Denis Barkats;
Richard E. Hills;
Edward B. Fomalont;
Bojan Nikolic
Show Abstract
We present the temporal phase stability of the entire ALMA system. We first verified the temporal phase stability: We observed a strong quasar for a long time (a few tens of minutes), derived the temporal structure function after the atmospheric phase correction using the water vapor radiometers (WVRs), and confirmed that the phase stability of all the baselines reached the ALMA specification. We then verified frequency transfer between bands: We observed a bright quasar and switched between the two frequency bands, and confirmed that the phase returned to the original values within the phase fluctuation. In addition to these results, we also studied the effectiveness of the WVR phase correction at various frequencies, baseline lengths, and weather conditions.
ALMA array element astronomical verification
Author(s):
S. Asayama;
L. B. G. Knee;
P. G. Calisse;
P. C. Cortés;
R. Jager;
B. López;
C. López;
T. Nakos;
N. Phillips;
M. Radiszcz;
R. Simon;
I. Toledo;
N. Whyborn;
H. Yatagai;
J. P. McMullin;
P. Planesas
Show Abstract
The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twelve-meter antennas and 12
seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter wavelength range. The ALMA
System Integration Science Team (SIST) is a group of scientists and data analysts whose primary task is to verify and
characterize the astronomical performance of array elements as single dish and interferometric systems. The full set of
tasks is required for the initial construction phase verification of every array element, and these can be divided roughly
into fundamental antenna performance tests (verification of antenna surface accuracy, basic tracking, switching, and on-the-fly rastering) and astronomical radio verification tasks (radio pointing, focus, basic interferometry, and end-to-end
spectroscopic verification). These activities occur both at the Operations Support Facility (just below 3000 m elevation)
and at the Array Operations Site at 5000 m.
Trajectory generation for parametric rotating scan patterns at the LMT
Author(s):
David R. Smith;
Kamal Souccar
Show Abstract
As main axis controllers for large, high precision telescopes have become more sophisticated, astronomers
are developing new approaches to observing. Rather than merely pointing at a particular set of coordinates
and tracking to account for the rotation of the Earth or for the ephemeris of the source, these new observing
techniques often call for a telescope to scan in a pattern around the nominal source coordinates. These motions
are conducted at higher rates and accelerations than traditional single point or raster maps, which introduces
additional complexity into the control. Additionally, these motions must work in conjunction with an existing
trajectory generator.
This paper describes how a general parametric rotating scan pattern has been implemented at the Large
Millimeter Telescope (LMT). The desired motion is combined with the existing trajectory generator and allows
the addition of a parametric scan pattern, defined for each axis. The pattern can also be continuously rotated at
a constant rate as the system tracks the source. The development allows for any parametric scan pattern, and
the particular case of a continuously rotating Lissajous pattern is addressed in detail.
Atacama compact array antennas
Author(s):
M. Saito;
J. Inatani;
K. Nakanishi;
H. Saito;
S. Iguchi
Show Abstract
The ACA (Atacama Compact Array) system is an important element of ALMA and consists of four ACA 12-m antennas
and twelve ACA 7-m antennas. The ACA system aims to acquire the total power data with four 12-m antennas and the
short baseline interferometer data with 7-m antennas. The ACA system also increases reliability of the interferometer
maps of astronomical sources larger than the field view of the 12-m antenna. The science performance of these antennas
has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in Atacama desert in northern
Chile since 2007. The pointing performance has been verified with a dedicated optical pointing telescope, the servo
performance is tested with angle encoders, and the surface accuracy has been measured with a radio holography method.
Both ACA 12-m antennas and 7-m antennas have been successfully demonstrated to meet the very stringent ALMA
specifications.
Very large millimeter/submillimeter array toward search for 2nd Earth
Author(s):
Satoru Iguchi;
Masao Saito
Show Abstract
ALMA (Atacama Large Millimeter/submillimeter Array) is a revolutionary radio telescope and its early scientific
operation has just started. It is expected that ALMA will resolve several cosmic questions and will give us a new cosmic
view. Our passion for astronomy naturally goes beyond ALMA because we believe that the 21st-century astronomy
should pursue the new scientific frontier. In this conference, we propose a project of the future radio telescope to search
for habitable planets and finally detect 2nd Earth as a migratable planet. Detection of 2nd Earth is one of the ultimate
dreams not only for astronomers but also for every human being.
To directly detect 2nd Earth, we have to carefully design the sensitivity and angular resolution of the telescope by
conducting trade-off analysis between the confusion limit and the minimum detectable temperature. The result of the
sensitivity analysis is derived assuming an array that has sixty-four (64) 50-m antennas with 25-;μm surface accuracy
mainly located within the area of 300 km (up to 3000 km), dual-polarization SSB receivers with the best noise
temperature performance achieved by ALMA or better, and IF bandwidth of 128 or 256 GHz.. We temporarily name this
telescope "Very Large Millimeter/Submillimeter Array (VLMSA)". Since this sensitivity is extremely high, we can have
a lot of chances to study the galaxy, star formation, cosmology and of course the new scientific frontier.
ACA phase calibration scheme with the ALMA water vapor radiometers
Author(s):
Yoshiharu Asaki;
Satoki Matsushita;
Koh-Ichiro Morita;
Bojan Nikolic
Show Abstract
In Atacama Large Millimeter/submillimeter Array (ALMA) commissioning and science verification we have
conducted a series of experiments of a novel phase calibration scheme for Atacama Compact Array (ACA). In
this scheme water vapor radiometers (WVRs) devoted to measurements of tropospheric water vapor content
are attached to ACA’s four total-power array (TP Array) antennas surrounding the 7 m dish interferometer
array (7 m Array). The excess path length (EPL) due to the water vapor variations aloft is fitted to a simple
two-dimensional slope using WVR measurements. Interferometric phase fluctuations for each baseline of the
7 m Array are obtained from differences of EPL inferred from the two-dimensional slope and subtracted from
the interferometric phases. In the experiments we used nine ALMA 12-m antennas. Eight of them were closely
located in a 70-m square region, forming a compact array like ACA. We supposed the most four outsiders to be
the TP Array while the inner 4 antennas were supposed to be the 7 m Array, so that this phase correction scheme
(planar-fit) was tested and compared with the WVR phase correction. We estimated residual root-mean-square
(RMS) phases for 17- to 41-m baselines after the planar-fit phase correction, and found that this scheme reduces
the RMS phase to a 70 – 90 % level. The planar-fit phase correction was proved to be promising for ACA, and
how high or low PWV this scheme effectively works in ACA is an important item to be clarified.
Functional safety for the Advanced Technology Solar Telescope
Author(s):
Scott Bulau;
Timothy R. Williams
Show Abstract
Since inception, the Advanced Technology Solar Telescope (ATST) has planned to implement a facility-wide functional
safety system to protect personnel from harm and prevent damage to the facility or environment. The ATST will deploy
an integrated safety-related control system (SRCS) to achieve functional safety throughout the facility rather than relying
on individual facility subsystems to provide safety functions on an ad hoc basis.
The Global Interlock System (GIS) is an independent, distributed, facility-wide, safety-related control system, comprised
of commercial off-the-shelf (COTS) programmable controllers that monitor, evaluate, and control hazardous energy and
conditions throughout the facility that arise during operation and maintenance.
The GIS has been designed to utilize recent advances in technology for functional safety plus revised national and
international standards that allow for a distributed architecture using programmable controllers over a local area network
instead of traditional hard-wired safety functions, while providing an equivalent or even greater level of safety.
Programmable controllers provide an ideal platform for controlling the often complex interrelationships between
subsystems in a modern astronomical facility, such as the ATST. A large, complex hard-wired relay control system is no
longer needed. This type of system also offers greater flexibility during development and integration in addition to
providing for expanded capability into the future. The GIS features fault detection, self-diagnostics, and redundant
communications that will lead to decreased maintenance time and increased availability of the facility.
Facility level thermal systems for the Advanced Technology Solar Telescope
Author(s):
LeEllen Phelps;
Gaizka Murga;
Mark Fraser;
Tània Climent
Show Abstract
The management and control of the local aero-thermal environment is critical for success of the Advanced Technology
Solar Telescope (ATST). In addition to minimizing disturbances to local seeing, the facility thermal systems must meet
stringent energy efficiency requirements to minimize impact on the surrounding environment and meet federal
requirements along with operational budgetary constraints. This paper describes the major facility thermal equipment
and systems to be implemented along with associated energy management features. The systems presented include the
central plant, the climate control systems for the computer room and coudé laboratory, the carousel cooling system
which actively controls the surface temperature of the rotating telescope enclosure, and the systems used for active and
passive ventilation of the telescope chamber.
Quasi-static wavefront control for the Advanced Technology Solar Telescope
Author(s):
Luke C. Johnson;
R. Upton;
T. Rimmele;
S. Barden
Show Abstract
The Advanced Technology Solar Telescope (ATST) requires active control of quasi-static telescope aberrations
in order to meet image quality standards set by its science requirements. Wavefront control is managed by
the Telescope Control System, with many telescope subsystems playing key roles. We present the design of
the ATST quasi-static wavefront and alignment control architecture and the algorithms used to control its four
active mirrors. Two control algorithms are presented, one that minimizes force on M1 actuators and another that
employs a neutral-pointing constraint on M2 to reduce pointing error. We also present simulations that generate
typical daily active mirror trajectories which correct optical misalignments due to changing gravitational and
thermal loads.
Optical design of the COSMO large coronagraph
Author(s):
Dennis Gallagher;
Steven Tomczyk;
Haiying Zhang;
Peter G. Nelson
Show Abstract
The Coronal Solar Magnetism Observatory (COSMO) is a facility dedicated to measuring magnetic
fields in the corona and chromosphere of the Sun. It will be located on a mountaintop in the Hawaiian
Islands and will replace the current Mauna Loa Solar Observatory (MLSO). COSMO will employ a
suite of instruments to determine the magnetic field and plasma conditions in the solar atmosphere and
will enhance the value of data collected by other observatories on the ground (SOLIS, ATST, FASR)
and in space (SDO, Hinode, SOHO, GOES, STEREO, DSCOVR, Solar Probe+, Solar Orbiter). The
dynamics and energy flow in the corona are dominated by magnetic fields. To understand the
formation of Coronal Mass Ejections (CMEs), their relation to other forms of solar activity, and their
progression out into the solar wind requires measurements of coronal magnetic fields. The COSMO
suite includes the Large Coronagraph (LC), the Chromosphere and Prominence Magnetometer
(ChroMag) and the K-Coronagraph. The Large Coronagraph will employ a 1.5 meter fuse silica singlet
lens and birefringent filters to measure magnetic fields out to two solar radii. It will observe over a
wide range of wavelengths from 500 to 1100 nm providing the capability of observing a number of
coronal, chromospheric, and photospheric emission lines. Of particular importance to measuring
coronal magnetic fields are the forbidden emission lines of Fe XIII at 1074.7 nm and 1079.8 nm. These
lines are faint and require the very large aperture. NCAR and NSF have provided funding to bring the
COSMO Large Coronagraph to a preliminary design review (PDR) state by the end of 2013.
Behavior of a horizontal air curtain subjected to a vertical pressure gradient
Author(s):
James Linden;
LeEllen Phelps
Show Abstract
We present the details on an experiment to investigate the behavior of an air curtain that is subjected to a transverse
pressure gradient. The setup simulates the conditions that will be present in the Advanced Technology Solar Telescope
(ATST), a 4-meter solar observatory that will be built on Haleakala, Hawaii. A test rig was built to replicate the region at
which the optical path crosses a temperature and pressure boundary between the telescope mount region, which is at the
ambient temperature and pressure, and a warmer, pressurized lab space directly below. Use of an air curtain in place of
an optically-transmitting window at the interface would allow science observations at a wider range of scientific
wavelengths. With the air curtain exhibiting transitional flow behavior across the boundary, and applied pressure
gradients of up to 6.5 Pa, we found that the air curtain was able to hold a pressure gradient of 0.25 Pa. As the applied
pressure was increased, transient turbulent regions formed at the interface, and predictable flow behavior only occurred
in the region closest to the air curtain blower. Computer modeling is used to validate the test data, identify laminar
regions of the air curtain where minimal image distortion would occur, and explore the relationship between the applied
pressure, effective pressure difference, and air curtain profile.
ATST telescope mount: machine tool or telescope
Author(s):
Paul Jeffers;
Günter Stolz;
Giovanni Bonomi;
Oliver Dreyer;
Hans Kärcher
Show Abstract
The Advanced Technology Solar Telescope (ATST) will be the largest solar telescope in the world, and will be able to
provide the sharpest views ever taken of the solar surface. The telescope has a 4m aperture primary mirror, however due
to the off axis nature of the optical layout, the telescope mount has proportions similar to an 8 meter class telescope.
The technology normally used in this class of telescope is well understood in the telescope community and has been
successfully implemented in numerous projects.
The world of large machine tools has developed in a separate realm with similar levels of performance requirement but
different boundary conditions. In addition the competitive nature of private industry has encouraged development and
usage of more cost effective solutions both in initial capital cost and thru-life operating cost.
Telescope mounts move relatively slowly with requirements for high stability under external environmental influences
such as wind buffeting. Large machine tools operate under high speed requirements coupled with high application of
force through the machine but with little or no external environmental influences.
The benefits of these parallel development paths and the ATST system requirements are being combined in the ATST
Telescope Mount Assembly (TMA). The process of balancing the system requirements with new technologies is based
on the experience of the ATST project team, Ingersoll Machine Tools who are the main contractor for the TMA and MT
Mechatronics who are their design subcontractors.
This paper highlights a number of these proven technologies from the commercially driven machine tool world that are
being introduced to the TMA design. Also the challenges of integrating and ensuring that the differences in application
requirements are accounted for in the design are discussed.
Performance introduction of a 2.5m telescope mount
Author(s):
Guomin Wang;
Bozhong Gu;
Shihai Yang;
Xiang Jiang;
Zhiyong Zhang;
Yu Ye;
Jin Xu
Show Abstract
In recent years, Nanjing Institute of Astronomical Optics and Technology (NIAOT) has made several telescopes for
observatories all around the world. In 2011 NIAOT just finished the development of a 2.5m optical/infrared telescope
mount. First part of this paper is to introduce the mount structure and their adjustment work. Second part is to give an
introduction of the mount performance test methods and test results finished on NIAOT workshop.
Installation and verification of high precision mechanics in concrete structures at the example of ALMA antenna interfaces
Author(s):
Volker Heinz;
Max Kraus;
Eduardo Orellana
Show Abstract
For the ALMA interferometer at the array operation facility near San Pedro de Atacama at 5.000 meters asl 192 concrete
antenna foundations had to be equipped with coupling points for 66 antennas. These antennas will be frequently moved
between the foundations and placed on these interfaces without further adjustment.
To position the ALMA antennas with the required accuracy, high precision inserts need to be installed in previously
casted concrete foundations. Very tight mechanical tolerances have to be applied to civil structures, with standard tolerances
of not less than millimeters. This is extremely difficult considering the material (mortar and steel in a concrete
slab) to be used and the environmental conditions on site. Special tools had to be designed and an installation and alignment
procedure developed, tested and improved. Important was to have a robust process, which allows highest precision
installation without major re-machining for approx 600 interface blocks. Installation material, which could cope with the
conditions, was specially tested for these requirements.
The geometry of the interface and other parameters such as horizontal and vertical stiffness must be verified after the
installation. Special metrology tools to measure reliable at micron level at high altitude had been selected.
The experience and knowledge acquired will be beneficial for the installation of any opto-mechanical device in civil engineering
structures, such as telescope and dome track rails, but also in optical interferometer installations. Metrology
requirements and environmental conditions in most of these cases are equally challenging.
E-ELT telescope main structure
Author(s):
Alfredo Orden Martínez;
Angel Dilla Martínez;
Noelia Ballesteros Pérez;
Manuel Alcantud Abellán
Show Abstract
The European Extra Large Telescope is ESO's biggest astronomical telescope project.
The E-ELT is an active and adaptive telescope. It has an astigmatic optical solution (five mirrors, including two flat
ones). The telescope structure is of alt-azimuth type able to support a primary mirror with an equivalent diameter of
40 m.
The telescope will be installed in a high-seismicity zone, in Cerro Armazones, Antofagasta Region, Chile, at an altitude
of 3046 metres above sea level. This has significantly affected the boundary conditions and safety aspects considered
during the project.
The scope of the paper describes the Telescope Main Structure configuration developed by Empresarios Agrupados
(Spain) during the FEED Studies performed from June 2009 to July 2011 in the frame of ESO Contracts.
Most of the solutions implemented were extrapolated from existing installations in which Empresarios Agrupados has
participated, adjusting for the extra large size of this new telescope.
Testing, characterization, and control of a multi-axis, high precision drive system for the Hobby-Eberly Telescope Wide Field Upgrade
Author(s):
Ian M. Soukup;
Joseph H. Beno;
Gary J. Hill;
John M. Good;
Charles E. Penney;
Timothy A. Beets;
Jorge D. Esguerra;
Richard J. Hayes;
James T. Heisler;
Joseph J. Zierer;
Gregory A. Wedeking;
Michael S. Worthington;
Douglas R. Wardell;
John A. Booth;
Mark E. Cornell;
Marc D. Rafal
Show Abstract
A multi-axis, high precision drive system has been designed and developed for the Wide Field Upgrade to the Hobby-
Eberly Telescope at McDonald Observatory. Design, performance and controls details will be of interest to designers of
large scale, high precision robotic motion devices. The drive system positions the 20-ton star tracker to a precision of
less than 5 microns along each axis and is capable of 4 meters of X/Y travel, 0.3 meters of hexapod actuator travel, and
46 degrees of rho rotation. The positioning accuracy of the new drive system is achieved through the use of highprecision drive hardware in addition to a meticulously tuned high-precision controller. A comprehensive understanding of the drive structure, disturbances, and drive behavior was necessary to develop the high-precision controller. Thorough testing has characterized manufacture defects, structural deflections, sensor error, and other parametric uncertainty. Positioning control through predictive algorithms that analytically compensate for measured disturbances has been developed as a result of drive testing and characterization. The drive structure and drive dynamics are described as well as key results discovered from testing and modeling. Controller techniques and development of the predictive algorithms are discussed. Performance results are included, illustrating recent performance of several axes of the drive system. This paper describes testing that occurred at the Center for Electromechanics in Austin Texas.
Enclosure rotation on the Large Binocular Telescope
Author(s):
James Howard;
Robert Meeks;
David Ashby;
Warren Davison;
James Wiese;
Jeff Urban;
Rick Hansen;
Jared Schuh
Show Abstract
After several years of operation the enclosure rotation system of the LBT is exhibiting wear and other performance
issues that may impact operations. This paper reviews the system design and assumptions used, describes the current
performance and observed symptoms, and discusses recent improvements made to improve performance and reliability.
The rotating enclosure of the LBT is a 2200 ton structure riding on four bogies with a total of 20 wheels. Identified
deficiencies include wheel bearing capacities, bogie misalignment, and rail loading. These are partially due to excess
enclosure weight, which was supposed to be 1600 tons, but also due to design errors.
The most serious problem was the failure of several wheel bearings. The bearings were not designed for field
serviceability, so a crash program began to determine how to replace them. This got us back on sky quickly, but a
review of the engineering calculations identified an error which led to the use of undersized bearings. A method of
installing a larger bearing was found, and these have been installed.
One set of bogie wheels are misaligned so severely the structure makes loud popping and banging noises when the
direction of building rotation changes. The bogie needs to be rotated about its vertical axis, but there was no provision in
the design for this.
The circular rail the bogies roll on is wearing faster than expected. The rails are extremely difficult to replace, so the
short term plan is to study the problem.
The 3,6 m Indo-Belgian Devasthal Optical Telescope: the hydrostatic azimuth bearing
Author(s):
Jonathan de Ville;
Maxime Piérard;
Christian Bastin
Show Abstract
AMOS SA has been awarded of the contract for the design, manufacturing, assembly, tests and on site installation
(Devasthal, Nainital in central Himalayan region) of the 3.6 m Indo-Belgian Devasthal Optical Telescope (IDOT).
The telescope has a Ritchey-Chrétien optical configuration with a Cassegrain focus equipped with one axial port and
two side ports. The primary mirror is a meniscus active mirror. The mount is an Alt-Az type with for the azimuth axis a
5 m diameter hydrostatic track. This paper presents the solution adopted by AMOS to meet the specific requirements for
the azimuth axis. The track is designed to be able to control the positioning of the telescope around the azimuth axis
with an accuracy of 0.05 arc second for all tracking configurations. The challenge came from this tight accuracy with a
mass in rotation weighting 125 tons. The azimuth track was mounted and tested in AMOS workshop; the tests and
performances are also discussed.
Enclosure design for the ARIES 3.6m optical telescope
Author(s):
A. K. Pandey;
Vishal Shukla;
Tarun Bangia;
R. D. Raskar;
R. R. Kulkarni;
A. S. Ghanti
Show Abstract
A 3.6-m, f/9 optical telescope is planned to be installed at Devasthal, India (Latitude:29° 21' 40'' N, Longitude: 79°
41' 04'' E, Altitude: 2450 m above msl). The telescope has Cassegrain focus and alt-azimuth mount. The design of
the telescope enclosure and the auxiliary building includes a fixed base enclosure, a telescope pier, a rotating dome
structure, an auxiliary building, ventilation and component handling systems. The design is optimized for thermal,
mechanical, structural, as well as for telescope installation and maintenance requirements. The design aims to
provide seeing limited images within the telescope enclosure. This paper presents design of the 3.6m telescope
enclosure.
An innovative alt-alt telescope for small observatories and amateur astronomers
Author(s):
M. Riva;
S. Basso;
R. Canestrari;
P. Conconi;
D. Fugazza;
M. Ghigo;
M. Landoni;
G. Pareschi;
P. Spanó;
R. Tomelleri;
F. M. Zerbi
Show Abstract
This paper want to show an innovative amateur oriented telescope with an unconventional alt-alt conguration.
The goal is to make a telescope with good optical quality reducing production costs by adopting a gimbal
based mounting to develop an alt-alt conguration suitable for a telescope. Reduce costs while preserving the
optical quality is a necessary condition to allow small groups of amateur astronomers, schools and cultural
clubs, with reduced economic resources, to acquire an astronomical instrument that encourages learning and
advancing astrophysical knowledge. This unconventional mechanism for the realization of a telescope alt-alt
provides signicant advantages. The traditional rotary motors coupled with expensive precision bearings are
replaced with two simple linear actuators coupled to a properly preloaded gimbal joint and the cell becomes the
primary structure of the telescope. A second advantage would be secured by mechanical simplicity evident in
the easy portability of the instrument. The frame alt-alt has some limitations on the horizon pointing but does
not show the zenith blind spot of the alt-az mount. A dedicated alt-alt pointing and tracking model is under
development to be compatible with commercial telescope softwares and with the proposed new mounting.
Prototype enclosure design for the Korea Microlensing Telescope Network (KMTNet)
Author(s):
N. Kappler;
L. Kappler;
W. M. Poteet;
H. K. Cauthen;
Byeong-Gon Park;
Chung-Uk Lee;
Seung-Lee Kim;
Sang-Mok Cha
Show Abstract
TBR Construction and Engineering (TBR) has under development for the Korea Astronomy and Space Science Institute (KASI), a project to provide three 1.6 meter optical telescopes observatories in three southern countries: Chile, South Africa, and Australia. The contracting team has chosen to develop a full scale prototype of the observatory. This will become a functional assembly and testing facility for all three project telescopes in Tucson, Arizona. This prototyping concept is meant to allow the optics team to make changes to the observatory as needed for the scientific mission while minimizing the expense of making changes in remote countries.
Initial alignment and commissioning plan for the LSST
Author(s):
William J. Gressler;
Jacques Sebag;
Chuck Claver
Show Abstract
The planned construction and completion of the Large Synoptic Survey Telescope (LSST) Project consists of phased
activities. The initial telescope construction period will transition to a multi-year commissioning phase, which will
conclude with final hand off to science operations. The initial telescope alignment will utilize laser tracker fiducials
and nodal aberration theory (NAT) to demonstrate Engineering First Light with a three-mirror optical system and
test camera, prior to the integration of the science camera. This plan exploits the diffraction limited on-axis image
quality of the three-mirror design. Commissioning consists of final integration of the three LSST subsystems
(Telescope, Camera, and Data Management), followed by on-sky science verification to show compliance with the
survey performance specifications.
Dark energy camera installation at CTIO: overview
Author(s):
Timothy M. Abbott;
Freddy Muñoz;
Alistair R. Walker;
Chris Smith;
Andrés Montane;
Brooke Gregory;
Roberto Tighe;
Patricio Schurter;
Nicole S. van der Bliek;
German Schumacher
Show Abstract
The Dark Energy Camera (DECam) has been installed on the V. M. Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. This major upgrade to the facility has required numerous modifications to the telescope and improvements in observatory infrastructure. The telescope prime focus assembly has been entirely replaced, and the f/8 secondary change procedure radically changed. The heavier instrument means that telescope balance has been significantly modified. The telescope control system has been upgraded. NOAO has established a data transport system to efficiently move DECam's output to the NCSA for processing. The observatory has integrated the DECam highpressure, two-phase cryogenic cooling system into its operations and converted the Coudé room into an environmentally-controlled instrument handling facility incorporating a high quality cleanroom. New procedures to
ensure the safety of personnel and equipment have been introduced.
Dark Energy Camera installation at CTIO: technical challenges
Author(s):
Freddy Muñoz A.;
Andrés Montane;
Roberto Tighe;
Michael Warner;
Timothy M. Abbott
Show Abstract
The Dark Energy Camera (DECam) is a new prime focus, wide-field imager for the V. M. Blanco 4-m telescope at CTIO. Instrumentation includes large, five-lens optical corrector mounted on hexapod mechanism for fine adjustment, filters, and a 519 Megapixel camera vessel; all integrated in a cage similar to the existing telescope prime focus structure. Currently Blanco allows a flip of this structure such that the f/8 secondary mirror, mounted on the back of the cage, points towards the primary mirror for Ritchey-Chretien observations. DECam will maintain this capability by attaching the existing F/8 mirror cell to the front of the new cage. Installation of this 8,600 kg instrument required the removal from the telescope of the primary mirror, the removal of the old prime focus assembly, and fine adjustment of large, over-constrained mechanisms followed by reassembly. A large facility shutdown was scheduled for this upgrade and several tools, fixtures, monitoring systems and procedures were developed in order to identify and then recover the optical alignment of the system, to control the distribution of stresses during tuning of the installation and to maintain the balance of the telescope with significant added mass. The final goal has been to maintain high performance of the telescope for both the existing f/8 Ritchey-Chretien focus mounted instruments and the new DECam instrument now in commissioning. The challenges presented in handling large elements, real-time monitoring, alignment, verification and feedback are described.
Korea Microlensing Telescope Network: science cases
Author(s):
Byeong-Gon Park;
Seung-Lee Kim;
Jae Woo Lee;
Byeong-Cheol Lee;
Chung-Uk Lee;
Cheongho Han;
Minjin Kim;
Dae-Sik Moon;
Hong-Kyu Moon;
Soo-Chang Rey;
Eon-Chang Sung;
Hwankyung Sung
Show Abstract
We present the science cases with the Korea Microlensing Telescope Network (KMTNet) which consists of three widefield
1.6 m telescopes distributed in Chile, South Africa, and Australia, respectively, providing unique continuous sky
coverage with the three telescopes. The primary scientific goal of the KMTNet project is to explore the structure and
diversity of planetary systems and variable objects. Since the system is mainly optimized to conduct gravitational
microlensing surveys, it will enable detections of very low-mass exoplanets, potentially down to the mass of Mars that
are inaccessible by other ground-based techniques. In addition to the primary science, it is possible to conduct a variety
of other observational programs with the KMTNet system, including photometric studies of nearby galaxies and galaxy
clusters, discovery of supernovae and their follow-up observations, and observations of near-Earth objects. We expect
synergies between the KMTNet project with other similar or complementary projects in the southern sky, such as
SkyMapper.
Design and development of a wide field telescope
Author(s):
Il Moon;
Sangon Lee;
Juhee Lim;
Ho-Soon Yang;
Hyug-Gyo Rhee;
Jae Bong Song;
Yun Woo Lee;
Jong Ung Lee;
Ho Jin
Show Abstract
A prototype of large wide field telescope is a Cassegrain telescope which covers 2° field of view with two hyperbolic mirrors, a 0.5 m primary mirror and a 0.2 m secondary mirror with multiple correction lenses. To fulfill the optical and mechanical performance requirements in design and development phase extensive finite element analyses using NX NASTRAN and optical analyses with CODE V and PCFRINGE have been conducted for the structure of optical system. Analyses include static deformation (gravity and thermal), frequency, dynamic response analysis, and optical performance evaluations for minimum optical deformation. Image motion is also calculated based on line of sight sensitivity equations integrated in finite element models. A parametric process was performed for the design optimization to produce highest fundamental frequency for a given weight, as well as to deal with the normal concerns about global performance.
Achieving high precision photometry for transiting exoplanets with a low cost robotic DSLR-based imaging system
Author(s):
Olivier Guyon;
Frantz Martinache
Show Abstract
We describe a low cost high precision photometric imaging system, which has been in robotic operation for one and half
year on the Mauna Loa observatory (Hawaii). The system, which can be easily duplicated, is composed of commercially
available components, offers a 150 sq deg field with two 70mm entrance apertures, and 6-band simultaneous photometry
at a 0.01 Hz sampling. The detectors are low-cost commercial 3-color CMOS array, which we show is an attractive costeffective
choice for high precision transit photometry. We describe the design of the system and show early results.
A new data processing technique was developed to overcome pixelization and color errors. We show that this technique,
which can also be applied on non-color imaging systems, essentially removes pixelization errors in the photometric
signal, and we demonstrate on-sky photometric precision approaching fundamental error sources (photon noise and
atmospheric scintillation). We conclude that our approach is ideally suited for exoplanet transit survey with multiple
units. We show that in this scenario, the success metric is purely cost per etendue, which is at less than $10000s per
square meter square degree for our system.
An active surface upgrade for the Delingha 13.7-m Radio Telescope
Author(s):
Dehua Yang;
Yong Zhang;
Guohua Zhou;
Aihua Li;
Kunxin Chen;
Zhenchao Zhang;
Guoping Li;
Yingxi Zuo;
Ye Xu
Show Abstract
An upgrade program is proposed for the Delingha 13.7-m radio telescope to implement active surface for multi-beam
observation at 3 mm wavelength. The upgrade involves three critical development aspects. One is the displacement
actuator, which must fit the existing position, space and connections of the panels and backup structure, meanwhile, must be as compact and lightweighted as possible. The second is that a new sub-reflector is necessitated by the multi-beam observation, where a new hyperbolic surface figure is optimized. The third, more crucial and difficult, is to realize active control of the actuators and real-time closed-loop of the full active surface. This paper is to present the progress of the development work, test and experiments associated with the three areas. With one of the spare panels of the telescope, an experiment system is carried out with six sets of actuator and control electronics. Another experiment system of a novel laser-based closed-loop measurement concept is also conducted with four smaller dummy panels. Both experiment setups have output expected results and further experiments are going on with them. In this paper, based on the two experiments, we will describe the special design and test of the actuator, including the design of its special mounting and connecting mechanisms. The design and manufacture and measurement of the new hyperbolic sub-reflector will be detailed as well as the principle, simulation and realization of the laser-based measurement system. Besides, the control strategy of the large scale use of the hundreds of actuators and EMI suppression are also covered.
Development of a compact precision linear actuator for the active surface upgrade of the Delingha 13.7-m radio telescope
Author(s):
Guohua Zhou;
Aihua Li;
Dehua Yang;
Zhenchao Zhang;
Guoping Li
Show Abstract
The Delingha 13.7-m radio telescope is to be upgraded with an active surface for multi-beam observation at 3 mm
wavelength. Its primary reflector is paved with 72 aluminum panels which are originally supported by 480 fixtures. One
of the critical tasks associated with the upgrade program is development of precision linear displacement actuators to
replace the panel fixtures hence to Listed first in the upgrade program is actively drive and position the panels. The linear
actuator is required to fit the existing positions, dimensions and connections of the panels and the backup structure, also
implicitly required to be as compact and lightweighted as possible. This paper is to report in detail the development and
experiment of the compact, folded, precision linear actuator according to given technique requirements and constraints,
including the description of the flexible adaption of the fixture of the actuators and the special design of the connecting
mechanism with the panels. The experiment system is established with one of the spare panels of the telescope, and six
sets of actuator and control electronics are included for driving the panel. This paper will present the test results
measured on a single actuator prototype as well as the actuators working together in the spare panel experiment. The test
results prove that the actuator manifests positioning accuracy of microns and load capacity of 12 kg. The related
connection and electronics design of the actuator also meets the requirements of the update program of the telescope.
Upgrading the TNT Telescope: remote observing and future perspectives
Author(s):
G. Di Rico;
M. Fiaschi;
G. Valentini;
A. Di Cianno;
A. Valentini
Show Abstract
The Teramo Normale Telescope (TNT) is a 0.72 m telescope operating at the INAF-Teramo since the 1994. At the end
of 2011, the whole system has been completely upgraded in order to improve the overall performance of the instrument
and to allow safe and full remote observations, without the need of local operators. The main results of this work is
setting up a reliable and modern system in a short while, and at the same time paving the way to further steps towards the
development of a fully robotic observatory. Starting by a general overview of the system we describe the most important
upgraded components and the possible next developments.
ESPRESSO: design and analysis of a Coudé-train for a stable and efficient simultaneous optical feeding from the four VLT unit telescopes
Author(s):
Alexandre Cabral;
André Moitinho;
João Coelho;
Jorge Lima;
Gerardo Ávila;
Bernard-Alexis Delabre;
Ricardo Gomes;
Denis Mégevand;
Filippo Zerbi;
Paolo Di Marcantonio;
Christophe Lovis;
Nuno C. Santos
Show Abstract
ESPRESSO is a fiber-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO
to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope),
and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest
stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT
at the Combined Coudé Laboratory (CCL), fed by four Coudé Trains, which brings the light from the Nasmyth platforms
of the four VLT Unit Telescopes to the CCL. A previous trade-off analysis, considering the use of mirrors, prisms, lenses
or fibers and several possible combinations of them, pointed towards a Full Optics solution, using only conventional
optics to launch the light from the telescope into the front-end unit. In this case, the system is composed of a set of
prisms and lenses to deliver a pupil and an image in the CCL, including an Atmospheric Dispersion Compensator. In this
paper, we present the optical design of the Coudé Trains, the opto-mechanical concept, the main characteristics and
expected performances.
Recent performance improvements for the Large Binocular Telescope primary mirror system
Author(s):
Robert L. Meeks;
David Ashby;
Chris Biddick;
Amjad Chatila;
Michael Gusick
Show Abstract
Over the last several years the primary mirror cell systems for the Large Binocular Telescope have been upgraded to
improve on-sky performance and observing efficiency. We describe improvements made to the support actuators and
mirror positioning system and explain how those changes have led to better performance and contributed to increased
reliability. Both systems have been substantially redesigned and remanufactured to allow the LBT primary mirror
systems to meet extremely precise performance requirements over a very broad temperature range. We also discuss the
mirror ventilation and thermal monitoring system and review its current status and potential upgrades to improve its
performance.
Modernization of the 1 meter Swope and 2.5 meter Du Pont telescopes at Las Campanas Observatory
Author(s):
Frank Perez;
Alan Bagish;
Greg Bredthauer;
Juan Espoz;
Patricio Jones;
Patricio Pinto
Show Abstract
The Observatories of the Carnegie Institution for Science have operated the 1 and 2.5-meter telescopes since the early
1970s with only minor changes to the original control systems. We discuss the replacement of the original 4004 microprocessor-
based telescope control system with modern high-speed servo controllers and motors, absolute main axis
encoders, modern closed-loop controls and PC-based main operating software. We also discuss the original relay-based
interlock systems that have been replaced with Programmable Logic Controllers (PLC) and have been interfaced into the
new telescope control system. The modernization of both telescopes also includes many hardware upgrades to allow for
remote observing and scripted automatic observations. These upgrades also include the modernization of shutter drives,
windscreens and dome controls to improve the reliability and safety required for remote observing from an existing
facility.
A happy conclusion to the SALT image quality saga
Author(s):
Lisa A. Crause;
Darragh E. O'Donoghue;
James E. O'Connor;
Francois Strumpfer;
Ockert J. Strydom;
Craig Sass;
Charl A. du Plessis;
Eben Wiid;
Jonathan Love;
Janus D. Brink;
Martin Wilkinson;
Chris Coetzee
Show Abstract
Images obtained with the Southern African Large Telescope (SALT) during its commissioning phase showed
degradation due to a large focus gradient and a variety of other optical aberrations. An extensive forensic investigation
eventually traced the problem to the mechanical interface between the telescope and the secondary optics that form the
Spherical Aberration Corrector (SAC). The SAC was brought down from the telescope in 2009 April, the problematic
interface was replaced and the four corrector mirrors were optically tested and re-aligned. The surface figures of the SAC
mirrors were confirmed to be within specification and a full system test following the re-alignment process yielded a
RMS wavefront error of just 0.15 waves. The SAC was re-installed on the tracker in 2010 August and aligned with
respect to the payload and primary mirror. Subsequent on-sky tests produced alarming results which were due to
spurious signals being sent to the tracker by the auto-collimator, the instrument responsible for controlling the attitude of
the SAC with respect to the primary mirror. Once this minor issue was resolved, we obtained uniform 1.1 arcsecond star
images over the full 10 arcminute field of view of the telescope.
Facility calibration unit of Hobby Eberly Telescope wide field upgrade
Author(s):
Hanshin Lee;
Gary J. Hill;
Brian L. Vattiat;
Michael P. Smith;
Marco Haeuser
Show Abstract
The Hobby-Eberly Telescope (HET) Wide-Field Upgrade (WFU) will be equipped with new Facility Calibration Unit
(FCU). The FCU is in support of VIRUS and the facility instruments and consists of the head and source box. The FCU
head, connected to the source box through two liquid light guides, is attached to the bottom of the WFU Wide-Field
Corrector (WFC) and can be deployed into the beam to inject calibration light through the WFC whenever calibration is
needed. A set of Fresnel lenses is used in the FCU head to mimic the caustics of M1 as much as possible to re-produce
the telescope’s focal plane illumination pattern. Various imaging/non-imaging optical components (e.g. Compound
Parabolic Concentrators, cone reflectors, condenser lenses) are used for efficient coupling between different types of
calibration lamps and light guides, covering wavelengths from 350nm to 1800nm. In addition, we developed an efficient
and tunable Light-Emitting Diode (LED) based source and coupler for UV and Visible spectral flat field calibration.
This paper presents the designs, prototypes, and as-built components / subsystems of the FCU.
Solid telescopes for interferometric enhancement of existing telescopes
Author(s):
Alberto Riva;
Mario Gai
Show Abstract
This paper describes a concept study for a simple and cost effective approach to upgrade of existing infrastructures. A conventional monolithic telescope can be endowed with a set of identical small telescopes combined coherently to enhance the resolution. The solid telescope represent a convenient solution for a simple and replicated small telescope. The solid telescope is intrinsically suited to be used in diffraction limited mode down to visible wavelengths. This may allow a viable dual feed mode for both guiding and phase referenced imaging. In this paper we analyze some of the critical engineering aspects and outline a possible implementation approach.
Optics and the mechanical system of the 62-cm telescope at the Severo Díaz Galindo Observatory in Guadalajara, Jalisco, México
Author(s):
Eduardo de la Fuente;
J. Manuel Nuñez;
Salvador Zazueta;
Salomon Eduardo Ibarra;
Benjamin García;
Benjamin Martínez;
José Luis Ochoa;
Gerardo Sierra;
Fransisco Lazo;
David Hirart;
Luis Corral;
Jorge L. Flores;
Jaime Almaguer;
Simon Kemp;
Silvana G. Navarro;
Alberto Nigoche-Netro;
Gerardo Ramos-Larios;
John Peter Phillips;
Arturo Chávez;
Guillermo García-Torales;
Oscar Blanco Alonso;
Tomas Oceguera-Becerra;
Durruty de Alba;
Ruben Bautista
Show Abstract
We present the results of a modification performed in the optical system of the 62 cm telescope (f/14.32) at observatory
“Severo Díaz Galindo” Universidad de Guadalajara, Mexico. This modification consists of a change of distance between
the primary and secondary mirrors from 1020 to 1135 mm. With this, a change in the image plane from 5200 mm to 600
mm, measured from the vertex of the primary mirror, is obtained. The latter allow to get the first astronomical images of
The Telescope. This modification was necessary because alignment errors, such as distance between primary and
secondary mirrors in the original system were presented. Besides, the telescope has a new accurate and adequate
mechanical system installed on November 2011. Details and the first images obtained, are here presented.
Folded Cassegrain sets of the Gran Telescopio Canarias (GTC)
Author(s):
Alberto Gomez;
Rubén Sanquirce;
Gaizka Murga;
Borja Etxeita;
Alberto Vizcargüenaga;
Ander San Vicente;
Esther Fernandez;
Oscar Vega;
Benjamín Siegel
Show Abstract
The Gran Telescopio Canarias (GTC) has been recently received two Folded Cassegrain Sets (FC-Sets) composed of an
instrument rotator and the corresponding Acquisition and Guiding (AG) optomechanics. IDOM has been the responsible
for the design, manufacturing, assembly and commissioning of the two units of FC-Sets.
The design combines a compact layout of the mechanical system, enhanced by an innovative cable wrap design,
resulting in a smooth and precise movement, whilst guaranteeing good access to important components and maximizing
the maintainability.
The custom design of the cable wrap as an evolution of the rolling loop type eliminates the need for a cable chain static
housing, minimizing weight and impact on the telescope tube. The AG Mechanics provides the required pointing and
focusing capabilities in a compact configuration.
In January 2010, IDOM is awarded the design and procurement of the two FC-Sets. The final design is approved by
GRANTECAN and the fabrication process starts in Nov 2011. The assembly and commissioning of both units are
completed in April 2011. Once the Factory Acceptance Tests finishes in Dec 2011, all the elements are delivered to the
Observatorio del Roque de los Muchachos (ORM). The Site Acceptance Tests are completed in Feb 2012.
Design, testing, and installation of a high-precision hexapod for the Hobby-Eberly Telescope dark energy experiment (HETDEX)
Author(s):
Joseph J. Zierer;
Joseph H. Beno;
Damon A. Weeks;
Ian M. Soukup;
John M. Good;
John A. Booth;
Gary J Hill;
Marc D Rafal
Show Abstract
Engineers from The University of Texas at Austin Center for Electromechanics and McDonald Observatory have
designed, built, and laboratory tested a high payload capacity, precision hexapod for use on the Hobby-Eberly telescope
as part of the HETDEX Wide Field Upgrade (WFU). The hexapod supports the 4200 kg payload which includes the
wide field corrector, support structure, and other optical/electronic components. This paper provides a recap of the
hexapod actuator mechanical and electrical design including a discussion on the methods used to help determine the
actuator travel to prevent the hexapod payload from hitting any adjacent, stationary hardware. The paper describes in
detail the tooling and methods used to assemble the full hexapod, including many of the structures and components
which are supported on the upper hexapod frame. Additionally, details are provided on the installation of the hexapod
onto the new tracker bridge, including design decisions that were made to accommodate the lift capacity of the Hobby-
Eberly Telescope dome crane. Laboratory testing results will be presented verifying that the performance goals for the
hexapod, including positioning, actuator travel, and speeds have all been achieved. This paper may be of interest to
mechanical and electrical engineers responsible for the design and operations of precision hardware on large, ground
based telescopes. In summary, the hexapod development cycle from the initial hexapod actuator performance
requirements and design, to the deployment and testing on the newly designed HET tracker system is all discussed,
including lessons learned through the process.
Prototype pipeline for LSST wavefront sensing and reconstruction
Author(s):
Charles F. Claver;
Srinivasan Chandrasekharan;
Ming Liang;
Bo Xin;
Enver Alagoz;
Kirk Arndt;
Ian P. Shipsey
Show Abstract
The Large Synoptic Survey Telescope (LSST) uses an Active Optics System (AOS) to maintain system alignment and surface figure on its three large mirrors. Corrective actions fed to the LSST AOS are determined from 4 curvature based wavefront sensors located on the corners of the inscribed square within the 3.5 degree field of view. Each wavefront sensor is a split detector such that the halves are 1mm on either side of focus. In this paper we describe the development of the Active Optics Pipeline prototype that simulates processing the raw image data from the wavefront sensors through to wavefront estimation on to the active optics corrective actions. We also describe various wavefront estimation algorithms under development for the LSST active optics system. The algorithms proposed are comprised of the Zernike compensation routine which improve the accuracy of the wavefront estimate. Algorithm development has been aided by a bench top optical simulator which we also describe. The current software prototype combines MATLAB modules for image processing, tomographic reconstruction, atmospheric turbulence and Zemax for optical ray-tracing to simulate the closed loop behavior of the LSST AOS. We describe the overall simulation model and results for image processing using simulated images and initial results of the wavefront estimation algorithms.
Active optics in Large Synoptic Survey Telescope
Author(s):
Ming Liang;
Victor Krabbendam;
Charles F. Claver;
Srinivasan Chandrasekharan;
Bo Xin
Show Abstract
The Large Synoptic Survey Telescope (LSST) has a 3.5º field of view and F/1.2 focus that makes the performance quite
sensitive to the perturbations of misalignments and mirror surface deformations. In order to maintain the image quality,
LSST has an active optics system (AOS) to measure and correct those perturbations in a closed loop. The perturbed
wavefront errors are measured by the wavefront sensors (WFS) located at the four corners of the focal plane. The
perturbations are solved by the non-linear least square algorithm by minimizing the rms variation of the measured and
baseline designed wavefront errors. Then the correction is realized by applying the inverse of the perturbations to the
optical system. In this paper, we will describe the correction processing in the LSST AOS. We also will discuss the
application of the algorithm, the properties of the sensitivity matrix and the stabilities of the correction. A simulation
model, using ZEMAX as a ray tracing engine and MATLAB as an analysis platform, is set up to simulate the testing and
correction loop of the LSST AOS. Several simulation examples and results are presented.
Keck 1 deployable tertiary mirror (K1DM3)
Author(s):
J. Xavier Prochaska;
Christoph Pistor;
Gerald Cabak;
David J. Cowley;
Jerry Nelson
Show Abstract
We aim to build a new tertiary mirror (M3) and its mount for the 10 m Keck I (K1) telescope at the W. M. Keck
Observatory (WMKO) to make its full observational capabilities available for time-sensitive scientific programs.. In
contrast to the existing tertiary mirror and mount, the device will rapidly deploy and rotate the mirror to any instrument
at a Nasmyth focus or, as desired, stow the mirror out of the light path to permit observations at the Cassegrain focus. In
this manner, the K1 deployable tertiary mirror (K1DM3) will enable observations with any of the K1 instruments on any
given night, and at any given time. The K1DM3 device will be integrated within the K1 telescope control system and
WMKO has committed to a new operations model that takes full advantage of this new capability.
Metrology systems of Hobby-Eberly Telescope wide field upgrade
Author(s):
Hanshin Lee;
Gary J. Hill;
Mark E. Cornell;
Brian L. Vattiat;
Dave M. Perry;
Tom H. Rafferty;
Trey Taylor;
Michael Hart;
Marc D. Rafal;
Richard D. Savage
Show Abstract
The Hobby-Eberly Telescope (HET) Wide-Field Upgrade (WFU) will be equipped with new closed-loop metrology systems to actively control the optical alignment of the new four-mirror Wide-Field Corrector (WFC) as it tracks sidereal motion with respect to the fixed primary mirror. These systems include a tip/tilt camera (TTCam), distance measuring interferometers (DMI), guide probes (GP), and wavefront sensors (WFS). While the TTCam and DMIs are to monitor the mechanical alignment of the WFC, the WFSs and GPs will produce direct measurement of the optical alignment of the WFC with respect to the HET primary mirror. Together, these systems provide fully redundant alignment and pointing information for the telescope, thereby keeping the WFC in focus and suppressing alignment driven field aberrations. In addition to these closed-loop metrology systems, we will have a pupil viewing camera (PVCam) and a calibration wavefront sensor (CWFS). The PVCam will be used for occasional reflectance measurement of the HET primary mirror segments in the standard R,G,B colors. The CWFS will provide the reference wavefront signal against which the other two WFS are calibrated. We describe the current snapshot of these systems and discuss lab/on-sky performance test results of the systems.
Optics derotator servo control system for SONG Telescope
Author(s):
Jin Xu;
Changzhi Ren;
Yu Ye
Show Abstract
The Stellar Oscillations Network Group (SONG) is an initiative which aims at designing and building a groundbased
network of 1m telescopes dedicated to the study of phenomena occurring in the time domain. Chinese
standard node of SONG is an Alt-Az Telescope of F/37 with 1m diameter. Optics derotator control system of
SONG telescope adopts the development model of "Industrial Computer + UMAC Motion Controller + Servo
Motor".1 Industrial computer is the core processing part of the motion control, motion control card(UMAC) is
in charge of the details on the motion control, Servo amplifier accepts the control commands from UMAC, and
drives the servo motor. The position feedback information comes from the encoder, to form a closed loop control
system. This paper describes in detail hardware design and software design for the optics derotator servo control
system. In terms of hardware design, the principle, structure, and control algorithm of servo system based on
optics derotator are analyzed and explored. In terms of software design, the paper proposes the architecture of
the system software based on Object-Oriented Programming.
Active optical control system design of the SONG-China Telescope
Author(s):
Yu Ye;
Songfeng Kou;
Dongsheng Niu;
Cheng Li;
Guomin Wang
Show Abstract
The standard SONG node structure of control system is presented. The active optical control system of the project is a
distributed system, and a host computer and a slave intelligent controller are included. The host control computer collects
the information from wave front sensor and sends commands to the slave computer to realize a closed loop model. For
intelligent controller, a programmable logic controller (PLC) system is used. This system combines with industrial
personal computer (IPC) and PLC to make up a control system with powerful and reliable.
The 3,6m Indo-Belgian Devasthal Optical: the active M1 mirror support
Author(s):
Maxime Pierard;
Carlo Flebus;
Nathalie Ninane
Show Abstract
AMOS SA has been awarded of the contract for the design, manufacturing, assembly, tests and on-site installation
(Nainital, Devasthal site at 2540 mm altitude) of the 3,6 m Indo-Belgian Devasthal Optical Telescope (IDOT).
The primary mirror is a meniscus active mirror. This paper describes the opto-mechanical design of the M1 unit and
provides some test results performed on sky to demonstrate the proper functioning of the active system.
Synchronous redundant control algorithm in the telescope drive system
Author(s):
Changzhi Ren;
Yong Niu;
Xiaoli Song;
Jin Xu;
Xiaoyan Li
Show Abstract
The modern large telescope is endowed with advanced imaging systems and active optics, resulting in very high
peak angular resolution. The drive systems for the telescope must consequently be able to guarantee a tracking accuracy
better than the telescope angular resolution, in spite of unbalanced and sudden loads such as wind gusts and in spite of a
structure that, because of its size, can not be infinitely stiff, which puts forward a great challenge to the telescope' drive
system. Modern telescope's drive system is complicated, which performance and reliability directly affect the telescope
tracking performance and reliability. Redundant technology is one of the effective ways to improve the security of the
system. This paper will introduce one redundant synchronous control method for direct drive torque motor of large
diameter telescope drive system, which can effectively improve the telescope drive system tracking precision and
improve the reliability, stability and anti-jamming ability.
The M2&M3 positioning control systems of a 2.5m telescope
Author(s):
Yu Ye;
Chong Pei;
Zhiyong Zhang;
Bozhong Gu
Show Abstract
The 2.5m optical/infrared telescope is an F/8 telescope comprising one Cassegrain foci, two Nasmyth foci and two
student Nasmyth foci. This paper presents a brief description of the physical structure, conceptual design, hardware
implementing measure and software structure in the positioning control system of M2&M3. The graphical user interface
application (Qt) is adopted to design the software. During the full working range the M2 focus and decenter achieve the
positioning repeatability is better than ±4μm and the M2 tilt is better than 10 μrad. The M3 angular positioning and
locking accuracy is better than 10 arcsec and repeatability is better than 2 arcsec RMS.
Progress of the active reflector antenna using laser angle metrology system
Author(s):
Yong Zhang;
Jie Zhang;
Dehua Yang;
Guohua Zhou;
Aihua Li;
Guoping Li
Show Abstract
An active reflector is one of the key technologies for constructing large telescopes, especially for the
millimeter/sub-millimeter radio telescopes. This report presents a new and substantial progress on the efficient laser
angle metrology system for the active reflector antenna of the large radio telescopes, with a plenty of experiments based
on a four-panel prototype system constructed by Nanjing Institute of Astronomical Optics and Technology (NIAOT).
The test results prove that this technology is workable for sub-millimeter radio telescopes both in accuracy and
time-response. Thus it can be applied to the reconstruction of the active reflector antenna in China and play a central role
in promoting the new area of sub-mm radio astronomy.
Performance comparison between two active support schemes for 1-m primary mirror
Author(s):
Dongsheng Niu;
Guomin Wang;
Bozhong Gu
Show Abstract
Active support scheme may decide the deformation of the optical surface figure of the primary mirror. Two active
support schemes have been designed for 1-m primary mirror, and the performance of each support scheme is conducted.
Finite element analysis (FEA) is employed to analyze the optical surface figures of the primary mirror, and optimizations
are carried out by using ANSYS for each support scheme to obtain the locations of the axial support. When the locations
are determined, axial support force sensitivities are calculated for the two support schemes in a case that a single axial
support has a force error of 0.5N. The correction ability of the active support system for both of support schemes are
analyzed when an arbitrary axial support is failure. Several low order Zernike modes are modeled with MATLAB
procedure, and active optics corrections are applied to these modes for the two active supports. Thermal deformation of
the mirror is also corrected for the two schemes.
Design, development, and testing of the DCT Cassegrain instrument support assembly
Author(s):
Thomas A. Bida;
Edward W. Dunham;
Ralph A. Nye;
Tomas Chylek;
Richard C. Oliver
Show Abstract
The 4.3m Discovery Channel Telescope delivers an f/6.1 unvignetted 0.5° field to its RC focal plane. In order to support
guiding, wavefront sensing, and instrument installations, a Cassegrain instrument support assembly has been developed
which includes a facility guider and wavefront sensor package (GWAVES) and multiple interfaces for instrumentation.
A 2-element, all-spherical, fused-silica corrector compensates for field curvature and astigmatism over the 0.5° FOV,
while reducing ghost pupil reflections to minimal levels. Dual roving GWAVES camera probes pick off stars in the
outer annulus of the corrected field, providing simultaneous guiding and wavefront sensing for telescope operations. The
instrument cube supports 5 co-mounted instruments with rapid feed selection via deployable fold mirrors. The corrected
beam passes through a dual filter wheel before imaging with the 6K x 6K single CCD of the Large Monolithic Imager
(LMI). We describe key development strategies for the DCT Cassegrain instrument assembly and GWAVES, including
construction of a prime focus test assembly with wavefront sensor utilized in fall 2011 to begin characterization of the
DCT primary mirror support. We also report on 2012 on-sky test results of wavefront sensing, guiding, and imaging
with the integrated Cassegrain cube.
Experience of primary surface alignment for the LMT using a laser tracker in a non-metrology environment
Author(s):
David M. Gale
Show Abstract
The 50-metre Large Millimeter Telescope (LMT) successfully completed first light observations in June 2011, operating
with an initial 32.5-metre diameter collecting area. This reduced-area primary surface consists of 84 reflector panels
measuring approximately 3x5m. During the construction phase, individual panels were assembled and adjusted to the
specified rms surface error off-site, then installed and aligned on the antenna using a total station. Prior to first-light
observations, panels were fine-tuned in piston, tip-tilt and twist using full-surface holography measurements to direct the movement of electromechanical actuators located at the four corners of each panel.
In preparation for the next observing season the 32.5m primary is being refurbished and re-aligned on-site, using a
commercial laser tracker for surface adjustment of each panel. For this task we have opted for the transfer of panels from the antenna surface to the telescope basement for adjustment, offering an enclosed environment with stable temperature, followed by reinstallation and measurement on the open-air antenna surface at night.
In this paper we present our experiences on the use of a laser tracker to conduct panel surface measurement and
adjustment on-site, at an isolated location 4,700m (15,000ft) above sea level and in the absence of dedicated metrology
facilities. In section 2 we present the primary surface concept deployed at the LMT. Section 3 discusses the laser tracker
equipment and data processing for panel surface measurement. Section 4 describes the panel adjustment process carried out in the site basement and presents examples of indoor panel metrology using the laser tracker. In section 5, we present our experiences to date of open-air measurement of panels installed on the antenna. Some conclusions are offered in section 6.
Using a laser tracker for active alignment on the Large Binocular Telescope
Author(s):
A. Rakich
Show Abstract
The Large Binocular Telescope (LBT) currently achieves collimation using a combination of collimation models and
closed-loop active correction schemes. Shack Hartmann wavefront sensors with off-axis guide stars are used for
Gregorian modes, and a closed-loop correction scheme is used for the prime-focus cameras. While in general this
combination serves to produce alignment residuals well below a good seeing limit within a few minutes of obtaining a
given target field, the uniquely asymmetrical structure of the LBT is prone to producing large deflections of the
telescope optics when the ambient temperature is changing unusually rapidly. These deflections are difficult to model
satisfactorily, and are an ongoing source of inefficiency in telescope operations. Furthermore, none of the current
approaches to telescope collimation are particularly "piston aware"; a situation that needs to be improved on now that the
LBT is commencing operations with the first of its beam combining instruments, LBTI. The laser tracker is a metrology
instrument capable of automatically measuring optical element positions with better than 100 micron precision within a
spherical volume of 30 m radius centered on the tracker head. With the ability to directly measure optics into position to
this accuracy built into the Telescope Control System (TCS), the LBT would always be starting observations from a
point of near-collimation, the component telescopes would be co-pointed, and the OPD would be well within the capture
range of the beam combining instrument's internal phasing systems. This paper describes first results from engineering
investigations into using the laser tracker to automatically align the optics on the LBT.
Generic misalignment aberration patterns and the subspace of benign misalignment
Author(s):
Paul L. Schechter;
Rebecca Sobel Levinson
Show Abstract
Q1: Why deploy N wavefront sensors on a three mirror anastigmat (TMA) and not N + 1?
Q2: Why measure M Zernike coefficients and not M + 1?
Q3: Why control L rigid body degrees of freedom (total) on the secondary and tertiary and not L + 1?
The usual answer: “We did a lot of ray tracing and N, M, and L seemed OK.”
We show how straightforward results from aberration theory may be used to address these questions. We consider, in particular, the case of a three mirror anastigmat.
An improved collimation algorithm for the Large Binocular Telescope using source extractor and an on-the-fly reconstructor
Author(s):
Douglas L. Miller;
Andrew Rakich;
Torsten Leibold
Show Abstract
A recent upgrade of the LBTO’s Wavefront Reconstruction algorithm in the Active Optics system has proven to reduce
the collimation time by a substantial amount and to provide a much more stable telescope collimation as observing
conditions change. The new reconstruction algorithm uses Source Extractor to detect the spots in a Shack-Hartmann wavefront sensor camera image. With information about which Shack spots are detected, a reconstructor matrix is calculated on-the-fly
that only includes the illuminated sub-apertures. This drastically improves the wavefront reconstruction for a highly
aberrated wavefront when many sub-apertures contain no information. This is generally the situation at the beginning
of the night when the collimation of the telescope is set only from models rather than on-sky information and
occasionally when a new observational target is acquired. Similarly, the undersized tertiary mirror can cause vignetting
of the pupil seen by the Shack-Hartmann wavefront sensor for far off-axis guide stars and again some sub-apertures
have no wavefront information. We will present a brief description of the Active Optics system used at the Gregorian focal stations at the LBTO, discuss the original wavefront reconstruction algorithm, describe the new Source Extractor algorithm and compare the
performance of these two approaches in several conditions (low signal to noise, highly aberrated wavefront, vignetted
pupil, poor seeing).
Features of a laser metrology subsystem for astrometric telescopes
Author(s):
Alberto Riva;
Mario Gai;
Mario G. Lattanzi
Show Abstract
In astrometric instrumentation a laser subsystem may be used for precise metrology of instrumental response.
Such subsystems do not require diraction limited imaging, but can be tailored to specic application needs.
We describe an interferometric arrangement for high precision monitoring of telescope line of sight and evaluate
its performance as a function of some design parameters. We deduce that good sensitivity can be achieved over
a signicant range of e.g. focusing conditions, provided proper cautions are adopted for detection and data
processing.
Conceptual design of a 5-m terahertz telescope at Dome A
Author(s):
Dehua Yang;
Hai Wang;
Yong Zhang;
Yi Chen;
Guohua Zhou;
Jingquan Cheng;
Guoping Li
Show Abstract
A 5-meter terahertz telescope is proposed by the Chinese Center for Antarctic Astronomy (CCAA) for the East
Antarctica site of the Dome A plateau. The Dome A 5-m terahertz telescope (DATE 5) will be operated at sub-millimeter
waveband taking the unique advantage of the transparent atmospheric windows between 200 and 350 μm wavelengths at Dome A. A preliminary design has been conducted according to the given technical requirements and the special environmental conditions at Dome A. A symmetric R-C Cassegrain optical system is designed for the telescope, with a primary f-ratio of 0.4 and a wide field of view of 10 arcmin. The magnification of the sub-reflector is 9.4, leading to the final focal ratio of 3.76 and the focus 0.2 m below the vertex of the primary reflector. To ensure surface accuracy of the reflectors precise as small as 10 um RMS, we consider using Carbon Fiber Reinforced Plastics (CFRP) to build the backup structure (BUS) of the primary reflector and the sub-reflector itself. An alt-azimuthal mounting is adopted and a tall base structure beneath the telescope is set up to lift the telescope above the low atmosphere turbulent layer. All the mechanics, as well as control electronics, are strictly designed to fit the lower temperature operation in the Dome A environment. This paper is to generally present the mentioned systematic optical, structural and electronic design of the DATE 5 telescope.
New Exoplanet Surveys in the Canadian High Arctic at 80 Degrees North
Author(s):
Nicholas M. Law;
Suresh Sivanandam;
Richard Murowinski;
Raymond Carlberg;
Wayne Ngan;
Pegah Salbi;
Aida Ahmadi;
Eric Steinbring;
Mark Halman;
James Graham
Show Abstract
Observations from near the Eureka station on Ellesmere Island, in the Canadian High Arctic at 80° North, benefit from 24-hour darkness combined with dark skies and long cloud-free periods during the winter. Our first astronomical surveys conducted at the site are aimed at transiting exoplanets; compared to mid-latitude sites, the continuous darkness during the Arctic winter greatly improves the survey’s detection effciency for longer-period transiting planets. We detail the design, construction, and testing of the first two instruments: a robotic telescope, and a set of very wide-field imaging cameras. The 0.5m Dunlap Institute Arctic Telescope has a 0.8-square-degree field of view and is designed to search for potentially habitable exoplanets around low-mass stars. The very wide field cameras have several-hundred-square-degree fields of view pointed at Polaris, are designed to search for transiting planets around bright stars, and were tested at the site in February 2012. Finally, we present a conceptual design for the Compound Arctic Telescope Survey (CATS), a multiplexed transient and transit search system which can produce a 10,000-square-degree snapshot image every few minutes throughout the Arctic winter.
An off-axis telescope concept for Antarctic astronomy
Author(s):
Gil Moretto;
Nicolas Epchtein;
Maud Langlois;
Isabelle Vauglin
Show Abstract
The Antarctic plateau offers exceptional atmospheric and environmental conditions for astronomical
observations over a wide range of wavelengths and uniquely favorable to infrared astronomy.
Exceptional low sky brightness throughout the near- and mid-infrared and a telescope facility
complying with the highest possible dynamic range for photometry, angular resolution and the widefield
leads to the possibility of a modest-sized 2m off-axis telescope achieving comparable
sensitivity to that of a larger ground-based 8-10m class telescope or a same sized space-based ones.
The package cushioning design of the first AST3 and its dynamics analysis
Author(s):
Haikun Wen;
Xuefei Gong;
Ru Zhang
Show Abstract
Dome A has been considered as one of the best observation sites on the earth. The First
AST3(three Antarctic Survey Telescopes) is on its way to Dome A by the 28th Chinese National
Antarctic research expedition. It will be the largest Optic telescope in Dome A after assembling and
testing in this austral summer. Firstly, this paper reports the method of collecting the vibration and
shock data from ShangHai to Dome A and analyses the data. Secondly, the package cushioning design
of the first AST3 is introduced in this paper according to the vibration and shock data. Finally, the
paper introduces the result of the dynamics analysis of the design and a test was done to verify the
performance of the package cushioning design. The dynamics analysis and the test indicate that the
package cushioning design can meet the demand of the Antarctic inland transportation.
Nonlinear disturbance to Large Optical Antarctic Telescope
Author(s):
Shihai Yang
Show Abstract
Large Optical Antarctic Telescope, LOAT hereafter, is a new research hotspot nowadays. For example, a 2.5m KDUST, e.g. Kunlun Dark UniverSe Telescope is on anvil. It's difficult for main axis of large telescope tracking system to track the target precisely with ultra-low speed because of nonlinear disturbances due to unique ultra-low temperature. This paper presents these nonlinear disturbances.
Where is Ridge A?
Author(s):
Geoff Sims;
Craig Kulesa;
Michael C. B. Ashley;
Jon S. Lawrence;
Will Saunders;
John W. V. Storey
Show Abstract
First identied in 2009 as the site with the lowest precipitable water and best terahertz transmission on Earth,
Ridge A is located approximately 150 km south of Dome A, Antarctica. To further rene this optimum location
prior to deployment in 2012 of a robotic THz observatory, we have modelled the atmospheric transmission as
a function of location over a 1,000,000 km square grid using three years of data from the Microwave Humidity
Sounder on the NOAA-18 satellite. The modelling identies a broad area of exceptionally low water vapour close
to the 4,000 metre elevation contour, reaching below 100 microns for extended periods of time.
Two years of polar winter observations with the ASTEP400 telescope
Author(s):
L. Abe;
J.-P. Rivet;
A. Agabi;
E. Aristidi;
D. Mekarnia;
I. Goncalves;
T. Guillot;
M. Barbieri;
N. Crouzet;
F. Fressin;
F.-X. Schmider;
Y. Fantei-Caujolle;
J.-B. Daban;
C. Gouvret;
S. Peron;
P.-Y. Petit;
A. Robini;
M. Dugue;
E. Bondoux;
T. Fruth;
A. Erikson;
H. Rauer;
F. Pont;
A. Alapini;
S. Aigrain;
J. Szulagyi;
P.-E. Blanc;
A. Le Van Suu
Show Abstract
The ASTEP program is dedicated to exo-planet transit search from the Concordia Station located at Dome C, Antarctica.
It comprises two instruments: a fixed 10cm refractor pointed toward the celestial South Pole, and a 400mm Newton
telescope with a 1x1 degree field of view. This work focuses on the latter instrument. It has been installed in November
2009, and has been observing since then during the two polar winters 2010 and 2011. After presenting the main science
observing programs, we review the telescope installation, performance, and describe its operating conditions as well as
the data reduction and handling strategy. The resulting lightcurves are generally very stable and of excellent quality, as
shown by continuous observations of WASP-19 that we present here.
HETDEX tracker control system design and implementation
Author(s):
Joseph H. Beno;
Richard Hayes;
Ron Leck;
Charles Penney;
Ian Soukup
Show Abstract
To enable the Hobby-Eberly Telescope Dark Energy Experiment, The University of Texas at Austin Center for
Electromechanics and McDonald Observatory developed a precision tracker and control system – an 18,000 kg robot to
position a 3,100 kg payload within 10 microns of a desired dynamic track. Performance requirements to meet science
needs and safety requirements that emerged from detailed Failure Modes and Effects Analysis resulted in a system of 13
precision controlled actuators and 100 additional analog and digital devices (primarily sensors and safety limit switches).
Due to this complexity, demanding accuracy requirements, and stringent safety requirements, two independent control
systems were developed. First, a versatile and easily configurable centralized control system that links with modeling
and simulation tools during the hardware and software design process was deemed essential for normal operation
including motion control. A second, parallel, control system, the Hardware Fault Controller (HFC) provides independent
monitoring and fault control through a dedicated microcontroller to force a safe, controlled shutdown of the entire system
in the event a fault is detected. Motion controls were developed in a Matlab-Simulink simulation environment, and
coupled with dSPACE controller hardware. The dSPACE real-time operating system collects sensor information; motor
commands are transmitted over a PROFIBUS network to servo amplifiers and drive motor status is received over the
same network. To interface the dSPACE controller directly to absolute Heidenhain sensors with EnDat 2.2 protocol, a
custom communication board was developed. This paper covers details of operational control software, the HFC,
algorithms, tuning, debugging, testing, and lessons learned.
An upgrade to the telescope control system (TCS) for the Canada-France-Hawaii Telescope
Author(s):
K. K. Y. Ho;
W. Cruise;
J. Thomas
Show Abstract
The Canada-France-Hawaii Telescope (CFHT) has been in operation since 1979. The Telescope Control System (TCS)
has undergone software changes since the beginning of science operation but the original hardware has largely been
untouched except for an upgrade to the time system and host computer. Telescope performance has not been an issue
although some improvements are desirable. However, parts obsolescence will become a problem as the telescope enters
it third decade of operation. Although there are sufficient spare parts currently, many are no longer readily available.
Some critical components, such as encoders and VME CPU boards are no longer available. The TCS upgrade project
addresses the obsolete and obsolescent issues to ensure operational capability through 2025. It seeks to modernize and
simplify the electronics and to take advantages of the advancement made in stand-alone servo controllers.
Automation of the OAN/SPM 1.5-meter Johnson telescope for operations with RATIR
Author(s):
Alan M. Watson;
Michael G. Richer;
Joshua S. Bloom;
Nathaniel R. Butler;
Urania Ceseña;
David Clark;
Enrique Colorado;
Antolín Córdova;
Alejandro Farah;
Lester Fox-Machado;
Ori D. Fox;
Benjamín García;
Leonid N. Georgiev;
J. Jesús González;
Gerardo Guisa;
Leonel Gutiérrez;
Joel Herrera;
Christopher R. Klein;
Alexander S. Kutyrev;
Francisco Lazo;
William H. Lee;
Eduardo López;
Esteban Luna;
Benjamín Martínez;
Francisco Murillo;
José Manuel Murillo;
Juan Manuel Núñez;
J. Xavier Prochaska;
José Luís Ochoa;
Fernando Quirós;
David A. Rapchun;
Carlos Román-Zúñiga;
Gennady Valyavin
Show Abstract
The Reionization And Transients Infra-Red (RATIR) camera is intended for robotic operation on the 1.5-meter Harold
Johnson telescope of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
This paper describes the work we have carried out to successfully automate the telescope and prepare it for RATIR. One
novelty is our use of real-time absolute astrometry from the finder telescopes to point and guide the main telescope.
Control system for the first three Antarctic Survey Telescopes (AST3-1)
Author(s):
Xiaoyan Li;
Daxing Wang;
Lingzhe Xu;
Jianlin Zhao;
Fujia Du;
Yue Zhang
Show Abstract
The first Three Antarctic Survey Telescope (AST3-1), a 50/68cm Schmidt-like equatorial-mount telescope, is the first
automated Chinese telescope operating on the Antarctic plateau. It is planned to be in operations at Dome A, the highest
peak on the Antarctic plateau, in 2012. The telescope is unmanned during night-time operations in the Austral winter.
The telescope optics and mechanics, as well as the motors and position sensors, are exposed to a very harsh environment.
The mechanics is enclosed with a foldable tent-like dome to prevent snow, diamond dust and ice. While the drive boxes,
most circuit, power supply and computers are located inside the warm instrumental cabin. This article describes the
challenges the telescope control system encountered in night-time operations, such as the power supply limit, the harsh
meteorological condition, unattended testing, automatic operation, remote control and telemetry, etc. Some solutions are
also discussed in this paper, which are applied on the AST3-1 and waiting for validation. AST3-1 is also an exploration
of a larger telescope on the Antarctic.
Development of an EtherCAT enabled digital servo controller for the Green Bank Telescope
Author(s):
Peter G. Whiteis;
Melinda J. Mello
Show Abstract
EtherCAT (Ethernet for Control Automation Technology) is gaining wide spread popularity in the automation
industry as a real time field bus based on low cost, Ethernet hardware. EtherCAT maximizes use of 100Mbps Ethernet
hardware by using a collision free ring topology, efficient Ethernet frame utilization (> 95%), and data exchange "on the
fly". These characteristics enable EtherCAT to achieve Master to Slave node data exchange rates of > 1000 Hz.
The Green Bank Telescope, commissioned in 2000, utilizes an analog control system for motion control of 8
elevation and 16 azimuth motors. This architecture, while sufficient for observations at frequencies up to 50GHz, has
significant limitations for the current scientific goals of observing at 115GHz. Accordingly, the Green Bank staff has
embarked on a servo upgrade project to develop a digital servo system which accommodates development and
implementation of advanced control algorithms.
This paper describes how the new control system requirements, use of existing infrastructure and budget
constraints led us to define a distributed motion control architecture where EtherCAT real-time Ethernet was selected as
the communication bus.
Finally, design details are provided that describe how NRAO developed a custom EtherCAT-enabled motor
controller interface for the GBT's legacy motor drives in order to provide technical benefits and flexibility not available
in commercial products.
Design and development of telescope control system and software for the 50/80 cm Schmidt telescope
Author(s):
T. S. Kumar;
R. N. Banavar
Show Abstract
In this paper, we describe the details of telescope controller design for the 50/80 cm Schmidt telescope at the
Aryabhatta Research Institute of observational sciencES. The GUI based software for commanding the telescope
is developed in Visual C++. The hardware architecture features a distributed network of microcontrollers over
CAN. The basic functionality can also be implemented using the dedicated RS232 port per board. The controller
is able to perform with negligible rms velocity errors. At fine speeds limit cycles are exhibited due to nonlinear
friction. At speeds over 3.90 × 10-02 radians/sec, the PI controller performs with peak errors less than 1%.
Upgrading the MMT primary mirror actuator test stand: a unique vehicle for evaluating EtherCAT as a future I/O standard for systems
Author(s):
Dusty Clark;
Skip Schaller
Show Abstract
The MMT Observatory (MMTO) uses a complex system of pneumatic actuators to support the telescope's 6.5m primary
mirror. For operational checkout after repair and to collect calibration data for use in the primary mirror support control software, the Steward Observatory Mirror Lab (SOML) built a test stand that accurately measures the output forces and moments from the actuator using a 6-DOF (degree of freedom) work plate. The electronics and software provided by SOML are outdated and needed replacing. In this report, we discuss the selection of EtherCAT as the data-acquisition hardware, the software development required, and the some aspects of using the test stand in the lab.
MMT nightly tracking logs: a web-enabled database for continuous evaluation of tracking performance
Author(s):
D. Clark;
J. D. Gibson;
D. Porter;
T. Trebisky
Show Abstract
Over the past few years, the MMT Observatory has developed a number of web browser front ends for operation
interfaces and staff access to internal databases. Among these is a facility for viewed reduced tracking logs in both time
series and FFTs for convenient examination of tracking performance. Part of the back-end software also keeps the
tracking data in a searchable database, allowing data over long periods of time to be collected and analyzed to look for
trends, the influence of environmental factors on tracking, and help detect tracking degradation in a timely manner.
Design and fabrication of three 1.6-meter telescopes for the Korea Microlensing Telescope Network (KMTNet)
Author(s):
W. M. Poteet;
H. K. Cauthen;
N. Kappler;
L. G. Kappler;
Byeong-Gon Park;
Chung-Uk Lee;
Seung-Lee Kim;
Sang-Mok Cha
Show Abstract
The KMTNet telescope Project, sponsored by The Korea Astronomy and Space Science Institute (KASI), is fabricating
three wide-field equatorial mount telescopes of 1.6 meter aperture to conduct continuous observations of the Galactic
bulge region to search for extra-solar planets. Southern latitude sites secured for these telescopes are SAAO (South
Africa), CTIO (Chile), and SSO (Australia). A prime-focus configuration, along with a four-lens corrector achieves the
2.8 degree diagonal FOV. The basic mechanical design utilizes a scaled-up version of the successful 2MASS Telescopes
built by the authors in the late 1990's. Scaling up of components has presented challenges requiring several iterations of
the detailed mechanical analysis as well as the optical analysis due to interaction with mounting assemblies for the
optical components. A flexure-style focus mechanism, driven by three precision actuators, moves the entire headring
assembly and provides real-time focus capability, and active primary mirror cooling is implemented for the Zerodur
primary. KMTNet engineering specifications are met with the current design, which uses Comsoft's Legacy PCTCS for
control. A complete operational telescope and enclosure are scheduled for installation in Tucson, AZ prior to shipping
the first hardware to CTIO in order to verify tracking, optical characteristics at various attitudes, and overall observatory
functionality. The cameras, being fabricated by The Ohio State University Department of Astronomy, Imaging Sciences
Laboratory (ISL), are proceeding in parallel with the telescope fabrication, and that interface is now fixed. Specifics of
the mechanical and optical design are presented, along with the current fabrication progress and testing protocols.
Introduction of Chinese SONG Telescope
Author(s):
Guomin Wang;
Songfeng Kou;
Dongsheng Niu;
Zhiyong Zhang;
Xiang Jiang;
Changzhi Ren
Show Abstract
SONG is initiated by Danish to design, build, and utilize a global network of eight 1-meter class telescopes to be
operated as a whole-Earth telescope. China has joined the international SONG project in 2009 and will build one 1-meter
telescope as the node of SONG global network in China. Now the telescope is during the period of building. This paper
will give an introduction of Chinese SONG telescope, including telescope requirements, telescope design and other
information.
Perspectives of astronomy in Kazakhstan: from new ground-based telescopes to space ones
Author(s):
Ch. T. Omarov;
Zh. Sh. Zhantayev
Show Abstract
Astronomical observations in Kazakhstan are carried out for over 60 years. The advantage of the geographical
location makes it possible to set and conduct programs of stationary ground-based observations, that from the most
observatories of other countries are difficult or impossible. However outdated technical condition of
scientific equipment, which include ground-based optical telescopes, poses a direct problem to the development of
astronomy in Kazakhstan. In addition, observational data in the other spectral bands from space telescopes are needed.
Therefore, in order to create a modern experimental astrophysical base today in Kazakhstan two projects are being put
forward in the frame of national space program: 1) a new optical telescope with a primary mirror 3.6 meters (completed
in 2016), and 2) participation in the international space project "World Space Observatory -Ultraviolet" that to be
launched in 2014.
Deployment status of the Las Cumbres Observatory Global Telescope
Author(s):
A. J. Pickles;
W. Rosing;
J. Martinez;
B. J. Fulton;
D. Sand
Show Abstract
Our global network of telescopes is designed to provide maximally available optical
monitoring of time variable sources, from solar system to extra-galactic objects, and ranging
in brightness from about 7-20m. We are providing a distributed network with varied apertures
but homogeneous instrumentation: optical imaging, with spectroscopic capabilities. A key
component is a single centralized process that accepts (in real time) and schedules TAC
approved observing requests across the network; then continuously updates schedules based
on status, weather and other availability criteria. Requests range from occasional to continuous
monitoring, at slow to high-speed cadences (imaging and fast photometry), and includes rapid
response to targets of opportunity. Each node of the network must be fully autonomous, with
software agents to control and monitor all functions, to provide auto-recovery as necessary,
and to announce their status and capabilities up the control structure. Real-time monitoring or
interaction by humans should be infrequent. Equipment is designed to be reliable over long
periods to minimize hands-on maintenance, by local or LCOGT staff. Our first 1m deployment
was to McDonald Obs. in April 2012. Eight more 1m telescopes are close to deployment to
complete the Southern ring, scheduled by end-2012.
The microwave holography system for the Sardinia Radio Telescope
Author(s):
G. Serra;
P. Bolli;
G. Busonera;
T. Pisanu;
S. Poppi;
F. Gaudiomonte;
G. Zacchiroli;
J. Roda;
M. Morsiani;
J. A. López-Pérez
Show Abstract
Microwave holography is a well-established technique for mapping surface errors of large reflector antennas, particularly those designed to operate at high frequencies.
We present here a holography system based on the interferometric method for mapping the primary reflector surface of the Sardinia Radio Telescope (SRT). SRT is a new 64-m-diameter antenna located in Sardinia, Italy, equipped with an
active surface and designed to operate up to 115 GHz.
The system consists mainly of two radio frequency low-noise coherent channels, designed to receive Ku-band digital TV signals from geostationary satellites. Two commercial prime focus low-noise block converters are installed on the radio telescope under test and on a small reference antenna, respectively. Then the signals are amplified, filtered and downconverted to baseband. An innovative digital back-end based on FPGA technology has been implemented to digitize two 5 MHz-band signals and calculate their cross-correlation in real-time. This is carried out by using a 16-bit resolution ADCs and a FPGA reaching very large amplitude dynamic range and reducing post-processing time. The final
holography data analysis is performed by CLIC data reduction software developed within the Institut de Radioastronomie Millimétrique (IRAM, Grenoble, France).
The system was successfully tested during several holography measurement campaigns, recently performed at the
Medicina 32-m radio telescope. Two 65-by-65 maps, using an on-the-fly raster scan with on-source phase calibration,
were performed pointing the radio telescope at 38 degrees elevation towards EUTELSAT 7A satellite. The high SNR
(greater than 60 dB) and the good phase stability led to get an accuracy on the surface error maps better than 150 μm
RMS.
Structural optimization of the outer ring of FAST Telescope
Author(s):
Xin-yu Zhang;
Hui Li;
Shi-mo Yang
Show Abstract
The two-axis steering mechanism installed in the FAST focus cabin can be seen as a universal joint consisting of two
ring beams and makes role in the process of real-time adjustment of the receiver orientation. The outer ring of the
mechanism is a large-span curve beam with strict mass and rigidity requirements. The aim of this paper is to develop a
simple and effective method for constructing a truss-shape structure for the outer ring under the upper-limit constraints
of certain structural weight and mid-span deflection. Two truss configurations for weight minimization problems are
presented. One assumes consistent beam height. The second design proposes varying heights along the ring. Analytical
deflections are given based on the theory of thin-walled beam in combination of bending and torsion. In numerical
optimization of the structure, some key geometrical parameters are selected to be optimized. The optimization is
subsequently achieved by the steepest descent method, which is based on the sensitivity analysis of the variables
(reduced to be dimensionless) in each iteration. Several sets of initial conditions for optimization have been generated
randomly. Corresponding optimum results have small mutual deviations. Finally a comparison of the two designs
considering stiffness-to-mass ratios is given in the numerical examples.
Experimental study on the damping of FAST cabin suspension system
Author(s):
Hui Li;
Jing-hai Sun;
Xin-yu Zhang;
Wen-bai Zhu;
Gao-feng Pan;
Qing-ge Yang
Show Abstract
The focus cabin suspension of the FAST telescope has structurally weak-stiffness dynamics with low damping
performance, which makes it quite sensitive to wind-induced vibrations. A reasonable estimation about the damping is
very important for the control performance evaluation of the prototype. It is a quite difficult task as the telescope is no at
available yet. In the paper, a preliminary analysis is first made on the aerodynamic damping. Then a series of
experimental models are tested for measuring the total damping. The scales of these models range from 10m to 50m in
diameter while 6 test parameters are specially designed to check the damping sensitivity. The Ibrahim time domain (ITD)
method is employed to identify the damping from the measured cabin response. The identification results indicate that
the lowest damping ratio of the models is about 0.2%~0.4%. Friction-type cabin-cable joint seems to have main
influence on the system damping.
Control algorithm for the petal-shape segmented-mirror telescope with 18 mirrors
Author(s):
Atsushi Shimono;
Fumihide Iwamuro;
Mikio Kurita;
Yuki Moritani;
Masaru Kino;
Toshinori Maihara;
Hideyuki Izumiura;
Michitoshi Yoshida
Show Abstract
A 3.8 m segmented telescope is planned to be built at the Okayama Astrophysical Observatory by the joint
program among Kyoto university, Nagoya university, NAOJ, and Nano-Optonics Energy Inc. This is the world’s
first optical-infrared telescope whose primary mirror is composed of “petal-shaped” segment mirrors.
To investigate the best layout of the displacement sensors as well as to study the control algorithm, we have
developed a simulation software for the segmented petaloid mirrors. This simulator calculates the vertical position
differences between the segments at the 60 displacement sensors based on the three-dimensional movements of
the 54 actuators, and enables us to test the control algorithms under various conditions including random noise
on the displacement sensors, random movement errors of the actuators, and unexpected lateral shifts of the
segments. The outputs of the simulator are not only the phase error of the primary mirror but also the PSF
image, taking the structure function of the optical surfaces into account.
Using a singular value decomposition method, we found that the 18 petal-shaped segments are controllable
within the required displacement errors of 15 nm under the following three conditions: 1) the displacement
measurement sensors are placed in staggered fashion between segments, 2) the displacement measurement sensors
are axisymmetrically placed with respect to the optical axis, and 3) the relative lateral shift and rotation of each
segment are less than 500 μm and 0.05 degree, respectively.
In this report, the control algorithm, requirements for the layout of the displacement measurement sensors,
and the simulated performance will be presented.
How to calibrate edge sensors on segmented mirror telescopes
Author(s):
Chris Shelton;
Lewis C. Roberts Jr.
Show Abstract
The next generation of large ground based telescopes use segmented mirrors. Sensors mounted on the edge of
the segments measure the relative heights of the segments. The segments are actively controlled in height by
three actuators per segment, but lateral motion is only passively constrained. Thus there will be some small
change in the gap and shear between segments as changing telescope orientation and temperature make small
distortions in the telescope structure. These "in-plane" motions place an additional performance burden on the
edge sensors, and on the precision with which they must be mounted relative to the optical surface. In addition,
both the scaling and offset of sensor edge height readings also vary with changes in gap.
Our method for correcting the in-plane motion induced errors in the primary mirror has three parts.
First, the edge sensors are modified to report segment-to-segment gap, as well as the height difference, to make
the in-plane segment positions observable. Second, the mirror segments are phased optically, at a set of zenith
angles and temperatures, to give a set of "measured sensor readings". Finally, during observing, a calibration
procedure combines these data into "desired sensor readings" which are optimal for the current telescope state.
We have included this calibration process in a control loop model of the Thirty Meter Telescope primary mirror
control system. We present our calibration method and the model.
Outdoors phasing progress of dispersed fringe sensing technology in NIAOT, China
Author(s):
Yong Zhang;
Xiangqun Cui;
Genrong Liu;
Yuefei Wang;
Jijun Ni;
Hongmei Li;
Yizhong Zeng;
Aihua Li;
Yeping Li;
Zhixu Wu
Show Abstract
A telescope with a larger primary mirror can collect much more light and resolve objects much better than one with a
smaller mirror, and so the larger version is always pursued by astronomers and astronomical technicians. Instead of using
a monolithic primary mirror, more and more large telescopes, which are currently being planned or in construction, have
adopted a segmented primary mirror design. Therefore, how to sense and phase such a primary mirror is a key issue for
the future of extremely large optical/infrared telescopes. The Dispersed Fringe Sensor is a non-contact method using
broadband point light sources and it can estimate the piston by the two-directional spectrum formed by the transmissive
grating's dispersion and lenslet array. In this paper we introduce you the current research progress of the successful
design, construction and alignment of our dispersed Hartmann sensors together with its design principles and simulations
for indoor segmented mirror experiment system and outdoor segmented mirror experiment system. We also conduct
many successful real phasing tests and phasing corrections in the visible waveband using our existing indoor and outdoor
segmented mirror optics platform. Finally, some conclusions are reached based on the test and correction of experimental
results.
The new TNG-DIMM: calibrations and first data analysis
Author(s):
Emilio Molinari;
A. G. de Gurtubai;
A. della Valle;
S. Ortolani;
J. San Juan;
A. F. Martinez Fiorenzano;
V. Zitelli
Show Abstract
Since 2011 a new differential image motion monitor (DIMM) works at Roque de los Muchachos Observatory close to
Telescopio Nazionale Galileo (TNG). The purpose of this instrument is to provide useful information about the optical
turbulence for the astronomical observations at TNG. We present the instrument and the first statistical results including
a relationship between the principal components analysis of local-ground atmospheric parameters and seeing.
Atmospheric turbulence measurements at Ali Observatory, Tibet
Author(s):
Liyong Liu;
Yongqiang Yao;
Jean Vernin;
Merieme Chadid;
Yiping Wang;
Hongshuai Wang;
Jia Yin;
Christophe Giordano;
Xuan Qian
Show Abstract
The atmospheric turbulence characteristics are important to evaluate the quality of ground-based astronomical
observatory. In order to characterize Ali observatory, Tibet. we have developed a single star Scidar (SSS) system,
which is able to continuously monitor the vertical profiles of both optical turbulence and wind speed. The main
SSS configuration includes a 40cm telescope and a CCD camera for fast sampling the star scintillation pattern.
The SSS technique analyzes the scintillation patterns in real time, by computing the spatial auto-correlation and
at least two cross-correlation images, and retrieves both C2
n (h) and V (h) vertical profiles from the ground up to
30km. This paper presents the first turbulence measurements with SSS at Ali observatory in October, 2011. We
have successfully obtained the profiles of optical turbulence and wind speed, as well as the key parameters for
adaptive optics, such as seeing, coherence time, and isoplanatic angle. The favourable results indicate that Ali
observatory can be an excellent astronomical observatory.
Dust concentration and soil properties at the TMT candidate sites
Author(s):
S. G. Els;
R. Riddle;
M. Schöck;
W. Skidmore;
T. Travouillon
Show Abstract
During the site testing campaign for the Thirty Meter Telescope (TMT) in addition to the optical conditions of the atmosphere, measurements of the soil surface properties were obtained also. The dust concentration in the air was measured by means of dust sensors which were mounted underneath the mount of the site monitoring telescopes. The ground head fluxes and soil temperatures were measured several centimeters into the ground. On Cerro Armazones it was also possible to conduct an experiment to measure heat conduction of the soil. In this paper, all of these measurements are described, the results and their potential use is summarized.
Surface layer turbulence measurements on the LSST site El Peñon using microthermal sensors and the lunar scintillometer LuSci
Author(s):
J. Sebag;
P. Zimmer;
J. Turner;
J. McGraw;
V. Krabbendam;
A. Tokovinin;
Edison Bustos;
M. Warner;
O. Wiecha
Show Abstract
Results from determining the optical turbulence profile (OTP) on the LSST site, El
Peñon, located on Cerro Pachón (Chile) are presented. El Peñón appears to be an
excellent observatory site with a surface layer seeing contribution on the order of 0.15”
with most of this seeing being produced below 20m. These measurements also helped to
confirm that the telescope is elevated high enough above ground. As part of the LSST site
characterization campaign, microthermal measurements were taken in order to determine
the contribution of the surface layer turbulence to the atmospheric seeing. Such
measurements are commonly used for this purpose where pairs of microthermal sensors
mounted on a tower measure atmospheric temperature differences. In addition, the lunar
scintillometer LuSci was installed on El Peñon for short campaigns near full moon for the
same purpose. LuSci is a turbulence profiler based on measuring spatial correlation of
moonlight scintillations. The comparison of the results from both instruments during
simultaneous data acquisition showed a remarkable temporal correlation and very similar
mean OTPs.
Overview of Site Monitoring at the SAAO
Author(s):
T. Pickering;
S. M. Crawford;
L. Catala;
D. Buckley;
A. Ziad;
R. Wilson
Show Abstract
We present a comprehensive review of the first two years of a site monitoring campaign at the South African Astronomical Observatory (SAAO) located outside Sutherland, South Africa. This campaign is in support of the Southern African Large Telescope (SALT), a 11-metre, fixed-elevation, optical telescope located at SAAO . The heart of this observing campaign involves continuous monitoring of the site by a MASS-DIMM instrument. The MASS-DIMM has been in routine use since March 2010 and its operation is now fully automated. At the beginning of this campaign, simultaneous observations were also made by a SLODAR instrument, which allows high resolution observations of the lower atmosphere. In August 2011 a two week campaign was carried out with a two-channel Generalized Seeing Monitor (GSM) telescope along with a lunar limb profiler (Profileur Bord Lunaire; PBL). Combined with the MASS-DIMM data these observations provide multiple independent measurements of atmospheric turbulence as a function of height. They also help improve the calibration of our site for more direct comparison to other major astronomical observatories. Our results so far indicate that the atmospheric conditions at the SAAO Sutherland site have deteriorated compared to past measurements. The ground layer accounts for the majority of the integrated seeing, while the free atmosphere seeing is comparable with other major sites.
Evaluations of new atmospheric windows at thirty micron wavelengths for astronomy
Author(s):
Takashi Miyata;
Shigeyuki Sako;
Takafumi Kamizuka;
Tomohiko Nakamura;
Kentaro Asano;
Mizuho Uchiyama;
Masahiro Konishi;
Mizuki Yoneda;
Naruhisa Takato;
Yuzuru Yoshii;
Mamoru Doi;
Kotaro Kohno;
Kimiaki Kawara;
Masuo Tanaka;
Kentaro Motohara;
Takeo Minezaki;
Toshihiko Tanabe;
Tomoki Morokuma;
Yoichi Tamura;
Tsutomu Aoki;
Takao Soyano;
Ken'ichi Tarusawa;
Hidenori Takahashi;
Shintaro Koshida;
Natsuko M. Kato
Show Abstract
Thirty micron has remained one of unexplored frontiers of ground-based astronomical observations. Recent developments of extreme high sites including the Chajnantor TAO site (5,640m) enable us to access the this wavelengths from the ground. The expected transmittance seems clear enough for astronomical observations, but practical evaluations based on astronomical data has not been carried out yet. We have analyzed images obtained at the 31.7 micron with a mid-infrared camera MAX38 attached on a mini-TAO 1.0-meter telescope. 109 images of a star IRC+10420 and 11,114 images of the sky have been reduced. Clear relationship between the measured photocurrents and the perceptible water vapor has been found. Simple estimation of the photocurrents with of the ATRAN model gives good agreements with the measurements, indicating that the ATRAN model reproduce the atmospheric transmittance reasonably well. This also supports our assumption that the scaling factor 0.85 of the PVW at the Chajnantor TAO site to the PWV at the APEX. The average transmittance in the 31.7 micron is achieved to be over 20% when the PWV below 0.6 mm. In some cases clear degradation up to 10% in the transmittance is found. It may be caused by droplets of liquid or iced water with a size over 10 micron although the causes are not exactly specified. Diurnal time variations of the sky photocurrents are also investigated. The sky is sometimes bright and usually unstable in the twilight time. On the other hand the sky around the noontime does not show clear difference from the night sky. It may suggest that the observing condition at the thirty micron windows remain good even in the daytime.
Atmospheric seeing measurements obtained with MISOLFA in the framework of the PICARD Mission
Author(s):
R. Ikhlef;
T. Corbard;
A. Irbah;
F. Morand;
M. Fodil;
B. Chauvineau;
P. Assus;
C. Renaud;
M. Meftah;
S. Abbaki;
J. Borgnino;
E. M. Cissé;
E. D'Almeida;
A. Hauchecorne;
F. Laclare;
P. Lesueur;
M. Lin;
F. Martin;
G. Poiet;
M. Rouzé;
G. Thuillier;
A. Ziad
Show Abstract
PICARD is a space mission launched in June 2010 to study mainly the geometry of the Sun. The PICARD mission has a ground program consisting mostly in four instruments based at the Calern Observatory (Observatoire de la Cˆote d’Azur). They allow recording simultaneous solar images and various atmospheric data from ground. The ground instruments consist in the qualification model of the PICARD space instrument (SODISM II: Solar Diameter Imager and Surface Mapper), standard sun-photometers, a pyranometer for estimating a global sky quality index, and MISOLFA a generalized daytime seeing monitor. Indeed, astrometric observations of the Sun using ground-based telescopes need an accurate modeling of optical effects induced by atmospheric turbulence. MISOLFA is founded on the observation of Angle-of-Arrival (AA) fluctuations and allows us to analyze atmospheric turbulence optical effects on measurements performed by SODISM II. It gives estimations of the coherence parameters characterizing wave-fronts degraded by the atmospheric turbulence (Fried parameter r0, size of the isoplanatic patch, the spatial coherence outer scale L0 and atmospheric correlation times). We present in this paper simulations showing how the Fried parameter infered from MISOLFA records can be used to interpret radius measurements extracted from SODISM II images. We show an example of daily and monthly evolution of r0 and present its statistics over 2 years at Calern Observatory with a global mean value of 3.5cm.
Optical system of Chinese SONG Telescope
Author(s):
Songfeng Kou;
Genrong Liu;
Guomin Wang
Show Abstract
The paper reports optical system of a 1 meter diameter telescope dedicated to Stellar Observations
Network Group (SONG) for the National Astronomical Observatories, CAS. SONG is an international
cooperative project, Optimize the design for Asteroseismology purposes. According to the prototype of
SONG, Chinese SONG telescope includes Cassegrain telescope, Nasmyth platform, Coudé train,
Coudé focal plane, Shack-Hartmann wavefront sensor and spectrograph. The telescope will provide a
field of view of 65 arcsec at the Nasmyth F/36.67 focus, 10 arcsec at the F/6 Coudé focus. The rotating
tertiary mirror directs the light to the two Nasmyth foci, one for Shack-Hartmann wavefront sensor, the
other for Nasmyth platform and spectrograph.
Design of an off-axis optical reflecting system
Author(s):
Y. V. Bazhanov;
V. B. Vlahko
Show Abstract
Existing off-axial optical systems aberration theories are based on series expansion of optical path function (eikonal
function). Numerical evaluations, conducted in this paper, have shown, that the most accurate results are obtained with
theory, based on series expansion of exact ray-tracing equations, where expressions for high-order aberration coefficients
include expressions for low order ones. We have used that very method in our search of optimal decision for off-axis
optical reflective telescope systems.
Dome flat-field system for 1.3-m Araki Telescope
Author(s):
Tomohiro Yoshikawa;
Yuji Ikeda;
Naofumi Fujishiro;
Shunsuke Ichizawa;
Akira Arai;
Mizuki Isogai;
Atsunori Yonehara;
Hideyo Kawakita
Show Abstract
We report the system/optics design and performance of the dome flat-field system for the Araki Telescope, a 1.3- m optical/near-infrared telescope at Koyama Astronomical Observatory in Japan. A variety of instruments are attached to the telescope. The optical imager, which is intended to search for exoplanets, requires an illumination flatness within 1% on the focal plane over the 17-arcmin FOV. Illumination flatness at both the pupil plane and the focal plane of the telescope is essential for calibration of the transmittance of the optical system. We devised an optical design for the flat-field system that satisfies illumination flatness at both the focal and pupil planes using the non-sequential ray tracing software LightTools. We considered far-field illumination pattern of the lamps, scattering surface reflectance distribution of the screen, telescope structure, primary/secondary mirrors, and mirror baffles. We achieved a flat illumination distribution of 0.9% at the focal plane. The systems performance was tested by comparison with a cloud-flat frame, which was derived by imaging cloud cover illuminated by city lights. The calibration data for the dome flat-field system agree well with the cloud-flat frame within 1% for the g′ and i′ bands of the imager, but the r0 band data does not meet the requirement (less than or equal to 2). Moreover, various instruments require a focal plane illuminance ranging over three orders of magnitude. We used six high-power (60W) halogen lamps; the output power is remotely controlled by a thyristor-driven dimmer and a bypass circuit to an autotransformer.
Fast and compact wide-field Gregorian telescope
Author(s):
Mehdi Bahrami;
Alexander V. Goncharov
Show Abstract
A traditional Gregorian telescope features an intermediate focus, which makes the system longer than an equivalent fnumber
Cassegrain design. One could shorten the Gregorian system by inserting a flat mirror before the secondary
mirror. We explore the potential of this compact configuration for sky survey imaging with relaxed requirements for
angular resolution. A 0.5 m f/1.4 telescope with 4 deg full field is presented. The modified design consists of two
elliptical mirrors and a folding flat in between. A plano-convex field flattener is used near the focal plane. The telescope
optical performance is analyzed and possible improvements are discussed based on aberration balancing. A special
emphasis is given to stay light analysis and baffle designs are considered.
Optical design for amateur reflecting telescopes based on tilted axial-symmetrical planoidal mirror
Author(s):
Sergey A. Chuprakov
Show Abstract
Two-mirrors aplanatic optical design for amateur telescopes up to 0.5m class is described. The optical system is low cost,
easy for adjusting, fast and large field of view can be used for visual and astrophotography. The method for calculation
of baffles for straight light protection is described. The optical performances and sample shots for the builted device are
presented.
Keywords: two-mirrors system, all-reflecting schmidt system, aplanatic system, protection from straight light, baffles,
obscuration, wide-field, telescopes for amateurs.
Preliminary optical design for the WEAVE two-degree prime focus corrector
Author(s):
Tibor Agócs;
Don Carlos Abrams;
Diego Cano Infantes;
Neil O'Mahony;
Kevin Dee;
Jean-Baptiste Daban;
Carole Gouvret;
Sebastien Ottogalli
Show Abstract
We present the preliminary optical design for a new two-degree refractive prime focus corrector for the 4.2m William
Herschel Telescope optimised for the wide-field multi-object spectrograph, WEAVE (WHT Enhanced Area Velocity
Explorer). From the two conceptual designs described previously [1], the counter-rotating atmospheric dispersion
corrector approach was selected and further optimized to meet the flat image surface requirement. The preliminary
design provides good polychromatic image quality. The PSF does not exceed 0.6 arcsec (80% encircled energy) over a
wavelength range from 370 to 1000nm covering a two degree FOV for zenith angles up to 65 degrees. We describe the
corrector's performance and the trade-off between telecentricity and the requirement for a flat image surface. We present
the results of the tolerance and thermal analyses, ghost and scattered light calculations and the finite element analysis
that are necessary to establish the PSF error budget for the corrector.
