Local thermal seeing modeling validation through observatory measurements
Dome and mirror seeing are critical effects influencing the optical performance of ground-based telescopes.
Computational Fluid Dynamics (CFD) can be used to obtain the refractive index field along a given optical path and
calculate the corresponding image quality utilizing optical modeling tools. This procedure is validated using
measurements from the Keck II and CFHT telescopes.
CFD models of Keck II and CFHT observatories on the Mauna Kea summit have been developed. The detailed models
resolve all components that can influence the flow pattern through turbulence generation or heat release. Unsteady
simulations generate time records of velocity and temperature fields from which the refractive index field at a given
wavelength and turbulence parameters are obtained.
At Keck II the Cn2 and l0 (inner scale of turbulence) were monitored along a 63m path sensitive primarily to turbulence
around the top ring of the telescope tube. For validation, these parameters were derived from temperature and velocity
fluctuations obtained from CFD simulations.
At CFHT dome seeing has been inferred from their database that includes telescope delivered Image Quality (IQ). For
this case CFD simulations were run for specific orientations of the telescope respect to incoming wind, wind speeds and
outside air temperature. For validation, temperature fluctuations along the optical beam from the CFD are turned to
refractive index variations and corresponding Optical Path Differences (OPD) then to Point Spread Functions (PSF) that
are ultimately compared to the record of IQ.
An aerodynamic study of the CFHT dome using water tunnel tests and CFD
Studies of astronomical seeing at the Canada France Hawaii Telescope (CFHT) site, from both inside and outside the
dome, show that the full potential of the excellent seeing conditions at the CFHT site has never been fully exploited.
These studies indicate that this is due to the classical unvented hemispherical CFHT dome. Tests have been performed
to identify the causes of the “pathologies” revealed by these seeing studies and to find ways of mitigating them. In
particular, we have investigated installing vents in the dome skin to improve air exchange between outside and inside the
enclosure. A number of vent geometries were tested using water tunnel models at the University of Washington
Aerodynamics Laboratory (UWAL). Relative flushing times for various dome slit to prevailing wind directions were
compared for the different vent geometries. The general flow characteristics observed with these low Reynolds number
tests were compared with computational fluid dynamics (CFD) simulations of the CFHT dome performed in
collaboration with the Thirty Meter Telescope (TMT) project, as well as low-speed wind-tunnel tests and visualization of
the flow around the actual observatory building.
LSST summit enclosure-facility design optimization using aero-thermal modeling
This paper describes Computational Fluid Dynamic (CFD) analyses combined with thermal
analyses for modeling the effects of passive ventilation, enclosure-building configuration and
topography on the optical performance of the Large Synoptic Survey Telescope (LSST). The
primary purpose of the analyses was to evaluate the seeing contribution of the major enclosure-facility
elements and to select the features to be adopted in the baseline design from among
various configurations being explored by the LSST project and the contracted architectural
In addition, one of several simulations for different telescope orientations is presented including
various wind-telescope relative azimuth angles. Using a post-processing analysis, the effects of
turbulence and thermal variations within the airflow around the buildings and inside the
telescope-enclosure configuration were determined, and the optical performance due to the
thermal seeing along the optical path was calculated.
Wind responses of the LSST secondary mirror
Myung K. Cho
Douglas R. Neill
The Large Synoptic Survey Telescope (LSST) optical design calls for a large annular 3.4 m diameter meniscus convex aspheric Secondary Mirror (M2). The M2 has a mass of approximately 1.5 metric tons and the optimized mirror support system consists of 72 axial actuators, mounted at the mirror back surface, and 6 tangent link lateral supports mounted around the outer edge. A fully integrated M2 Finite Element Model (FEM) including the mirror and the support systems has been developed to investigate the performance of the M2 assembly and to determine the image degradation due to dynamic wind loading. Detailed wind response analysis was performed based on the input from Computational Fluid Dynamics (CFD) simulations. Image quality calculations of the time history responses and Power Spectrum Density (PSD) are addressed.
Systems engineering implementation in the preliminary design phase of the Giant Magellan Telescope
Like many telescope projects today, the 24.5-meter Giant Magellan Telescope (GMT) is truly a complex system. The primary and secondary mirrors of the GMT are segmented and actuated to support two operating modes: natural seeing and adaptive optics. GMT is a general-purpose telescope supporting multiple science instruments operated in those modes. GMT is a large, diverse collaboration and development includes geographically distributed teams.
The need to implement good systems engineering processes for managing the development of systems like GMT becomes imperative. The management of the requirements flow down from the science requirements to the component level requirements is an inherently difficult task in itself. The interfaces must also be negotiated so that the interactions between subsystems and assemblies are well defined and controlled.
This paper will provide an overview of the systems engineering processes and tools implemented for the GMT project during the preliminary design phase. This will include requirements management, documentation and configuration control, interface development and technical risk management. Because of the complexity of the GMT system and the distributed team, using web-accessible tools for collaboration is vital. To accomplish this GMTO has selected three tools: Cognition Cockpit, Xerox Docushare, and Solidworks Enterprise Product Data Management (EPDM). Key to this is the use of Cockpit for managing and documenting the product tree, architecture, error budget, requirements, interfaces, and risks. Additionally, drawing management is accomplished using an EPDM vault. Docushare, a documentation and configuration management tool is used to manage workflow of documents and drawings for the GMT project. These tools electronically facilitate collaboration in real time, enabling the GMT team to track, trace and report on key project metrics and design parameters.
System engineering of the Atacama Large Millimeter/submillimeter Array
The Atacama Large Millimeter/submillimeter Array (ALMA) will be composed of 66 high precision antennae located at
5000 meters altitude in northern Chile. This paper will present the methodology, tools and processes adopted to system
engineer a project of high technical complexity, by system engineering teams that are remotely located and from
different cultures, and in accordance with a demanding schedule and within tight financial constraints. The technical and
organizational complexity of ALMA requires a disciplined approach to the definition, implementation and verification of
the ALMA requirements. During the development phase, System Engineering chairs all technical reviews and facilitates
the resolution of technical conflicts. We have developed analysis tools to analyze the system performance, incorporating
key parameters that contribute to the ultimate performance, and are modeled using best estimates and/or measured values
obtained during test campaigns. Strict tracking and control of the technical budgets ensures that the different parts of the
system can operate together as a whole within ALMA boundary conditions. System Engineering is responsible for
acceptances of the thousands of hardware items delivered to Chile, and also supports the software acceptance process. In
addition, System Engineering leads the troubleshooting efforts during testing phases of the construction project. Finally,
the team is conducting System level verification and diagnostics activities to assess the overall performance of the
observatory. This paper will also share lessons learned from these system engineering and verification approaches.
Management of the JWST MIRI pFM environmental and performance verification test campaign
Örs Hunor Detre
The Mid-Infrared Instrument (MIRI) is one of four scientific instruments on the James Webb Space Telescope (JWST)
observatory, scheduled for launch in 2018. It will provide unique capabilities to probe the distant or deeply dust-enshrouded
regions of the Universe, investigating the history of star and planet formation from the earliest universe to
the present day. To enable this the instrument optical module must be cooled below 7K, presenting specific challenges
for the environmental testing and calibration activities.
The assembly, integration and verification (AIV) activities for the proto-flight model (pFM) instrument ran from March
2010 to May 2012 at RAL where the instrument has been put through a full suite of environmental and performance tests
with a non-conventional single cryo-test approach.
In this paper we present an overview of the testing conducted on the MIRI pFM including ambient alignment testing,
vibration testing, gravity release testing, cryogenic performance and calibration testing, functional testing at ambient and
operational temperatures, thermal balance tests, and Electro-Magnetic Compatibility (EMC) testing. We discuss how
tests were planned and managed to ensure that the whole AIV process remained on schedule and give an insight into the
lessons learned from this process. We also show how the process of requirement verification for this complex system
was managed and documented. We describe how the risks associated with a single long duration test at operating
temperature were controlled so that the complete suite of environmental tests could be used to build up a full picture of
Developing an instrument simulator: experience feedback from the JWST/NIRSpec and VLT/MUSE simulators
The Centre de Recherche Astrophysique de Lyon (CRAL) has recently developed two instrument simulators
for spectrographic instruments. They are based on Fourier optics, and model the whole chain of acquisition,
taking into account both optical aberrations and diffraction effects, by propagating a wavefront through the
instrument, according to the Fourier optics concept. One simulates the NIRSpec instrument, a near-infrared
multi-object spectrograph for the future James Webb Space Telescope (JWST). The other one models the
Multi Unit Spectroscopic Explorer (MUSE) instrument, a second-generation integral-field spectrograph for the
Very Large Telescope (VLT). The two simulators have been developed in different contexts (subcontracted
versus developed internally), and for very different instruments (space-based versus ground-based), which
strengthen the CRAL experience. This paper describes the lessons learned while developing these simulators:
development methods, phasing with the project, points to focus on, getting data, interacting with scientists
and users, etc.
Transitioning from conceptual design to construction performance specification
On successful completion of a conceptual design review by a funding agency or customer, there is a transition phase
before construction contracts can be placed. The nature of this transition phase depends on the Project's approach to
construction and the particular subsystem being considered.
There are generically two approaches; project retention of design authority and issuance of build to print contracts, or
issuance of subsystem performance specifications with controlled interfaces.
This paper relates to the latter where a proof of concept (conceptual or reference design) is translated into performance
based sub-system specifications for competitive tender. This translation is not a straightforward process and there are a
number of different issues to consider in the process. This paper deals with primarily the Telescope mount and Enclosure
The main subjects considered in this paper are:
• Typical status of design at Conceptual Design Review compared with the desired status of
Specifications and Interface Control Documents at Request for Quotation.
• Options for capture and tracking of system requirements flow down from science / operating
requirements and sub-system requirements, and functional requirements derived from reference
• Requirements that may come specifically from the contracting approach.
• Methods for effective use of reference design work without compromising a performance based
• Management of project team's expectation relating to design.
• Effects on cost estimates from reference design to actual.
This paper is based on experience and lessons learned through this process on both the VISTA and the ATST projects.
Usability-driven evolution of a space instrument
The use of resources in the cradle-to-grave timeline of a space instrument might be significantly improved by
considering the concept of usability from the start of the mission. The methodology proposed here includes giving early
priority in a programme to the iterative development of a simulator that models instrument operation, and allowing this
to evolve ahead of the actual instrument specification and fabrication. The advantages include reduction of risk in
software development by shifting much of it to earlier in a programme than is typical, plus a test programme that uses
and thereby proves the same support systems that may be used for flight.
A new development flow for an instrument is suggested, showing how the system engineering phases used by the space
agencies could be reworked in line with these ideas. This methodology is also likely to contribute to a better
understanding between the various disciplines involved in the creation of a new instrument. The result should better
capture the science needs, implement them more accurately with less wasted effort, and more fully allow the best ideas
from all team members to be considered.
Building information models for astronomy projects
A Building Information Model is a digital representation of physical and functional characteristics of a building. BIMs
represent the geometrical characteristics of the Building, but also properties like bills of quantities, definition of COTS
components, status of material in the different stages of the project, project economic data, etc.
The BIM methodology, which is well established in the Architecture Engineering and Construction (AEC) domain for
conventional buildings, has been brought one step forward in its application for Astronomical/Scientific facilities. In
these facilities steel/concrete structures have high dynamic and seismic requirements, M&E installations are complex
and there is a large amount of special equipment and mechanisms involved as a fundamental part of the facility. The
detail design definition is typically implemented by different design teams in specialized design software packages. In
order to allow the coordinated work of different engineering teams, the overall model, and its associated engineering
database, is progressively integrated using a coordination and roaming software which can be used before starting
construction phase for checking interferences, planning the construction sequence, studying maintenance operation,
reporting to the project office, etc.
This integrated design & construction approach will allow to efficiently plan construction sequence (4D). This is a
powerful tool to study and analyze in detail alternative construction sequences and ideally coordinate the work of
different construction teams.
In addition engineering, construction and operational database can be linked to the virtual model (6D), what gives to the
end users a invaluable tool for the lifecycle management, as all the facility information can be easily accessed, added or
This paper presents the BIM methodology as implemented by IDOM with the E-ELT and ATST Enclosures as
Managing successful industry engagement: the Australian SKA Pathfinder experience
The management of industry engagement has been one of the challenges in realising the AU$ 154M Australian Square
Kilometre Array Pathfinder (ASKAP). ASKAP has evolved both in scope and scale during its aggressive delivery
timeline (2007 – 2012); furthermore its relationship to the proposed international Square Kilometre Array (SKA) radio
telescope has had to be carefully managed to ensure expectations remained realistic. In this paper I describe how CSIRO
has navigated these challenges, forging excellent working relationships with a range of national and international
companies, complimented by the establishment of a supportive national industry consortium.
Astrometric instrument modeling in the context of Gaia astrometric verification: tasks and activities
Detailed knowledge of instrument parameters and observing conditions is crucial for the achievement of micro- arcsecond precision and accuracy. It has come to be a key ingredient for optimal definition of data reduction and calibration procedures, since the variation of instrumental response over the field of view with wavelength and in time is both critical and often unavoidable. With this work we provide an overview of Astrometric Instrument Model (AIM) system within the Astrometric Verification Unit for the reduction of the Gaia data. We recall on the original motivations for its development, the changes occurred during the last two years and the actual AIM structure, pointing out the most critical parts in relation to the modeling of the astrometric instrument and of the scientific treatment of the Gaia data. While waiting for the Gaia operations to start, we present first results of AIM system from the on-going testing campaign of the Gaia data reduction software systems.
The Information Management Tool (IMT) of Gaia DPAC and its potential as tool for large scale software development projects
The Gaia Data Processing and Analysis Consortium (DPAC) is developing the required software to handle and
process the data collected during ESA’s Gaia astronomy mission. DPAC consist of more than 400 scientists
and engineers developing several dozens of large software packages. Such a large software development project
requires adequate progress monitoring techniques. DPAC has developed IMT as a semi automated monitoring
tool. In this paper we will describe the IMT system, the results it provides, and the experiences in view of usage
withing the DPAC management process. Also the potential usage of IMT in other large scientific projects is
The organization and management of the Virtual Astronomical Observatory
G. Bruce Berriman
Robert J. Hanisch
T. Joseph W. Lazio
The U.S. Virtual Astronomical Observatory (VAO http://www.us-vao.org/) has been in operation since May 2010. Its goal is to enable new science through efficient integration of distributed multi-wavelength data. This paper describes the management and organization of the VAO, and emphasizes the techniques used to ensure efficiency in a distributed organization. Management methods include using an annual program plan as the basis for establishing contracts with member organizations, regular communication, and monitoring of processes.
Managing distributed software development in the Virtual Astronomical Observatory
Janet D. Evans
Raymond L. Plante;
The U.S. Virtual Astronomical Observatory (VAO) is a product-driven organization that provides new scientific
research capabilities to the astronomical community. Software development for the VAO follows a lightweight
framework that guides development of science applications and infrastructure. Challenges to be overcome include
distributed development teams, part-time efforts, and highly constrained schedules. We describe the process we
followed to conquer these challenges while developing Iris, the VAO application for analysis of 1-D astronomical
spectral energy distributions (SEDs). Iris was successfully built and released in less than a year with a team distributed
across four institutions. The project followed existing International Virtual Observatory Alliance inter-operability
standards for spectral data and contributed a SED library as a by-product of the project. We emphasize lessons learned
that will be folded into future development efforts. In our experience, a well-defined process that provides guidelines to
ensure the project is cohesive and stays on track is key to success. Internal product deliveries with a planned test and
feedback loop are critical. Release candidates are measured against use cases established early in the process, and
provide the opportunity to assess priorities and make course corrections during development. Also key is the
participation of a stakeholder such as a lead scientist who manages the technical questions, advises on priorities, and is
actively involved as a lead tester. Finally, frequent scheduled communications (for example a bi-weekly tele-conference)
assure issues are resolved quickly and the team is working toward a common vision.
Observatory facility staff requirements and local labor markets
Current large observatories, both in operation and projects in development or construction, face the challenge
to find skilled personnel for integration and operation. Typical locations of these observatories are found to
be remote, mainly due to electromagnetic pollution prevention, which in many if not all cases reduces the
attractiveness of the work posts. Additional budgetary limitations restrict the recruitment radius for certain
positions to the local labor market. This paper outlines these staffing constraints in more detail and elaborates
on the need for training programs on various levels, which can be costly. This, in turn, drives the need for
creative retention efforts. Therefore, financial modeling, contingency, risk and quality management, and the
reliability, availability, and maintainability of an observatory are directly coupled to the local embedding in the
labor market of the host country.
Astronomical large projects managed with MANATEE: management tool for effective engineering
M. L. García-Vargas
This paper describes MANATEE, which is the Management project web tool developed by FRACTAL, specifically
designed for managing large astronomical projects. MANATEE facilitates the management by providing an overall view
of the project and the capabilities to control the three main projects parameters: scope, schedule and budget.
MANATEE is one of the three tools of the FRACTAL System & Project Suite, which is composed also by GECO
(System Engineering Tool) and DOCMA (Documentation Management Tool). These tools are especially suited for those
Consortia and teams collaborating in a multi-discipline, complex project in a geographically distributed environment.
Our Management view has been applied successfully in several projects and currently is being used for Managing
MEGARA, the next instrument for the GTC 10m telescope.
The important role of maintenance in the functionality and life of the observatories: the international standard S1000D for ALMA antennas
Prepare user and maintenance manuals for all the instruments and equipment of Large Observatories working in harsh environment, requires great efforts to be complete as well as user friendly. For this purpose, a standardized system such as S1000D, widely used in aerospace industry, was firstly investigated and then adopted representing undoubtedly one leap forward. Specifically in the ALMA project, this standardized system was applied for the maintenance manual of the European antennas. This choice led to a series of benefits which will be outlined in this paper through a brief explanation of the S1000D standard and some excerpts of the manual. The benefits mainly consist in the time saved during the writing and editing of the maintenance manual, its completeness due to the module based workflow and its readiness of use for the end user.
The Large Synoptic Survey Telescope project management control system
Jeffrey P. Kantor
The Large Synoptic Survey Telescope (LSST) program is jointly funded by the NSF, the DOE, and private institutions
and donors. From an NSF funding standpoint, the LSST is a Major Research Equipment and Facilities (MREFC)
project. The NSF funding process requires proposals and D&D reviews to include activity-based budgets and schedules;
documented basis of estimates; risk-based contingency analysis; cost escalation and categorization.
"Out-of-the box," the commercial tool Primavera P6 contains approximately 90% of the planning and estimating
capability needed to satisfy R&D phase requirements, and it is customizable/configurable for remainder with relatively
little effort. We describe the customization/configuration and use of Primavera for the LSST Project Management
Control System (PMCS), assess our experience to date, and describe future directions.
Examples in this paper are drawn from the LSST Data Management System (DMS), which is one of three main
subsystems of the LSST and is funded by the NSF. By astronomy standards the LSST DMS is a large data management
project, processing and archiving over 70 petabyes of image data, producing over 20 petabytes of catalogs annually, and
generating 2 million transient alerts per night. Over the 6-year construction and commissioning phase, the DM project is
estimated to require 600,000 hours of engineering effort. In total, the DMS cost is approximately 60% hardware/system
software and 40% labor.
But I'm an engineer—not a contracts lawyer!
Industrial partners, commercial vendors, and subsystem contractors play a large role in the design and construction of
modern telescopes. Because many telescope projects carry relatively small staffs, engineers are often required to perform
the additional functions of technical writing, cost estimating, and contract bidding and negotiating. The skills required to
carry out these tasks are not normally taught in traditional engineering programs. As a result, engineers often learn to
write Request for Proposals (RFPs), select vendors, and negotiate contracts by trial-and-error and/or by adapting
previous project documents to match their own requirements. Typically, this means that at the end of a contract the
engineer has a large list of do's, don'ts, and lessons learned for the next RFP he or she must generate. This paper will
present one such engineer's experience writing and bidding proposal packages for large telescope components and
subsystems. Included are: thoughts on structuring SOWs, Specs, ICDs, and other RFP documents; modern methods for
bidding the work; and systematic means for selecting and negotiating with a contractor to arrive at the best value for the
Assembly, integration, and verification (AIV) in ALMA: series processing of array elements
Nicholas D. Whyborn;
Lewis B. G. Knee
Joseph P. McMullin
The Atacama Large Millimeter/submillimeter Array (ALMA) is a joint project between astronomical organizations in
Europe, North America, and East Asia, in collaboration with the Republic of Chile. 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. It is the responsibility of ALMA AIV to deliver the fully assembled, integrated, and verified antennas
(array elements) to the telescope array.
After an initial phase of infrastructure setup AIV activities began when the first ALMA antenna and subsystems became
available in mid 2008. During the second semester of 2009 a project-wide effort was made to put in operation a first 3-
antenna interferometer at the Array Operations Site (AOS). In 2010 the AIV focus was the transition from event-driven
activities towards routine series production. Also, due to the ramp-up of operations activities, AIV underwent an
organizational change from an autonomous department into a project within a strong matrix management structure.
When the subsystem deliveries stabilized in early 2011, steady-state series processing could be achieved in an efficient
and reliable manner. The challenge today is to maintain this production pace until completion towards the end of 2013.
This paper describes the way ALMA AIV evolved successfully from the initial phase to the present steady-state of array
element series processing. It elaborates on the different project phases and their relationships, presents processing
statistics, illustrates the lessons learned and relevant best practices, and concludes with an outlook of the path towards
Incentive contracts for development projects
David T. Finley
Finding a contract vehicle that balances the concerns of the customer and the contractor in a development project can be difficult. The customer wants a low price and an early delivery, with as few surprises as possible as the project progresses. The contractor wants sufficient cost and schedule to cover risk. Both want to clearly define what each party will provide. Many program offices do not want to award cost plus contracts because their funding sources will not allow it, their boards do not want an open ended commitment, and they feel like they lose financial control of the project. A fixed price incentive contract, with a mutually agreed upon target cost, provides the owner with visibility into the project and input into the execution of the project, encourages both parties to save costs, and stimulates a collaborative atmosphere by aligning the respective interests of customers and contractors.
PS2: managing the next step in the Pan-STARRS wide field survey system
William S. Burgett
The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) is unique among the existing or planned
major ground-based optical survey systems as the only "distributed aperture" system. The concept of increasing system
étendue by replicating small telescopes and digital cameras presents both management opportunities and challenges. The
focus in this paper is on management lessons learned from PS1, and how those have been used to form the management
plan for PS2. The management plan components emphasized here include technical development, financial and schedule
planning, and critical path and risk management. Finally, the status and schedule for PS2 are presented.
Integrated telescope model for the James Webb Space Telescope
J. S. Knight;
D. S. Acton
Integrated modeling is a valuable tool for analyzing complex optical-mechanical systems such as the James Webb Space
Telescope. An implementation, the Integrated Telescope Model (ITM), has been developed for JWST to analyze the
performance of the Observatory. ITM is an end-to-end physical math model starting from stellar photons through the
image produced by the science data pipeline. The model also includes all effects that contribute to the formation of the
image including pointing errors, vibration and thermal distortions of the optical system, and the mechanical response of
the mirrors and actuation devices. A time domain interface to the attitude control system rounds out the capabilities.
The model is used over the life-cycle of the JWST program including: development, verification and on-orbit operation.
ITM is used to perform verification analysis on the set of test data resulting in a statistical assessment of the expected
observatory performance. This capability offers numerous advantages to the verification of the system, validation of the
wavefront sensing and control (WFS&C) system along with system level studies for design assessments. ITM has been
developed to interface to the ground control system in the same way as the actual observatory. This allows it to be used
as substitute for the Observatory for training, mission planning and operational trades.
The LSST camera instrument model
D. Kirk K. Gilmore
The design of the Large Synoptic Survey Telescope (LSST) requires a camera system of unprecedented size and complexity. Achieving the science goals of the LSST project, through design, fabrication, integration, and operation, requires a thorough understanding of the camera performance. Essential to this effort is the camera modeling which defines the effects of a large number of potential mechanical, optical, electronic or sensor variations which can only be captured with sophisticated instrument modeling that incorporates all of the crucial parameters. This paper presents the ongoing development of LSST camera instrument modeling and details the parametric issues and attendant analysis involved with this modeling.
The MUSE project face to face with reality
M. Le Floch;
J. E. Migniau;
MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument built for ESO (European Southern
Observatory) to be installed in Chile on the VLT (Very Large Telescope). The MUSE project is supported by a
European consortium of 7 institutes.
After the critical turning point of shifting from the design to the manufacturing phase, the MUSE project has now
completed the realization of its different sub-systems and should finalize its global integration and test in Europe.
To arrive to this point many challenges had to be overcome, many technical difficulties, non compliances or
procurements delays which seemed at the time overwhelming. Now is the time to face the results of our organization, of
our strategy, of our choices. Now is the time to face the reality of the MUSE instrument.
During the design phase a plan was provided by the project management in order to achieve the realization of the
MUSE instrument in specification, time and cost. This critical moment in the project life when the instrument takes
shape and reality is the opportunity to look not only at the outcome but also to see how well we followed the original
plan, what had to be changed or adapted and what should have been.
Modeling the instrumental polarization of the VLT and E-ELT telescopes with the M&m's code
M. de Juan Ovelar
T. van Werkhoven
Polarimetry is a particularly powerful technique when imaging circumstellar environments. Currently most telescopes include more or less advanced polarimetric facilities and large telescopes count on it for their planet-finder instruments like SPHERE-ZIMPOL on the VLT or EPICS on the future E-ELT. One of the biggest limitations of this technique is the instrumental polarization (IP) generated in the telescope optical path, which can often be larger than the signal to be measured. In most cases this instrumental polarization changes over time and is dependent on the errors affecting the optical elements of the system. We have modeled the VLT and E-ELT telescope layouts to characterize the instrumental polarization generated on their optical paths using the M&m's code, an error budget and performance simulator for polarimetric systems. In this study we present the realistic Mueller matrices calculated with M&m's for both systems, with and without the setups to correct for the IP, showing that correction can be achieved, allowing for an accurate polarimetric performance.
CODEX optical stability under microvibration environment: Is the Nasmith focal station suitable or not?
F. M. Zerbi
This paper wants to address the opto-mechanical stability of the Codex instrument pending onto vibration environment. CODEX is a study for an high resolution spectrograph for the European ELT. In particular the aim of the work is a preliminary verification of the instrument performances if mounted at the E-ELT Folded Nasmith location. Hence Dynamic environment of the Coudé and the folded Nasmith locations were alternatively applied to the optical layout to verify the image performances in terms of image displacements and FWHM deformations. In addition damping strategies has been verified for the improvement of the performances.
One-shot focusing using the entropy as a merit function
We present a method for measuring focus aberrations on wide field telescopes based on an entropy analysis of a
single image. First, we calibrate the system using the evolution of the entropy as a function of the position in the
field and the focuser position. This gives us a model defining the tilt of the sensor and the field curvature. Then,
using a single image at a given position of the focuser in which the mean defocus is unknown, we can compute
the position where the focuser must be set in order to minimize the focus aberration over the whole field.
Modelling the optical pathway of the Large Binocular Telescope
We dynamically model the Large Binocular Telescopes optical path using a linear system approach. The model is
derived from experiments conducted at the telescope. These experiments will be described and we will explain the
possibilities and difficulties in extracting a simulation model from measured data. The model also incorporates
disturbances, such as wind forces and single excitations induced by vibrating machinery. We will show, why it is
necessary to measure structural vibrations at the LBT and why we follow a model based approach in estimating
the mirror’s oscillatory motions. Some simulation results will be presented and compared to measured time series
and a conclusion will be drawn. An outlook will be given on how the observer can be implemented.
Reconstruction of the attitude of the Gaia spacecraft
F. van Leeuwen;
A. G. A. Brown
Gaia is an ESA mission due to be launched in 2013 and will be dedicated to astrometry. The attitude of the spacecraft
Gaia is an important part of the data processing of the mission because the astrometry will be calculated with respect to the
attitude. Therefore we need a very accurate characterisation of the attitude of the satellite during the observations in order
to get the best output from the mission.
We simulate the attitude of Gaia using the Dynamical Attitude Model (DAM). It is a simulation developed to achieve a
detailed understanding of the Gaia attitude and to provide realistic input data for testing the software pipeline. DAM takes
into account perturbations as well as internal hardware components controlling the satellite as the control system, sensors
and micro-Newton thrusters.
We study the errors in the simulated data, specifically the attitude reconstruction when fitting the Gaia reference attitude
with B-splines. We analyse the effect of different parameters and provide an estimation of the expected noise in the scientific
output of the mission due to the noise in the attitude reconstruction.
Modeling for instrument diagnostics: Gaia non-nominal configurations impact on astrometric performance
The Gaia payload is a highly sophisticated system and many of its instrumental behaviors will be tested at proper accuracy only during the operational phase. However simulation results are critical parts for developing system integration, as well as for understanding unexpected behavior during commissioning and operations. The data analysis procedures are sensitive to several instrument parameters, as their variation over the field and with time. We focused our dissertation on the study and analysis of non-nominal configurations effects on astrometric accuracy, putting also in evidence the level of the effects that the difference between the design data and as-built data can produce if not adequately taken into account. We identify and quantify the effects. We move from this forward analysis to look at the data and perform instrument monitoring and diagnostic procedures, an essential activity for the verification of GAIA measurements. We conducted the study in the context of the Astrometric Verification Unit.
E-ELT seismic devices analysis and prototype testing
During the E-ELT Dome and Foundations FEED Study, IDOM developed a Base Control System for protection of the
E-ELT Main Structure against the effect of high level earthquakes. The proposed design was aimed to provide an
effective isolation during heavy seismic events, whereas in normal observation conditions it presented a high stiffness to
avoid interferences with the pointing accuracy of the telescope.
In a subsequent phase, a representative prototype was envisaged by IDOM, in close collaboration with GERB, to
evaluate the performance of this system, correlate the results from prototype testing with the behaviour predicted by a
calculation model and finally validate the design conceived during the FEED Study.
The assessment of the results from the prototype tests has been focused on checking the level of compliance with the
demanded requirements: 1) the Base Control System isolates the upper structure from ground in case of high magnitude
seismic events; 2) in operational conditions, the system -by means of Preloaded Devices (PLDs)- provides a stiff
interface with the ground; 3) regarding the performance of the PLDs, the finite element model simulates accurately the
non-linear behaviour, particularly the zero crossing when the direction of the excitation changes; 4) there is no
degradation of the stiffness properties of the seismic devices, after being submitted to a heavy seismic event.
The prototype was manufactured by GERB and pseudo-integrated tests were performed on a shaking table at the
premises of the Institute of Earthquake Engineering (IZIIS) in Skopje, Macedonia.
A new optomechanical structural optimization approach: coupling FEA and raytracing sensitivity matrices
The design of astronomical instrument is growing in dimension and complexity following ELT class telescopes. The availability of new structural material like composite ones is asking for more robust and reliable designing numerical tools. This paper wants to show a new opto-mechanical optimization approach developed starting from a previously developed integrated design framework. The Idea is to reduce number of iteration in a multi- variable structural optimization taking advantage of the embedded sensitivity routines that are available both in FEA software and in raytracing ones. This approach provide reduced iteration number mainly in case of high number of structural variable parameters.
Dynamic analysis of the active control system for the CGST
The Chinese Giant Solar Telescope (CGST) is the China’s next generation solar telescope with an aperture of 8 m in
diameter. The unique feature of the CGST is its ring primary, which facilitates the polarization detection and thermal
control. The CGST is now in its design and development phase. A mosaic mirror with 24 trapezoidal segments is a
candidate for its primary mirror, which highly relies on a segment active control system to achieve competitive optical
quality of a monolithic mirror. The CGST is designed to operate in open-air observation mode, its active control system
thus faces new challenges. As the CGST has an aperture larger than that of current solar telescopes, and as the magnitude
of wind load in open air is greater than that of a stellar telescope with a similar aperture yet under the protection of a
dome and/or an enclosure. Furthermore, as a mosaic mirror, high precision real-time tip sensing is required to serve the
feedback of its control system. The accuracy depends on integration time (or working bandwidth) when an optical
metrology is adopted, which should match the bandwidth of the segment control system. In this paper, a dynamic
analysis of the segment control system of the CGST is presented. We demonstrate how the dynamic interaction between
the segment control system and the telescope structure impacts the telescope’s optical performance under wind
disturbances. The dynamic analysis helps to understand the bandwidth limit for the segment control system, and further
to clarify technical requirements for tip sensing implementation, telescope structure design and wind shielding design.
ALMA band 3 cartridge maintenance plan
Under the "Memorandum of Understanding between the National Radio Astronomy Observatory/Associated Universities Incorporated, Herzberg Institute of Astrophysics (HIA) and the University of Calgary related to Canadian ALMA Construction Phase Work Packages", HIA is committed to deliver a suite of seventy-three Band 3 100 GHz receiver cartridges to the ALMA Project. After the acceptance of each cartridge at the Front End Integration Centers, HIA is responsible to perform any post-delivery maintenance, repair and rework of the cartridges for a warranty period of up to one year. This paper defines a framework for the maintenance and repair services for the Band 3 cartridges after the post-delivery warranty period has expired. This framework consists of a detailed work breakdown structure, timelines and labour effort estimates of the major tasks related maintenance and repair services of ALMA Band 3 cartridges.
Product and quality assurance processes and ECSS compliance within a science ground segment using Gaia as an example
The ESA satellite Gaia aims to measure the main astrometric parameters and generate an astrometric catalogue
of 109 objects with an accuracy on the micro-arcsec level. To reach this goal the European scientific community
has formed the Gaia Data Processing and Analysis Consortium (DPAC). DPAC includes the Science Operation
Centre (SOC) at ESAC and together they constitute the Gaia science ground segment, including a total of more
than 400 scientists and engineers. Such a large group of developers represent a massive development effort which
requires effective quality monitoring and assurance mechanisms and reporting structures to be in place. In this
paper we will outline the procedures and mechanisms setup within the consortium to assure that DPAC software
products and the necessary hardware will be ready when they are needed and fulfill their expectations. The
experiences gathered in the employed PA/QA process, which is based on the relevant ECSS standards, will be
described and will prove useful for other projects of similarly large scale.
The pre-research of the deploy technology for the large aperture space astronomical telescope
The spherical primary mirror (Mb) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is
segmented and composed of 37 hexagonal sub-mirrors, and segmented active optics method is successfully developed in
it. LAMOST project has passed through the project acceptance in 2009. The success of LAMOST makes deployable
primary mirror possible. The deployable large aperture space astronomical telescope is one of the most development
potential space observation spacecrafts in the future. This paper is targeted at the reflecting Schmidt telescope LAMOST,
which has a 6.67X6.05m primary mirror. The feasibility of the deployable structure of the large reflecting space
telescope's primary mirror has been mainly researched. The analysis of the design scheme for the deployable primary
mirror has been carried out, and according to the feature and the design of LAMOST, a subdivision type deployment
scheme has been given; The locating principle of the both side wings and the locking device after deployment has been
analyzed; In addition the problems in the process of deployment is also preliminary discussed. This paper is targeted at
the reflecting Schmidt telescope LAMOST, which has a 6.67X6.05 primary mirror. The feasibility of the deployable
structure of the large reflecting telescope's primary mirror has been mainly researched. The analysis of the design
scheme for the deployable primary mirror has been carried out, and according to the feature and the design of LAMOST,
a subdivision type deployment scheme has been given; The locating principle of the both side wings and the locking
device after deployment has been analyzed; In addition the problems in the process of deployment have been preliminary
GAIA mock-up: an educational demonstrative GAIA model
Mario G. Lattanzi;
Maria Teresa Crosta;
Gaia is ESA's next-generation space mission aimed at global astrometry at the microarcsecond level. Its science
case is devoted to the understanding of our Galaxy's structure, evolution and composition. The GAIA payload
includes two identical telescopes separated by a Basic Angle whose variations in time must be measured with
very high accuracy, to fulll the astrometry goal. To this purpose, an interferometric sub-system, the Basic
Angle Monitoring Device (BAMD), has been introduced. The BAMD optical concept is based on a pair of
laser beams per telescope, producing fringes on a dedicated CCD. The basic measurement principle of BAMD
consists in monitoring the stability of the fringe pattern phase. We are developing a demonstrator of the BAMD
for educational purposes, considered representative of the driving design concept for the Gaia microarcsecond
astrometry. In this paper we describe the design guidelines and analyze some of the key elements related to the
demonstration of the basic angle monitoring concept.
VST system engineering and management of commissioning
This paper describes the system engineering work at the VLT Survey Telescope on the ESO’s Paranal observatory. The
error budget, as well as many subsystems and their integration in the overall telescope system, have been deeply
reviewed in the last years of construction and commissioning. The lessons learned in the management of the
commissioning of a complex system in a remote site are also analyzed.
Analysis and optimization of the SONG telescope
SONG is an international initiative to design, build, and utilize a global network of eight 1-meter class
telescopes to be operated as a whole-Earth telescope. The telescope is composed of system of azimuth axis, rotating
table, fork, system of elevation axis, top-ring, up and down truss, system of primary mirror and so on. For an
astronomical telescope mount, having a high stiffness to support the mirror cell and instruments is its basic function.
Finite element method (FEM) is a powerful tool to help structure design engineer to achieve this goal. In this paper, with
the help of ANSYS, the static and modal analysis, calculation and optimization of the SONG telescope mount will be
given. The modal result which is used for avoiding resonance and fatigue failure of the telescope acquire natural
frequency of telescope. The FEM results show that the structure, designed for SONG telescope, is feasible and reliable
and have a high stiffness-to-weight ratio to meet the optical demands.
Use of failure modes and effects analysis in design of the tracker system for the HET wide-field upgrade
In support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), the Center for Electromechanics at The
University of Texas at Austin was tasked with developing the new Tracker and control system to support the HETDEX
Wide-Field Upgrade. The tracker carries the 3,100 kg Prime Focus Instrument Package and Wide Field Corrector
approximately 13 m above the 10 m diameter primary mirror. Its safe and reliable operation by a sophisticated control
system, over a 20 year life time is a paramount requirement for the project. To account for all potential failures and
potential hazards, to both the equipment and personnel involved, an extensive Failure Modes and Effects Analysis
(FMEA) was completed early in the project. This task required participation of all the stakeholders over a multi-day
meeting with numerous follow up exchanges. The event drove a number of significant design decisions and requirements
that might not have been identified this early in the project without this process. The result is a system that has multiple
layers of active and passive safety systems to protect the tens of millions of dollars of hardware involved and the people
who operate it. This paper will describe the background of the FMEA process, how it was utilized on HETDEX, the
critical outcomes, how the required safety systems were implemented, and how they have worked in operation. It should
be of interest to engineers, designers, and managers engaging in complex multi-disciplinary and parallel engineering
projects that involve automated hardware and control systems with potentially hazardous operating scenarios.
MESSI: the METIS instrument software simulator
Instrument software simulators are becoming essential both for supporting the instrument design and for planning the
future operations. In this paper we present the Software Simulator developed for the METIS coronagraph, an instrument
of the Solar Orbiter ESA mission. We describe its architecture and the modules it is composed of, and how they
interchange data to simulate the whole acquisition chain from the photons entering the front window to the stream of
telemetry? data received and analysed on ground.
Each software module simulates an instrument subsystem by combining theoretical models and measured subsystem
properties. A web-based application handles the remote user interfaces of the Institutions of the METIS Consortium,
allowing users from various sites to overview and interact with the data flow, making possible for instance input and
output at intermediate nodes.
Description of the modes of use of the simulator, both present and future, are given with examples of results. These
include not only design-aid tasks, as the evaluation and the tuning of the image compression algorithms, but also those
tasks aimed to plan the in-flight observing sequences, based on the capability of the simulator of performing end to end
simulations of science cases.
Thermo-structural analysis of stresses during fabrication of an optical element for the APF camera
The Automated Planet Finder (APF) is a new telescope on Mount Hamilton with an instrument designed and built by
UCO. During the development of the instrument's camera lens assembly the largest optical element fractured during
fabrication. The glass grade is a relatively robust material and not known for any special sensitivity. Transient thermal
and structural FEA modeling was performed on the element geometry for several glass materials to better understand the
mechanics involved and the relative nature of the properties and response of the glass that failed. Results show that the
glass in question yielded the highest surface stresses of all those considered and high internal stresses as well. The
analysis technique described here is a simple tool that can be used to evaluate a material and make valid comparisons
China SONG telescope tracking system based on direct drive technology
SONG (Stellar Oscillations Network Group) is a Danish initiative to design and build a global network of 1-m class telescopes. The plan is to design and build a global network of small telescopes located at 8 existing observatories around the world. The scientific goals of SONG need to obtain long-term and continuous observations (weeks to months). The group behind the SONG proposal has devised a new and innovative concept to overcome these problems in a cost-effective way. China, as one of the eight sites, its 1-m class telescope can achieve the goal for long time continuous, uninterrupted, full automatic observation and works in the diffraction limit condition. At the same time the telescope must realize 0.3 arc second tracking precision without guide star, which is a very challenge and difficult task for 1 meter telescope tracking system .This paper discusses the design and analysis of Chinese song telescope control system,ecpecially, its tracking system .
An end-to-end instrument model for the proposed E-ELT instrument METIS
The optimal performance of an instrument relies critically on accurate performance estimates during its design phase. They need to be modeled to give the science and engineering teams a preview of the performance of the instrument, to guide the design process, to prove the capabilities of the instrument and to prepare science ready software tools before the instrument is operational. METIS, the Mid-infrared E-ELT Imager, is an instrument concept for the E-ELT that covers the thermal infrared wavelengths from 2:9 – 14 μm (L, M and N band). It contains a diffraction limited imager and an integral field high resolution spectrograph. The instrument consists of two independent units, the imager and the spectrograph, and is entirely encased in a cryostat to maintain the stable low temperatures required for good performance at mid-infrared wavelengths. METIS was identified in the instrument roadmap as the third instrument for the E-ELT, after two first light instruments. Because in the mid-infrared the Earth's atmosphere and the telescope mirrors radiate and produce a very high thermal background, it is crucial to develop techniques and mechanisms to measure and reduce this background, to achieve the desired performance of an E-ELT. To demonstrate the capabilities of METIS, years before the actual instrument is built and can be tested, we are developing an end-to-end instrument model, which will simulate the full capacity of METIS. The structure of the model and first results of the performance evaluation are shown.
A new calculation of LAMOST optical vignetting
A new method to calculate the optical vignetting of LAMOST (Large Sky Area Muti-Object Fiber Spectroscopic
Telescope) is presented. With the pilot survey of LAMOST, it is necessary to have thorough and quantitative estimation
and analysis on the observing efficiency which is affected by various factors: the optical system of the telescope and the
spectrograph that is vignetting, the focal instrument, and the site condition. The wide field and large pupil of LAMOST
fed by a Schmidt reflecting mirror, with a fixed optical axis coinciding with the local polar axis, lead to significant
telescope vignetting, caused by the effective light-collecting area of the corrector, the light obstruction of the focal-plate,
and the size of the primary mirror. A calculation of the vignetting has been presented by Xue et al. (2007), which
considered 4 meter circle limitation and based on ray-tracking. In fact, there is no effect of the 4 meter circle limitation,
so that we compute the vignetting again by means of obtaining the ratio of effective projected area of the corrector. All
the results are derived by AUTOCAD. Moreover, the vignetting functions and vignetting variations with declination at
which the telescope is pointed and the position considered in the focal surface are presented and analysed. Finally,
compared with the ray-tracing method to obtain the vignetting before, the validity and availability of the proposed
method are illustrated.
WaFER: a tool to derive the focal surface of millimeter wave telescopes and characterize their optical response
In the framework of the Italian Space Agency (ASI) Technological Developments aimed at the measurement of the
Cosmic Microwave Background (CMB) polarization, a method to define and characterize focal surfaces of millimeter
wave telescopes has been implemented in a software package named WaFER (Wave Front Error evaluatoR). The
purpose of this tool is to rapidly optimize and characterize wide focal planes providing valuable information to study and
optimize high performance telescope configurations. This method is based on the GRASP9 Multi-Reflector GTD for the
computation of the weighted wave front error and the software output is the 3D focal surface as the region that
minimizes this figure of merit, in terms of feed locations and orientations, for polarization measurements. In addition
WaFER provides the main descriptive parameters of the main beams iteratively calculated with the GRASP9 Physical
Optics, using the information derived for the evaluated focal surface. The method has been applied at several telescope
configurations and WaFER could be used to define the focal surface of any reflector antenna system that can be studied
with GRASP9. It can be used to characterize the main beam descriptive parameters also in terms of polarization
properties and straylight. Finally, an estimate of the computational time is reported for each computational step (focal
surface evaluation, main beam simulations, polarization alignment).