Proceedings Volume 6269

Ground-based and Airborne Instrumentation for Astronomy

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Proceedings Volume 6269

Ground-based and Airborne Instrumentation for Astronomy

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Volume Details

Date Published: 23 June 2006
Contents: 12 Sessions, 193 Papers, 0 Presentations
Conference: SPIE Astronomical Telescopes + Instrumentation 2006
Volume Number: 6269

Table of Contents

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Table of Contents

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  • Overview of Instrumentation at Major Observatories I
  • Overview of Instrumentation at Major Observatories II
  • Optical Imaging
  • Optical Spectroscopy
  • Infrared Imaging
  • Infrared Spectroscopy I
  • Infrared Spectroscopy II
  • New Methods
  • ELT Instrumentation
  • Poster Session A
  • Poster Session B
  • Poster Session C
Overview of Instrumentation at Major Observatories I
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Instrumentation development at the W.M. Keck Observatory
The W.M. Keck Observatory is now in its 12th year of science operations, and the development of new instruments, and upgrades to existing ones, continues to be an important part of our science driven strategic plan, which emphasizes state of the art instrumentation, continued advances in high angular resolution astronomy and faint-object spectroscopy. Our program is starting to deliver the third generation of instruments. The first of these, OSIRIS, was delivered in February 2005 and is now in shared risk operation. OSIRIS is the second instrument at the Observatory to be routinely used with laser guide star adaptive optics (LGS AO) on the Keck II telescope. LGS AO is now a regularly offered observing mode with a steadily increasing number of nights being made available to our community. AO developments underway at the Observatory include new wavefront controllers for the Keck I and Keck II AO systems, and the development of a solid state laser for the Keck I telescope (in collaboration with the Gemini Observatory). The development of Keck-Keck interferometry continues, with the V2 capability offered for routine observing and the Nuller in the commissioning process. Other developments include our next third generation instrument, a near-IR multi-object spectrograph (MOSFIRE), and a detector upgrade for the red channel of the LRIS instrument. Our atmospheric dispersion corrector (ADC) for the Cassegrain focus of the Keck I telescope is nearing completion, and the detector upgrade for the HIRES spectrograph has been in routine operation for over a year. We are also developing a new acquisition, guiding and image quality monitoring system to replace all of the visible wavelength instrument guiders and acquisition cameras at the Observatory.
Instrumentation at the ESO VLT
The ESO Very Large Telescope (VLT) on Paranal mountain in northern Chile comprises four 8.2m diameter "Unit Telescopes"; three 1.8m movable outrigger telescopes (shortly to be 4) for interferometry and the enclosures for two survey telescopes - the 2.6m VST to be used in the visible and the 4m class, infrared VISTA telescope which will both start commissioning in 2006. Here I will give an overview of the accompanying large instrument development programme which has so far delivered 9 operational facility instruments for the UT's (plus a visitor focus) and 2 major instruments for the interferometric focus. In addition, the laser guide star facility to be used to generate artificial (sodium) stars for the adaptive optics assisted instruments NACO and SINFONI is being commissioned; the optical and infrared cameras for the survey telescopes are almost ready; the CRIRES high resolution infrared spectrograph is being commissioned on UT1; the infrared imager HAWK-I is being assembled at ESO Garching; four major second generation instruments for the UTs (X-Shooter, KMOS, MUSE and SPHERE) are at various stages of development throughout Europe and Phase A studies of three second generation interferometric instruments (MATISSE, VSI and GRAVITY) have just been launched.
Current and future Subaru instruments
The status and performance of the first-generation instruments of the Subaru Telescope are reviewed together with their open use statistics and some of the science outcomes. Four second-generation instruments under fabrication are also introduced.
Past, present, and future instrumentation at Gemini Observatory
First, a status report is given for the on-going (Phase 2) instruments under construction now for Gemini. These instruments will be deployed during 2006 and 2007 at Gemini-South and collectively represent the end of an era of instrument building within the Gemini Partnership. Next, scientific applications and technical details for the next generation of "Aspen" instruments is described. These advanced future instruments will support breakthrough research in areas like extra-solar planets, dark matter, and dark energy. Gemini's ambitious adaptive optics development program in both current and future Aspen instruments is also described. Finally, a look back at some of the trials and tribulations of building instruments at Gemini is presented, with an eye toward the lessons of yesterday, how they helped mold today's program, and how they will likely impact the procurement of future instruments at Gemini.
Present and future instrumentation for the Hobby-Eberly Telescope
The Hobby-Eberly Telescope (HET) is an innovative large telescope of 9.2 meter aperture, located in West Texas at McDonald Observatory. 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. The HET has been taking science data for six years. Work over the past two years has improved performance significantly, replacing the mirror coatings and installing metrology equipment to provide feedback that aids tracking and alignment of the primary mirror segments. The first phase of HET instrumentation includes three facility instruments: the Low Resolution Spectrograph (LRS), the Medium Resolution Spectrograph (MRS), and High Resolution Spectrograph (HRS). The current status of these instruments is described. A major upgrade of HET is planned that will increase the field of view to 22 arcminutes diameter, replacing the corrector, tracker and prime focus instrument package. This wide field upgrade will feed a revolutionary new integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX).
Overview of Instrumentation at Major Observatories II
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GTC facility instruments: main features and readiness status
The Gran Telescopio Canarias (GTC) 10.4m telescope will be having its first light soon after this meeting. A fairly complete set of science instruments are being prepared for installation at the GTC soon after first light or a couple of year after in the case of the second generation instruments. In this talk I will describe the main features of the various instruments and discuss their completion status. In particular I will dwell on the Tuneable filters combined with a wide field and charge shuffling capabilities of OSIRIS, Elmer's outstanding throughput, and the thermal IR polarimetry and coronagraphy capabilities of CanariCam. I will also show the wide field multi-object K band spectroscopic capabilities of EMIR, the first of the second-generation instruments. Finally, I will describe CIRCE, a near IR camera being offered by the UF for GTC, and FRIDA, a near IR AO geared imager and IFU spectrograph meant to exploit the GTC AO system.
An overview of instrumentation for the Large Binocular Telescope
An overview of instrumentation for the Large Binocular Telescope is presented. Optical instrumentation includes the Large Binocular Camera (LBC), a pair of wide-field (27' × 27') mosaic CCD imagers at the prime focus, and the Multi-Object Double Spectrograph (MODS), a pair of dual-beam blue-red optimized long-slit spectrographs mounted at the straight-through F/15 Gregorian focus incorporating multiple slit masks for multi-object spectroscopy over a 6' field and spectral resolutions of up to 8000. Infrared instrumentation includes the LBT Near-IR Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (LUCIFER), a modular near-infrared (0.9-2.5 μm) imager and spectrograph pair mounted at a bent interior focal station and designed for seeing-limited (FOV: 4' × 4') imaging, long-slit spectroscopy, and multi-object spectroscopy utilizing cooled slit masks and diffraction limited (FOV: 0'.5 × 0'.5) imaging and long-slit spectroscopy. Strategic instruments under development for the remaining two combined focal stations include an interferometric cryogenic beam combiner with near-infrared and thermal-infrared instruments for Fizeau imaging and nulling interferometry (LBTI) and an optical bench near-infrared beam combiner utilizing multi-conjugate adaptive optics for high angular resolution and sensitivity (LINC-NIRVANA). In addition, a fiber-fed bench spectrograph (PEPSI) capable of ultra high resolution spectroscopy and spectropolarimetry (R = 40,000-300,000) will be available as a principal investigator instrument. The availability of all these instruments mounted simultaneously on the LBT permits unique science, flexible scheduling, and improved operational support.
Status of the Southern African Large Telescope (SALT) first-generation instruments
D. A. H. Buckley, E. B. Burgh, P. L. Cottrell, et al.
"First light" of the Southern African Large Telescope was declared on 1 Sep 2005 and the first scientific programs have now begun. This paper discusses the completion and commissioning of the first-light instruments: the UV-visible imaging camera, SALTICAM, and the prime focus imaging spectrograph, the Robert Stobie Spectrograph (RSS). The innovative aspects and tight constraints on the design of these prime focus instruments are described, as well as the first scientific results. These instruments, which are all seeing limited, operate in the UV-visible region (320 - 900 nm), and will provide capabilities for broad and narrow band imaging, long-slit and multi-object spectroscopy (R ~ 6000 for seeing limit), spectropolarimetry and Fabry-Perot imaging spectroscopy (R ~ 320-9,000). Time resolved studies are an important aspect of the overall SALT science drivers and special efforts were made to ensure an ability to run at ~10 Hz, with minimal dead time, by employing frame transfer CCDs. Finally, we present the design and status of the fiber-fed high resolution echelle spectrograph, SALTHRS, the last of the "first generation" SALT instruments.
Optical Imaging
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HyperSuprime: project overview
HyperSuprime is a next generation wide field camera proposed for the 8.3 m Subaru Telescope. The targeted field of view is larger than 1.5 deg in diameter, which will give us roughly 10 times increase of the survey speed compared with the existing prime focus camera (Suprime-Cam). An overview of the current status of the feasibility study is given.
The LSST camera system overview
The LSST camera is a wide-field optical (0.35-1um) imager designed to provide a 3.5 degree FOV with better than 0.2 arcsecond sampling. The detector format will be a circular mosaic providing approximately 3.2 Gigapixels per image. The camera includes a filter mechanism and, shuttering capability. It is positioned in the middle of the telescope where cross-sectional area is constrained by optical vignetting and heat dissipation must be controlled to limit thermal gradients in the optical beam. The fast, f/1.2 beam will require tight tolerances on the focal plane mechanical assembly. The focal plane array operates at a temperature of approximately -100°C to achieve desired detector performance. The focal plane array is contained within an evacuated cryostat, which incorporates detector front-end electronics and thermal control. The cryostat lens serves as an entrance window and vacuum seal for the cryostat. Similarly, the camera body lens serves as an entrance window and gas seal for the camera housing, which is filled with a suitable gas to provide the operating environment for the shutter and filter change mechanisms. The filter carousel can accommodate 5 filters, each 75 cm in diameter, for rapid exchange without external intervention.
LINC-NIRVANA: optical design of an interferometric imaging camera
Combining the two 8.4 m telescopes of the Large Binocular Telescope 1(LBT) offers the unique possibility to achieve diffraction limited images with 23 m spatial resolution. This requires an interferometric superposition of the two telescope beams in a Fizeau-type interferometer. LINC-NIRVANA delivers a 10 arcsec x 10 arcsec panoramic field of view with 5 mas pixel size. In addition to delivering diffraction limited, single-telescope images, the optics have several additional constraints imposed by interferometric operation. In this paper, we describe the evolution of the optical design and how the individual optical subsystems were developed in parallel to provide optimal combined performance. We also present an alignment strategy to setup the optics and to achieve zero optical path difference.
Tunable H-alpha Lyot filter with advanced servo system and image processing: instrument design and new scientific results with the Dutch Open Telescope
Felix C. M. Bettonvil, Robert H. Hammerschlag, Peter Sütterlin, et al.
The Dutch Open Telescope (DOT; http://dot.astro.uu.nl) on La Palma is a revolutionary open solar telescope, on an excellent site, on top of a transparent tower of steel framework, and uses natural air flow to minimize local seeing. The DOT is a high-resolution multi-wavelength imager capable of long-duration time series aiming at magnetic fine structure, topology and dynamics in the photosphere and low- and high chromosphere. In this paper we describe the latest addition to the multi-wavelength imaging system: a Lyot H-alpha camera channel operating at a wavelength of 656.3 nm, being of major interest for high-chromospheric phenomena. The channel is operated strictly synchronous with the other channels and all data are speckle reconstructed. The channel permits profile sampling and delivers Dopplergrams in a 15 second time cadence, up to several hours long and adding up to a total data amount of 1.6 Terabyte/day. A dedicated computer (DSP, DOT Speckle Processor) has been built for processing the data overnight.
Optical Spectroscopy
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IMACS: the wide-field imaging spectrograph on Magellan-Baade
Alan Dressler, Tyson Hare, Bruce C. Bigelow, et al.
Bigelow & Dressler1 reported on the design and construction of IMACS - the Inamori-Magellan Areal Camera and Spectrograph. IMACS was installed on the Magellan-Baade 6.5-m telescope at the Carnegie Institution's Las Campanas Observatory in Chile in August, 2003, and was phased into regular operation in the remaining months of that year (Osip et al2). IMACS is now the most-used instrument on the Baade telescope, accounting for 63% of the nights available for astronomy in the 2005 observing year. IMACS has two basic operating modes. A single 6-inch beam refractive collimator feeds either (1) an f/4 all-spherical refractive camera delivering 0.11 arcsec/pixel, or (2) a double-asphere refractive camera with oil-coupled multiplets producing a scale of 0.20 arcsec/pixel. The detector for both foci is an 8K x 8K mosaic camera of 8 SITe 2K x 4K 15 μ CCDs. The collimator and f/4 camera have performed to design specifications and have delivered 0.45 arcsec images across the 15 arcmin square field. The f/2 camera has delivered images of 0.55 to 0.65 arcsec across its 27 arcmin diameter field in excellent seeing (FWHM ~ 0.40 arcsec). The f/4 camera uses 6-inch reflecting gratings to obtain spectroscopy at multiple resolutions ranging from R=1350-9375; the f/2 camera uses three 6-inch grisms to achieve resolutions of R=450, 600, and 900 over its larger field. We routinely cut hundreds of slits in 30-inch diameter, stainless steel, spherical-shell slitmasks with a commercial laser system. Alignment procedures for observing are simple and efficient, typically requiring 5-10 minutes per set-up. IMACS - an unusually versatile instrument - includes an IFU built by Durham University with two 5" x 8" (f/2) or 4" x 7" (f/4) apertures, each sampled by 1000 optical fibers. A Multi-Object Echelle mode, which can obtain 10-15 full wavelength R=20000 spectra, has been fully tested and has now started regular operation. The Maryland-Magellan Tunable Filter (MMTF) has been lab tested and will be commissioned in June 2006. In early 2007, Gladder's Image-Slicing Multislit Option (GISMO) will be ready for testing, and a second Mosaic CCD camera - which will simplify operations, increase sensitivity, and allow rapid access to both f/2 and f/4 modes - is under construction. We report on the design challenges posed and met by the variety of operating modes and stringent performance requirements. We describe some issues encountered in the past two years in bringing such a complex, multi-mode instrument to the Magellan Observatory.
Performance of AAOmega: the AAT multi-purpose fiber-fed spectrograph
AAOmega is the new spectrograph for the 2dF fibre-positioning system on the Anglo-Australian Telescope. It is a bench-mounted, double-beamed design, using volume phase holographic (VPH) gratings and articulating cameras. It is fed by 392 fibres from either of the two 2dF field plates, or by the 512 fibre SPIRAL integral field unit (IFU) at Cassegrain focus. Wavelength coverage is 370 to 950nm and spectral resolution 1,000-8,000 in multi-Object mode, or 1,500-10,000 in IFU mode. Multi-object mode was commissioned in January 2006 and the IFU system will be commissioned in June 2006. The spectrograph is located off the telescope in a thermally isolated room and the 2dF fibres have been replaced by new 38m broadband fibres. Despite the increased fibre length, we have achieved a large increase in throughput by use of VPH gratings, more efficient coatings and new detectors - amounting to a factor of at least 2 in the red. The number of spectral resolution elements and the maximum resolution are both more than doubled, and the stability is an order of magnitude better. The spectrograph comprises: an f/3.15 Schmidt collimator, incorporating a dichroic beam-splitter; interchangeable VPH gratings; and articulating red and blue f/1.3 Schmidt cameras. Pupil size is 190mm, determined by the competing demands of cost, obstruction losses, and maximum resolution. A full suite of VPH gratings has been provided to cover resolutions 1,000 to 7,500, and up to 10,000 at particular wavelengths.
Performance of the PMAS 3D spectrophotometer
Unlike some integral field units (IFUs) in front of conventional slit spectrographs, PMAS is a dedicated fiber-optical integral field spectrograph, featuring two different types of IFUs to address both high spatial resolution and wide field-of-view (FoV) in a single instrument. The instrument was designed, built, and tested completely in-house at the Astrophysical Institute Potsdam from 1996 to 2000. It was commissioned at the Calar Alto 3.5m Telescope in May 2001. PMAS employs an all-refractive fiber spectrograph, built with CaF2 optics, to provide good transmission and high image quality over the entire nominal wavelength range. A set of user-selectable reflective gratings provides low to medium spectral resolution in first order of approx. 1.5, 3.2, and 7 Å, depending on the groove density (1200, 600, 300 gr/mm). The standard IFU uses a 16×16 element lens array, which provides seeing-limited sampling in a relatively small field-of-view (FOV) in one of three magnifications (8×8, 12×12, or 16×16 arcsec2, respectively). The additional fiber bundle IFU (PPak) expands the FOV to a hexagonal area with a footprint of 65×74 arcsec2.
The multi-object double spectrographs for the Large Binocular Telescope
R. W. Pogge, B. Atwood, S. R. Belville, et al.
Ohio State is building two identical Multi-Object Double Spectrographs (MODS), one for each of the f/15 Gregorian foci of the Large Binocular Telescope (LBT). Each MODS is a high-throughput optical low- to medium-resolution CCD spectrometer operating in the 320-1000nm range with a 6.5-arcminute field-of-view. A dichroic distributes the science beam into separately-optimized red and blue channels that provide for direct imaging and up to 3 spectroscopic modes per channel. The identical MODS instruments may be operated together with digital data combination as a single instrument giving the LBT an effective aperture of 11.8-meter, or separately configured to flexibly use the twin 8.4-meter apertures. This paper describes progress on the integration and testing of MODS1, and plans for the deployment of MODS2 by the end of 2008 at the LBT.
Probing unexplored territories with MUSE: a second generation instrument for the VLT
R. Bacon, S. Bauer, P. Boehm, et al.
The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph under preliminary design study. MUSE has a field of 1x1 arcmin2 sampled at 0.2x0.2 arcsec2 and is assisted by the VLT ground layer adaptive optics ESO facility using four laser guide stars. The simultaneous spectral range is 0.465-0.93 μm, at a resolution of R~3000. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. This makes MUSE a unique and tremendously powerful instrument for discovering and characterizing objects that lie beyond the reach of even the deepest imaging surveys. MUSE has also a high spatial resolution mode with 7.5x7.5 arcsec2 field of view sampled at 25 milli-arcsec. In this mode MUSE should be able to obtain diffraction limited data-cubes in the 0.6-0.93 μm wavelength range. Although the MUSE design has been optimized for the study of galaxy formation and evolution, it has a wide range of possible applications; e.g. monitoring of outer planets atmosphere, environment of young stellar objects, super massive black holes and active nuclei in nearby galaxies or massive spectroscopic surveys of stellar fields in the Milky Way and nearby galaxies.
VisIRIS: a visible/IR imaging spectropolarimeter based on a birefringent fiber-optic image slicer
HaoSheng Lin, Alex Versteegh
High-resolution imaging spectropolarimetry in the visible and infrared wavelengths is the most effective and accurate observational diagnostic tool for many astrophysical problems, but many among them also require a spatially resolved two-dimensional field of view. However, it is difficult to achieve simultaneous three-dimensional (x, y, and λ) coverage using instruments with a conventional design. A conventional spectrograph achieves three-dimensional coverage either by scanning a tunable filter through the spectral window of interest, or by scanning a diffraction-grating-based long-slit spectrograph through the target region. Scanning in either spectral or spatial direction unavoidably degrades the quality of the data, and is time consuming. This paper describes a new visible/IR imaging spectropolarimeter design based on a novel birefringent fiber-optic image slicer and multiple-slit spectrograph. With this design, simultaneous 3-D imaging spectropolarimetry of astronomical objects with a large field of view and high spatial and spectral resolution can be achieved.
Getting ELMER ready for science: laboratory tests
Elmer is an imager and spectrograph in the visible range that has been designed and managed within the GTC Project Office. Elmer will be installed at the telescope at the beginning of the commissioning phase. The observing modes of the instrument are: Imaging, Long Slit, Mask and Slit-less multi-object Spectroscopy, Fast Photometry and Fast short-slit Spectroscopy. The pupil elements are a set of conventional broad band and narrow band filters as well as a set of prisms, grisms and VPHs, that allow spectroscopy with resolving powers of 200, 1000 and 2500 between 365 and 1000nm. Elmer has been exhaustively tested and each of its observing modes has been fully characterized at the laboratory. This contribution summarizes the results of this Test Plan, showing the excellent performance of Elmer in both, Imaging and Spectroscopy modes that, together with the GTC, will lead to a powerful scientific return.
A multipurpose fiber-fed VPHG spectrograph for LAMOST
A multipurpose fiber-fed double-beam Schmidt spectrograph using VPHG (volume phase holographic gratings) is under construction for LAMOST (The Large Sky Area Multi-Object Fiber Spectroscopic Telescope). There are 16 such spectrographs (hereafter referred to as LRSs) for the project. The spectrographs are designed with wavelength coverage from 370 to 900 nm, with spectral resolutions of 1000-10000, and with multi-object capability over a 5 degrees field of view. Each spectrograph will be accommodating 250 fibers of 320 microns diameter (corresponding 3.3 arcsecs). The 200 mm diameter collimated beam is split into two separate channels. The blue channel is optimized for 370nm-590nm, and the red channel for 570nm-900nm. The LRS can work in several varied resolution modes. The optical design and performance is described. The spectrograph is of simple design with moderate image quality and good throughput. Progress on the construction of LRS is reported as well.
Instruments without optics: an integrated photonic spectrograph
In recent years, a great deal of emphasis has been placed on achieving the diffraction limit with large aperture telescopes. For a well matched focal-plane instrument, the diffraction limit provides the highest possible angular resolution and sensitivity per pixel. But it offers another key advantage as we now show. Conventionally, as the telescope aperture D grows, the instrument size grows in proportion to D, and the cost increases as D2 or faster. However, an instrument that operates at the diffraction limit can break the trend of spiralling costs. In traditional instruments, the light must pass through a succession of large lenses, mirrors and gratings, making it difficult to conserve the integrity of such a small psf. An alternative approach, as we now show, is to couple the diffraction-limited beam directly into an integrated photonic spectrograph operating in low-order modes.
Accurate time-resolved optical photospectroscopy with superconducting tunnel junction arrays
D. D. E. Martin, P. Verhoeve, T. Oosterbroek, et al.
Superconducting Tunnel Junctions (STJs) have been extensively investigated as photon detectors covering the range from near-infrared to X-ray energies. A 10×12 array of Tantalum/Aluminium junctions has been integrated into the S-Cam3 camera for ground based astronomy. With this camera, the European Space Agency has performed multiple astronomical observations of optical sources using the William Herschel 4.2m telescope at La Palma and the Agency's 1-m Optical Ground Station telescope at Tenerife. Compared to its predecessor, this new instrument features a 10"×12" field-of-view, an optimized IR rejection reducing baseline noise and increasing optical light throughput and ultra-stable operations. In this paper, we review the instrument's architecture and describe the system's performance and in particular the energy resolution and count-rate capabilities of the detector arrays. Finally, we shall present first astronomical images taken during the Optical Ground Station's 2005 and 2006 campaigns which demonstrate the system's timing, photometric and spectroscopic capabilities.
The exoplanet hunter HARPS: unequalled accuracy and perspectives toward 1 cm s-1 precision
We present results from the first two years of operations of the HARPS spectrograph installed on the ESO 3.6m telescope at La Silla Observatory, Chile. This instrument, primarily built to detect extrasolar planetary systems, was designed to achieve the highest radial velocity precision ever, thanks to high mechanical and environmental stability, stable illumination, accurate wavelength calibration and tracking of instrumental drifts. HARPS has demonstrated a long-term accuracy at the 1 m s-1 level and below, exploring a new regime in RV precision. We present recent improvements in the wavelength calibration process, including the creation of a new ThAr reference atlas and the use of a much larger number of lines to fit the wavelength solution. We have also investigated the intrinsic stability of ThAr calibration lamps and show that they are able to provide a long-term wavelength reference at or below the 1 m s-1 level. Other instrumental error sources such as guiding accuracy and photon noise are discussed and a global error budget is presented. These efforts to further improve the RV precision are also part of a broader study to build a ultra-high accuracy spectrovelocimeter for the ESO OWL telescope, the CODEX project. The aim of this instrument is to reach an accuracy of 1 cm s-1 over timescales of at least ten years. This requires to push down the limits of present-day calibration techniques and to explore new technologies able to provide ultra-precise Doppler measurements.
SPHERE: A planet finder instrument for the VLT
The Planet Finder instrument for ESO's VLT telescope, scheduled for first light in 2010, aims to detect giant extra-solar planets in the vicinity of bright stars and to characterise the objects found through spectroscopic and polarimetric observations. The observations will be done both within the Y, J, H and Ks atmospheric windows (~0.95 - 2.32μm) by the aid of a dual imaging camera (IRDIS) and an integral field spectrograph (IFS), and in the visible using a fast-modulation polarization camera (ZIMPOL). The instrument employs an extreme-AO turbulence compensation system, focal plane tip-tilt correction, and interferential coronagraphs. We describe briefly the science goals of the instrument and deduce the top-level requirements. The system architecture is presented, including brief descriptions of each of the main sub-systems. Expected performance is described in terms of end-to-end simulations, and a semi-analytic performance-estimation tool for system-level sensitivity analysis is presented.
Infrared Imaging
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Detecting the polarization signatures of extra-solar planets
J. H. Hough, P. W. Lucas, J. A. Bailey, et al.
Direct detection of the light scattered from extra-solar planets is important in establishing the planet's mass, radius, albedo and nature of the particles in the planetary atmosphere. We describe, and present results from, a new optical polarimeter (PlanetPol) designed to reach fractional polarizations of 10-6 or better from ground-based telescopes, necessary to detect the polarization signature of unresolved hot-Jupiters.
Design of a polarimeter for extrasolar planetary systems characterization
Unpolarized light from the central star that is reflected by exoplanets, protoplanetary disks, and debris disks becomes partially polarized by the reflection process. Imaging polarimetry is therefore the ideal way to discriminate between the polarized light from circumstellar environments and the unpolarized light from the nearby central star. A sensitivity of 10-5 (fraction of polarized intensity to the total intensity) must be achieved to detect exoplanets; 10-4 is sufficient for disks. Based on extensive experience in precision polarimetry of the Sun, the newly formed experimental astrophysics group at Utrecht University, The Netherlands, will design, build, and use a high-precision imaging polarimeter for use at the 4.2-meter William Herschel Telescope. Since systematic errors typically limit conventional imaging polarimeters to about 10-3, laboratory setups and theoretical models will be used to understand and then minimize and/or calibrate systematic errors. Published catalogues of exoplanets and stars that harbor disks will guide extensive observations with this new polarimeter. The effort will focus on retrieving fundamental properties of circumstellar environments that cannot be obtained with other observational approaches.
Clio: a 3-5 micron AO planet-finding camera
Clio is an adaptive-optics camera mounted on the 6.5 meter MMT optimized for diffraction-limited L' and M-band imaging over a ~ 15" field. The instrument was designed from the ground up with a large well-depth, fast readout thermal infrared (~ 3_5μm) 320 by 256 pixel InSb detector, cooled optics, and associated focal plane and pupil masks (with the option for a coronograph) to minimize the thermal background and maximize throughput. When coupled with the MMT's adaptive secondary AO (two warm reflections) system's low thermal background, this instrument is in a unique position to image nearby warm planets, which are the brightest in the L' and M-band atmospheric windows. We present the current status of this recently commissioned instrument that performed exceptionally during first light. Our instrument sensitivities are impressive and are sky background limited: for an hour of integration, we obtain an L'-band 5 σ detection limit of of 17.0 magnitudes ~ 80%) and an M-band limit of 14.5 (Strehl ~ 90%). Our M-band sensitivity is lower due to the increase in thermal sky background. These sensitivities translate to finding relatively young planets five times Jupiter mass (MJup) at 10 pc within a few AU of a star. Presently, a large Clio survey of nearby stellar systems is underway including a search for planets around solar-type stars, M dwarfs, and white dwarfs. Even with a null result, we can place strong constraints on planet distribution models.
Concept and science of HiCIAO: high contrast instrument for the Subaru next generation adaptive optics
Motohide Tamura, Klaus Hodapp, Hideki Takami, et al.
Direct exploration of exoplanets is one of the most exciting topics in astronomy. Our current efforts in this field are concentrated on the Subaru 8.2m telescope at Mauna Kea, Hawaii. Making use of the good observing site and the excellent image quality, the infrared coronagraph CIAO (Coronagraphic Imager with Adaptive Optics) has been used for various kinds of surveys, which is the first dedicated cold coronagraph on the 8-10m class telescopes. However, its contrast is limited by the low-order adaptive optics and a limited suppression of the halo speckle noise. HiCIAO is a new high-contrast instrument for the Subaru telescope. HiCIAO will be used in conjunction with the new adaptive optics system (188 actuators and/or its laser guide star - AO188/LGSAO188) at the Subaru infrared Nasmyth platform. It is designed as a flexible camera comprising several modules that can be configured into different modes of operation. The main modules are the AO module with its future extreme AO capability, the warm coronagraph module, and the cold infrared camera module. HiCIAO can combine coronagraphic techniques with either polarization or spectral simultaneous differential imaging modes. The basic concept of such differential imaging is to split up the image into two or more images, and then use either different planes of polarization or different spectral filter band-passes to produce a signal that distinguishes faint objects near a bright central object from scattered halo or residual speckles. In this contribution, we will outline the HiCIAO instrument, its science, and performance simulations. The optical and mechanical details are described by Hodapp et al. (2006)1. We also present a roadmap of Japanese facilities and future plans, including ASTRO-F (AKARI), SPICA, and JTPF, for extrasolar planet explorations.
HAWK-I: the new wide-field IR imager for the VLT
HAWK-I is a new wide-field infrared camera under development at ESO. With four Hawaii-2RG detectors, a 7.5 arcminute square field of view and 0.1 arcsecond pixels, it will be an optimum imager for the VLT, and a major enhancement to existing and future infrared capabilities at ESO. HAWK-I will eventually make use of ground-layer AO achieved through a deformable secondary mirror/laser guide star facility planned for the VLT.
The VISTA infrared camera
G. B. Dalton, M. Caldwell, A. K. Ward, et al.
We describe the integration and test phase of the construction of the VISTA Infrared Camera, a 64 Megapixel, 1.65 degree field of view 0.9-2.4 micron camera which will soon be operating at the cassegrain focus of the 4m VISTA telescope. The camera incorporates sixteen IR detectors and six CCD detectors which are used to provide autoguiding and wavefront sensing information to the VISTA telescope control system.
The UKIRT wide-field camera (WFCAM): commissioning and performance on the telescope
The UKIRT Wide-Field Camera (WFCAM) was commissioned in two phases between October and December 2004, and March and April 2005. It has been carrying out full-scale sky survey operations since May 2005. This paper describes the commissioning process and compares actual performance on the telescope with specifications in four key areas: optical image quality including delivered FWHM and ghosting etc., noise and sensitivity in the infrared and on the visible autoguider, array artifacts such as crosstalk and persistent images, and observing efficiency. A comprehensive program of science verification was carried out before commencing the UKIRT Infrared Deep Sky Survey (UKIDSS).
CFHT-WIRCam: interlaced science and guiding readout with the Hawaii-2RG IR sensor
Marc R. Baril, Jeff Ward, Douglas Teeple, et al.
CFHTs experience with interlacing science and guide pixel readout using the Hawaii-2RG infrared sensors on WIRCam has been problematic due to timing limitations inherent to this approach as well as unexpected behaviour in the sensors themselves. These problems have been overcome by implementing high-speed readout (1.4 s per read) for WIRCam's array of four Hawaii-2RG sensors, obviating the need for interlaced readout. The effect of the reset anomaly on the science and guide frames has been minimized by introducing suitable delays and a clocking scheme that does not significantly impact the minimum exposure time of the camera.
MegaMIR: a Fizeau thermal infrared camera for the LBTI
A. K. Mainzer, Erick Young, John Hong, et al.
The Megapixel Mid-infrared Instrument (MegaMIR) is a proposed Fizeau-mode camera for the Large Binocular Telescope operating at wavelengths between 5 and 28 μm. The camera will be used in conjunction with the Large Binocular Telescope Interferometer (LBTI), a cryogenic optical system that combines the beams from twin 8.4-m telescopes in a phase coherent manner. Unlike other interferometric systems, the co-mounted telescopes on the LBT satisfy the sine condition, providing diffraction-limited resolution over the 40" field of view of the camera. With a 22.8-m baseline, MegaMIR will yield 0.1" angular resolution, making it the highest resolution wide field imager in the thermal infrared for at least the next decade. MegaMIR will utilize a newly developed 1024 x 1024 pixel Si:As detector array that has been optimized for use at high backgrounds. This new detector is a derivative of the Wide-field Infrared Survey Explorer (WISE) low-background detector. The combination of high angular resolution and wide field imaging will be a unique scientific capability for astronomy. Key benefits will be realized in planetary science, galactic, and extra-galactic astronomy. High angular resolution is essential to disentangle highly complex sources, particularly in star formation regions and external galaxies, and MegaMIR provides this performance over a full field of view. Because of the great impact being made by space observatories like the Spitzer Space Telescope, the number of available targets for study has greatly increased in recent years, and MegaMIR will allow efficient follow up science.
FORCAST: the facility mid-IR camera for SOFIA
We report on new development and testing of FORCAST, the Faint Object infraRed Camera for the SOFIA Telescope. FORCAST will offer dual channel imaging in discrete filters at 5 - 25 microns and 30 - 40 microns, with diffraction-limited imaging at wavelengths > 15 microns. FORCAST will have a plate scale of 0.75 arcsec per pixel, giving it a 3.2 arcmin x 3.2 arcmin FOV on SOFIA. In addition, a set of grisms will enable FORCAST to perform long slit and cross-dispersed spectroscopic observations at low to moderate resolution (R ~ 140 - 1200) in the bandpasses 4.9 - 8.1 microns, 8.0 - 13.3 microns, 17.1 - 28.1 microns, and 28.6 - 37.4 microns. FORCAST has seen first light at the Palomar 200 inch telescope. It will be available for astronomical observations and facility testing at SOFIA first flight.
Infrared Spectroscopy I
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VISIR two years after its installation at the VLT
VISIR is the mid-infrared instrument installed in 2004 at the Cassegrain focus of MELIPAL, one of the four 8-meter telescopes of the European Very Large Telescope program. This cryogenic instrument, optimized for diffraction-limited performances in both mid-infrared atmospheric windows (N and Q bands), combines imaging capabilities and long-slit grating spectroscopy with spectral resolutions up to R=25000 at 10 μm and 12500 at 20 μm. The contract to design and build VISIR was signed in November 1996 between the European Southern Observatory (ESO) and a French-Dutch consortium of institutes led by Service d'Astrophysique of Commissariat a l'Energie Atomique (CEA). After extensive tests in the laboratory, VISIR was shipped to Paranal in March 2004. After successful commissioning between May and August 2004 and science verification between September 2004 and January 2005, routine science operations started in April 2005. The status of VISIR after 2 years of operation at the telescope is reviewed. This complex instrument, which features 14 cryogenic actuators to set the various observing possibilities, has been working without technical failure. The on-sky sensitivities are close to expectations. The median seeing conditions at Paranal (about 0.8-0.9 arcsec in the visible) are an issue to get routinely diffraction-limited images. Simple tip tilt adaptative corrections would be needed. For bright enough sources (a few Jansky), the so-called "burst mode", which allows to store up to 1500 individual frames (10-50 ms each) can be used to retrieve, off-line, diffraction-limited angular resolution (0.3 arcsec at 10 microns).
Performance of the Gemini near-infrared spectrograph
Jonathan H. Elias, Bernadette Rodgers, Richard R. Joyce, et al.
The Gemini Near-Infrared Spectrograph (GNIRS) has been in successful use on the Gemini South 8-m telescope for over two years. We describe the performance of the instrument and discuss how it matches the expectations from the design. We also examine the lessons to be learned regarding the design and operation of similar large cryogenic facility instruments.
Commissioning of the IRMOS MEMS spectrometer
The Infrared Multi-Object Spectrometer employs a novel approach to slit definition by using a rapidly configured array of 848 x 600 MEMS mirrors. Developed by a collaboration between STScI, NASA/GSFC, and KPNO, IRMOS provides low to medium resolution spectroscopy of several tens of simultaneous targets in the Z, J, H, and K bands. IRMOS is presently undergoing commissioning to become a facility instrument at Kitt Peak National Observatory in 2006. We report on the success of this concept, the performance of the Texas Instruments DMD array of MEMS mirrors in this application, and our ongoing software development. Examples of observations using both a "Point and Click" approach to slit positioning and the synthesis of full aperture integral field spectroscopy using Hadamard slit mask patterns are presented.
MOIRCS: multi-object infrared camera and spectrograph for SUBARU
MOIRCS is a new Cassegrain instrument of Subaru telescope, dedicated for wide field imaging and multi-object spectroscopy in near-infrared. MOIRCS has been constructed jointly by Tohoku University and the Subaru Telescope and saw the first light in Sept., 2004. The commissioning observations to study both imaging and spectroscopic performance were conducted for about one year. MOIRCS mounts two 2048 × 2048 HAWAII2 arrays and provides a field of view of 4' x 7' with a pixel scale of 0."117. All-lens optical design is optimized for 0.8 to 2.5 μm with no practical chromatic aberration. Observations confirm the high image quality over the field of view without any perceptible degradation even at the field edge. The best seeing we have obtained so far is FWHM=0."18. A novel design of MOIRCS enables us to perform multi-object spectroscopy with aluminum slit masks, which are housed in a carrousel dewar and cooled to ~ 110 K. When choosing MOS mode, a manipulator pulls out a slit mask from the carrousel into the MOIRCS main dewar and sets it properly at the Cassegrain focus. The carrousel is shuttered by a gate valve, so that it can be warmed and cooled independently to exchange slit-mask sets during daytime. We have tested various configurations of 30 or more multi-slit positions in various sky fields and found that targets are dropped at the centers of slits or guide holes within a dispersion of about 0.3 pixels (0."03). MOIRCS has been open to common use specifically for imaging observations since Feb. 2006. The MOS function will be available in next August.
FLAMINGOS-2: the facility near-infrared wide-field imager and multi-object spectrograph for Gemini
Stephen Eikenberry, Richard Elston, S. Nicholas Raines, et al.
We report on the design and status of the FLAMINGOS-2 instrument - a fully-cryogenic facility near-infrared imager and multi-object spectrograph for the Gemini 8-meter telescopes. FLAMINGOS-2 has a refractive all-spherical optical system providing 0.18-arcsecond pixels and a 6.2-arcminute circular field-of-view on a 2048×2048-pixel HAWAII-2 0.9-2.4 μm detector array. A slit/decker wheel mechanism allows the selection of up to 9 multi-object laser-machined plates or 3 long slits for spectroscopy over a 6×2-arcminute field of view, and selectable grisms provide resolutions from ~1300 to ~3000 over the entire spectrograph bandpass. FLAMINGOS-2 is also compatible with the Gemini Multi- Conjugate Adaptive Optics system, providing multi-object spectroscopic capabilities over a 3×1-arcminute field with high spatial resolution (0.09-arcsec/pixel). We review the designs of optical, mechanical, electronics, software, and On- Instrument WaveFront Sensor subsystems. We also present the current status of the project, currently in final testing in mid-2006.
EMIR: the GTC NIR multi-object imager-spectrograph
F. Garzón, D. Abreu, S. Barrera, et al.
EMIR, currently entering into its fabrication and AIV phase, will be one of the first common user instruments for the GTC, the 10 meter telescope under construction by GRANTECAN at the Roque de los Muchachos Observatory (Canary Islands, Spain). EMIR is being built by a Consortium of Spanish and French institutes led by the Instituto de Astrofisica de Canarias (IAC). EMIR is designed to realize one of the central goals of 10m class telescopes, allowing observers to obtain spectra for large numbers of faint sources in an time-efficient manner. EMIR is primarily designed to be operated as a MOS in the K band, but offers a wide range of observing modes, including imaging and spectroscopy, both long slit and multiobject, in the wavelength range 0.9 to 2.5 μm. It is equipped with two innovative subsystems: a robotic reconfigurable multislit mask and disperssive elements formed by the combination of high quality diffraction grating and conventional prisms, both at the heart of the instrument. The present status of development, expected performances, schedule and plans for scientific exploitation are described and discussed. The development and fabrication of EMIR is funded by GRANTECAN and the Plan Nacional de Astronomia y Astrofisica (National Plan for Astronomy and Astrophysics, Spain).
The GIANO-TNG spectrometer
E. Oliva, L. Origlia, C. Baffa, et al.
GIANO is an infrared (0.9-2.5 μm cross-dispersed echelle spectrometer designed to achieve high resolution, high throughput, wide band coverage and very high stability for accurate radial velocity measurements. It also includes polarimetric capabilities and a low resolution mode with RS ~ 400 and complete 0.75-2.5 μm coverage. This makes it a very versatile, common user instrument which will be permanently mounted and available on the Nasmyth-B foci of the Telescopio Nazionale Galileo (TNG) located at Roque de Los Muchachos Observatory (ORM), La Palma, Spain. The project is fast-track and relies on well known, relatively standard technologies. It has been recognized as one of the top priority instrumental projects of INAF (the Italian National Institute of Astronomy) and received its first financing for the phase-A study in October 2003. Integration in the laboratory is planned to start before the end of 2006, commissioning at the telescope is foreseen within 2007 and scientific operations in 2008. One of the most important scientific goals is the search for rocky planets with habitable conditions around low-mass stars. If completed on time, GIANO will be the first and only IR instrument operating worldwide providing the combination of efficiency, spectral resolution, wavelength coverage and stability necessary for this type of research. With its unique combination of high and low resolution modes, GIANO will also be a very flexible common-user instrument ideal e.g. for quantitative spectroscopy of brown dwarfs, stars and stellar clusters as well as for the determination of the spectral energy distribution of faint/red objects such as high redshift galaxies. The expected limiting magnitudes are such that GIANO will be able to deliver good quality HR spectra of any 2MASS object and LR spectra of any object detected in the UKIDSS large area survey.
OSIRIS: a diffraction limited integral field spectrograph for Keck
We present an overview of the OSIRIS integral field spectrograph which was recently commissioned on the Keck II Telescope. OSIRIS works with the Keck Adaptive Optics system and utilizes an infrared transmissive lenslet array to sample a rectangular field of view at close to the Keck diffraction limit. By packing the spectra close together (2 pixel rows per spectrum) and using the Rockwell Hawaii-2 detector (wavelengths between 1 and 2.5 microns), we achieve a relatively large field of view (up to 6."4) while maintaining full broad-band spectral coverage at a resolution of 3800. Among the challenges of the instrument are: a fully cryogenic design (approximately 250 kg are brought down to 55K); four spatial scales from 0."02 to 0."10; extremely low wavefront error (approximately 25 nm of non-common path error); large all aluminum optics for the spectrograph; extremely repeatable spectral formats; and a sophisticated data reduction pipeline. OSIRIS also serves as a starting point for our design of IRIS which is a planned integral field spectrograph for the Thirty Meter Telescope.
FMOS: the fiber multiple-object spectrograph IV: current status of OHS-based spectrograph
Fumihide Iwamuro, Toshinori Maihara, Kouji Ohta, et al.
The Fiber Multiple-Object Spectrograph for Subaru Telescope (FMOS) is quite large instrument composed of the prime focus unit, the fiber bundle unit, and the two infrared spectrographs. Among these units, a part of the prime focus unit and one of the spectrograph were transported from Kyoto University to the Subaru Observatory in the middle of 2005. We present the optical and the mechanical components of the spectrograph, which was reassembled on the new floor of the Subaru dome. We also show the preliminary results of the optical alignment and the cooling test of the instrument at the summit of Mauna Kea.
Design of the KMOS multi-object integral-field spectrograph
Ray Sharples, Ralf Bender, Richard Bennett, et al.
KMOS is a near-infrared multi-object integral field spectrometer which has been selected as one of a suite of second-generation instruments to be constructed for the ESO VLT in Chile. The instrument will be built by a consortium of UK and German institutes working in partnership with ESO and is currently at the end of its preliminary design phase. We present the design status of KMOS and discuss the most novel technical aspects and the compliance with the technical specification.
The first high resolution silicon immersion grating spectrograph
Jian Ge, Daniel McDavitt, Bo Zhao, et al.
We report the development of the first high resolution cross-dispersed silicon immersion grating spectrometer. This instrument is called the Florida IR Silicon immersion grating specTrometer (FIRST). FIRST can produce R = 50,000 under a 0.6 arcsec seeing and simultaneously cover 1.3-1.8 μm with a 1kx1k HgCdTe array at the Apache Point Observatory 3.5 meter telescope. FIRST has a 50 mm diameter collimated beam and the overall instrument is within a volume of 0.8x0.5x0.5 m3. The high dispersion, large wavelength coverage and small instrument volume become possible due to the use of a silicon immersion grating (54.7 deg blaze angle and 50 mm diameter entrance pupil) with extremely high dispersion power (3.4 times dispersion power of a conventional echelle) and coarse grooves (16.1 l/mm, coarser than the commercially available echelles). The silicon immersion grating used in a lab bench mounted Czeney-Turner spectrograph with an only 25 mm diameter collimated beam and a 100 um core fiber has produced R = 55,000 cross-dispersed solar spectra. This instrument is designed to precisely measure radial velocities of low mass stars, M dwarfs for detecting 5-10 Earth mass planets. The estimated Doppler precision is ~ 3 m/s for a J = 9 M5V dwarf in 15 min at the APO 3.5m telescope.
The TEDI instrument for near-IR radial velocity surveys
The TEDI (TripleSpec Externally Dispersed Interferometry) is an interferometric spectrometer that will be used to explore the population of planets around the lowest mass stars. The instrument, to be deployed on the Palomar 200 Cassegrain mount, includes a stabilized Michelson interferometer combined with a medium resolution, broad band (0.8 - 2.4 micron) spectrograph, TripleSpec. We describe the instrument design and its application to Doppler velocimetry and high-resolution spectroscopy.
Infrared Spectroscopy II
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FIFI LS: the far-infrared integral field spectrometer for SOFIA
FIFI LS is a far-infrared integral field spectrometer for the SOFIA airborne observatory. The instrument is designed to maximize the observing efficiency by simultaneous and nearly independent imaging of the field-of-view in two medium spectral resolution bands. We present a summary of the FIFI LS design and the current status of instrument development. Its unique features as the large far-infrared photoconductor detectors, its integral field concept, and control system will be highlighted. Special attention will be given to the Extended Observing Opportunity Program, which will allow general access to FIFI LS on SOFIA.
Characterizing the system performance of FIFI LS: the field-imaging far-infrared line spectrometer for SOFIA
FIFI LS is a Field-Imaging Line Spectrometer designed for the SOFIA airborne observatory. The instrument will operate in the far infrared wavelength range between 42 to 210 microns. Two spectrometer bands from 42 - 110 microns ('blue' channel) and 110 - 210 microns ('red' channel) allow simultaneous and independent diffraction limited 3D imaging over a field of view of 6 x 6 and 12 x 12 arcseconds respectively. Both spectrometer channels use Littrow mounted diffraction gratings, a set of anamorphic collimators, and a reflective integral field unit. Two large scale 25 x 16 pixel Ge:Ga detector arrays are utilized, axially stressed in the red channel and only slightly stressed in the blue channel. The spectral resolution of the instrument varies between R = 1400 to 6500 depending on wavelength. The sensitivity of the instrument will allow background limited performance over the entire wavelength range. We present test results for the components in the optical path of FIFI LS including grating efficiencies, filter characteristics, detector performance, and optical throughput. Based on our measurements we characterized and optimized the overall system performance to maximize observing efficiency - one of the major instrument design criteria.
Development and future use of the echelon-cross-echelle spectrograph on SOFIA
The Echelon-cross-Echelle Spectrograph (EXES) will provide the Stratospheric Observatory for Infrared Astronomy (SOFIA) with high spectral resolution capabilities in the mid-infrared. EXES will have a maximum spectral resolving power of 100,000 along with lower resolution options (R=10,000; R=3000). EXES on SOFIA will provide sensitivity and spectral resolution never before available from an orbital or sub-orbital platform. Because of the wealth of molecular features in the EXES spectral range, 4.5 to 28.3 μm, and the dramatic reduction in telluric atmospheric interfence provided by SOFIA, EXES will be particularly relevant for studies of the solar system, star formation and the interstellar medium. We report on the EXES design and current status, provide descriptions of observing modes and sensitivity estimates, discuss the calibration and likely data products, and describe the potential gains of incorporating a 1024 × 1024, low-background, Si:As detector array.
Grism spectroscopy with FLITECAM
FLITECAM, a near-infrared instrument being developed at the UCLA Infrared lab, will be the first light infrared instrument for NASA's SOFIA aircraft. In addition to its imaging capability, FLITECAM has been equipped with three direct-ruled KRS-5 grisms, allowing observations in 9 spectral bands, and giving nearly continuous spectral coverage from 1 to 5.5 microns. The design favors regions of the spectrum that are heavily attenuated except at high altitudes. The grisms are used with a dual-width long slit to yield a spectral resolution of R~1700 at high resolution and R~900 at low resolution. This resolution is better than that of the IRAS, ISO or KAO spectrometers, and covers a spectral regime left unsampled by the Spitzer Space Telescope. When used on the SOFIA, FLITECAM's spectroscopic mode will allow astronomical investigation of near-infrared features at a low water vapor overburden. The grism spectroscopic mode has been demonstrated on the Shane 120 inch telescope at Lick Observatory by observations of astronomical targets of interest, especially the PAH feature at 3.3 microns in HII regions and young planetary nebulae.
New Methods
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An image motion compensation system for the multi-object double spectrograph
We discuss the performance of the Image Motion Compensation System (IMCS) for the Multi-Object Double Spectrograph (MODS). The system performs closed-loop image motion compensation, actively correcting for image motion in the spectrograph's focal plane caused by large scale structural bending due to gravity as well as other effects such as temperature fluctuation and mechanism flexure within the instrument. Not only does the system control instrumental flexure to within the specifications (0.1 pixels on the science CCD, or 1.5 μm), but it also has proven to be an excellent diagnostic tool for assembling and testing the spectrograph. We describe both the final performance of the system as deployed in the spectrograph as well as the instrumental tests made possible by the IMCS.
Coupling light into optical fibres near the diffraction limit
The burgeoning field of astrophotonics explores the interface between astronomy and photonics. Important applications include photonic OH suppression at near-infrared wavelengths, and integrated photonic spectroscopy. These new photonic mechanisms are not well matched to conventional multi-mode fibre bundles, and are best fed with single or few-mode fibres. We envisage the largest gains in astrophotonics will come from instruments that operate with single or few mode fibres in the diffraction limited or near diffraction limited regime. While astronomical instruments have largely solved the problem of coupling light into multi-mode fibres, this is largely unexplored territory for few-mode and single-mode fibres. Here we describe a project to explore this topic in detail, and present initial results on coupling light into single and few-mode fibres at the diffraction limit. We find that fibres with as few as ~ 5 guided modes have qualitatively different behaviour to single-mode fibres and share a number of the beneficial characteristics of multi-mode fibres.
Advances in diamond-turned surfaces enable unique cost-effective optical system solutions
Corning has developed a number of manufacturing and test techniques to meet the challenging requirements of imaging hyperspectral optical systems. These processes have been developed for applications in the short-wave visible through long-wave IR wavelengths. Optical designs for these imaging systems are typically Offner or Dyson configurations, where the critical optical components are powered gratings and slits. Precision alignment, system athermalization, and harsh environmental requirements, for these systems drive system level performance and production viability. This paper will present the results of these techniques including all aluminum gratings and slits, innovative grating profiles, snap together self-aligning mechanical designs, and visible test techniques for IR systems.
POSM: a new concept for fiber positioning
Anna Moore, Rich Dekany, Damien Jones, et al.
The Gemini/Subaru WFMOS project has given the stimulus for considering new concepts for massively multiplexed fiber positioning schemes. The problem of acquiring many thousands of objects within a ~1.5° field at Subaru's ~f/2 prime-focus station represents a challenge to normal concepts of fiber positioning. Solutions usually involve imposing limits to the patrol field of each fiber. Using this simplification, a new concept is proposed which moves objects onto a fixed array of fibers rather than moving the fiber themselves. Such a scheme may simplify the manufacturing and assembly processes and may result in a more robust solution compatible with the challenging prime-focus environment. We describe the POSM concept and present an initial opto-mechanical layout.
A high-contrast coronagraph for the MMT using phase apodization: design and observations at 5 microns and 2 λ/D radius
We report on the first implementation of phase apodization for high-contrast imaging at close inner working angle. It is designed for use in the 5 micron M band with the adaptive optics system at the MMT, which uses a deformable secondary for low thermal background and achieves a Strehl ratio of 90% at 5 microns. The method uses a diamond-turned ZnSe phase plate located at a cold pupil stop to diffract starlight into an "anti-halo" which suppresses the Airy diffraction pattern over a semi-circular region around the star. The design was optimized for strong suppression from the first bright Airy ring out to the control radius achievable with the MMT deformable secondary, about 9 λ/D. The time-averaged PSF of a bright star agrees well with the design profile, the core with FWHM of 0.18 arcsec showing the diffraction-limited resolution of the full aperture. At 0.34 arcsec radius (2 λ/D) the floor level is 3.5x10-3 of the central peak, limited by residual atmospheric errors with 3 m wavelength across the aperture. The measured fluctuations at this radius averaged over 20 seconds are 2.5x10-4 rms (9 magnitudes down from the peak). With the addition of active feedback to control residual speckles caused by static wavefront errors and with longer exposures, we project that exoplanet searches should reach 5 σ sensitivity level > 10 magnitudes in an hour of integration.
The Keck-I Cassegrain atmospheric dispersion corrector
We describe the design and construction of the Atmospheric Dispersion Corrector (ADC) for the Keck-I Cassegrain focus. This is a "linear" or "longitudinal" ADC with fused silica prisms slightly over 1-meter in diameter. It is designed to operate at zenith distances up to 60 degrees and over a 20 arcminute field-of-view with negligible impact on image quality and throughput, and to provide dispersion compensation from 0.31 to 1.1 microns. During the design phase, it was realized that the LADC design effectively displaces the optical axis of the telescope as the prisms separate, leading to (a) a tilting of the focal surface, and (b) a change in telescope pointing. Both effects can have significant consequences, particularly for off-axis instruments, and should be carefully considered in selecting this ADC design. We also discuss in some detail the broad-band anti-reflection coatings, which consist of silica Sol-gel over MgF2. The Keck ADC is currently undergoing final assembly and testing at the UCO/Lick Observatory Instrument Labs, and will be commissioned in late 2006.
Grism performance for mid-IR (5-40 micron) spectroscopy
This paper addresses the performance of a suite of grisms as part of an Astrobiology Science and Instrument Development (ASTID) Program to implement a moderate resolution spectroscopic capability in the mid/far-IR facility instrument FORCAST for the Stratospheric Observatory For Infrared Astronomy (SOFIA). A moderate resolution mid-IR spectrometer on SOFIA will offer advantages not available to either ground or space-based instruments after the Spitzer Space Telescope ceases operation in ~2008. SOFIA will begin operations in 2008 and will have an operational lifetime of ~20 years. From aircraft altitudes, it will be possible to cover a wide range of wavelengths, particularly in the critical 5-9 micron band, where detection of astrobiologically interesting molecules have key spectral signatures that are not accessible from the ground The FORCAST grism suite consists of six grisms: four monolithic Si grisms and two KRS-5 grisms. These devices will allow long-slit low-resolution (R = 100-300) and short-slit, cross-dispersed high-resolution spectroscopic modes (R = 800-1200) over select wavelengths in the 5-40 μm spectral range and enable observing programs to gather both images and spectra in a single SOFIA flight. The silicon grisms demonstrate a new family of dispersive elements with good optical performance for spectroscopy from 1.2-8 μm and beyond 18 μm. After SOFIA flies, the grism modes in FORCAST will complement other first generation instruments on SOFIA and provide follow-up capability of bright sources observed with Infrared Spectrograph (IRS) on Spitzer. This paper highlights the design of the grism suite for FORCAST and the current laboratory cryogenic performance of the silicon grisms.
ELT Instrumentation
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ELT instrument concepts: impact on telescope and adaptive optics design
We report on the development of instrument concepts for a European ELT, expanding on studies carried out as part of the ESO OWL concept. A range of instruments were chosen to demonstrate how an ELT could meet or approach the goals generated by the OPTICON science team, and used to push the specifications and requirements of telescope and adaptive optics systems. Preliminary conclusions are presented, along with a plan for further more detailed instrument design and technology developments. This activity is supported by the European Community (Framework Programme 6, ELT Design Study, contract number 011863).
Instrument concepts and scientific opportunities for TMT
David Crampton, Luc Simard
The Thirty-Meter Telescope Project (TMT) aims to build a diffraction-limited, 30-m segmented mirror telescope with first light set for 2014 and first science operations for 2015. The telescope, its comprehensive adaptive optics architecture and its instruments are being designed as an end-to-end system in order to meet the demands of AO-based science. The TMT Scientific Advisory Committee (SAC) has defined challenging scientific programs ranging from the tomographic exploration of the cosmic web of intergalactic hydrogen to extrasolar planets and has identified a suite of instrumental capabilities that will be required to carry them out during the first decade of TMT operation. The TMT instrumentation program has just completed a feasibility phase in which seven instrument concepts were studied. These studies have yielded innovative concepts that stretch the TMT discovery space and system-wide performance, and they are helping define detailed requirements for the telescope and observatory subsystems. Highlights from these studies are summarized and discussed.
On the performance of ELT instrumentation
We discuss the possibility of improving the optical efficiency of ELT instruments by reducing the number of optical surfaces with highly aspheric optics generated by deformable mirrors (DMs). Preliminary analysis shows that a 2 aspheric mirror design could in principle replace a traditional optical design with a complex series of ~ 10 lenses, providing a potential gain in efficiency of ~ 20% as well as a significant gain in compactness. New OH suppression systems based on technologies from the photonics world become available that may ultimately allow to reduce the near IR sky brightness by 2 to 4 magnitudes, depending on wavelength. The potential performance of an ELT with OH suppression is similar in imaging and significantly higher in spectroscopy than JWST.
Conceptual design for the High Resolution Optical Spectrograph on the Thirty-Meter Telescope: a new concept for a ground-based high-resolution optical spectrograph
We present a conceptual design for a High Resolution Optical Spectrograph (HROS) for the Thirty Meter Telescope, a 30-m primary aperture ground-based telescope currently under development (www.tmt.org). To decouple downstream optics sizes from the size of the seeing disk and/or AO performance, we use fiber fed IFUs to generate a 0.1" pseudo-slit. The use of multiple IFUs instead of a slit also allows for spatially resolved spectroscopy, multi-object spectroscopy, positionable sky sampling, and insertion of a simultaneous wavelength calibration signal into the beam. Instead of a cross-dispersed echelle design, our concept uses a dichroic tree to provide spectral separation. The dichroics feed 32 independent first-order spectrographs that cover the 310 to 1100 nm optical waveband at a nominal spectral resolution of R=100,000. This approach allows for the optimization of coatings and on-blaze grating performance in each channel, resulting in high efficiency, near-uniform dispersion, and reduced program risk and cost due to the high degree of component commonality. We also discuss the general applicability of this concept for achieving high resolution spectroscopy in the next generation of ground-based instrumentation.
QuantEYE: a quantum optics instrument for extremely large telescopes
We have carried out a conceptual study for an instrument (QuantEYE) capable to detect and measure photon-stream statistics, e.g. power spectra or autocorrelation functions. Such functions increase with the square of the detected signal, implying an enormously increased sensitivity at the future Extremely Large Telescopes, such as the OverWhelmingly Large (OWL) telescope of the European Southern Observatory (ESO). Furthermore, QuantEYE will have the capability of exploring astrophysical variability on microsecond and nanosecond scales, down to the quantum-optical limit. Expected observable phenomena include instabilities of photon-gas bubbles in accretion flows, p-mode oscillations in neutron stars, and quantum-optical photon bunching in time. This paper describes QuantEYE, an instrument aimed to realize the just described science, proposed for installation at the ESO OWL telescope focal plane. The adopted optical solution is relatively simple and possible with actual technologies, the main constraint essentially being the present limited availability of very fast photon counting detector arrays. Also some possible alternative designs are described, assuming a future technology development of fast photon counting detector arrays.
WFOS: a wide field optical spectrograph for the Thirty Meter Telescope
WFOS (Wide Field Optical Spectrograph) will provide near-UV, visible and near-IR multi-object spectroscopy and imaging capabilities for the TMT (Thirty Meter Telescope). The instrument concept is a multi-barrel approach, with four separate fields on the telescope focal plane providing a total of 92.4 square arcminutes of coverage. The core wavelength coverage is 340nm to 1000nm with an optional near-IR extension to 1.6 microns. Each barrel feeds two cameras allowing simultaneous spectral coverage in the blue and red. Spectral resolutions range from R150 to R7500 for a 0.75" slit using standard ruled transmission gratings and VPH technology. A GLAO (Ground Layer Adaptive Optics) system utilizing the TMT adaptive secondary mirror is included in the instrument concept. This paper describes the scientific goals for WFOS and the overall instrument mechanical, optical and system design.
A wide-field IR spectrograph for the Giant Magellan Telescope
Daniel Fabricant, Edward Hertz, Warren Brown, et al.
The Giant Magellan Telescope, with seven 8.4 meter primary mirrors, is taking shape as one of the most powerful telescopes of the next generation. We describe a conceptual design for a powerful 0.85 to 2.50 μm imaging spectrograph that addresses a 7' by 7' field of view for imaging and a 5' by 7' field of view for spectroscopy at the GMT's f/8 Gregorian focus. The all-refractive optical design presses the limits of available lens blank diameters, but delivers excellent images (~0.15" 80% encircled energy) with just four collimator elements and five camera elements. The collimated beam diameter is 300 mm, and the detector is a 6K by 10K array. The spectrograph will use interchangeable slit masks, and an assortment of VPH and conventional surface relief gratings. Each of the entire J, H, or K bands can be observed with a resolution of 3000. The scientific potential of ground layer adaptive optics (GLAO) using a constellation of sodium laser guide stars appears to be very high in the near infrared. Simulations suggest that 0.2" FWHM images may be achieved across the entire 7' by 7' field of view of the spectrograph. We describe the design of the GLAO system with a versatile opto-mechanical design that allows rapid changeover between GLAO and seeing-limited observations.
MIDIR/T-OWL: the thermal/mid-IR instrument for the E-ELT
MIDIR is a combined thermal/mid-infrared imager and spectrograph for the European Extremely Large Telescope (EELT). It will operate in the infrared L, M, N, and Q-band to 20μm with a goal to extend the wavelength coverage to 27μm if the atmospheric properties of the site are sufficiently good. MIDIR will offer imaging and spectroscopic modes over a wide range in spectral resolution. MIDIR will be designed for diffraction limited performance, requiring an optimized, cryogenic adaptive optics (AO) system. The conceptual study of MIDIR is part of a suite of eight ELT instrument "small studies" partly funded by the EU [1]. The study is being performed by an international consortium of Leiden Observatory, Astron, MPIA, UK-ATC, and ESO. The high level instrument requirements for MIDIR have been directly derived from numerous important science cases. In this paper we discuss the science case for MIDIR, provide a summary of the technical specifications, discuss the requirements on the AO system, and estimate the sensitivity in various observing modes. More technical details on the instrument are given in a parallel paper at this conference [2].
Calibration techniques for next-generation astronomical systems
Historically, few astronomical measurements have required sub-percent accuracy in photometry. Measuring SNIa fluxes in order to determine cosmological parameters, however, often requires the comparison of images from different telescopes, and at different redshifts. This can introduce a myriad of sources of error. Conventional methods of data reduction are intrinsically flawed, either making assumptions about the effects of wavelength dependence in the response function of the system or, when K-corrections are not performed, neglecting them altogether. We consider the advantages of a method utilizing a direct, spectrally-resolved measurement of the entire system's response function relative to a calibrated photodiode.
Poster Session A
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The CCD imaging systems for LAMOST
Sicheng Zou, Gang Wang
The CCD imaging systems for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) are being designed and built in the National Astronomical Observatories of China (NAOC). LAMOST is to be equipped with 16 low-resolution spectrographs (LRS) with a total 32 CCD cameras. Each CCD camera consists of a LN2 cooling system, a CCD controller and a large-format scientific-grade CCD with 4K*4K pixels, two output registers and four output amplifiers. The CCD controller enables low readout noise, photometric stability and software-selectable switching from single- to four- output amplifier readout modes. The whole 32 CCD cameras need to be communicated with several network-connected computers. The computer cluster allows synchronized processes of accumulation and readout of CCD systems and rapid, reliable data transfer from CCD cameras. We introduce the current design of above components as well as its performance. And the design schedule of the CCD imaging systems for LAMOST is reported.
Near-infrared direct vision prism for wide-wavelength coverage spectroscopy at the Subaru Telescope
We have developed a low spectral resolution prism unit for the IRCS at the Subaru Telescope, which covers the wavelength range from 2 μm to 4 μm simultaneously. As the prism has high throughput compared to grism, it is an efficient observing mode for 3-μm water ice band and rapidly time varying objects such as asteroid. We report preliminary results of the performance verifications of the prism unit.
A large-format imager for the SkyMapper Survey Telescope
The Research School of Astronomy and Astrophysics (RSAA) of the Australian National University (ANU) at Mt Stromlo Observatory is developing a wide-field Cassegrain Imager for the new 1.3m SkyMapper Survey Telescope under construction for Siding Spring Observatory, NSW, Australia. The Imager features a fast-readout, low-noise 268 Million pixel CCD mosaic that provides a 5.7 square degree field of view. Given the close relative sizes of the telescope and Imager, the work is proceeding in close collaboration with the telescope's manufacturer, Electro Optics Systems Pty Ltd (Canberra, Australia). The design of the SkyMapper Imager focal plane is based on E2V (Chelmsford, UK) deep depletion CCDs. These devices have 2048 x 4096 15 micron pixels, and provide a 91% filling factor in our mosaic configuration of 4 x 8 chips. In addition, the devices have excellent quantum efficiency from 300nm-950nm, near perfect cosmetics, and low-read noise, making them well suited to the all-sky ultraviolet through near-IR Southern Sky Survey to be conducted by the telescope. The array will be controlled using modified versions of the new IOTA controllers being developed for Pan-STARRS by Onaka and Tonry et al. These controllers provide a cost effective, low-volume, high speed solution for our detector read-out requirements. The system will have an integrated 6-filter exchanger, and Shack-Hartmann optics, and will be cooled by closed-cycle helium coolers. This paper will present the specifications, and opto-mechanical and detector control design of the SkyMapper Imager, including the test results of the detector characterisation and manufacturing progress.
Optics integration of the OMM wide-field visible camera (Panoramix-II)
The advent of wide-field imagers on large telescopes (Megacam at CFHT, Suprime-Cam at Subaru, and others) with degree-wide fields of view is largely motivated by a renewed interest in our own solar system, in the history of the Milky Way and its neighbors, and in the large-scale structure of the Universe. Smaller, university-based telescopes can of course also benefit from wide-field imagery. We present in this paper the design and first results of Panoramix-II, the new wide-field imager of the Mont Megantic Observatory (OMM). This instrument is conceptually a focal reducer designed to image and correct the F/8 cassegrain focal plane of the telescope onto a pair of 2KX4K EEV detectors. The camera is optimized for the SLOAN g' (410-550 nm), r' (550-690 nm), i' (690-850 nm) and z' (850-950 nm) wave bands. The sky will be imaged onto the focal plane at an image scale of 0.52 arcsecond per 13.5 μm pixel. The design image quality is 1.00 arcsecond 50% diffraction encircled energy over the central 35 arcmin field and no images worse than 1.25 arcsecond over the 49 arcminute diameter camera field. The optical design distortion at the corners is less than 1%. The Panoramix-II camera has a filter wheel at the internal stop. Panoramix-II can also support the FaNTOmM photon-counting camera used in conjunction with a Fabry-Perot interferometer to provide spectrometric data.
Simplifying the prime focus corrector of the Discovery Channel Telescope
The Discovery Channel Telescope (DCT) is planned to have a state-of-the-art prime focus corrector which was described previously. The initial design contained I-line glasses which had long procurement times. Goodrich Corp. undertook a study funded by Lowell Observatory to determine whether significant savings in cost and schedule would be possible with an acceptable reduction in the performance of the telescope. This paper reports on changes in the optical design of the wide-field optical corrector (WFOC) with a view to eliminating the long-lead materials. The consequent changes in performance are also discussed. The required FWHM of the telescope was relaxed somewhat and the imaging requirements of the ultraviolet (U) band were eliminated. The new design meets the two-degree field of view requirement and recovers most of the performance in the ultraviolet.
The prime focus imaging spectrograph for the Southern African Large Telescope: structural and mechanical design and commissioning
The Prime Focus Imaging Spectrograph (PFIS) is a first light instrument for the Southern African Large Telescope (SALT). PFIS is a versatile instrument designed to operate in a number of scientific modes by utilizing volume phase holographic gratings, Fabry-Perot etalons, and polarimetric optics, which are manipulated in and out of the beam using various placement mechanisms. The instrument is mounted at the prime focus 15m above the primary mirror and tilted at 37°. This remote placement and the need for 240° of rotation about the optical axis raises important design issues with mass, flexure and access. The instrument structure provides the interface to the telescope Prime Focus Instrument Platform (PFIP) as well as support points for all the optics, mechanisms and electrical equipment. The structure is a welded open truss of hollow, square-section Invar beams. The open truss provides the highest stiffness to weight ratio and minimizes the effect of wind loading, while the use of Invar negates the effects of thermal expansion. It has been designed using finite element analysis in conjunction with an optical tolerance analysis of the optics nodes to minimize effective image motion under the varying gravity load. The fundamentals of the design of the structure to minimize the flexure and its effect on image motion, the motivation for using the open Invar truss structure, and the design of the remotely operated mechanisms are discussed. In 2005 PFIS was installed and commissioned on SALT in South Africa. Included in this text are some of the results and experiences of taking PFIS into operation.
The Dark Energy Survey instrument design
We describe a new project, the Dark Energy Survey (DES), aimed at measuring the dark energy equation of state parameter, w, to a statistical precision of ~5%, with four complementary techniques. The survey will use a new 3 sq. deg. mosaic camera (DECam) mounted at the prime focus of the Blanco 4m telescope at the Cerro-Tololo International Observatory (CTIO). DECam includes a large mosaic camera, a five element optical corrector, four filters (g,r,i,z), and the associated infrastructure for operation in the prime focus cage. The focal plane consists of 62 2K x 4K CCD modules (0.27"/pixel) arranged in a hexagon inscribed within the 2.2 deg. diameter field of view. We plan to use the 250 micron thick fully-depleted CCDs that have been developed at the Lawrence Berkeley National Laboratory (LBNL). At Fermilab, we will establish a packaging factory to produce four-side buttable modules for the LBNL devices, as well as to test and grade the CCDs. R&D is underway and delivery of DECam to CTIO is scheduled for 2009.
ELT site prospect in Morocco: aerosol characterization
In order to prospect for good astronomical sites in Morocco, we make a preliminary study in terms of aerosol characterization. For that purpose we use AERONET data and the Aerosol Index provided by Earth Probe platform. After establishing a good correlation between the aerosol optical thickness (AOT) and the aerosol index (AI) in three sites located in the area of interest, we try to extrapolate to areas where AERONET data are not available. The studied areas are: Marrakech, Dakhla located in Morocco, and Izana in the Canary Islands. These areas exhibit a predominance of desert dust aerosol particles. The altitude seems to be the predominant factor influencing the distribution of the aerosol optical thickness during the year. A full characterization of these sites makes possible a determination of the aerosol optical thickness of neighbouring areas.
A new-generation multi-object high throughput Doppler instrument for a planet survey at the SDSS Telescope
We report the design of a new generation multi-object high throughput Doppler instrument and first light results at the Sloan Digital Sky Survey (SDSS) telescope. This instrument, capable of simultaneously monitoring 60 stars for planet detection, is called the W.M. Keck Exoplanet Tracker (or Keck ET) thanks to the generous gift from the W.M. Keck Foundation. It is designed for a planet survey around hundreds of thousands of stars with V =8-13 for detecting tens of thousands of planets in 2006-2020. The Doppler precision is between 3-25 m/s depending on the star magnitude. We also report a new planet detected with a prototype single object version ET instrument at the KPNO Coude Feed/2.1 m telescopes. The extrasolar planet, ET-1 (HD 102195b), has a minimum mass of 0.49 Jupiter masses and orbits a V = 8.1 G8V star with a 4.1 day period. The planet was identified using the Coude Feed 0.9 meter telescope in spring 2005. This is the first time an extrasolar planet around a star fainter than V=8 magnitude has been discovered with an under 1 meter size astronomical telescope and Doppler instrument. This planet discovery is possible due to the extremely high throughput of the instrument, 49% measured from the fiber output end to the detector.
Wide field spectrograph concepts for the European Extremely Large Telescope
We report on the science case high level specifications for a wide field spectrograph instrument for an Extremely Large Telescope (ELT) and present possible concepts. Preliminary designs are presented which resort to different instrument concepts: monolithic integral field (IFU), multi-IFU, and a smart tunable filter. This work is part of the activities performed in the work package 'Instrumentation' of the 'ELT Design Study', a programme supported by the European Community, Framework Programme 6.
Simultaneous spectral differential imaging with a focal plane holographic diffuser
Direct exoplanet detections are limited by the speckle noise of the point spread function (PSF). This noise can be reduced by subtracting PSF images obtained simultaneously in adjacent narrow spectral bands using a multichannel camera (MCC). Experiments have shown that speckle attenuation performances are severely degraded by differential optical aberrations between channels that decorrelate the PSFs of the different spectral bands. We present a new technique which can greatly alleviate this problem: the introduction of a holographic diffuser at the focal plane of the MCC. The holographic diffuser converts the PSF image into an incoherent illumination scene that is then re-imaged with the MCC. This imaging process is equivalent to a convolution of the scene with the PSF of each channel of the MCC. The optical aberrations in the MCC then affect only the convolution kernel of each channel and not the PSF globally, resulting in more correlated images. We report laboratory measurements with a dual channel prototype (1.575 μm and 1.625 μm) to validate this approach. We achieved a speckle noise suppression factor of 12-14, which is ~4-6 times better than what has been achieved by existing MCCs.
Design of a multi-object high-throughput low-resolution fiber spectrograph for WFMOS
We present the preliminary optical and optomechanical design of a high throughput, fiber spectrograph for the Gemini/Subaru Wide-Field, Fiber-Fed, Multi-Object Spectrograph (WFMOS) designed with the principle goal of studying the nature of dark energy via enormous high-redshift spectroscopic surveys. Developed from an original Sloan Digital Sky Survey design this multi-object spectrograph utilizes all-refractive cameras, volume phase holographic gratings, and state-of-the-art CCD detectors to produce a peak instrument throughput of ~ 70%. The instrument produces 292 spectra simultaneously in two channels covering the bandpass 390 < λ < 1000 nm with a mean spectral resolution, λ/FWHM, of R ~ 1700. WFMOS will employ approximately ten of these fiber spectrographs on an 8 m class telescope to capture nearly 3000 spectra simultaneously. When used in a nod & shuffle mode of operation these spectrographs will facilitate spectroscopy of faint 0.5 < z < 3.5 galaxies with unprecedented efficiency.
VIRUS: a massively replicated integral-field spectrograph for HET
We present the design of, and the science drivers for, the Visible Integral-field Replicable Unit Spectrograph (VIRUS). This instrument is made up of 145 individually small and simple spectrographs, each fed by a fiber integral field unit. The total VIRUS-145 instrument covers ~30 sq. arcminutes per observation, providing integral field spectroscopy from 340 to 570 nm, simultaneously, of 35,670 spatial elements, each 1 sq. arcsecond on the sky. This corresponds to 15 million resolution elements per exposure. VIRUS-145 will be mounted on the Hobby-Eberly Telescope and fed by a new wide-field corrector with 22 arcminutes diameter field of view. VIRUS represents a new approach to spectrograph design, offering the science multiplex advantage of huge sky coverage for an integral field spectrograph, coupled with the engineering multiplex advantage of >100 spectrographs making up a whole. VIRUS is designed for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) which will use baryonic acoustic oscillations imprinted on the large-scale distribution of Lyman-α emitting galaxies to provide unique constraints on the expansion history of the universe that can constrain the properties of dark energy.
Data reduction software of the X-shooter spectrograph
P. Goldoni, F. Royer, P. François, et al.
We present the Data Reduction Software (DRS) being developed at APC, Paris Observatory, Amsterdam University and ESO for the X-shooter echelle spectrograph. X-shooter is the first VLT second generation instrument, expected to be operational in 2008. The DRS will be fully integrated in the ESO VLT system and it will use the ESO Common Pipeline Library. We discuss the data reduction related to slit and IFU observations. X-shooter data have two main characteristics, on the one hand the exceptionally wide band (0.3-2.4 μm) covered in a single exposure, and on the other hand the spectral format with highly curved orders and tilted lines. The reduction process is described and the critical issues related to the above characteristics, notably the sky subtraction, the optimal extraction, and the construction of 1D/2D/3D output products, are addressed. Some aspects of the spectrophotometric calibration are also discussed.
Design of HERMES: a high-resolution fiber-fed spectrograph for the Mercator Telescope
Gert Raskin, Hans Van Winckel, Holger Lehmann
HERMES is a high-resolution fiber-fed echelle spectrograph combining high throughput with high instrumental stability. The optical design is based on a large R2.7 echelle grating, operating in quasi-Littrow and white-pupil configuration, using a double-prism cross-disperser. It records the complete spectrum from 380 to 900 nm in a single exposure on a monolithic 2kx4.5k pixels CCD. HERMES offers 1) a high-resolution and high-efficiency observation mode through a 80-μm optical fiber (2.5 arcsec sky aperture) equipped with a two-slice image slicer, resulting in a resolution of λ/Δλ = 85000 and a peak-efficiency higher than 25%; and 2) a high-stability mode through a 60-μm fiber (2.15 arcsec sky aperture, R = 55000) equipped with a double fiber scrambler for improved spectrograph illumination stability. The latter mode is intended for high-precision radial velocity measurements and it offers the possibility of recording the spectrum of a wavelength calibration lamp simultaneously and interlaced with the stellar spectrum for precise tracking of instrumental drifts. To optimize instrumental stability, the spectrograph will be housed in a temperature and pressure controlled chamber, and it will operate in one fixed optical configuration. This instrument has a wide astronomical scope, going from asteroseismology to binary star research and chemical studies of stars and circumstellar material. HERMES is currently under construction and will be mounted on the 1.2-meter Mercator Telescope at the Roque de Los Muchachos Observatory on La Palma.
Simultaneous infrared-visible imager/spectrograph: a multi-purpose instrument for the Magdalena Ridge Observatory 2.4-m telescope
M. B. Vincent, E. V. Ryan
The Simultaneous Infrared-Visible Imager/Spectrograph (SIRVIS) is a planned multi-purpose instrument for the Magdalena Ridge Observatory 2.4 m telescope located west of Socorro, NM. The primary science drivers are asteroid studies, the rapid response to astrophysical transient phenomena and observations of artificial targets such as satellites. For asteroid science, the wavelength range 0.39-2.5 μm gives the most mineralogically diagnostic information on surface compositions using standard filters and low-resolution, R ~ 200, spectroscopy. For transients, the telescope's rapid 10°/second slew rate will facilitate acquisition of data on any target within one minute of receipt of notice. For artificial targets, simultaneous two-color imaging will assist in unique determinations and overall condition monitoring. SIRVIS has two channels, a cryogenic NIR channel covering 0.85-2.5 μm at 0.27 arcsec/pixel, and an ambient temperature-pressure visible channel covering 0.39-1.0 μm at 0.15 arcsec/pixel. The beam is split by a cryogenic, red-pass dichroic mirror located between the telescope focal plane and the respective collimators. Both channels use refractive optics. The instrument is being designed to initially phase in the visible channel, then the NIR channel, and readily accommodate upgrades. For sky subtraction, the telescope is nodded between 30-60 second NIR integrations. Long visible integrations are made possible by shifting the CCD charge in sync with the nod.
The spectrum of Th-Ar hollow-cathode lamps in the 900-4500 nm region: establishing wavelength standards for the calibration of VLT spectrographs
Florian Kerber, Gillian Nave, Craig J. Sansonetti, et al.
The European Southern Observatory (ESO), the Space Telescope European Co-ordinating Facility (ST-ECF), and the US National Institute of Standards and Technology (NIST) are collaborating to study Th-Ar hollow cathode lamps as used for the calibration of VLT (Very Large Telescope) spectrographs. In the near IR only a limited number of wavelength standards are available. The density and distribution of lines in Ne or Kr lamps, for example, are inadequate for high-resolution spectroscopy. Th-Ar hollow cathode lamps provide a rich spectrum in the UV-visible region and have been used in astronomy for a long time; current examples at ESO include the spectrographs UVES and FLAMES. The Th spectrum from 278 nm to about 1000 nm was studied at high resolution about 20 years ago (Palmer and Engleman, 1983). Two studies of the Th-Ar spectrum in the near IR have recently been published, but neither work is directly applicable to the calibration of IR astronomical spectrographs at ESO. We report new measurements using the 2-m UV/visible/IR Fourier transform spectrometer (FTS) at NIST that establish more than 2000 lines as wavelength standards in the range 900 nm to 4500 nm. This line list is used as input for a physical model that provides the wavelength calibration for the Cryogenic High-Resolution IR Echelle Spectrometer (CRIRES), ESO's new high resolution (R~100,000) IR spectrograph at the VLT. We also present first calibration results from laboratory testing of CRIRES. The newly established wavelength standards will also be available for use by X-shooter and other spectrographs in the future. Measurements of the variation of the spectrum of Th-Ar lamps as a function of operating current allow us to optimise the spectral output in terms of relative intensity and line density for operation on the telescope. Since Th and Ar line intensities show a different response with respect to operating current, such measurements can be used as a diagnostic tool for distinguishing the gas and metal lines. Our findings show that Th-Ar lamps hold the promise of becoming a standard source for wavelength calibration in near IR astronomy.
Noise studies of externally dispersed interferometry for Doppler velocimetry
Externally Dispersed Interferometry (EDI) is the series combination of a fixed-delay field-widened Michelson interferometer with a dispersive spectrograph. This combination boosts the spectrograph performance for both Doppler velocimetry and high resolution spectroscopy. The interferometer creates a periodic comb that multiplies against the input spectrum to create moire fringes, which are recorded in combination with the regular spectrum. Both regular and high-frequency spectral components can be recovered from the data - the moire component carries additional information that increases the signal to noise for velocimetry and spectroscopy. Here we present simulations and theoretical studies of the photon limited Doppler velocity noise in an EDI. We used a model spectrum of a 1600K temperature star. For several rotational blurring velocities 0, 7.5, 15 and 25 km/s we calculated the dimensionless Doppler quality index (Q) versus wavenumber ν. This is the normalized RMS of the derivative of the spectrum and is proporotional to the photon-limited Doppler signal to noise ratio.
Measurements of stellar magnetic fields with FORS 1 in spectropolarimetric mode
S. Hubrig, T. Szeifert, M. Schöller, et al.
In the last two years, the use of FORS 1 (FOcal Reducer low dispersion Spectrograph with polarimetric capability), mounted on the 8-m Kueyen telescope, led to a number of important advances in the studies of stellar magnetic fields. At the very beginning of these studies only the grism 600B was used with FORS 1 in polarimetric mode, providing the possibility to obtain both Stokes I and Stokes V as a function of wavelength in a spectral region from below the Balmer jump to Hβ. However, very useful circular polarimetry has also been obtained with grisms 600R, 1200G, and, very recently, with the grism 600I, which allows to study both the Ca II infrared triplet lines and the hydrogen Paschen lines. We describe here the recent scientific results achieved for studies of stellar magnetic fields using different FORS 1 instrumental settings.
A study of the UVES instrumental polarization
S. Hubrig, N. Nesvacil, G. Mathys, et al.
Previous studies of strongly magnetic stars with spectral lines resolved into their magnetically split components showed for some stars systematic differences in the mean field modulus values determined from high resolution spectra obtained with different spectrographs at different observatories. It is suspected that they result from modification of the linear polarisation of the spectral lines of the star by the optical train. Since this polarisation varies from star to star, the resulting effect also differs from one star to the next. As high resolution spectra obtained with the Ultraviolet and Visible Echelle Spectrograph (UVES) at the ESO VLT are nowadays used for the measurement of stellar surface magnetic fields, we recently conducted a study of the UVES instrumental polarisation. For this purpose, we carried out a large number of measurements of magnetically split Zeeman components in the spectra of magnetic stars taken with various instrumental settings using different dichroics, the highest resolution image slicer and the depolarizer. Our measurements show no evidence for the presence of a UVES instrumental polarisation.
Implementation of interference filters in the UV-Visual Echelle Spectrograph (UVES)
The purpose of the recent installation of eight interference filters in UVES is to isolate certain echelle orders to allow the use of a maximal slit length of 30". The typical decker height of the spectrograph slit for science operations is usually of the order of 10-12". The central wavelength of each filter was chosen to permit observations of the most important emission lines in extended objects. We discuss the performance of these filters and show the first science images obtained with the test run.
A fiber feed system for a multiple object Doppler instrument at Sloan Telescope
Xiaoke Wan, Jian Ge, Pengcheng Guo, et al.
A fiber feed system has been developed to allow a new generation multiple object Doppler instrument, called the WM Keck Exoplanet Tracker, simultaneously tracking 59 stars for high precision radial velocity measurements for planet detection, and switching among over 500 targets per night. The system includes 27 plug fiber bundles and 3 instrument fiber bundles, and each fiber bundle includes 22 fibers. Individual fibers of a plug fiber bundle are plugged to a plate to receive star lights, and then they are grouped together to form a compact 22-fiber connector. An instrument fiber bundle with a matching fiber bundle connector can connect and disconnect with the plug fiber bundle. The 45 m long instrument fiber bundles deliver the light from the telescope to an environment controlled instrument room in distance. We characterizes the light loses including the position and pointing error of plug connectors, the fiber end reflection, fiber misalignment at the mating connectors, focal ratio degradation and fiber absorption through the long fiber link. All fiber bundles are tested and average total throughput of 61% is achieved.
An optical spectrograph design for a new-generation multiple object Doppler instrument
This paper describes an optical spectrograph design for the W.M. Keck Exoplanet Tracker (ET) multi-object Doppler radial velocity instrument. The Keck ET is currently installed at the Sloan 2.5m telescope (Ge et al. this proceedings), and is capable of simultaneously monitoring 60 stars with high precision for a planet survey. The spectrograph consists of an entrance slit, collimator optics, a Volume Phase Holographic (VPH) grating, camera optics and a 4kx4k CCD camera, and provides a spectral resolution of R =5000, with a 180 mm diameter collimated beam. The collimator and camera optics (300 mm largest diameter) are made of two standard optical grade glasses: BK7 and F2, respectively. The spectrograph is transmissive and optimized for delivering high throughput and high image quality over the entire operation bandwidth: 500-590 nm. The f/4 input beams from the Keck ET interferometer are converted to f/1.5 beams on the detector by this spectrograph, and form 60 stellar fringe spectra.
A multi-object multi-field spectrometer and imager for a European ELT
One of the highlights of the European ELT Science Case book is the study of resolved stellar populations, potentially out to the Virgo Cluster of galaxies. A European ELT would enable such studies in a wide range of unexplored, distant environments, in terms of both galaxy morphology and metallicity. As part of a small study, a revised science case has been used to shape the conceptual design of a multi-object, multi-field spectrometer and imager (MOMSI). Here we present an overview of some key science drivers, and how to achieve these with elements such as multiplex, AO-correction, pick-off technology and spectral resolution.
BESO: a high-resolution spectrograph for the Hexapod-Telescope
Ingo Steiner, Walter Seifert, Otmar Stahl, et al.
BESO (Bochum Echelle Spectrograph for OCA) is a high-resolution echelle spectrograph which is built by the Ruhr-Universitaet, Bochum and the Landessternwarte Heidelberg. It will be operated with the 1.5m Hexapod-Telescope at the Observatorio Cerro Armazones (OCA), Chile - the new observatory of the Ruhr-Universitaet and the Universidad Catolica del Norte in Antofagasta. The site at 2800m altitude is located 30 km east of Paranal and provides superb observing conditions. BESO is fiber-coupled to the Hexapod-Telescope, covers a spectral range of 370 to 840nm with a resolution of 48,000. Instrument controls are embedded in the ALMA Common Software environment. The spectrograph is part of a monitoring project that studies the variability of young stars and AGN.
The optical design of the X-shooter for the VLT
P. Spanò, B. Delabre, A. Norup Sørensen, et al.
The overall optical design of X-Shooter, the second generation, wide band, intermediate resolution, high efficiency, three-arms spectrograph for the VLT, is presented. We focus on the optical design of the three optimized arms, covering UVB (300-550 nm), VIS (550-1000 nm), and NIR (1000-2300 nm) wavelength ranges, including spectrographs and pre-slit optics. All spectrographs share the same original "4C" concept (Collimator Correction of Camera Chromatism). We describe also the auxiliary optics, such as dichroics, acquisition and guiding unit. Performances analysis are summarized.
The integral field spectrograph of SPHERE: the planet finder for VLT
SPHERE is an instrument designed and built by a consortium of French, German, Italian, Swiss and Dutch institutes in collaboration with ESO. The project is currently in its Phase B. The main goal of SPHERE is to gain at least one order of magnitude with respect to the present VLT AO facility (NACO) in the direct detection of faint objects very close to a bright star, especially giant extrasolar planets. Apart from a high Strehl ratio, the instrument will be designed to reduce the scattered light of the central bright star and subtract the residual speckle halo. Sophisticated post-AO capabilities are needed to provide maximum detectivity and possibly physical data on the putative planets. The Integral Field Spectrograph (IFS), one of the three scientific channels foreseen in the SPHERE design, is a very low resolution spectrograph (R~20) which works in the near IR (0.95-1.35 μm), an ideal wavelength range for the ground based detection of planetary features. Its goal is to suppress speckle to a contrast of 107, with a goal of 108, and at the same time provide spectral information in a field of view of about 1.5 × 1.5 arcsecs2 in proximity of the target star. In this paper we describe the overall IFS design concept.
The X-shooter spectrograph: a new concept of mechanical assembly for a multiple-arm Cassegrain instrument
X-shooter is a second generation VLT instrument currently under construction by a Consortium of Institutes from Denmark, Italy, The Netherlands, France and ESO. X-shooter is designed to acquire intermediate (5000-10000) resolution spectra of single objects in an unprecedented wide wavelength coverage (320-2500 nm). In order to maximize efficiency the beam is divided into 3 arms (UV, VIS and NIR) by a system of dichroics. X-shooter is designed for the Cassegrain focus of one VLT unit. The mechanical assembly has to provide specific solutions to maintain 3 arms within the strict tolerances required by the intermediate resolution, during the typical motions of the Cassegrain focal station. It must as well ensure the permanent co-alignment of the 3 slits and the stability of the spectral format on the focal plane of each arm, allowing long intervals between calibration exposures. The above requirements have been met via an innovative mechanical design merging passive stiffness and active control to obtain a light, accessible and functional assembly. This paper gives a description of the X-shooter mechanical assembly with main emphasis on the common "backbone" structure and the UV- and VIS spectrograph arms.
A high-resolution optical spectrograph for the Thirty Meter Telescope: design and performance
We have completed a conceptual design study of the High Resolution Optical Spectrograph for the Thirty Meter Telescope project. We propose the use of a fiber fed integral field unit and a dichroic tree to achieve R=100,000 spectroscopy from 310 to 1100 nm independent of AO performance. The system relies on the dichroic tree to provide coarse wavelength selection, and 32 first order spectro-graph benches. This approach allows for simultaneous optimization of grating and detector performance for all wavelengths, resulting in high efficiency, near uniform dispersion, and reduced program risk and cost due to the high degree of component commonality. We present projected performance and design details.
The Carnegie Planet Finder Spectrograph
Jeffrey D. Crane, Stephen A. Shectman, R. Paul Butler
The Carnegie Planet Finder Spectrograph is being constructed for use at the Magellan Telescopes at Las Campanas Observatory in Chile. Its primary scientific objective is the detection of extrasolar planets through monitoring of stellar radial velocity variations. The spectrograph is being optimized for high precision measurement of these velocities with a resolution goal of 1 m s-1. The optical design includes all spherical, standard optical glass and calcium fluoride lenses that function as both camera and collimator in a double-pass configuration. A prism cross-disperser is also used in double-pass and provides a minimum order separation of 4.0 arcsec. An R4 echelle grating is illuminated near true Littrow and provides complete wavelength coverage between 390 nm and 620 nm. Spectral resolution is 38,000 when using a 1 arcsec slit, although slit widths as small as 0.2 arcsec are available. An iodine cell is used to superimpose well-defined absorption features onto spectra to serve as a fiducial wavelength scale, and a thorium argon lamp is available for traditional wavelength calibrations. The spectrograph is currently under construction and is scheduled for commissioning in the second quarter of 2007.
The optical design of the wide field optical spectrograph for the Thirty Meter Telescope
John S. Pazder, Murray Fletcher, Chris Morbey
WFOS (Wide Field Optical Spectrograph) is a multi-object spectrograph for the TMT (Thirty Meter Telescope) project. A ten month WFOS feasibility study has been undertaken and the resulting optical design is presented. The instrument concept is a multi-barrel approach, comprising four identical instruments placed about the optical axis. A novel off-axis collimator has been utilized with catadioptric cameras. Minimizing fabrication risk has been central to the design, with aspheric surfaces and exotic materials being avoided where possible. The field sizes of the barrels and grating sizes were selected based on optical element manufacturability and dispersion element diffraction efficiency.
X-shooter UV- to K-band intermediate-resolution high-efficiency spectrograph for the VLT: status report at the final design review
X-shooter is a single target spectrograph for the Cassegrain focus of one of the VLT UTs where it will start to operate in 2008. The instrument covers in a single exposure the spectral range from the UV to the K' band. It is designed to maximize the sensitivity in this spectral range through the splitting in three arms with optimized optics, coatings, dispersive elements and detectors. It operates at intermediate resolutions (R=4000-14000, depending on wavelength and slit width) with fixed echelle spectral format (with prism cross-dispersers) in the three arms. The project has completed the Final Design Review in June 2006. In this status report, the overall concept is summarized and new results on the dichroics, the active flexure compensation system, the operation modes and the expected performance are given. The instrument is being built by a Consortium of Institutes from Denmark, France, Italy and the Netherlands in collaboration with ESO. When in operation, its wide spectral range observing capability will be unique at very large telescopes.
The integral field unit for Echellette Spectrograph and Imager at Keck II
We report on the design, development and commissioning of an Integral Field Unit (IFU) that has been built for the Echellette Spectrograph and Imager (ESI) at the W.M. Keck Observatory. This image slicer-based IFU, which was commissioned in the spring of 2004 covers a contiguous field of 5.65 x 4.0 arcseconds in 5 slices that are 1.13 arcseconds wide. The IFU passes a spectral range of 0.39-1.1 um with a throughput of between 45% and 60% depending on wavelength and field position. The IFU head resides in an ESI slit mask holder, so that ESI may be converted to the IFU mode remotely by selecting the appropriate slit mask position. This IFU is the first of a family of designs for the spectrograph, providing a range of field-coverages and dispersions.
Preliminary optical design for a 2.2 degree diameter prime focus corrector for the Blanco 4 meter telescope
We describe a five element corrector for the prime focus of the 4 meter Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile that will be used in conjunction with a new mosaic CCD camera as part of the proposed Dark Energy Survey (DES). The corrector is designed to provide a flat focal plane and good images in the SDSS g, r, i, and z filters. We describe the performance in conjunction with the scientific requirements of the DES, particularly with regard to ghosting and weak-lensing point spread function (PSF) calibration.
Preliminary design of the collision avoidance device on the fiber positioning units of LAMOST
Chao Zhai, Zhikun Zhou, Yi Jin, et al.
This paper constructed two protecting methods of diminishing the collision during the opposite movement of the adjoining fiber unit in the LAMOST Positioning System. Auto-positioning mode is applied to every fiber positioning unit of LAMOST Positioning System. The observing region is a circular region with the diameter of 33 mm. To ensure the whole focal plane is covered by the observing region of 4000 fiber units, there must be superposition of observing region of each adjoining fiber units, which induced the collision of adjoining fiber holder in the movement process and resulted in the failing of orientation and mangling of structure. The mode of avoiding the collision comprises two methods. One is hard protected mode, according to this method sensors are installed at each fiber positioning unit, then the motion of the fiber units will be stopped immediately when the adjoining fiber units close to a dangerous distance. The other is soft protected mode, which deliberates every situation of software from the observation programming to the motion path designing for avoiding the collision. This paper expounds the designing and achievement of these two methods mentioned formally.
Study on observation planning of LAMOST focal plane positioning system and its simulation
Fiber Positioning System of LAMOST focal plane based on subarea thinking, adopts a parallel controllable positioning plan, the structure is designed as a round area and overlapped each other in order to eliminate the un-observation region. But it also makes the observation efficiency of the system become an important problem. In this paper According to the system, the model of LAMOST focal plane Observation Planning including 4000 fiber positioning units is built, Stars are allocated using netflow algorithm and mechanical collisions are diminished through the retreat algorithm, then the simulation of the system's observation efficiency is carried out. The problem of observation efficiency of LAMOST focal plane is analysed systemic and all-sided from the aspect of overlapped region, fiber positioning units, observation radius, collisions and so on. The observation efficiency of the system in theory is describes and the simulation indicates that the system's observation efficiency is acceptable. The analyses play an indicative role on the design of the LAMOST focal plane structure.
Implementary scheme of parallel controllable optical fiber positioning system for LAMOST
The aims of LAMOST(Large Area Multi-Object Fiber Spectroscope Telescope) optical fibers positioning system is carrying out 4000 fibers minutely position quickly on the focal plane plate. Base on the dividing domain, we are putting forward parallel controllable optical fiber positioning system, this system consists of several parts as follows: In the focal plate of LAMOST, A aluminous alloy plate with plate diameter 1.75 m, globe radius is 20m. Over 4000 holes are bored on the focal plate; one optical fiber positioning unit of double revolving freedom device is inserted in each holes of focal plate, it is drived by two micro-stepping motor and positioning one fiber-end, focal plate is sustained by 8 steel tubes on the focal mechanical framework; for driving 8000 stepping motors, a control system is needed; and a measuring system with 4K surface CCD is used to calibrate the fiber's position, besides a few accessorial devices for example 4000 wire and fiber setting up need to plan elaborately, According to plan, parallel controllable fiber positioning system will be made in the next three years.
Preliminary study on the measurement system for LAMOST small focal plane fiber positioning system
Yi Jin, Xiaozheng Xing, Chao Zhai, et al.
LAMOST is National Ninth Five Great Scientific Project. In the fiber positioning system, geometrical coordinates of fibers need to be measured in order to verify the precision of fiber positioning. The small focal plane system for LAMOST includes more than 200 fiber positioning units and its diameter is 500mm, so it's difficult to cover it using only one area CCD. For measuring wide field of view, the measurement system based on one CCD rotating is designed. The CCD camera is placed on a mechanism liked a pan head and can rotate around two vertical axes. When the CCD camera rotates in a certain way, the measuring scope becomes a ring. When the initial angle of CCD is changed the size of the ring changed too, so the wide field of view is measured. In this plan different measuring has overlapped regions and one fiber point may be measured for several times. After the camera's calibration the different imaging points will be transformed to the same coordinate system using photogrammetry method and the average value of them is the final value in order to eliminate the imaging error and transformation error. The realization of the measurement system based on CCD rotation is described.
Development of simultaneous imaging polarimeter
Kenta Fujita, Maiko Nishida, Yoichi Itoh, et al.
Accurate polarization measurements are obtained by modern imaging polarimeter and spectro-polarimeter that often employ a rotating λ/2 retarder plate and a Wollaston prism. In this configuration, the linear Stokes parameter U is measured after the measurements of the Q parameter by rotating the retarder plate, or vice versa. However, the resultant accuracy is not satisfactory, because of the tracking error of the telescope and changes in atmospheric conditions. In order to enhance the polarimetric accuracy and observational efficiency, we are constructing an imaging polarimeter which can measure the two linear Stokes parameters Q and U, simultaneously. The polarimeter features an unpolarized beam splitter and two Wollaston prisms, allowing the simultaneous acquisition of the four polarized images without moving parts.
HyperSuprime: imaging optics
We summarize the optical design of the wide-field corrector for HyperSuprime which is being considered as a next generation prime focus camera for Subaru Telescope. Two optical designs are investigated under several design constraints such as image quality, field curvature, focal length, etc. The corrector with 2 degree field of view attains good image quality at the wavelength between 600 nm and 1100 nm although the first lens is large (1.2 m in diameter) and three aspherical surfaces are required. The image quality for shorter wavelength than 600 nm is fair. The incident light blocked at the edge of the field is only 20% and the transmission is more than 80% if the multi-layer coating applied for the current Subaru prime focus corrector is available. The corrector with 1.5 degree field of view is designed as a smaller version of 2 degree corrector. The properties and performance of 1.5 degree corrector resemble those of 2 degree corrector, but 1.5 degree corrector has a merit that the focal plane is flat. The availability of large fused-silica blank up to about 200 kg is promising.
LUCIFER status report: Summer 2006
H. G. Mandel, I. Appenzeller, W. Seifert, et al.
LUCIFER (LBT NIR Spectrograph Utility with Camera and Integral-Field Unit for Extragalactic Research) is a NIR spectrograph and imager for the LBT (Large Binocular Telescope) working in the wavelength range from 0.9 to 2.5 microns. Two instruments are built by a consortium of five German institutes (Landessternwarte Heidelberg (LSW), Max Planck Institut for Astronomy (MPIA), Max Planck Institut for Extraterrestric Physics (MPE), Astronomical Institut of the Ruhr-University Bochum (AIRUB) and Fachhochschule for Technics and Design Mannheim (FHTG). All major components for the first instrument have been manufactured or are in the final stage of procurement. While integration and testing of LUCIFER 1 started in spring 2006 at the MPIA in Heidelberg, the cryostat for LUCIFER 2 has been sent to the MPE in Garching for system integration tests of the MOS-unit and testing of the mask cabinet exchange. The control electronics for the basic instrument has been manufactured, the MOS control electronics has been integrated and is being debugged. The MOS control software is under development by AIRUB. Fabrication and integration of components for LUCIFER 2 have started.
HyperSuprime: electronics
A next generation wide-field camera HyperSuprime proposed for the 8.2m Subaru telescope is planed to employ 176 2kx4k CCDs to cover a 2 degrees diameter field of view. The readout electronics is one of important parts of the instrument. The CCD has four signal outputs, and all of the CCDs are readout in 10 to 20 seconds. The total image size becomes 2.8 Gbytes which should be transferred to the observing room within the readout time. Furthermore, the instrument will be mounted on the prime focus of the telescope. To decrease the size, weight, and power consumption are important themes for HyperSuprime. We will present our effort and the possibilities discussed to realize the readout electronics.
BLAST autonomous daytime star cameras
We have developed two redundant daytime star cameras to provide the fine pointing solution for the balloon-borne submillimeter telescope, BLAST. The cameras are capable of providing a reconstructed pointing solution with an absolute accuracy < 5". They are sensitive to stars down to magnitudes ~ 9 in daytime float conditions. Each camera combines a 1 megapixel CCD with a 200mm f/2 lens to image a 2° × 2.5° field of the sky. The instruments are autonomous. An internal computer controls the temperature, adjusts the focus, and determines a real-time pointing solution at 1 Hz. The mechanical details and flight performance of these instruments are presented.
LAIWO: a new wide-field CCD camera for Wise Observatory
Harald Baumeister, Cristina Afonso, Karl-Heinz Marien, et al.
LAIWO is a new CCD wide-field camera for the 40-inch Ritchey-Chretien telescope at Wise Observatory in Mitzpe Ramon/Israel. The telescope is identical to the 40-in. telescope at Las Campanas Observatory, Chile, which is described in [2]. LAIWO was designed and built at Max-Planck-Institute for Astronomy in Heidelberg, Germany. The scientific aim of the instrument is to detect Jupiter-sized extra-solar planets around I=14-15 magnitude stars with the transit method, which relies on the temporary drop in brightness of the parent star harboring the planet. LAIWO can observe a 1.4 x 1.4 degree field-of-view and has four CCDs with 4096*4096 pixels each The Fairchild Imaging CCDs have a pixel size of 15 microns. Since they are not 2-side buttable, they are arranged with spacings between the chips that is equal to the size of a single CCD minus a small overlap. The CCDs are cooled by liquid nitrogen to a temperature of about -100 °C. The four science CCDs and the guider CCD are mounted on a common cryogenic plate which can be adjusted in three degrees of freedom. Each of these detectors can also be adjusted independently by a similar mechanism. The instrument contains large shutter and filter mechanisms, both designed in a modular way for fast exchange and easy maintenance.
HyperSuprime: mechanics
A next generation wide-field camera, HyperSuprime, proposed for the 8.2m Subaru telescope is planned to employ 126 2k x 4k CCDs to cover a 1.5 degrees diameter field of view. This field of view is nearly ten times wider than the current prime focus camera, Suprime-Cam. The larger HyperSuprime must be designed to minimally impact the Subaru Telescope when installed. It should fit in the existing Inner-Hub and also the Top Unit Exchanger. The space and weight constraints are severe considering the tight optical tolerance. To achieve this, the we will adopt CFRP (Carbon Fiber Reinforced Plastic) for major mechanical structure.
CCD testing and characterization for dark energy survey
J. Estrada, T. Abbott, B. Angstadt, et al.
A description of the plans and infrastructure developed for CCD testing and characterization for the DES focal plane detectors is presented. Examples of the results obtained are shown and discussed in the context of the device requirements for the survey instrument.
The Oxford SWIFT integral field spectrograph
We present the design of the Oxford SWIFT integral field spectrograph, a dedicated I and z band instrument (0.65μm micron - 1.0μm micron at R~4000), designed to be used in conjunction with the Palomar laser guide star adaptive optics system (PALAO, and its planned upgrade PALM-3000). It builds on two recent developments (i) the improved ability of second generation adaptive optics systems to correct for atmospheric turbulence at wavelengths less than or equal to 1μm micron, and (ii) the availability of CCD array detectors with high quantum efficiency at very red wavelengths (close to the silicon band edge). Combining these with a state-of-the-art integral field unit design using an all-glass image slicer, SWIFT's design provides very high throughput and low scattered light. SWIFT simultaneously provides spectra of ~4000 spatial elements, arranged in a rectangular field-of-view of 44 × 89 pixels. It has three on-the-fly selectable pixel scales of 0.24", 0.16" and 0.08'. First light is expected in spring 2008.
Poster Session B
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Exoplanet detection with simultaneous spectral differential imaging: effects of out-of-pupil-plane optical aberrations
Imaging faint companions (exoplanets and brown dwarfs) around nearby stars is currently limited by speckle noise. To efficiently attenuate this noise, a technique called simultaneous spectral differential imaging (SSDI) can be used. This technique consists of acquiring simultaneously images of the field of view in several adjacent narrow bands and in combining these images to suppress speckles. Simulations predict that SSDI can achieve, with the acquisition of three wavelengths, speckle noise attenuation of several thousands. These simulations are usually performed using the Fraunhofer approximation, i.e. considering that all aberrations are located in the pupil plane. We have performed wavefront propagation simulations to evaluate how out-of-pupil-plane aberrations affect SSDI speckle noise attenuation performance. The Talbot formalism is used to give a physical insight of the problem; results are confirmed using a proper wavefront propagation algorithm. We will show that near-focal-plane aberrations can significantly reduce SSDI speckle noise attenuation performance at several λ/D separation. It is also shown that the Talbot effect correctly predicts the PSF chromaticity. Both differential atmospheric refraction effects and the use of a coronagraph will be discussed.
Fibre modal noise issues in astronomical spectrophotometry
Jason C. W. Corbett, Jeremy Allington-Smith
Fibre modal noise is a photometric uncertainty in a spectrographic resolution element found in high dispersion, high signal to noise spectra. This paper describes how the noise manifests itself and the theory used to describe it. Using a rigorous modal coupling analysis we then show the theories used to date must be called into question due to the changes in the statistics of modal noise with changes in the modal power distribution which occur with arbitrary illumination of the fibre.
LIINUS/SERPIL: a design study for interferometric imaging spectroscopy at the LBT
LIINUS/SERPIL is a design study to augment LBTs interferometric beam combiner camera LINC-NIRVANA with imaging spectroscopy. The FWHM of the interferometric main beam at 1.5 micron will be about 10 mas, offering unique imaging and spectroscopic capabilities well beyond the angular resolution of current 8-10m telescopes. At 10 mas angular scale, e.g., one resolution element at the distance of the Galactic Center corresponds to the average diameter of the Pluto orbit (79 AU), hence the size of the solar system. Taking advantage of the LBT interferometric beam with an equivalent maximum diameter of 23 m, LIINUS/SERPIL is an ideal precursor instrument for (imaging) spectrographs at extremely large full aperture telescopes. LIINUS/SERPIL will be built upon the LINC-NIRVANA hardware and LIINUS/SERPIL could potentially be developed on a rather short timescale. The study investigates several concepts for the optical as well as for the mechanical design. We present the scientific promises of such an instrument together with the current status of the design study.
Conceptual design for a high resolution infrared spectrograph for the 8-m Gemini telescopes
The High-Resolution Near-InfraRed Spectrograph (HRNIRS) concept for the Gemini telescopes combines a seeing limited R ~ 70000 cross-dispersed mode and an MCAO-fed near diffraction-limited R ~ 30000 multi-object mode into a single compact instrument operating over the 1 - 5 μm range. The HRNIRS concept was developed in response to proposals issued through the Aspen instrument process by Gemini. Here we review the science drivers and key functional requirements. We present a general overview of the instrument and estimate the limiting performance.
ISLE: a general purpose near-infrared imager and medium-resolution spectrograph for the 1.88-m telescope at Okayama Astrophysical Observatory
Kenshi Yanagisawa, Yasuhiro Shimizu, Kiichi Okita, et al.
ISLE is a near-infrared (1.0-2.5μm) imager and spectrograph for the Cassegrain focus (f/18) of the 1.88 m telescope at Okayama Astrophysical Observatory. The detector is a HAWAII 1024 × 1024 HgCdTe Array, which covers 4.2 × 4.2 arcmin2 field of view with a pixel scale of 0.25 arcsec/pixel. ISLE also provides medium (R=300 - 4800) resolution long-slit (4 arcmin long spectroscopic capabilities using reflection gratings. A dedicated front-end electronics for the detector achieved a readout noise of 8 electrons by the conventional Fowler sampling, and a operation scheme that combined with a number of discarded readout greatly suppressed the reset anomaly. The measured limiting magnitudes were J=18.6 and K=17.7 (imaging of point sources at S/N=10 for 10 min. exposure).
FRIDA: integral-field spectrograph and imager for the adaptive optics system of the Gran Telescopio Canarias
J. A. López, V. Bringas, S. Cuevas, et al.
FRIDA (inFRared Imager and Dissector for the Adaptive optics system of the Gran Telescopio Canarias) has been designed as a diffraction limited instrument that will offer broad and narrow band imaging and integral field spectroscopy (IFS) capabilities with low, intermediate and high spectral resolutions to operate in the wavelength range 0.9 - 2.5 μm. The integral field unit is based on a monolithic image slicer and the imaging and IFS observing modes will use the same Rockwell 2Kx2K detector. FRIDA will be based at a Nasmyth focus of GTC, behind the AO system. The main design characteristics of FRIDA are described in this contribution. FRIDA is a collaborative project between the main GTC partners, namely, Spain, Mexico and Florida, lead by UNAM.
Optical design of the KMOS slicer system
KMOS is a 2nd generation instrument in project for the VLT. It is an NIR multi-object integral-field spectrograph capturing 24 fields of 2.8" ×2.8" anywhere on a 7.2' field. The 24 fields are fed to 24 IFUs with a resolution of 0.2". KMOS is made of 3 stages: the pickoff system which captures the 24 images, the slicer system and the spectrographs. The slicer system is then the optical link between the 24 images captured by the pickoff system and the 3 slits in front of the 3 spectrographs. It is made of 24 Advanced Image Slicer systems similar to the GNIRS IFU except for 2 modifications: there are 3 mirrors with power in the fore-optics instead of 2 and there are 2 lines of pupil mirrors instead of one. The fore-optics of each system is made of 3 off-axis aspheric mirrors that accomplish a series of task: transfer the field image, position the pupil, magnify the image, give an anamorphic magnification to the image, and give a high image quality. The possibility of rotating the image with the fore-optics has also been studied.
WINERED: a warm near-infrared high-resolution spectrograph
We are developing a new near-infrared high-resolution (Rmax = 100,000) and high-sensitive spectrograph WINERED, which is specifically customized for short NIR bands at 0.9-1.35 μm. WINERED employs the following two novel approaches in the optical system: (1) portable design with a ZnSe immersion grating and (2) warm optics without any cold stops. These concepts result in several essential advantages as follows: easy to build, align, and maintain; these result in a short development time and low cost. WINERED employs a VIRGO HgCdTe 2k × 2k array by Raytheon as the detector. We are developing our own array control system that aims at a low readout noise (< 10 e-) with a readout time of about 3 sec. Our goal is to achieve a high sensitivity of R = 100,000 for a NIR spectroscopy of 15 mag and 17 mag point sources with 4 m and 10 m telescopes, respectively. We have just finalized the optical design and produced a prototype electronics, which are described in the companion papers by Yasui et al. and Kondo et al., respectively. We plan to complete this instrument by the end of 2008 and hope to attach it to various 4 to 10 m telescopes as a PI-type instrument.
Design of the TMT mid-infrared echelle: science drivers and design overview
J. H. Elias, J. S. Carr, M. J. Richter, et al.
We present a discussion of the science drivers and design approach for a high-resolution, mid-infrared spectrograph for the Thirty-Meter Telescope. The instrument will be integrated with an adaptive optics system optimized for the midinfrared; as a consequence it is not significantly larger or more complex than similar instruments designed for use on smaller telescopes. The high spatial and spectral resolution possible with such a design provides a unique scientific capability. The design provides spectral resolution of up to 120,000 for the 4.5-25 μm region in a cross-dispersed format that provides continuous spectral coverage of up to 2% to 14 μm. The basic concept is derived from the successful TEXES mid-infrared spectrograph. To facilitate operation, there are separate imaging channels for the near-infrared and the mid-infrared; both can be used for acquisition and the mid-infrared imaging mode can be used for science imaging and for guiding. Because the spectrograph is matched to the diffraction limit of a 30-m telescope, gains in sensitivity are roughly proportional to the square of the telescope diameter, opening up a volume within the Galaxy a thousand times greater than existing instruments.
Design of the HiCIAO instrument for the Subaru Telescope
Klaus W. Hodapp, Motohide Tamura, Ryuji Suzuki, et al.
HiCIAO, the High-Contrast Coronographic Imager for Adaptive Optics, is a coronographic simultaneous differential imager for the Subaru Telescope Nasmyth focus. It is designed primarily to search for faint companions, brown dwarves and young giant planets, around nearby stars, but will also allow observations of disks around young stars and of emission line regions near other bright central sources. HiCIAO will work in conjunction with the new Subaru Telescope 188 actuator adaptive optics system. It is designed as a flexible, experimental instrument that will grow from the initial, simple coronographic system into more complex, innovative coronographic optics as these technologies become available. The main component of HiCIAO is an infrared camera optimized for spectral simultaneous differential imaging that uses a 2.5 μm HAWAII-2RG detector array operated by a Rockwell Sidecar ASIC.
Cosmic web imager
We are developing the Cosmic Web Imager (CWI) to detect and map emission from the intergalactic medium (IGM). CWI will observe the strong, redshift UV resonance lines of Lyα 1216, CIV 1550, and OVI 1033 over 3600-9000 Å to trace IGM at 1 < z < 7. CWI is an integral-field spectrograph designed for the Hale Telescope at Palomar Observatory. CWI combines in a novel way three mature and extensively used instrumental techniques. The Integral Field Unit (IFU) provides a wide 2D field of view of 60 × 40 arcsec2 for observing extended emission over a large region. The spectrograph using Volume-Phase Holographic gratings have high peak diffraction efficiency and are tunable for covering a large bandpass with a single grating. A low read noise CCD combined with source/background shiftand-nod allowing control of systematics and Poisson-imited sky subtraction to observe the low surface brightness universe. With a resolution of R=10,000 CWI is sensitive to limiting surface brightness ranging from 25 - 27.5 mag/arcsec2 (10 min - 8 hours integration). Recent high resolution simulations predict Lyα Fluorescence from IGM at 100 - 1000 LU1. CWI with sensitivity of ~200 LU improves the current observational effort by an order of magnitude and enables us to explore wide range of overdensity (δ ~ 30 - 104) testing the standard model of structure formation in the universe. CWI also serves as the counter part to the balloon borne integral-field spectrograph Faint Intergalactic medium Redshifted Emission Balloon (FIREBALL) currently being built and planned to be launched in Summer 2007. FIREBALL will observe Lyα Fluorescence from IGM at z = 0.7. CWI combined with FIREBALL will enable us to observe the evolution of IGM and the low surface brightness universe.
An infrared integral field spectrograph specialized for speckle suppression and the direct detection of extrasolar planets
Quasi-static speckles are the main source of noise preventing the direct detection of exoplanets around bright stars. We are investigating the use of an infrared (1.5-2.4 μm) integral field spectrograph (IFS) specialised for speckle suppression and the detection of self-luminous giant planets. This paper presents the optical design and laboratory results obtained with a TIGER-type IFS prototype based on a microlens array. A similar IFS will be used for the Gemini Planet Imager (GPI). Preliminary speckle-suppression performances of the IFS along with simulations are presented.
Design tradeoffs for a high spectral resolution mid-infrared echelle spectrograph on the Thirty-Meter Telescope
A. T. Tokunaga, T. Bond, J. Elias, et al.
A feasibility design study was undertaken to assess the requirements of a mid-infrared echelle spectrograph (MIRES) with a resolving power of 120,000 and its associated mid-infrared adaptive optics (MIRAO) system on the Thirty-Meter Telescope. Our baseline design incorporates a 2K×2K Si:As array or array mosaic for the spectrograph and a 1K×1K Si:As array for the slit viewer. Various tradeoffs were studied to minimize risk and to optimize the sensitivity of the instrument. Major challenges are to integrate the spectrograph to the MIRAO system and, later, to an adaptive secondary, the procurement of a suitable window and large KRS-5 lenses, and the acquisition of large format mid-IR detector arrays suitable for the range of background conditions. We conclude that the overall risk is relatively low and there is no technical reason that should prevent this instrument from being ready for use at first light on the Thirty- Meter Telescope.
The spectrometer optics of GIANO-TNG
S. Gennari, I. Mochi, S. L. Donati, et al.
GIANO is a cryogenic cross-dispersed spectrometer operating at near IR wavelengths (0.9-2.5 microns). The aim of the optical design is to obtain wide spectral coverage, high resolution, large throughput and high spectral stability in a sufficiently compact instrument which can be built and cooled using relatively simple and inexpensive technologies. This ambitious goal is achieved using a 3-mirrors anastigmat in double-pass which acts both as collimator and camera. The collimated beam has a diameter of 100 mm and feeds a commercial 23.2 lines/mm echelle grating. Cross-dispersion is performed by prisms which also operate in double pass. By inserting a flat mirror before the grating, the instrument changes its face (hence the name "GIANO") and transforms into a low resolution spectrometer with a unique combination of spectral coverage, resolution and efficiency.
The mechanics and cryogenics of GIANO-TNG
GIANO is a cryogenic cross-dispersed spectrometer whose optics consist of aspheric aluminum mirrors, glass flats, cross-dispersing prisms and a grating fixed onto a ~1.5×1.0 m aluminum bench. The primary aim of the project is to achieve the highest possible image quality and spectral stability essential for precise radial velocity measurements. The instrument also includes other observing modes which are obtained by inserting a flat mirror or a prism at different positions in the optical path. This flexibility is achieved without affecting the stability and performances of the primary, high resolution mode. We describe here the cryo-mechanical design which has been optimized to these purposes.
The preslit system of GIANO-TNG
P. Bruno, F. Leone, E. Oliva, et al.
GIANO-TNG is an ultra-stable infrared (0.9-2.5 μm) high resolution cross-dispersed spectrometer designed to operate at a fixed position relative to the telescope axis. It therefore requires a pre-slit opto-mechanical system which takes care of field de-rotation and auto-guiding. Taking advantage of the structure already existing for SARG (the high resolution optical spectrometer of the Telescopio Nazionale Galileo, TNG) we are developing a system which provides a large (2 arcmin) field of view for offset guiding and includes, as separate and selectable elements, a gas absorption cell and a polarimetric module where the analyzers work in a collimated beam.
Calibration of the ZnSe pre-disperser on ESO's cryogenic IR echelle spectrograph (CRIRES): comparison of the first results from CRIRES and the laboratory data from CHARMS
The European Southern Observatory (ESO), the Space Telescope European Co-ordinating Facility (ST-ECF) and Goddard Space Flight Center (NASA) are collaborating to study the refractive index of ZnSe at cryogenic temperatures. The pre-disperser prism of ESO's Cryogenic high-resolution IR Echelle Spectrograph (CRIRES) for the Very Large Telescope (VLT) is made of ZnSe. CRIRES covers the wavelength range from 950 - 5000 nm at a resolution of 100,000 and is operated at about 65 K. Recent measurements at NASA GSFC's cryogenic high accuracy refraction measuring system (CHARMS) have established the index of refraction for ZnSe both as a function of wavelength and temperature. These data are being used as input for a physical model that provides the wavelength calibration for CRIRES. Here we present the latest results from CHARMS and a comparison with measurements obtained during CRIRES' laboratory testing. Our results highlight the value of high accuracy laboratory measurements of the optical properties of materials for the design and operation of astronomical instrumentation. This also illustrates the use of such data in instrument physical models for high fidelity calibration of spectrographs.
Preliminary optical design for the TMT mid-infrared adaptive optics system and echelle spectrograph
We present a preliminary optical design for a mid-infrared, high-resolution spectrograph (MIRES), together with an integrated adaptive optics system optimized for the mid-infrared, intended for use on a 30-meter telescope. The design includes laser guide star wavefront sensors, a near-infrared natural guide star wavefront sensor with a patrol field of 60 arcseconds, and near-infrared and mid-infrared imaging channels, in addition to the cross-dispersed spectrograph itself. The spectrograph provides resolution of up to 120,000 and continuous spectral coverage over multiple cross-dispersed orders, with high efficiency between 4.5 and 25 microns.
FMOS: The fiber multi-object spectrograph V results of early PIR engineering run
Masahiko Kimura, Toshinori Maihara, Fumihide Iwamuro, et al.
Fibre Multi-Object Spectrograph (FMOS) is one of the second-generation instruments of Subaru Telescope. FMOS is consisted of a number of subsystems; the Prime focus unit for IR (called PIR), the fibre positioning system/connector units, and the two spectrographs. The PIR and one spectrograph were made in Kyoto University, and were brought to the Subaru telescope last spring. The PIR attached to the telescope and stellar images were obtained for optical alignment in July and October last year. We report on these engineering run in this proceeding.
FLAMINGOS-2 OIWFS
Brian Leckie, William Gardhouse, Murray Fletcher, et al.
An On-Instrument Wavefront Sensor (OIWFS) designed, built and tested by the National Research Council of Canada (NRC) for the FLoridA Multi-object Imaging Near-IR Grism Observational Spectrometer (FLAMINGOS) is described. The University of Florida is building the FLAMINGOS-2 IR spectrograph for the Gemini Observatory as a near copy of the original multi-telescope FLAMINGOS instrument. NRC/HIA was subcontracted to build the OIWFS based on the Gemini Multi-Object Spectrograph (GMOS) design. The FLAMINGOS-2 OIWFS patrols the bulk of the FLAMINGOS-2 field-of-view and will accept the Gemini f/16 input beam as well as the f/30 beam from the Gemini Multi-Conjugate Adaptive Optics (MCAO) system. The portion of the probe arm that enters the FLAMINGOS-2 field-of-view is cooled, to avoid contaminating the infrared images. The OIWFS uses the same CCD and CCD controller as was used on GMOS (e2v CCD39 and ARC GENII). Mechanically, the OIWFS is a modified version of the GMOS OIWFS. It comprises two stacked rotational stages, each operating on a single bearing. The top stage supports an optics package, which includes a lenslet array, pickoff arm and CCD. The optical design uses a four subaperture Shack-Hartmann lenslet array. The mechanism is controlled using EPICS based software that includes GUI engineering screens. Test results showing the OIWFS to be fully compliant with design specifications are presented.
A high-spectral resolution tandem Fabry-Perot spectrometer for 17-micrometer wavelength
Takahiro Nagayama, Tetsuya Nagata, Takahiro Zenno, et al.
We present our high spectral resolution tandem Fabry-Perot (FP) spectrometer for detecting the pure rotational transition line of molecular Hydrogen S (1) at 17.035 μm. It is designed to be attached to a new dedicated 1 m telescope planned to be put at a dry and high-altitude site. The spectrometer has two sequentially placed FP units (order 1000 and 99 with finesse >50) consisting of ZnSe etalons and one narrow band filter. We will be able to obtain high spectral resolution of R=50,000 at 17.035 μm. The ZnSe etalons of 110mm diameter with >94% reflectance are to be provided from Barr Associates. The interval and tilt of etalons are sensed and regulated by piezo actuators and newly-developed capacitance sensors, which resolve 100nm in vacuum and 30K environment. By changing the interval, we change the wavelength of transmission up to 17.2 μm, corresponding toν = 3000 km/s. We adopt an on-axis catadioptric system, in which the two FP units are placed. The focal plane detector is a Raytheon SB-774, 320×240 pixel array of Si:As, yielding 9.1 × 6.8 arcmin2 field of view with 1.7 arcsec pixel scale. To suppress the thermal background radiation and dark current of the Si:As detector, the system is cooled down to 6K at the detector and 35K for the whole optical system by two refrigerators. The development of spectrometer will be completed in 2007.
First results and current development of SpIOMM: an imaging Fourier transform spectrometer for astronomy
A.-P. Bernier, F. Grandmont, J.-F. Rochon, et al.
We present an overview of SpIOMM, an Imaging Fourier Transform Spectrometer (IFTS) for astronomy developed at University Laval in collaboration with ABB, INO and the Canadian Space Agency. SpIOMM, attached to the 1.6 meter (f/8) telescope at the Observatoire du mont Megantic in Quebec. It is a Michelson-type interferometer capable of obtaining the visible spectrum (from 350 nm to 900 nm) of every light source within its 12 arcminute circular field of view. This design will allow the correction of variable sky transmission. It consists of a dual output port and the total throughput is exploited by two CCDs used as detectors. We present the concept and design of this unique instrument. A metrology system combined with a dynamic alignment assures a good sampling and mirror alignment during the entire acquisition sequence. This particular servo control is explained and demonstrated and its capabilities and performance are discussed. We introduce the use of specific bandpass filters centered on the most important groups of emission lines which, when combined with spectral folding algorithms, allows us to reach high spectral resolution (R = 25 000, or 1 cm-1). Astronomical data collected by SpIOMM in 2004-2005 are also presented.
The UK FMOS spectrograph
G. B. Dalton, I. J. Lewis, D. G. Bonfield, et al.
We describe the build phase of the UK FMOS spectrograph, a 200 fibre cooled OH Suppression infrared spectrograph being constructed as part of Subaru's Fibre Multi Object Spectroscopy facility. Here we describe recent UK activities within the FMOS programme and the likely schedule for commissioning at Subaru.
Development of configurable slit unit for GTC-EMIR
The Configurable Slit Unit (CSU) for EMIR shall enable the possibility to generate a multi-slit configuration, a long slit, or an imaging aperture at the entrance focal plane of the GTC-EMIR instrument. The CSU is therefore a cryogenic reconfigurable slit mechanism. It contains 100 sliding bars which can be positioned within the 307x307mm wide aperture of EMIR's instrument field of view. The development of the CSU has been a challenging task for several reasons: the high number of elements to control to configure a single observing pattern; the nominal working temperature of 77 K at which all the functionalities have to be accomplished, the stringent requirements in both accuracy and repeatability for most of the functionalities and the rotating nature of the EMIR instrument. The combination of these requirements urged the need to develop new pioneering concepts for actuation and position measurement. An actuation mechanism has been developed based on a piezo drive concept. A dedicated incremental, endless capacitive measurement system has been developed to measure the position of each separate bar. Both technologies are successfully realized in the demonstration programme that has been launched to prove the feasibility of the CSU concept. Besides actuation and position control of the bars, also thermal behavior of the CSU concept have been evaluated within the demonstration programme.
Design of the Gemini near-infrared spectrograph
The Gemini Near-Infrared Spectrograph (GNIRS) supports a variety of observing modes over the 1-5 μm wavelength region, matched to the infrared-optimized performance of the Gemini 8-m telescopes. We describe the optical, mechanical, and thermal design of the instrument, with an emphasis on challenging design requirements and how they were met. We also discuss the integration and test procedures used.
Optical design of the high-resolution near-infrared spectrograph
HRNIRS is an extremely versatile high-resolution infrared facility spectrograph designed for the Gemini South telescope. Operating over the 1.05 - 5.5 micron wavelength range, it has the capability to carry out a wide range of scientific programs by incorporating two separate modes of operation. The first is a conventional single slit cross-dispersed mode providing spectral resolution R ~ 70000 with a 0.4 arcsec slit over as much as an octave in wavelength, thus covering most of the JHK or LM windows in a single observation. In this mode the spectrograph accepts the Gemini seeing-limited f/16 input over a small field. A built-in modulator and polarizer allow HRNIRS to measure both linear and circular polarization. The second mode is a moderately-high resolution (R ~ 30000) spectrograph observing multiple objects simultaneously within a 2 arcmin field fed by the f/33.2 Gemini MCAO beam. In this paper, we discuss the optical design considerations, present the resulting design and show that the predicted performance meets the design requirements.
Enhancements over the electronic control for OSIRIS-Gtc Fabry-Perot tunable filters
Guillermo A. Herrera, José V. Gigante, Enrique Joven, et al.
OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) is the optical Day One instrument for the 10.4m Spanish telescope GTC (Gran Telescopio Canarias). The instrument spectral range covers from 365 up to 1000 nm. One of the most important elements of OSIRIS is its two commercial ICOS ET100 wide field Fabry-Perot tunable filters, that will provide a powerful tool to analyse faint emission line objects. Currently, the unique controller available for such device is the so called CS100. Due to the necessity of improvement and addition of some specifications of such controller, a first prototype electronic module has been made and tested successfully. Now, it has developed the final product: a compact mini-module integrated in the CS100 controller, offering a 16-bit resolution over the full range cavity spacing; be able to synchronize cavity changes with an external trigger; full remote control over the front panel of the device and capability to monitor all their signals. It also offers the possibility to load a preprogrammed table sequence of cavity spacing changes, programmable security limits of dynamic range and slew rate applied; and it has high stability over time too. The electronic control is based on an embedded microcontroller into a FPGA.
Opto-mechanical design of the KMOS spectrograph module
Matthias Tecza, Ian J. Lewis, James Lynn, et al.
We present the optical and mechanical design of the KMOS spectrograph module together with a detailed analysis of its performance. KMOS is a cryogenic near-infrared multi-object spectrograph being developed as a second-generation instrument for the VLT by a consortium of UK and German institutes. Three identical spectrograph modules provide Nyquist sampled spectra in the wavelength range covering the atmospheric bands z, J, H, and K with a resolving power exceeding 3200. The spectrographs are fully achromatic over the bands and the single mirror collimator and six-element camera, together with six high efficiency gratings provide high throughput. The optical performance analysis includes amongst others the spectral resolving power and variation of the PSF as a function of the pupil illumination.
Mechanical design of the Gemini high resolution near-infrared spectrograph
The High-resolution Near-infrared Spectrograph (HRNIRS) concept for the Gemini telescopes combines a seeing-limited R ~ 70000 cross-dispersed mode and a MCAO-fed near diffraction-limited R ~ 20000 multi-object mode into a single compact instrument operating over the 0.9-5.5μm range. We describe the mechanical design, emphasizing the challenging design requirements and how they were met. The approach of developing the optical and mechanical designs in concert and utilizing proven working concepts from the Gemini Near Infra-Red Spectrograph were key elements of the design philosophy. Liang, et al. provides a detailed discussion of the optical design, Hinkle, et al. describes the science cases and requirements as well as a general overview, and Eikenberry, et al. describes the systems engineering and performance aspects of HRNIRS.
GMTNIRS: the high resolution near-IR spectrograph for the Giant Magellan Telescope
D. T. Jaffe, D. J. Mar, D. Warren, et al.
We present a conceptual design for a powerful, high-resolution near-infrared spectrograph for the Giant Magellan Telescope (GMT). This instrument, the Giant Magellan Telescope Near-Infrared Spectrograph (GMTNIRS), uses silicon immersion gratings as the primary dispersing elements. The design has two modules, one for 1.1-2.4 μm for use under native seeing conditions and one for 3-5.5 μm to be used with adaptive optics. The resulting design is physically compact and allows us to cover entire infrared atmospheric windows in a single exposure with resolving powers up to 100,000.
Fabrication and performance of silicon immersion gratings for infrared spectroscopy
Jasmina P. Marsh, Douglas J. Mar, Daniel T. Jaffe
Silicon immersion gratings open up the possibility of compact infrared spectrometers with high throughput, high spectral resolution, and extensive instantaneous coverage. The performance of the diffraction gratings that we have been developing over the past 15 years has reached the level where it can exceed that of commercially available diffraction gratings. We have produced science-grade immersion grating echelles with coarsely spaced grooves on silicon substrates appropriate for applications in the near-infrared (1.1-5μm). Devices in the current generation have excellent throughput (60%-80%) and display diffraction-limited performance over apertures of 20 mm or more. Tests of the gratings done in reflection are in good agreement with tests done in immersion. We assess the current state of the silicon grating technology as well as discuss further developments necessary for making gratings on larger silicon substrates.
The MOAO system of the IRMOS near-infrared multi-object spectrograph for TMT
David R. Andersen, Stephen S. Eikenberry, Murray Fletcher, et al.
The near-Infrared Multi-Object Spectrograph (IRMOS) for TMT is one of the most powerful astronomical instruments ever envisioned. The combination of the collecting area of TMT, the unique image-sharpening capabilities of the Multi-Object Adaptive Optics (MOAO) system, and the multiplexing advantage of the multi-object integral-field spectra provided by the IRMOS back-end make it capable of addressing some of the leading scientific challenges of the coming decades. Here we present an overview of one potential IRMOS concept and then focus on the MOAO system. In particular we will describe our concept for the laser and natural guide star wavefront sensors, deformable mirrors and the calibration system of MOAO. For each of these design elements, we describe the key trade studies which help define each subsystem. From results of our studies, we assemble a MOAO ensquared energy budget. We find that 50% of the energy is ensquared within the 50 milli-arcsecond spatial pixel of the IRMOS integral field units for a wavelength of 1.65μm. Given the requirements placed on the MOAO system to achieve this performance, large ensquared energies can be achieved with even finer plate scales for wavelengths longer than 1.5μm.
FISICA: the Florida imager slicer for infrared cosmology and astrophysics
Stephen Eikenberry, S. Nicholas Raines, Nicolas Gruel, et al.
We report on the design, fabrication, and on-sky performance of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of "monolithic" powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. Finally, we present performance results from observations with FISICA at the KPNO 4-m telescope and comparisons of FISICA performance to other available IFUs on 4-m to 8-m-class telescopes.
TEXES on Gemini
TEXES is a versatile mid-infrared spectrograph, which has been used on the NASA IRTF since 2000. It is capable of high spectral resolution (R ≈ 100,000), which is well suited for observations of interstellar and circumstellar molecules and ions, as well as molecules in planetary and stellar atmospheres. It has been installed on Gemini North where its point source sensitivity is expected to improve by a factor of 7, and its angular resolution will improve by 8/3.
Infrared multi-object spectrograph of MOIRCS
The design, development, operation and current performance of MOS (multi-object spectroscopy) mode of MOIRCS is described. MOIRCS (Multi-Object Infrared Camera and Spectrograph) is one of the second-generation instruments for the Subaru Telescope and provides imaging and MOS modes with a 4' × 7' field of view for a wavelength range from 0.85 to 2.5 μm. To achieve near-infrared (NIR) MOS up to K-band, MOS mode uses multi-slit masks and a mask exchange system in a cryogenic environment. The masks are housed in a vacuum dewar attached to the MOIRCS main dewar and separated by a large gate valve. The mask dewar is equipped with its own cryogenic cooler and a vacuum pump and is capable of storing eighteen masks. The masks are made of thin aluminum foil. Slits are cut with a laser, with software that corrects for the effects of thermal contraction. The masks are cooled to below 130 K in the mask dewar and transported to the focal plane in the main dewar through the gate valve with a linear motion manipulator. An interlock is equipped on the mask exchange system to secure the cryogenic instrument from accident. Replacing masks can be done in the daytime without breaking the vacuum of the main dewar by isolating the mask dewar with the gate valve. Acquisition occurs by iteratively taking on-sky images through alignment holes on the mask until the rotation and offset between alignment stars and alignment holes become small enough. MOIRCS/MOS mode will be open to the public in late 2006.
UTIRAC: University of Tokyo infrared array control system developed for WINERED
Sohei Kondo, Kentaro Motohara, Chikako Yasui, et al.
We are developing a 2K × 2K format array control system (UTIRAC: University of Tokyo InfraRed Array Control system) for "WINERED", which is a new high-resolution (Rmax = 100, 000) near-infrared (0.9-1.35 μm) spectrograph being built at the Institute of Astronomy, University of Tokyo. UTIRAC has the following two characteristics: (1) applicable to various infrared array (with Amp-ADC integrated boards which enables easy increase/decrease of the number of input channels) and (2) based on the MESSIA5 system (for clock generation and frame acquisition) developed by National Astronomical Observatory of Japan. The goals of UTIRAC are low readout noise (< 10 e-) and readout speed of 200 kHz/pix (for the Raytheon VIRGO array). Working tests of each board and integration test with MESSIA5 system have been completed. As a next step, we are going to test VIRGO MUX for operation 4 with outputs and to evaluate readout noise. In the near future, we will increase the number of input channels on a single Amp-AD board from one to four for the operation of arrays with 16 outputs.
WINERED: optical design of warm infrared echelle spectrograph
Chikako Yasui, Yuji Ikeda, Naoto Kobayashi, et al.
We are developing a short near-infrared (λ=0.9-1.35μm) high-resolution (Rmax=100,000) and high-sensitivity spectrograph "WINERED" by using several unique approaches. We adopt a classical cross-dispersed configuration for the optical system because it provides the best balance between the system throughput, alignment tolerances, and image quality (thereby producing high spectral resolution). Our design has four characteristics: (1) a ZnSe immersion echelle grating is used to realize a compact optical system even with Rmax=100,000; (2) a volume phase holographic (VPH) grating is used as across-disperser (in comparison with the classical reflective grating, the VPH grating decreases the camera optics and provides higher throughput); (3) a cooled refractive lens system is used for the camera optics; and (4) a reflective echelle grating can be replaced with the above-mentioned immersion grating to cover a wider wavelength range with Rmax=28,000. We have found a compact solution with high performance: all spots are well within 2×2 pixels throughout the entire detector array and the total throughput is more than 25% for all modes.
First results with OSIRIS: NIR-imaging spectroscopy at the diffraction limit
OSIRIS is an integral field infrared spectrograph designed for the Keck Adaptive Optics System. It utilizes an array of lenses and the latest infrared detector to simultaneously obtain more than 3000 spectra over a rectangular field of view (up to 48x64 spatial elements). In its broad band mode (16x64 spectra), each spectrum contains more than 1700 wavelength channels and covers an entire infrared band at a resolution of 3800. Due to the extremely low backgrounds between night sky lines and at AO spatial samplings, the instrument is also extremely sensitive. Here we present first results obtained during commissioning of the instrument following First Light in February 22, 2005. We demonstrate the performance of the instrument, in particular together with the Keck Observatory's adaptive optics system and provide a flavor of the science addressed with OSIRIS.
Near-infrared integral-field spectroscopy of HD209458b
Daniel Angerhausen, Alfred Krabbe, Christof Iserlohe
We present first results of an exploratory study to use integral field spectroscopy to observe extrasolar planets. We focus on transiting 'Hot Jupiters' and emphasize the importance of observing strategy and exact timing. We demonstrate how integral field spectroscopy compares with other spectroscopic techniques currently applied. We have tested our concept with a time series observation of HD209458b obtained with SINFONI at the VLT during a superior conjunction.
The NIR upgrade to the SALT Robert Stobie Spectrograph
The near infrared (NIR) upgrade to the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT), RSS/NIR, extends the spectral coverage of all modes of the visible arm. The RSS/NIR is a low to medium resolution spectrograph with broadband imaging, spectropolarimetric, and Fabry-Perot imaging capabilities. The visible and NIR arms can be used simultaneously to extend spectral coverage from approximately 3200 Å to 1.6 μm. Both arms utilize high efficiency volume phase holographic gratings via articulating gratings and cameras. The NIR camera is designed around a 2048x2048 HAWAII-2RG detector housed in a cryogenic dewar. The Epps optical design of the camera consists of 6 spherical elements, providing sub-pixel rms image sizes of 7.5 ± 1.0 μm over all wavelengths and field angles. The exact long wavelength cutoff is yet to be determined in a detailed thermal analysis and will depend on the semi-warm instrument cooling scheme. Initial estimates place instrument limiting magnitudes at J = 23.4 and H(1.4-1.6 μm) = 21.6 for S/N = 3 in a 1 hour exposure well below the sky noise.
The measurement of profile tolerance for the small focal plane plate of LAMOST
Zengxiang Zhou, Chao Zhai, Xiaozheng Xing, et al.
One essential technology of the entire project of LAMOST(Large-sky-area multiobjec fiber spectroscopic telescope) is the focal plane plate on which is installed over 4000 fiber units. The telescope receives the light passes through the reflector of MA (the reflecting Schmidt plate) and MB (the spherical mirror), forms focusing image in the focal plane. And through optical fiber the light is introduced to the spectroscope by the fiber units. So the focal plane is the basic of the plane installed 4000 fiber units, and influence the imaging quality of the whole system. In the project of LAMOST, the focal plane plate is a part of sphere which radius is 19880mm and the diameter of it is about 1750mm, but the surface area of the focal plane plate approximate 1/8000 of the whole global. Thereby the measurement of the focal plane plate which profile tolerance low than 40μm to obtain the reliable and accurate results is a difficult problem to deal with. All the installation of the fiber units and mending the focal plane are based on the measurement. We try to use CMM(Coordinate Measurement Machine) to survey the processed Small Focal Plane which diameter is 445mm. And we will carry on the analysis for several kinds of test and the data processing method to compare and optimize, finally determines the actual application plan.
Control software and user interface for the Canarias Infrared Camera Experiment (CIRCE)
The Canarias InfraRed Camera Experiment (CIRCE) is a near-infrared visitor instrument for the 10.4-meter Gran Telescopio Canarias (GTC). This document shows CIRCE software. It will have two major functions: instrument control and observatory interface. The instrument control software is based on the UFLIB library, currently used to operate FLAMINGOS-1 and T-ReCS (as well as the CanariCam and FLAMINGOS-2 instruments under development in the University of Florida). The software interface with the telescope will be based on a CORBA server-client architecture. Finally, the user interface will consist of two java-based interfaces for the mechanism/detector control, and for quick look and analysis of data.
KASINICS: KASI Near-Infrared Camera System
The Korea Astronomy and Space Science Institute (KASI) is building the KASI Near Infrared Camera System (KASINICS) for the 61-cm telescope at the Sobaeksan Optical Astronomy Observatory (SOAO) in Korea. With KASINICS we will mostly do time monitoring observations, e.g., thermal variations of Jovian planet atmospheres, variable stars, and blazars. We use a 512 x 512 InSb array (Aladdin III Quadrant, Raytheon Co.) for L-band observations as well as J, H, and Ks-bands. The field-of-view of the array is 6 x 6 arcmin with 0.7 arcsec/pixel. Since the SOAO 61-cm telescope was originally designed for visible band observations, we adopt an Offner relay optical system with a Lyot stop to eliminate thermal background emission from the telescope structures. In order to minimize weight and volume, and to overcome thermal contraction problems, we optimize the mechanical design of the camera using the finite-element-method (FEM) analysis. Most of the camera parts including the mirrors are manufactured from the same melt of aluminum alloy to ensure homologous contraction from room temperature to 70 K. We also developed a new control electronics system for the InSb array (see the other paper by Cho et al. in this proceedings). KASINICS is now under the performance test and planned to be in operation at the end of 2006.
The Canarias Infrared Camera Experiment (CIRCE): optical and opto-mechanical design and manufacture
We report on the design status of the Canarias InfraRed Camera Experiment (CIRCE), a near-infrared visitor instrument for the 10.4 meter Gran Telescopio Canarias (GTC). In addition to functioning as a 1-2.5 micron imager, CIRCE will have the capacity for narrow-band imaging, low-and moderate- resolution grism spectroscopy, and imaging polarimetry. CIRCE's all-reflective aspheric optical design offers excellent throughput and image quality. We present an analysis of the optical layout and the progress of the opto-mechanical design and manufacture.
Removal of central obscuration and spiders for coronagraphy
We present a method to remove the central obscuration and spiders, or any kind of geometry inside a telescope pupil. The technique relies on the combination of a first focal plane diffracting mask, and a complex amplitude pupil mask. In this combination, the central obscuration and eventual spider arms patterns in the re-imaged pupil (after the diffracting mask) are filled with coherent light. Adding an appropriate complex amplitude pupil mask allows virtually any kind of pupil shaping (in both amplitude and/or phase). We show that the obtained output pupil can feed a high efficiency coronagraph (any kind) with a very reasonable overall throughput and good performance even when considering pointing errors. In this paper, we specifically assess the performance of this technique when using apodized entrance pupils. This technique is relevant for ground based telescopes foreseeing the advent of higher order (so called ExAO) adaptive optics systems providing very high Strehl ratios. Some feasibility points are also discussed. adaptive optics systems providing very high Strehl ratios. Some feasibility points are also discussed.
SIRPOL: a JHKs-simultaneous imaging polarimeter for the IRSF 1.4-m telescope
Ryo Kandori, Nobuhiko Kusakabe, Motohide Tamura, et al.
We describe a polarimeter for the near-infrared camera SIRIUS mounted on the IRSF 1.4 m telescope in South Africa. The polarimeter, SIRPOL, consists of an achromatic (1-2.5 μm) wave plate rotator unit and a polarizer located upstream of the camera, both of which are at a room temperature. This minimizes the effect of the mirrors in the camera on instrumental polarization. The combination of the polarimeter with the SIRIUS camera enables a deep (J = 19.2 mag, 5σ in one hour) and wide-field (7.7' × 7.7') imaging polarimetry at JHKs simultaneously. The three color near-infrared polarimetry is useful for understanding the properties of dust grains that cause scattering and absorption in various environments (e.g., star forming regions, late-type stars, and galaxies). Using IRSF and SIRPOL, wide-field near-infrared polarization surveys in various star-forming regions are being conducted, starting from 2006, which aim to study both reflection nebulae associated with young stars and interstellar polarizations of background stars. In this contribution, we describe the hardware and software of SIRPOL and report its first results on the telescope.
Observational capabilities and technical solutions of a thermal and MIR instrument at E-ELT
A MIR instrumentation study for a European ELT has been performed by a Dutch consortium led by the Leiden Observatory (The Netherlands) and the Max-Planck-Institut fur Astronomie in Heidelberg (Germany). MIR imaging and spectroscopic observational capabilities are compared to contemporary IR to sub-millimeter facilities, especially concentrating on the MIR-capabilities of JWST(MIRI). Our best effort calculation of the sensitivity for both MIR imager and spectrograph indicate a huge discovery potential in numerous areas from our planetary system to the high redshift Universe (see [6269-75] during this conference). Here we concentrate on the technical aspects of such an instrument, offering diffraction limited direct imaging capabilities over the wavelength range from 3.5μm up to 20μm or even 27μm, as well as medium to high resolution spectroscopy for the same wavelength range. To make use of the extreme spatial resolution, the spectrograph is planned to include an integral field unit.
The REMIR cryogenics restyling
F. Vitali, J. L. Lizon, G. Ihle, et al.
REMIR is the NIR camera of the automatic REM (Rapid Eye Mount) Telescope located at ESO-La Silla Observatory (Chile) and dedicated to monitor the afterglow of Gamma Ray Burst events. During the last two years, the REMIR camera went through a series of cryogenics problems, due to the bad functioning of the Leybold cryocooler Polar SC7. Since we were unable to reach with Leybold for a diagnosis and a solution for such failures, we were forced to change drastically the cryogenics of REMIR, going from cryocooler to LN2: we adopted an ad-hoc modified Continuous Flow Cryostat, a cryogenics system developed by ESO and extensively used in ESO instrumentation, which main characteristic is that the LN2 vessel is separated from the cryostat, allowing a greater LN2 tank, then really improving the hold time. In this paper we report the details and results of this operation.
Status of the EMIR mechanical system
V. Sánchez, S. Barrera, S. Becerril, et al.
EMIR is the NIR multi-object imager and spectrograph for the GTC (Gran Telescopio Canarias). The instrument ADR (Advanced Design Review) was held successfully in March 2006. During the AD phase, a number of mechanical concepts were tested on development prototypes to ensure the feasibility of the PDR proposed designs. This presentation contains an overview of the current mechanical status of the instrument, as well as the prototypes development. It contains the prototype tests results of the collimator first lens barrel, the support trusses, the grisms wheel and the demonstration programme for the cryogenic reconfigurable slit mechanism.
The LINC-NIRVANA IR cryostat
The MPIA is leading an international consortium of institutes building an instrument called LINC-NIRVANA. The instrument will combine the light from the two 8.4 m primary mirrors of the LBT. The beam combiner will operate at wavelengths between 1.1 and 2.4 microns, using a Hawaii2 detector. A volume of about 1.6 m high with a diameter of about 0.65 m is required for the cold optics. The size of the instrument and the high requirements on vibrations brought us to a new approach for the cooling of the cryostat, which has never been tried in astronomy. The cryostat will be cooled by a flow of Helium gas. The cooler which cools the gas will be placed far away on a different level in the telescope building. The cold helium will be fed through long vacuum isolated transfer lines to the instrument cryostat. Inside the cryostat a tube will be wrapped around the mounting structure of the cold optics. The first hardware arrived at the MPIA in 2005 and the system will soon be tested in our labs.
Integration and first results of the CAMCAO NIR camera
This paper presents the integration and first results for the CAMCAO NIR camera. The camera was built for the ESO Multi-conjugate Adaptive optics Demonstrator, where it is presently operating, to evaluate the feasibility of this Adaptive Optics technique. On a second phase it will work directly at the Nasmyth focus of the VLT. CAMCAO is a high resolution, wide field of view NIR camera, that is using the 2k×2k HgCdTe HAWAII- 2 infrared detector from Rockwell Scientific, controlled by the ESO IRACE system. The camera operates in the near infrared region between 1.0 μm and 2.5 μm wavelength using an eight position filter wheel with J, H, K', K-continuum and Brγ filters. Both the integration experience and the results obtained in the mechanical, vacuum, cryogenics and optical tests are presented, including all relevant parameters in the ESO specifications. The requirement of mechanical stiffness together with light weight was achieved yielding a total weight of less than 90 Kg. The camera fulfills both cryogenic and vacuum stability requirements. The temperature within the detector is maintained at 80K by an accurate control loop, ensuring mK stability, after cooling down the detector at a rate kept below 0.5 K/min. The optical performance tests were made using a Fizeau interferometer both for the individual optical components and complete setup. The infrared optical validation measurements were performed by re-imaging a point source in the camera focal plane and measuring the PSF with the detector. The computed Strehl ratio reached 95% in the central region of the FoV, with values larger than 90% in a area covering 88% of the focal plane.
A proposed implementation of a ground layer adaptive optics system on the Gemini Telescope
We describe a simple and cost-effective concept for implementing a Ground Layer Adaptive Optics (GLAO) system on Gemini that will feed all instruments mounted at the Cassegrain focus. The design concept can provide a GLAO correction to any of the current or future seeing-limited optical or near-infrared Gemini instruments. The GLAO design uses an adaptive secondary mirror and provides a significant upgrade to the current telescope acquisition-and-guide system while reusing and building upon the existing telescope facilities and infrastructure. This paper discusses the overall design of the GLAO system including optics, opto-mechanics, laser guide star facilities, natural and laser guide stars wavefront sensors. Such a GLAO system will improve the efficiency of essentially all observations with Gemini and also will help with scheduling since it virtually eliminates poor seeing.
Addition of a polarization analysis capability to the Fan Mountain near infrared camera
David McDavid, Srikrishna Kanneganti, Chan Park, et al.
A small research grant from the AAS has enabled the addition of a pair of MgF2 Wollaston prism polarization analyzers to the Fan Mountain Near Infrared Camera (FanCam). FanCam is a HAWAII-1 (1K × 1K HgCdTe) near infrared camera attached to the 0.8m Cassegrain reflector at Fan Mountain Observatory, 15 miles south of Charlottesville, Virginia. It images an 8.5 × 8.5 arcmin field of view with 0.51 arcsec pixels through a variety of broad band and narrow band filters, including JHKs, Brγ, and H2. The polarizers are mounted in one of the two camera filter wheels in the cold collimated beam near the re-imaged pupil and are oriented such that the direction of the separation of the split polarized images from one prism is rotated 45° relative to that from the other prism. The linear Stokes parameters of uncrowded point sources over a 7.5 × 7.5arcmin field of view may be measured by aperture photometry of pairs of images acquired through the two prisms. Initial obervations of polarized and unpolarized standard stars show that measurements of the degree of polarization are repeatable to within a few tenths of a percent, consistent with photon counting statistics. More standard star observations will be necessary to determine precisely the instrumental polarization and position angle offsets, but they appear to be stable and reasonably small.
Control system architecture for AMICA: the Antarctic NIR/MIR camera for IRAIT
The IRAIT project is aimed at preparing the first permanent observatory, a 80 cm class telescope, at Dome C, a site located at 3200 height on the Antarctic plateau. To exploit the high-quality and low-sky-background conditions offered by the site in spectral regions beyond 20 μm, IRAIT telescope will be equipped at its Nasmyth focus by a dual feed infrared camera: a near/medium infrared camera (AMICA) designed to be operated by a Si:As detector array sensitivity in the range 5-28 μm, and a In:Sb detector array covering the shorter spectral range down to J band. AMICA is a joint effort of several Italian institutions (OAMI, OATO, OAPD) led by the Teramo Observatory, belonging to Istituto Nazionale di Astrofisica (INAF). The importance of this instrument is twofold: AMICA is expected to provide extensive surveys of the southern sky in K,L,M,N and Q bands, and to give a direct estimate of the observational quality of this highly promising site. To face the prohibitive Antarctic environment, the telescope should be fully robotic and operations for the telescope and its instrumentation remotely controlled. Careful consideration is to be devoted to the design and integration of the control system, besides the accurate insulation for all the equipment. In the present paper we will provide an overview of the AMICA camera focused on the detectors control electronics, the solutions adopted to reduce the impact with a severe environment and the present status of the project.
FLITECAM: a 1-5 micron camera and spectrometer for SOFIA
Ian S. McLean, Erin C. Smith, T. Aliado, et al.
FLITECAM is a 1-5 micron infrared camera for NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA). A 1024 ×1024 InSb ALADDIN III detector and large refractive optics provide a field of view of almost 8 arc minutes in diameter with a scale of just under 0.5 arc seconds per pixel. The instrument is cooled by a double liquid helium and liquid nitrogen cryostat. Using a collimated beam of about 26 mm diameter, a low resolution spectroscopic mode is also available using direct-ruled KRS5 grisms and fixed slits of either 1" or 2" width and 60" length to yield resolving powers of R~1700 and 900 respectively. FLITECAM has been partially commissioned at the 3-m Shane telescope of Lick Observatory where the f/17 optics of this telescope provides almost the same plate scale as SOFIA. Astronomical observing requests (scripts) and a real-time data reduction pipeline (DRP) for dithered image patterns have been demonstrated. The performance of the instrument during ground-based trials is illustrated.
The LINC-NIRVANA patrol camera
LINC-NIRVANA is the IR Fizeau interferometric imager of the Large Binocular Telescope (LBT) in Arizona. Here we describe in particular the design, realization and preliminary tests of the so-called Patrol Camera. It can image (in the range 600-900 nm) the same 2 arcmin FoV seen by the Medium- High-Wavefront Sensor (MHWS), adequately sampled to provide the MHWS star enlargers with the positions of the FoV stars with an accuracy of 0.1 arcsec. To this aim a diffraction-limited performance is not required, while a distortion free focal plane is needed to provide a suitable astrometric output. Two identical systems will be realized, one for each single arm, which corresponds to each single telescope. We give here the details concerning the optical and mechanical design, as well as the CCD and the control system. The interfaces with LINC-NIRVANA are also presented both in terms of matching the carbon fiber optical bench and developing of suitable software procedures. Since the major components have been already gathered, the laboratory tests and the integration are currently in progress.
Poster Session C
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CORONA: progress report on the Dome C prototype APKC coronagraph
G. Guerri, J. B. Daban, F. Vakili, et al.
We outline the concept and laboratory results of our coronagraphic testbed which has been shipped on automn 2005 to Dome C in Antarctica. We also describe the principle of our coronagraph achromatization and the laboratory first data like the coronographic nulling results which attain more than 103 at least. The future development of our experiment for a much larger telescope is also outlined. We finally present CORONA's on-sky first results.
The gas absorption cell for GIANO-TNG
F. D'Amato, E. Oliva, L. Origlia
GIANO is an high resolution cross-dispersed spectrometer operating at near IR wavelengths (0.9-2.5 microns). One of its primary aims is to measure radial velocities of cool stars with an accuracy of a few m/sec. To this purpose, the spectrometer requires a gas absorption cell which should ideally produce several hundreds of measurable lines distributed over the whole wavelengths range. We show that this can be conveniently achieved using a combination of halogen hydrates, namely HCl, HBr and HI. We present and discuss the design and development of such a cell.
Development of a test N-band image slicer: optical design
A spectrometer with integral field units on large optical/infrared telescopes enables efficient spectroscopy of moderately extended objects. In future mid-infrared observations with 30m class telescopes, where circumstellar disks larger than the spatial resolution will be major targets, such efficient observations are strongly desirable. Here we present an optical design of our new N-band image slicing spectrometer to test basic techniques for future image slicing spectrometers on larger telescopes. Our prototype image slicer follows the idea of the advanced image slicer considering not only object images but also pupil images and is optimized for the N-band (10 micron atmospheric window). Five slicing mirrors and five pupil mirrors are used to slice the field of view and make a rearranged pseudo slit image. The pseudo slit image is collimated, dispersed by a grating, and imaged on a Si:As 320x240 array. For the slicing mirrors, we plan to use polished stainless mirrors of 300 micron width. The spectral resolution is set as about 200. We plan to put an imaging optics module for target aquisition in addition to the simple image slicer module. The whole optics is designed to be compact (about 600mm x 450mm x 300 mm), which will allow us to make test observations easily with various telescopes.
A new acquisition, guiding, and image quality monitoring system for the W.M. Keck Observatory
Acquiring a desired object in the field of view, focusing the telescope and then guiding during the exposure are essential aspects of making astronomical observations. The majority of facilities provided for these functions at the Observatory are more than 10 years old. The operability and technical performance of these facilities are known to impact the efficiency of observing. The current systems provide only limited capabilities for monitoring the quality of the image delivered by the telescope. Notably, the Keck telescopes are the only large telescopes that do not provide automatic focus control. The goal of this project is to develop an integrated system for acquisition, guiding and image quality measurement for the Keck telescopes. In this paper we report on the design of the hardware and software for the new system. The system will consist of three major components: a visible wavelength band acquisition camera, image quality measurement capability, and software for acquisition, guiding and image quality monitoring. This system will replace the acquisition and guiding hardware and software for existing instruments and also become the observatory standard for new instruments. The expected benefits to science include increased efficiency for spectroscopic observations, improved quality for imaging observations, and valuable supplementary data on delivered image quality during all observations. The cameras will be equipped with photometric filters and will be calibrated to enable auxiliary science functions such as photometry. Observing efficiency will be improved with the increased sensitivity of the acquisition cameras, the improved performance of guiding and focusing, and more efficient acquisition and setup of observations.
The imaging Bragg tunable filter: a new path to integral field spectroscopy and narrow band imaging
An entirely new type of imaging tunable filter has been developed by Photon etc. and the California Institute of Technology. The Volume Bragg Grating based device is able to select a single wavelength for each pixel in a full camera field. The demonstration tabletop prototype was able to select images with a 2 nm bandwidth from 400 to 750 nm. Data cubes were produced through a wavelength scan from which a spectrum per pixel can be extracted. The prototype showed no image distortion, a very stable instrument profile, and high efficiency. The compact and robust tunable filter can operate from 350 nm to 2.5 mm with bandwidths from 3 Å to 200 nm, showing a great potential for both ground based and space astronomy.
Calibration method with separation patterns of a single-camera
Weimin Li, Jiaru Chu, Hao Meng, et al.
Such as in LAMOST (Large Sky Area Multi-Object Fiber Spectroscopy Telescope), many photometric measurement systems need to reach sub-pixel accuracy with area scan CCD camera. The separation patterns are used to calibrate a single-camera with high precision. Several separation calibration patterns with small size are put on the position of object plane of the camera. Each pattern has some spot array with high precision. The position of each reference point on the image plane of the camera is calculated. The coordinates of the reference points on the calibration patterns are used to calibrate the camera. The curved-surface fitting method is applied to fit the perspective relationship between the object plane and the image plane. The integer pattern with large dimension can be replaced by the several small differential patterns in the situation of large field. The difficulty to manufacture the large pattern is avoided. The experimental results show that the mean value of residual error is less than 0.002mm with the separation calibration method.
Performance of F2T2 tandem tunable etalon
Alan Scott, Maniyar Javed, Roberto Abraham, et al.
COM DEV Ltd. is building a tandem tunable Fabry-Perot etalon to be mounted inside the Flamingos-2 imaging spectrograph on the Gemini South Telescope. The Flamingos-2 Tandem Tunable Filter has a target spectral resolution of R~800 and a clear aperture of 60 mm, and will be fed by the telescope's Multi-Conjugate Adaptive Optics system. The system is designed to undertake ultra-deep searches for "First-Light" sources at redshifts of z = 7-10 using foreground gravitational lensing. This paper describes preliminary characterization and expected performance F2T2.
Initial operations of a water vapour monitor (IRMA) at Gemini South, Las Campanas Observatories, and in the TMT site testing role
Since February 2005, an Infrared Radiometer for Millimeter Astronomy (IRMA) has been measuring precipitable water vapour levels in Chile at the Gemini South site on Cerro Pachon with a second unit added at the Las Campanas observatories site in August 2005. We have also started data collection with three additional IRMA units at three locations for the TMT site testing effort. After a number of technical modifications to ensure reliable operations at much lower sites than IRMA was designed for, 6 months of near continuous pwv data have been collected at both existing telescope sites and several months of data at TMT candidate locations. These data are enabling us to compare the sites on diurnal as well as seasonal timescales.
New progress of research on the measuring system for the fiber position of LAMOST
Jia Lei, Wang Gang
Some new important progresses of the measuring system for fiber position of LAMOST (Large Area Multi-Object Fiber Spectroscope Telescope) are introduced in this paper. This improved model is based on the principle of calculating the photometric gravity's center of the fiber's CCD digital image, which was discussed in the previews paper [3]. More effective image manipulation and data processing methods have been used to improve the measuring precision. How to make a standard target as big as the size of the whole focal plane of LAMOST for calibration between the CCD camera and the focal plane of LAMOST in measurement was an unsolvable problem in the primary measure model, and it has been resolved in the proved design and will be shown next in this article.
RINGO: a novel ring polarimeter for rapid GRB followup
I. A. Steele, S. D. Bates, D. Carter, et al.
We describe the design and construction of a novel optical ring-polarimeter (RINGO) for the Liverpool Telescope. The instrument is designed for rapid (< 5 minutes) followup observations of Gamma Ray Bursts in order to measure the early time polarization and its evolution for the first time. Sensitivity calculations and data reduction procedures are described, and the results of on-sky commissioning presented. The instrument is now on the telescope and in routine use during GRB followup.
VPHGs abused
The introduction of high efficiency Volume Phase Holographic Gratings (VPHGs) in astronomy led to a double think about instrumentation. Old instruments await miracles and new instrumentations are in search of a different look. Indeed the non conventional uses of dispersing elements can open new possibilities in instrumentation design. Counterdispersing couples of VPHGs are best suitable for narrow and medium band filtering. Their easy handling and macro movements will allow also a tunability of the filtering which promises good performances and robust control system. Multiplication or cascades of this principle will lead to the design of complex multi-imaging instrumentations. Also multi order spectroscopy can take advantage of VPHG smart positioning. Slanting and multilayers in their manufacturing as well as optimized optical geometries can be exploited in order to reach high performance, large spectral coverage spectrographs. We present here a set of concepts which can be applicated to very generation of astronomical instrumentations.
Photometrical scrambling gain and focal ratio degradation in fibers for astronomical instruments
Gerardo Avila, Paul Singh, Maja Albertsen
Optical fibres with extreme optical scrambling gains are required when used to link telescopes to spectrographs for the measurement of very high accuracy radial velocities. We started to study systematically the scrambling properties of optical fibres and in particular, the new FBP fibres from Polymicro and the high numerical aperture fibres from Crystal Fibre. The gain in photometrical scrambling by mechanical fibre scramblers is shown. The degradation of the focal ratio by these fibres is also reported. Finally, we present the first evaluation of a slit light pipe to homogenize the flux of several fibres arranged on a line in order to get a uniform slit aperture.
Calibration strategies for instrumental polarization at the 10-5 level
Many current instrumental developments for both solar and nighttime telescopes are directed at measuring the polarization state of the incoming light in addition to determining its spatial, temporal and/or spectral properties. Such polarimeters need to be sensitive down to a polarization degree of the order of 10-5 e.g. to employ the full range of diagnostics to accurately measure solar magnetic fields or to enable direct imaging of extrasolar planetary systems. At the low polarization degree of these observations, it is crucial to accurately know the polarization properties of the instrument itself. Since instrumental polarization is inevitable for any telescopic configuration with oblique reflections or refractions, it is always necessary to cope with it by means of calibration in combination with (limited) forward modeling. I present general strategies based on discrete Fourier analysis for the calibration of instrumental polarization to enable astronomical (spectro-)polarimetry at the 10-5 level. The technique only assumes the presence of a freely rotatable polarizer and (quarter) wave plate to create known input polarization states. The Fourier components of the observed output polarization contain information about the full instrumental polarization, as well as about non-ideal effects in the calibration elements, polarized input to the calibration unit and non-linear response of the detector.
Revitalizing the LNA 1.6-m telescope with a versatile instrument support module
In recent years, much astronomical observation has migrated to large shared facilities in excellent locations, e.g. Gemini, Keck, VLT, etc., often leaving underutilized smaller telescopes such as the 1.6M at the Brazilian National Observatory Pico Dos Dias (OPD). This is unfortunate, because research can often be done more cost-effectively on such telescopes, saving time on larger facilities. Smaller telescopes are also good platforms for the development and testing of new instruments. We have designed a new facility Instrument Support Module for the 1.6M. It will be under construction soon and should significantly increase the usefulness of the telescope at relatively low cost. The design is modular and incorporates a number of features. These include the capability of switching between up to four simultaneously mounted instruments; an inexpensive corrector that improves image quality and increases field size; a tip-tilt liquid prism; continuous auto focus; a facility guide/tip-tilt camera; a comparison lamp projector; and a target acquisition camera. This paper describes the design of the ISM and tests being performed to determine if the seeing of the site warrants building the tip-tilt module. The ISM design is straightforward and would be relatively easy to adapt for use on similar telescopes.
Performance of large chemically etched silicon grisms for infrared spectroscopy
D. J. Mar, J. P. Marsh, D. T. Jaffe, et al.
FORCAST is a mid/far-IR camera for use on NASA's SOFIA airborne observatory. We are fabricating monolithic silicon grisms to retrofit a spectroscopic capability for this facility-class instrument without affecting the imaging optics. The grisms will operate in the 5-8, 17-28, and 28-37 μm wavelength ranges. We will cover the 5-8 μm range in one exposure at a resolving power R=1200 with a 2 arcsecond slit using two grisms with one serving as a cross-disperser. For the 17-28 and 28-37 μm ranges, the resolving powers are R~140, 250 when used in low order with a slit of 3 arcseconds. We illustrate aspects of fabrication and testing during the grism development, and summarize the performance of the gratings at near- and mid-IR wavelengths. These gratings rely on procedures that can be used for modest sized (~10 cm) silicon pieces, thereby providing dispersive elements with good optical performance and large slit width-resolving power products from 1.2-8.1 μm and beyond 17 μm.
Flexure mounts for high-performance astronomical lenses
Robert Fata, Vladimir Kradinov, Daniel Fabricant
We have developed practical, high performance flexure mounts for large astronomical lenses in the Binospec spectrograph. Flexure mounts are an attractive alternative to the widely used elastomeric lens mounts when high axial stiffness is a priority and coupling fluids are incompatible with elastomers. We describe coupling fluid seals for the flexure mounts.
Ground-layer turbulence profiling using a lunar SHABAR
Anna Moore, Eric Aristidi, Michael Ashley, et al.
Profiling the ground layer turbulence for daytime seeing applications using an array of photodiodes has been documented in literature, in particular by Beckers who coined the term "SHABAR" for the instrument, short for Shadow Band Ranger. In this case the photodiodes measure the variation of solar intensity as a function of time and the correlation of scintillation between spatially separated scintillometers can be used to derive structure constant values for the lower 100m or so. More recently SHABARs have been applied to night time atmospheric profiling using the moon as the extended source, such as the Pan-STARRS lunar SHABAR, a more challenging venture given the lower structure constant values and therefore higher sensitivity required. We present a summary of the lunar SHABAR currently operating at the Antarctic site of Dome C, one of the three Gattini site testing instruments for the Italian-led IRAIT project. The SHABAR was designed with low noise performance in mind and for low temperature operation. Ground layer profiling is of particular importance at the Dome C site during winter-time as it is known the majority of the integrated seeing measured at ground level is created in a turbulent layer very close to the ground.
Wide-field imaging on 8- to 100-meter class telescopes
It is generally believed that very fast cameras imaging large Fields of View translate into huge optomechanics and mosaics of very large contiguous CCDs. It has already been suggested that seeing limited imaging cameras for telescopes whose diameters are larger than 20m are considered virtually impossible for a reasonable cost. It has also been suggested that using existing technology and at a moderate price, one can build a Smart Fast Camera, a device that placed on aberrated Field of View, including those of slow focal ratios, is able to provide imaging at an equivalent focal ratio as low as F/1, with a size that is identical to the large focal ratio focal plane size. The design allows for easy correction of aberrations over the Field of View. It has low weight and size with respect to any focal reducer or prime focus station of the same performance. It can be applied to existing 8m-class telescopes to provide a wide field fast focal plane or to achieve seeing-limited imaging on Extremely Large Telescopes. As it offers inherently fast read-out in a massive parallel mode, the SFC can be used as a pupil or focal plane camera for pupil-plane or Shack-Hartmann wavefront sensing for 30-100m class telescopes. Basing upon Smart Fast Camera concept, we present a study turned to explain the pliability of this instrument for different existing telescopes.
IRMOS: The near-infrared multi-object spectrograph for the TMT
Stephen Eikenberry, David Andersen, Rafael Guzman, et al.
We present an overview of the near-InfraRed Multi-Object Spectrograph (IRMOS) for the Thirty Meter Telescope, as developed under a Feasibility Study at the University of Florida and Herzberg Institute of Astrophysics. IRMOS incorporates a multi-object adaptive optics correction capability over a 5-arcminute field of regard on TMT. Up to 20 independently-selectable target fields-of-view with ~2-arcsec diameter can be accessed within this field simultaneously. IRMOS provides near-diffraction-limited integral field spectroscopy over the 0.8-2.5 μm bandpass at R~1,000-20,000 for each target field. We give a brief summary of the Design Reference science cases for IRMOS. We then present an overview of the IRMOS baseline instrument design.
AGAR-AGAR: a high-efficiency narrow-band imager for ELTs
Daniela Tresoldi, Riccardo Felletti, Andrea Bianco, et al.
The thinking about possible instruments for the future ELTs has just started and the current phase allows to pursue non-traditional solutions. Following the guidelines of the Science Case for an ELT1,2 our team searched for possible intersections with innovative technologies we currently deal with in our research. We found that Volume Phase Holographic Gratings and advanced dichroics could be suited to design a non-traditional narrow band imager. We propose in this paper a comparative analysis of a VPHG based and a dichroic based configurations for the imager.
Development of the readout controller for KASINICS
Korea Astronomy and Space Science Institute (KASI) is developing the KASI Near Infrared Camera System (KASINICS) which will be installed on the 61 cm telescope at the Sobaeksan Optical Astronomy Observatory (SOAO) in Korea. KASINICS is equipped with a ALADDIN III Quadrant (512×512 InSb array, manufactured by Raytheon). For this instrument, we make a new IR array control electronics system. The controller consists of DSP, Bias, Clock, and Video boards which are installed on a VME bus system. The DSP board includes TMS320C6713, FPGA, and 384MB SDRAM. Clock patterns are downloaded from a PC and stored on the FPGA. USB 2.0 is used for the communication with the PC and UART for the serial communication with peripherals. Each of two video boards has 4 video channels. The Bias board provides 16 voltage sources and the Clock board has 15 clock channels. Our goal of readout speed is 10 frames sec-1. We have successfully finished operational tests of the controller using a 256×256 ROIC (CRC744). We are now upgrading the system for the ALADDIN III array. We plan to operate KASINICS by the end of 2006.
Development of an IFU for diffraction-limited 3D spectropolarimetry
Deqing Ren, Christoph Keller, Claude Plymate
Ground-based telescopes can achieve diffraction-limited images when equipped with adaptive optics (AO). A major limitation of AO is the small field of view, which is due to the limited isoplanatic patch size. Nevertheless, conventional long-slit spectrographs cannot sample the entire AO-corrected field of view in a single exposure. However, equipped with a modern, large detector array, the Integral Field Unit (IFU) technique will allow a 3-dimensional (3-D) data cube to be recorded simultaneously over the entire AO corrected field of view, with a conventional long-slit spectrographs. We are building a state-of-the-art image slicer IFU for the National Solar Observatory's (NSO) McMath-Pierce Solar Telescope (McMP). This will be the first time that an advanced image slicer IFU is used for 3-D spectroscopy and polarimetry at a solar telescope. The IFU consists of 25 slices that will sample a 6.25" x 8" AO corrected field of view simultaneously, and produces a 200" long slit for diffraction-limited 3-D spectroscopy and polarimetry. This IFU 3-D technique will provide the most high spatial, high temporal resolution with high throughput for solar spectroscopy and polarimetry. This is critical for state-of-the-art spectral diagnosis of solar velocity and magnetic fields. We discuss the design, construction, and testing of this new IFU.
Simulating diffractions and chromatic effects in the microlens array in searching for extrasolar planets with SPHERE IFS
Observations of extrasolar planets using Integral Field Spectroscopy (IFS), if coupled with an extreme Adaptive Optics system and analyzed with a Simultaneous Differential Imaging technique (SDI), are a powerful tool to detect and characterize extrasolar planets directly; they enhance the signal of the planet and, at the same time, reduces the impact of stellar light and consequently important noise sources like speckles. We developed a simulation code able to test the capabilities of this IFS-SDI technique for different kinds of planets and telescopes, modeling the atmospheric and instrumental noise sources, and the main results of this code have been presented in Ref.1. This code, although it takes into account many parameters and sources of noise, can still be improved, and in order to do it we studied in detail two aspects that have been neglected in the first version of the code: the not uniform illumination of the microlenses and the speckle undersampling. The results of these studies are presented here.
The visible-light broad-band imager for ATST: preliminary design
Han Uitenbroek, Alexandra Tritschler, Hyun Kyoung An, et al.
This poster outlines the conceptual design of the Visible-light Broad-band Imager (VBI) instrument for the Advanced Technology Solar Telescope (ATST) as it follows from scientific requirements. The VBI is scheduled to be the first-light instrument of the ATST, highlighting the telescope's high spatial resolution capabilities.