The Large Synoptic Survey Telescope (LSST) Project is a public-private partnership now half way through the 8- year construction period. LSST construction was initiated in 2014 by the US National Science Foundation to build the observing system within a $473M budget and in time to start the survey in October 2022. The US Department of Energy also participates by funding the camera fabrication with a budget of $168M. LSST will construct the system to conduct a wide fast deep survey of the entire visible sky and to process and serve the data to the US, Chilean, and international contributors without any proprietary period. The designs have matured around the 3-mirror wide field optical system; an 8.4 meter primary, 3.4 meter secondary, and 5 meter tertiary mirror that feed three refractive elements and a 64 cm 3.2 gigapixel focal plane camera. The data management system will reduce, transport, alert, archive roughly 15 terabytes of data produced nightly, and will serve raw and catalog data on daily and annual timescales throughout the 10-year survey. Additional access portals and tools will extend the scientific reach to education and public outreach efforts for students and non-professionals. LSST has completed key elements of the system with hardware being sent to the observing site on Cerro Pachón, Chile, factory integration efforts underway, and the focal plane assembly process started. Software development continues as an open-source project and completed demonstrations of key algorithm performance on existing data sets. LSST continues to plan an on-time and on-budget completion.
This paper describes the status and details of the large synoptic survey telescope1,2,3 mount assembly (TMA). On June 9th, 2014 the contract for the design and build of the large synoptic survey telescope mount assembly (TMA) was awarded to GHESA Ingeniería y Tecnología, S.A. and Asturfeito, S.A. The design successfully passed the preliminary design review on October 2, 2015 and the final design review January 29, 2016. This paper describes the detailed design by subsystem, analytical model results, preparations being taken to complete the fabrication, and the transportation and installation plans to install the mount on Cerro Pachón in Chile. This large project is the culmination of work by many people and the authors would like to thank everyone that has contributed to the success of this project.
At the core of the Large Synoptic Survey Telescope (LSST) three-mirror optical design is the primary/tertiary (M1M3) mirror that combines these two large mirrors onto one monolithic substrate. The M1M3 mirror was spin cast and polished at the Steward Observatory Mirror Lab at The University of Arizona (formerly SOML, now the Richard F. Caris Mirror Lab at the University of Arizona (RFCML)). Final acceptance of the mirror occurred during the year 2015 and the mirror is now in storage while the mirror cell assembly is being fabricated. The M1M3 mirror will be tested at RFCML after integration with its mirror cell before being shipped to Chile.
The Large Synoptic Survey Telescope (LSST) has a 3.5º field of view and F/1.2 focus that makes the performance quite
sensitive to the perturbations of misalignments and mirror surface deformations. In order to maintain the image quality,
LSST has an active optics system (AOS) to measure and correct those perturbations in a closed loop. The perturbed
wavefront errors are measured by the wavefront sensors (WFS) located at the four corners of the focal plane. The
perturbations are solved by the non-linear least square algorithm by minimizing the rms variation of the measured and
baseline designed wavefront errors. Then the correction is realized by applying the inverse of the perturbations to the
optical system. In this paper, we will describe the correction processing in the LSST AOS. We also will discuss the
application of the algorithm, the properties of the sensitivity matrix and the stabilities of the correction. A simulation
model, using ZEMAX as a ray tracing engine and MATLAB as an analysis platform, is set up to simulate the testing and
correction loop of the LSST AOS. Several simulation examples and results are presented.
Results from determining the optical turbulence profile (OTP) on the LSST site, El
Peñon, located on Cerro Pachón (Chile) are presented. El Peñón appears to be an
excellent observatory site with a surface layer seeing contribution on the order of 0.15”
with most of this seeing being produced below 20m. These measurements also helped to
confirm that the telescope is elevated high enough above ground. As part of the LSST site
characterization campaign, microthermal measurements were taken in order to determine
the contribution of the surface layer turbulence to the atmospheric seeing. Such
measurements are commonly used for this purpose where pairs of microthermal sensors
mounted on a tower measure atmospheric temperature differences. In addition, the lunar
scintillometer LuSci was installed on El Peñon for short campaigns near full moon for the
same purpose. LuSci is a turbulence profiler based on measuring spatial correlation of
moonlight scintillations. The comparison of the results from both instruments during
simultaneous data acquisition showed a remarkable temporal correlation and very similar
The Large Synoptic Survey Telescope (LSST) Project is a public-private partnership that is well into the
design and development of the complete observatory system to conduct a wide fast deep survey and to
process and serve the data. The telescope has a 3-mirror wide field optical system with an 8.4 meter
primary, 3.4 meter secondary, and 5 meter tertiary mirror. The reflective optics feed three refractive
elements and a 64 cm 3.2 gigapixel camera. The LSST data management system will reduce, transport,
alert and archive the roughly 15 terabytes of data produced nightly, and will serve the raw and catalog data
accumulating at an average of 7 petabytes per year to the community without any proprietary period. The
project has completed several data challenges designed to prototype and test the data management system
to significant pre-construction levels. The project continues to attract institutional partners and has acquired
non-federal funding sufficient to construct the primary mirror, already in progress at the University of
Arizona, build the secondary mirror substrate, completed by Corning, and fund detector prototype efforts,
several that have been tested on the sky. A focus of the project is systems engineering, risk reduction
through prototyping and major efforts in image simulation and operation simulations. The project has
submitted a proposal for construction to the National Science Foundation Major Research Equipment and
Facilities Construction (MREFC) program and has prepared project advocacy papers for the National
Research Council's Astronomy 2010 Decadal Survey. The project is preparing for a 2012 construction
Extracting science from the LSST data stream requires a detailed knowledge of the properties of the LSST catalogs and
images (from their detection limits to the accuracy of the calibration to how well galaxy shapes can be characterized).
These properties will depend on many of the LSST components including the design of the telescope, the conditions
under which the data are taken and the overall survey strategy. To understand how these components impact the nature
of the LSST data the simulations group is developing a framework for high fidelity simulations that scale to the volume
of data expected from the LSST. This framework comprises galaxy, stellar and solar system catalogs designed to match
the depths and properties of the LSST (to r=28), transient and moving sources, and image simulations that ray-trace the
photons from above the atmosphere through the optics and to the camera. We describe here the state of the current
simulation framework and its computational challenges.
The Large Synoptic Survey Telescope (LSST) project has evolved from just a few staff members in 2003 to about 100 in
2010; the affiliation of four founding institutions has grown to 32 universities, government laboratories, and industry.
The public private collaboration aims to complete the estimated $450 M observatory in the 2017 timeframe. During the
design phase of the project from 2003 to the present the management structure has been remarkably stable. At the same
time, the funding levels, staffing levels and scientific community participation have grown dramatically. The LSSTC
has introduced project controls and tools required to manage the LSST's complex funding model, technical structure and
distributed work force. Project controls have been configured to comply with the requirements of federal funding
agencies. Some of these tools for risk management, configuration control and resource-loaded schedule have been
effective and others have not. Technical tasks associated with building the LSST are distributed into three subsystems:
Telescope & Site, Camera, and Data Management. Each sub-system has its own experienced Project Manager and
System Scientist. Delegation of authority is enabling and effective; it encourages a strong sense of ownership within the
project. At the project level, subsystem management follows the principle that there is one Board of Directors, Director,
and Project Manager who have overall authority.
The Large Synoptic Survey Telescope (LSST) will continuously image the entire sky visible from Cerro Pachon
in northern Chile every 3-4 nights throughout the year. The LSST will provide data for a broad range of science
investigations that require better than 1% photometric precision across the sky (repeatability and uniformity)
and a similar accuracy of measured broadband color. The fast and persistent cadence of the LSST survey
will significantly improve the temporal sampling rate with which celestial events and motions are tracked. To
achieve these goals, and to optimally utilize the observing calendar, it will be necessary to obtain excellent
photometric calibration of data taken over a wide range of observing conditions - even those not normally
considered "photometric". To achieve this it will be necessary to routinely and accurately measure the full
optical passband that includes the atmosphere as well as the instrumental telescope and camera system. The
LSST mountain facility will include a new monochromatic dome illumination projector system to measure the
detailed wavelength dependence of the instrumental passband for each channel in the system. The facility will
also include an auxiliary spectroscopic telescope dedicated to measurement of atmospheric transparency at all
locations in the sky during LSST observing. In this paper, we describe these systems and present laboratory
and observational data that illustrate their performance.
The Large Synoptic Survey Telescope (LSST) is a large (8.4 meter) wide-field (3.5 degree) survey telescope, which will
be located on the summit of Cerro Pachón in Chile. The survey mission requires a short slew and settling time of 5
seconds for a 3.5 degree slew. This is significantly faster than similar aperture telescopes. Since the optical system does
not include a fast steering mirror the telescope has stringent vibration limitations during observation. Meeting these
requirements is facilitated by the compact mount riding on a robust pier which produces high natural frequencies, an
advanced control system to minimize vibration excitation and reaction mass dampers. The telescope mount design is an
altitude over azimuth welded and bolted assembly fabricated from mild steel. It supports the primary / tertiary mirror cell
assembly, the secondary mirror cell assembly and the camera assembly. The mount design enables the removal of these
optical assemblies for servicing and recoating. Retractable / deployable platforms have also been provided for accessing
the camera on telescope. As a result of the wide field of view, the optical system is unusually susceptible to stray light
consequently the mount must incorporate substantial light baffling. The dynamic characteristics of the steel reinforced
concrete pier were enhanced by utilizing two different wall thicknesses, an unusually large diameter of 16 meter and
anchoring the foundation in unweathered bedrock. The entire pier and mount assembly has been designed to be invariant
with azimuth and elevation angle to enhance the effectiveness of the advanced control system.
The Large Synoptic Survey Telescope (LSST) flat-fields must repeatedly trace not only the spatial response variations,
but also the chromatic response through the entire optical system, with an accuracy driven by the photometric
requirements for the LSST survey data. This places challenging requirements on the LSST Calibration Dome Screen,
which must uniformly illuminate the 8.4-meter diameter telescope pupil over its 3.5-degree field of view at desired
monochromatic wavelengths in a way that allows the measurement of the total system throughput from entrance pupil to
the digitization of charge in the camera electronics. This includes the reflectivity of the mirrors, transmission of the
refractive optics and filters, the quantum efficiency of the sensors in the camera, and the gain and linearity of the sensor
read-out electronics. The baseline design uses a single tunable laser and includes an array of discrete projectors. The
projected flux of light produced by the screen must fill the entire telescope pupil and provide uniform illumination to 1%
at the focal plane and to within 0.25% over any optical trajectory within 0.5 degrees of each other. The wavelength of
light is tunable across the LSST bandpass from 320 nm to 1080 nm. The screen also includes a broad-band ("white")
light source with known Spectral Energy Density (SED) that spans the same range of wavelengths.
Meeting the stringent slew and settling requirements of the Large Synoptic Survey Telescope (LSST) will require an
exceptionally stiff mount. The unique three mirror design and large, 64 cm diameter, focal plane preclude the use of a
fast steering mirror or active focal plane. Consequently, a smooth (low vibrations) drive and bearing system is also
required. This combination of smooth motion and high stiffness is best achieved with hydrostatic bearings. Hydrostatic
bearings have historically proven use for the support of azimuth and elevation axes of telescopes due to these
performance advantages. In addition to the known benefit of mount stiffness and tracking accuracy from exceedingly
low friction, the hydrostatic bearing provides a wide range of geometric possibilities for large telescopes, reference 1.
This paper analyzes various bearing arrangements for the azimuth and elevation axes of the Large Synoptic Survey
Telescope to conceptualize the greatest stiffness for the mount and provide data to determine system performance.
The Large Synoptic Survey Telescope Project is a public-private partnership that has successfully
completed the Concept Design of its wide-field ground based survey system and started several long-lead
construction activities using private funding. The telescope has a 3-mirror wide field optical system with an
8.4 meter primary, 3.4 meter secondary, and 5 meter tertiary mirror. The reflective optics feed three
refractive elements and a 64 cm 3.2 gigapixel camera. The telescope will be located on the summit of Cerro
Pachón in Chile. The LSST data management system will reduce, transport, alert, archive the roughly 15
terabytes of data produced nightly, and will serve the raw and catalog data accumulating at an average of 7
petabytes per year to the community without any proprietary period. This survey will yield contiguous
overlapping imaging of 20,000 square degrees of sky in 6 optical filter bands covering wavelengths from
320 to 1080nm. The project continues to attract institutional partners and has acquired non-federal funding
sufficient to construct the primary mirror, already in progress at the University of Arizona, and fund
detector prototype efforts, two of the longest lead items in the LSST. The project has submitted a proposal
for construction to the National Science Foundation Major Research Equipment and Facilities Construction
(MREFC) program and is preparing for a 2011 funding authorization.
Heidenhain position tape encoders are in use on almost all modern telescopes with excellent results. Performance of
these systems can be limited by minor mechanical misalignments between the tape and read head causing errors at the
grating period. The first and second harmonics of the measured signal are the dominant errors, and have a varying
frequency dependant on axis rate. When the error spectrum is within the mount servo bandwidth it results in periodic
telescope pointing jitter. This paper will describe an adaptive error correction using elliptic interpolation of the raw
signals, based on the well known compensation technique developed by Heydemann . The approach allows the
compensation to track in real time with no need of a large static look-up table, or frequent calibrations. This paper also
presents the results obtained after applying this approach on data measured on the SOAR telescope.
A wind pressures PSD measured on the Gemini South Telescope was applied to the FEA model of
the LSST telescope to determine the RMS motions of the principal optical systems. These motions
were then converted to the time domain. The time domain motions were analyzed in the ZEMAX®
software to determine the wind induced image degradation. This degradation was shown to be
The LSST project has acquired an all sky IR camera and started to investigate its effectiveness in cloud monitoring. The
IR camera has a 180-degree field of view. The camera uses six filters in the 8-12 micron atmospheric window and has a
built in black body reference and visible all sky camera for additional diagnostics. The camera is installed and in nightly
use on Cerro Pachon in Chile, between the SOAR and Gemini South telescopes. This paper describes the measurements
made to date in comparison to the SOAR visible All Sky Camera (SASCA) and other observed atmospheric throughput.
The objective for these tests is to find an IR camera design to provide the survey scheduler with real-time measured
conditions of clouds, including high cirrus to better optimize the observing strategy.
Cylindrical (carousel) and spherical dome designs for the Large Synoptic Survey Telescope (LSST) were analyzed for
air flow characteristics using computational fluid dynamic models. The primary objective was to determine the level of
dome flushing achieved with natural ventilation and representative site wind conditions. The domes were 30 meters in
diameter at the base, designed to enclose the LSST and provide adequate space for servicing requirements with the
smallest possible major dimensions. The carousel style enclosure allowed moderately superior flushing with better
uniformity which will produce superior local seeing conditions. Since the cylindrical style enclosure was also
determined to be less costly, this concept was chosen as the baseline enclosure design for the LSST.
An active tangent link system was developed to provide transverse support for large thin meniscus mirrors. The support
system uses six tangent links to control position and distribute compensating force to the mirror. Each of the six tangent
links utilizes an electromechanical actuator and an imbedded lever system working through a load cell and flexure. The
lever system reduces the stiffness, strength and force resolution requirements of the electromechanical actuator and
allows more compact packaging. Although all six actuators are essentially identical, three of them are operated quasi
statically, and are only used to position the optic. The other three are actively operated to produce an optimal and
repeatable distribution of the transverse load. This repeatable load distribution allows for a more effective application of
a look up table and reduces the demands on the active optics system.
A control system was developed to manage the quasi static force equilibrium servo loop using a control matrix that
computes the displacements needed to correct any force imbalance with good convergence and stability.
This system was successfully retrofitted to the 4.3 meter diameter, 100 mm thick SOAR primary mirror to allow for
more expeditious convergence of the mirror figure control system. This system is also intended for use as the transverse
support system for the LSST 3.4 meter diameter thin meniscus secondary mirror.
The Large Synoptic Survey Telescope (LSST) baseline design includes aluminum coating for the large mirrors in its 3 element modified Paul Baker optical design. The 8.4 meter diameter of the primary provides a significant challenge to the LSST coating plans however such coatings have successfully achieved for this size aperture. LSST also recognizes that the use of mirror coatings with higher reflectivity and durability would significantly benefit its science by increasing its overall throughput and improving its operational efficiency. LSST has identified Lawrence Livermore National Laboratory (LLNL) blue-shifted protected silver coating as a possible candidate to provide this blue wavelength performance. A study has been started to assess the performance of these and other coatings in the observatory environment. We present the details of this ongoing program, the results obtained so far, and related coating tests results. LSST has also engaged in collaboration with the Gemini Telescope in the development and testing of an Al-Ag coating based on their current recipe. The first results of these tests are also included in this report.
The Large Synoptic Survey Telescope (LSST) will be a large, wide-field ground-based telescope designed to obtain sequential images of the entire visible sky every few nights. The LSST, in spite of its large field of view and short 15 second exposures, requires a very accurate pointing and tracking performance. The high efficiency specified for the whole system implies that observations will be acquired in blind pointing mode and tracking demands calculated from blind pointing as well.
This paper will provide a high level overview of the LSST Control System (LCS) and details of the Telescope Control System (TCS), explaining the characteristics of the system components and the interactions among them. The LCS and TCS will be designed around a distributed architecture to maximize the control efficiency and to support the highly robotic nature of the LSST System. In addition to its control functions, the LCS will capture, organize and store system wide state information, to make it available for monitoring, evaluation and calibration processes. An evaluation of the potential communications middleware software to be utilized for data transport, is also included.
The project for the proposed Large Synoptic Survey Telescope (LSST) performed more than two years of data
collection, site evaluation, and analysis to support the selection of its prime site. LSST assessment was based on
using an existing site with existing infrastructure and historical performance information. A large and diverse set of
comparative information was compiled for potential sites using results from other site campaigns, measurements
from existing large telescopes, new astro-climate measurements, logistical and feasibility information, and from
existing satellite and climate databases. Several analyses were performed on these data including the assessment of
survey performance using the LSST operation simulator. An independent site selection committee of experts
provided recommendations to the Project leading to three finalist sites, one in Mexico, and two in northern Chile.
The finalist sites were assessed thoroughly with additional data collection from all-sky cameras and site proposals.
Cerro Pachon in Chile was selected to be the site for LSST after a difficult decision between the high quality final
candidates. This paper describes the data, analysis and approach used to support the site evaluation.
Science studies made by the Large Synoptic Survey Telescope will reach systematic limits in nearly all cases. Requirements for accurate photometric measurements are particularly challenging. Advantage will be taken of the rapid cadence and pace of the LSST survey to use celestial sources to monitor stability and uniformity of photometric data. A new technique using a tunable laser is being developed to calibrate the wavelength dependence of the total telescope and camera system throughput. Spectroscopic measurements of atmospheric extinction and emission will be made continuously to allow the broad-band optical flux observed in the instrument to be corrected to flux at the top of the atmosphere. Calibrations with celestial sources will be compared to instrumental and atmospheric calibrations.
The 4.1-meter SOuthern Astrophysical Research (SOAR) Telescope mount and drive systems have been commissioned and are in routine operation. The telescope mount, the structure and its full drive systems, was fully erected and tested at the factory prior to reassembly and commissioning at the observatory. This successful approach enabled complete integration, from a concrete pier to a pointing and tracking telescope, on the mountain, in a rapid 3-month period. The telescope mount with its high instrument payload and demanding efficiency requirements is an important component for the success of the SOAR scientific mission. The SOAR mount utilizes rolling element bearings for both azimuth and elevation support, counter torqued sets of gear motors on azimuth and two frameless torque motors built into the elevation axles. Tracking jitter and its associated spectra, pointing errors and their sources, bearing friction and servo performances are critical criteria for this mount concept and are important factors in achieving the mission. This paper addresses the performance results obtained during the integration, commissioning, and first light periods of the telescope mount system.
This paper describes the design and summarizes the performance of the recently completed SOAR telescope Active Optical System (AOS). This system is unique in that it uses a thin, solid 4.3-meter diameter ULE lightweight meniscus primary mirror only 100 mm thick. The figure of the primary mirror surface is controlled with 120 electro-mechanical actuators that are force feedback controlled. The telescope is calibrated against the sky using a calibration wave-front sensor; as this calibration progresses, feedback forces, initially set from finite element analysis predictions, are replaced with sky database look-up tables. The system also includes a 0.6-meter diameter secondary mirror articulated by a hexapod for real-time optical alignment of the telescope, a 0.6-meter class tertiary mirror that also works as a 50 Hz tip tilt corrector to compensate for atmospheric turbulence and a rotary turret mechanism for directing the light to either of two nasmyth or three-bent cassegrain instrument ports. An operation control system interfaces with the telescope control system and each of the hardware assemblies.
The paper provides an overview of the design of each assembly as well as summarizes results of performance testing the system.
Development of the 4.1 meter SOuthern Astrophysical Research (SOAR) Telescope is now complete. All baseline systems are in place and extensive commissioning activities have been performed with and without the primary optics installed in the telescope. The facility and dome have been under observatory operations and TCS control for a year of testing and tuning. The altitude over azimuth telescope mount was integrated on the mountain in a rapid 3-month period due to the complete assembly and testing performed at the factory prior to delivery. Early mount testing and successful integration into the Telescope Control System (TCS) without the optical system was accomplished on the sky through use of two separate small aperture telescopes fixed to the structure. One of these, the "feed telescope" was also pivotal in early testing of the calibration wavefront sensor and SOAR optical imager by directing focused light to these separate instruments. The SOAR optical system, with its 4.1 meter clear aperture, 100 cm thick, ULEtm primary mirror, its lightweight ULEtm secondary, and its fast tip tilt ULEtm tertiary has been delivered and installed in the telescope. This system was also assembled as an electrically connected system and individually optically tested under a visible interferometer at the factory enabling rapid integration and a short commissioning period on telescope. In this paper we present the project status, a summary of the commissioning period, and the performance data for the completed telescope and its major components.
The 8.4m Large Synoptic Survey Telescope (LSST) is a wide-field telescope facility that will add a qualitatively new capability in astronomy. For the first time, the LSST will provide time-lapse digital imaging of faint astronomical objects across the entire sky. The LSST has been identified as a national scientific priority by diverse national panels, including multiple National Academy of Sciences committees. This judgment is based upon the LSST's ability to address some of the most pressing open questions in astronomy and fundamental physics, while driving advances in data-intensive science and computing. The LSST will provide unprecedented 3-dimensional maps of the mass distribution in the Universe, in addition to the traditional images of luminous stars and galaxies. These mass maps can be used to better understand the nature of the newly discovered and utterly mysterious Dark Energy that is driving the accelerating expansion of the Universe. The LSST will also provide a comprehensive census of our solar system, including potentially hazardous asteroids as small as 100 meters in size. The LSST facility consists of three major subsystems: 1) the telescope, 2) the camera and 3) the data processing system. The baseline design for the LSST telescope is a 8.4m 3-mirror design with a 3.5 degree field of view resulting in an A-Omega product (etendue) of 302deg2m2. The camera consists of 3-element transmisive corrector producing a 64cm diameter flat focal plane. This focal plane will be populated with roughly 3 billion 10μm pixels. The data processing system will include pipelines to monitor and assess the data quality, detect and classify transient events, and establish a large searchable object database. We report on the status of the designs for these three major LSST subsystems along with the overall project structure and management.
The 4.1 meter Southern Astrophysical Research (SOAR) Telescope is now entering the operations phase, after a period of construction and system commissioning. The SOAR TCS implemented in the LabVIEW software package, has kept pace throughout development with the installation of the other telescope subsystems, and has proven to be a key component for the successful deployment of SOAR. In this third article of the SOAR TCS series, we present the results achieved when operating the SOAR telescope under control of the SOAR TCS software. A review is made of the design considerations and the implementations details, followed by a presentation of the software extensions that allows a seamless integration of instruments into the system, as well as the programming techniques that permit the execution of remote observing procedures.
Development of the SOuthern Astrophysical Research (SOAR) Telescope is nearing completion atop Cerro Pachón in Chile. The facility and many accessory systems have been completed and are operational. The dome is installed and in the final stages of debugging, the telescope mount is being assembled on site after a successful trial integration and complete test at the contractor's facility, and the optical system is well on its way to completion later this year. Many instruments are under development with one in the final phases of integration and laboratory testing. This paper summarizes the status of the major subsystems, provides measured performance parameters where available, and outlines the remaining plans for the telescope development and subsequent commissioning.
Development of the SOAR telescope is currently underway. Project plans include many tactics for smooth assembly, integration, and validation of this new facility to be located on Cerro Pachon at the Cerro Tololo Inter-American Observatory in Chile. A small project team has been established to manage and engineer the development of the major subsystems that are combined in this high image quality 4.2-meter diameter telescope. The status and plans for the development of the 28m telescope are discussed. A modest-sized facility building is under construction by CTIO, the organization appointed to operate the facility for the SOAR partners. Each telescope subsystem is contracted on a firm fixed price basis and will include complete performance testing at the contractor's facility before acceptance and shipment to the site. To ensure seamless integration, representatives of each contractor will come to the site for assembly and testing in place. They join personnel from the Project Office, the new operations staff, and the CTIO maintenance organization to form integrated product teams for subsystem integration, SOAR eases integration by using and mandating common, commercial control software. The contractors, the SOAR team, and the instrument buildings are making extensive use of LabVIEW/BridgeVIEW running under Linux (with real-time extensions as necessary) on compactPCI chassis. The telescope will include sufficient instrumentation, including a possible adaptive optics system, to allow system testing and optimization. An exceptionally large instrument payload ensures that instruments can remain in place upon the telescope as they are delivered and brought on line.
The SOAR Telescope project has embarked on the development of a very high quality 4.2-meter diameter optical telescope to be sited on Cerro Pachon in Chile. The telescope will feature an image quality of 0.18 arc seconds, a moderate field of 11 arc minutes, a very large instrument payload capacity for as many as 9 hot instruments, and an Active Optical System optimized for the optical to near IR wavelengths. The active optical system features a 10 cm thick ULETM primary mirror supported by 120 electro- mechanical actuators for a highly correctable surface. the 0.6 meter diameter secondary is articulated by a hexapod for real time optical alignment. The 0.6-meter class tertiary will provide fast beam steering to compensate for atmospheric turbulence at 50 hertz and a turret for directing the light to either of two nasmyth or three-bent cassegrain ports. Both the secondary and tertiary are light- weighted by machining to achieve cost-effective low weight mirrors. This paper discusses the unique features of this development effort including many commercial products and software programs that enable its technical feasibility and high cost efficiency.
The Hobby-Eberly telescope (HET) is a recently completed 9- meter telescope designed to specialize in spectroscopy. It saw first light in December 1996 and during July 1997, it underwent its first end-to-end testing acquiring its first spectra of target objects. We review the basic design of the HET. In addition we summarize the performance of the telescope used with a commissioning spherical aberration correlator and spectrograph, the status of science operations and plans for the implementation of the final spherical aberration corrector and facility class instruments.
The Hobby Eberly Telescope features a unique eleven-meter spherical primary mirror consisting of a single steel truss populated with 91 ZerodurTM mirror segments. The 1 meter hexagonal segments are fabricated to 0.033 micron RMS spherical surfaces with matched radii to 0.5 mm. Silver coatings are applied to meet reflectance criteria for wavelengths from 0.35 to 2.5 micron. To support the primary spectroscopic uses of the telescope the mirror must provide a 0.52 arc sec FWHM point spread function. Mirror segments are co-aligned to within 0.0625 ar sec and held to 25 microns of piston envelope using a segment positioning system that consists of 273 actuators (3 per mirror), a distributed population of controllers, and custom developed software. A common path polarization shearing interferometer was developed to provide alignment sensing of the entire array from the primary mirror's center of curvature. Performance of the array is being tested with an emphasis on alignment stability. Distributed temperature measurements throughout the truss are correlated to pointing variances of the individual mirror segments over extended periods of time. Results are very encouraging and indicate that this mirror system approach will prove to be a cost-effective solution for large optical collecting apertures.
Experience in bringing into operation the 91-segment primary mirror alignment and control system, the focal plane tracker system, and other critical subsystems of the HET will be described. Particular attention is given to the tracker, which utilizes three linear and three rotational degrees of freedom to follow sidereal targets. Coarse time-dependent functions for each axis are downloaded to autonomous PMAC controllers that provide the precise motion drives to the two linear stages and the hexapod system. Experience gained in aligning the sperate mirrors and then maintaining image quality in a variable thermal environments will also be described. Because of the fixed elevation of the primary optical axis, only a limited amount of time is available for observing objects in the 12 degrees wide observing band. With a small core HET team working with McDonald Observatory staff, efficient, reliable, uncomplicated methodologies are required in all aspects of the observing operations.
The 11-meter primary mirror of the Hobby-Eberly Telescope consists of 91 hexagonal segments. Each segment is 1 meter across (flat to flat). The unique design of this telescope allows for a spherical radius of curvature on each segment. Requirements are that each segment's radius of curvature match to within +/- 0.5 mm of the nominal 26,165 mm radius, and that the surface figure be within 0.033 micrometers RMS. The optical fabrication, testing, and assembly of these segments will be discussed along with a description of the segment mounting scheme.
The Spectroscopic Survey Telescope is being constructed by a consortium of universities at McDonald Observatory in the Davis Mountains of Texas. Principal partners are the University of Texas at Austin and the Pennsylvania State University. Also participating are Stanford University and the University of Munich and University of Gottingen in Germany. We describe the specific design attributes which enable the SST to be constructed for a fraction of the cost of astronomical telescopes of comparable size. Such unique features as identical spherical mirror segments, selective figuring for constant mirror mount deformation, air bearing azimuth rotation system, and pre-fabricated architectural type domes are employed. Emphasis is on simplification of design, reduction of part count and mass, and utilization of lessons learned from other recent large telescope projects.