We discuss plans for the construction of a 15-m class telescope located in the high Atacama desert of Northern Chile. The baseline concept is a segmented mirror telescope optimized for operation at wavelengths longer than 3.5 microns but capable of working at shorter wavelengths. An adaptive secondary will be used to achieve diffraction limited imaging while maintaining low emissivity. The facility will be designed for eventual remote/robotic operation and include a number of instruments designed to take advantage of the low precipitable water vapor and good seeing conditions.

The Southern African Large Telescope (SALT) is a 10-m class optical/IR segmented mirror telescope based on the groundbreaking, low cost, Hobby-Eberly Telescope (HET) design. Approval to construct and operate SALT, which will be the largest single optical telescope in the Southern Hemisphere, was given by the South African Government in November 1999, after sufficient guarantees of matching funding from international partners were secured. Facility construction started in January 2001, and SALT is due to start operations by December 2004. SALT will enable a quantum leap in astronomical research capability in Southern Africa, and indeed the continent, where currently the largest telescope is a modest 1.9-m, dating to the 1940s. A substantial amount of design work for SALT has been completed, sourced from multiple suppliers, with ~60% South African content. South African industry is well equipped to handle the construction of most of the telescope, the exceptions being the glass ceramic mirror blanks (from LZOS in Russia), the polishing and ion figuring of these (Eastman Kodak in the USA), and fabrication of the four-element spherical aberration corrector (SAGEM in France). This paper will present (1) the scientific requirements, (2) the specified performance of SALT, (3) the basic design, with emphasis on the innovative modifications to the HET design that enable significantly improved performance, (4) the progress and status of the project, currently in its construction phase, (5) the first generation instrument suite, (6) the management and organisation of the project and (7) the international partnership in SALT.

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is a quasi-meridian reflecting Schmidt telescope with a clear aperture of 4-meter, a focal length of 20-meter and a field of view of 5-degree, dedicated for spectroscopic sky survey. The telescope will be located at the Xinglong Station of National Astronomical Observatory, China, as a national facility open to the astronomical community. The project was planned to be completed in 2004, with its budget of RMB 235 millions yuan (about 28 M$). The project is well in progress, with various sub-systems and their parts in critical reviews or kick-out for manufacturing early or late. Here we report the current status of the project generally. Other authors in this conference will describe details for individual parts of the project.

The National University of Mexico has made an effort towards the design of a large telescope able to beat the empirical cost vs. diameter law and provide our astronomical community with a facility for future research. This has led us to develop a series of solutions to critical problems in telescope design and manufacture. We first present a brief review of our current telescope concept, together with a progress report and plans. Recent site testing studies of San Pedro Martir (Observatorio Astronomico Nacional) in Baja California are reviewed. Finally, we describe in more detail innovative ideas in topics that are relevant to other segmented telescope projects: segment polishing, phasing and thin membrane mirrors.

A new 76.2-cm aperture handicapped accessible telescope exhibiting novel design features is nearing completion for installation within the Space Sciences Laboratory building on the main campus of the University of Denver. This Student Astronomy Laboratory (SAL) instrument incorporates a Coude’ optical path working in combination with a vertical periscope to bring the optical beam to a location inside a 4^th floor laboratory room, where visible and IR observations can be made. The primary and secondary mirrors are arranged in the afocal Mersenne configuration to provide a collimated, compacted beam that is folded through the rotating Right Ascension and Declination axes of the telescope mounting. A pair of optical flats then directs the compacted beam downward into the indoor laboratory, through visible or IR band auxiliary condensing telescopes, to locations where visual observers (including those in wheelchairs) or visible or IR instruments can be accommodated. The mounting uses large inner race diameter preloaded turntable bearings in each axis and provides a rotary stage at the payload flange to cancel image rotation associated with the Coude’ configuration. Long baseline interferometry is planned between the SAL and the DU Meyer-Womble Observatory on Mt. Evans, Colorado.

The Mayall 4-meter telescope on Kitt Peak is a successful and productive telescope now approaching its thirtieth anniversary. Originally designed at 150 inches, built at 158 inches, and with an effective aperture or 3.81m, it is from the generation of thick mirror, equatorially mounted telescopes. At a moderate altitude site, the Mayall had in the past upheld the prejudice that ground-based observing delivers about 1" seeing at best, and that it is no surprise to be considerably fuzzier. Changes in engineering, computer control, and our understanding of telescope seeing, have led to the new generation of lightweight mirrors with complex active support and advanced thermal control, running on altitude-azimuth mounts inside compact, low-volume enclosures. Such telescopes routinely deliver sub-arcsecond seeing, often down below 0.5" even from 'traditional' sites, and even sharper from higher and more remote sites to which access has been developed over recent decades. Nevertheless, what we have learned can be successfully applied to older telescopes: the Mayall telescope is a case in point, since it now regularly provides sub-arcsecond image quality. We discuss the significant improvements in thermal management and active control of the Mayall system over the last several years, as well as the difficulty of evaluating such changes, especially separating different effects. We also discuss future adjustments to and tuning of existing sub-systems, possible changes to the telescope environment, and planned new features. It takes effort and continual attention to detail, but older facilities can still be world class.

The control system of LAMOST telescope is highly distributed real time system, and the time base is crucial. During the motion tracking for 4000 celestial objects being simultaneously observed the alt-azimuth mount has to be driven on two axes in a servo loop to follow the motion of the objects in a timing system that has to be precise to the level of a few milliseconds. The GPS-based timing system has been developed in the lab of Nanjing Institute of Astronomical Optics & Technology (NIAOT). This paper describes a Net Time Server (NTS) that maintains the Coordinated Universal Time (UTC) derived from GPS, and distributes the time to precisely synchronize the client computer clocks across a network. The NTS is built on real time OS QNX4.25 platform. With help of a GPS receiver at hand, the NTS reaches the precision of 0.1 millisecond, and the time precision across LAN computers served by the NTS can meet the requirements for different time critical tasks in LAMOST control.

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.

The Visible and Infrared Survey Telescope for Astronomy (VISTA) project started in 2000 following a Joint Infrastructure Fund award (JIF) to a consortium of 18 UK Universities . The JIF proposal was for a 4 metre class telescope with the ability to mount a visible and an infrared wide field camera. The UK Astronomy Technology Centre successfully tendered for the management of the project of developing and building the telescope in two phases. The initial phase was intended to review the proposed design and carry out a conceptual study. The second phase being the development, manufacture and commissioning of this design. As a result of the first phase, a conceptual design based on an f/1 primary mirror telescope and cold baffle IR camera has been developed. The IR Camera focal plane has been sized to accommodate sixteen 2k × 2k IR detectors, putting VISTA at the forefront of IR Survey Astronomy. The project team have developed this conceptual design into formal ITT's to allow the design and manufacture to commence. The telescope will be sited at the ESO Observatory in Paranal and is due for completion in 2006.

The 4m Advance Technology Solar Telescope (ATST) will be the most powerful solar telescope in the world, providing a unique scientific tool to study the Sun and possibly other astronomical objects, such as solar system planets. We briefly summarize the science drivers and observational requirements of ATST. The main focus of this paper is on the many technical challenges involved in designing a large aperture solar telescope. The ATST project has entered the design and development phase. Development of a 4-m solar telescope presents many technical challenges. Most existing high-resolution solar telescopes are designed as vacuum telescopes to avoid internal seeing caused by the solar heat load. The large aperture drives the ATST to an open-air design, similar to night-time telescope designs, and makes thermal control of optics and telescope structure a paramount consideration. A heat stop must reject most of the energy (13 kW) at prime focus without introducing internal seeing. To achieve diffraction-limited observations at visible and infrared wavelengths, ATST will have a high order (order 1000 DoF) adaptive optics system using solar granulation as the wavefront sensing target. Coronal observations require occulting in prime focus, a Lyot stop and contamination control of the primary. An initial set of instruments will be designed as integral part of the telescope. First telescope design and instrument concepts will be presented.

The Atacama Large Millimeter Array, or ALMA, is an international telescope project which will be built over the coming decade in Northern Chile. With over 7000 m² of collecting area comprised of 64 12m antennas arrayed over baselines up to 14 km in extent, ALMA will provide images of unprecedented clarity and detail. One revolutionary feature of ALMA will be its ability to combine interferometric and single telescope data, providing complete flux recovery. ALMA will cover a spectral wavelength range from 7mm to 0.3 mm or shorter wavelengths, providing astronomy with its first detailed look at the structures which emit millimeter and submillimeter photons, the most abundant photons in the Universe.

The National Radio Astronomy Observatory (NRAO) is undertaking a major expansion of the Very Large Array (VLA), the most powerful and flexible radio instrument in the world. This VLA Expansion Project combines the existing infrastructure with state-of-the-art electronics and instrumentation to improve the scientific capabilities of the array by a factor 10 or more in all key observational parameters. Some of the most important advances include: (1) replacing the existing waveguide with optical fiber, allowing total bandwidths of up to 16 GHz, rather than the current 200 MHz; (2) installing wideband receiver systems, for continuous coverage of the entire centimeter radio spectrum from ≤1 to 50 GHz; (3) building a new correlator, able to provide as many as 262,144 frequency channels with flexible, variable resolutions between 4 MHz and 1 Hz; (4) adding ~8 new stations at distances up to 300 km from the current VLA, allowing spatial resolution as high as a few milliarcseconds on both synchrotron and thermal sources. The design and development effort for the first phase of this project has already begun, and we are currently developing a proposal for the new antennas needed for the high-resolution New Mexico Array. There are three major partners in the EVLA: NRAO; the Herzberg Institute of Astrophysics (HIA), funded by the National Research Council (NRC) of Canada; and the Mexican National Council for Science and Technology (CONACyT). We plan to finish the entire project within a decade. The EVLA will inaugurate a new era in radio astronomy, allowing extinction-free imaging of star-forming galaxies out to z>5, measurements of the three-dimensional structure of magnetic fields in objects ranging from the Sun to nearby galaxies, and parallaxes and proper motion measurements of pulsars spread throughout the Galaxy. The EVLA is intended not to perform a single, particular experiment, but to provide an essential tool across the entire range of modern astrophysics.

We present a summary of the Large Millimeter Telescope Project and its present status. The Large Millimeter Telescope (LMT) is a joint project of the University of Massachusetts (UMass) in the USA and the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) in Mexico to build a 50m-diameter millimeter-wave telescope. The LMT is being built at an altitude of 4600 m atop Volcan Sierra Negra, an extinct volcanic peak in the state of Puebla, Mexico, approximately 100 km east of the city of Puebla. Construction of the antenna is now well underway, and it is expected to be completed in 2004.

The Large Binocular Telescope (LBT) Project is a collaboration between institutions in Arizona, Germany, Italy, and Ohio. The first of two 8.4-meter borosilicate honeycomb primary mirrors for LBT is being polished at the Steward Observatory Mirror Lab this year. The second of the two 8.4-meter mirror blanks waits its turn in the polishing queue. The baseline optical configuration of LBT includes adaptive infrared secondaries of a Gregorian design. The F/15 secondaries are undersized to provide a low thermal background focal plane which is unvignetted over a 4-arcminute diameter field-of-view. These adaptive secondary mirrors with 672 voice-coil actuators are now in the early stages of fabrication. The interferometric focus combining the light from the two 8.4-meter primaries will reimage the two folded Gregorian focal planes to three central locations for phased array imaging. The telescope elevation structure accommodates swing arm spiders which allow rapid interchange of the various secondary and tertiary mirrors as well as prime focus cameras. The telescope structure accommodates installation of a vacuum bell jar for aluminizing the primary mirrors in-situ on the telescope. The telescope structure was fabricated and pre-assembled in Italy by Ansaldo-Camozzi in Milan. The structure was disassembled, packed and shipped to Arizona. The enclosure was built on Mt. Graham and is ready for telescope installation.

Modern scientific and technological projects are increasingly in competition over scientific aims, technological innovation, performance, time and cost. They require a dedicated and innovative organization able to satisfy contemporarily various technical and logistic constraints imposed by the final user, and guarantee the satisfaction of technical specifications, identified on the basis of scientific aims. In order to satisfy all the above, the management has to be strategically innovative and intuitive, by removing, first of all, the bottlenecks that are pointed out, usually only at the end of the projects, as the causes of general dissatisfaction. More than 30 years spent working on complex multidisciplinary systems and 20 years of formative experience in managing contemporarily both scientific, technological and industrial projects have given the author the possibility to study, test and validate strategies for parallel project management and integrated design, merged in a sort of unique optimized task, using the newly-coined word "Technomethodology". The paper highlights useful information to be taken into consideration during project organization to minimize the program deviations from the expected goals and describe some of the basic meanings of this new advanced method that is the key for parallel successful management of multiple and interdisciplinary activities.

Although Systems Engineering has been widely applied to the defence industry, many other projects are unaware of its potential benefits when correctly applied, assuming that it is an expensive luxury. It seems that except in a few instances, telescope projects are no exception, prompting the writing of this paper. The authors postulate that classical Systems Engineering can and should be tailored, and then applied to telescope projects, leading to cost, schedule and technical benefits. This paper explores the essence of Systems Engineering and how it can be applied to any complex development project. The authors cite real-world Systems Engineering examples from the Southern African Large Telescope (SALT). The SALT project is the development and construction of a 10m-class telescope at the price of a 4m telescope. Although SALT resembles the groundbreaking Hobby-Eberly Telescope (HET) in Texas, the project team are attempting several challenging changes to the original design, requiring a focussed engineering approach and discernment in the definition of the telescope requirements. Following a tailored Systems Engineering approach on this project has already enhanced the quality of decisions made, improved the fidelity of contractual specifications for subsystems, and established criteria testing their performance. Systems Engineering, as applied on SALT, is a structured development process, where requirements are formally defined before the award of subsystem developmental contracts. During this process conceptual design, modeling and prototyping are performed to ensure that the requirements were realistic and accurate. Design reviews are held where the designs are checked for compliance with the requirements. Supplier factory and on-site testing are followed by integrated telescope testing, to verify system performance against the specifications. Although the SALT project is still far from completion, the authors are confident that the present benefits from Systems Engineering on the project will be felt through telescope commissioning and testing.

Systems Engineering has been used throughout the development of the Visible and Infrared Survey Telescope for Astronomy (VISTA). VISTA was originally conceived as being a classic 4m telescope with wide-field imaging capability. The UK Astronomy Technology Centre (UK ATC) radically changed this thinking by treating the whole design as one system, integrating the camera optics into the telescope design. To maximise the performance, an f/1 primary mirror was adopted resulting in a very compact telescope and enclosure. Amongst other benefits, this reduced the overall mass of the telescope from 250 to 90 tonnes. During this optimisation process, the concept of a direct imaging K-short camera was developed. This development, in conjunction with an increase in IR field of view, produced a system with uniform image quality and throughput across a 350 mm diameter focal plane, 1.65 degree field. While this has presented some major engineering challenges, the approach has produced a system which is both scientifically rewarding and achievable. The optimisation, design trade-offs and Technical Specification developed in the conceptual design phase were achieved through a systems analysis approach. This paper describes some of the key systems engineering decisions and the tools employed to achieve them. Current systems engineering activities are described and future plans outlined.

Industry is a bridge which links scientific thought with its concrete possibility to realize something operative and functional. In the last fifteen years, Astronomy has undergone a total revolution: telescopes are getting bigger and bigger and even more efficient. Enclosures are being more and more integrated into scientific performances. From NTT to VLT, from LBT to ALMA, to VST and to VISTA: there is always an industrial contribution in the development of the biggest astronomic projects. A comparison between scientific and technological research, a synergy that leads to the future.

LAMOST is a unique telescope, its optical axis is on the meridian plane with a 25 degree inclination to the horizontal, the optical path is 60 meters, much longer than that of traditional telescope, that causes much more serious dome seeing problems. To improve the seeing around telescope, studies are carrying out on the enclosure thermal performance design, that include ventilation, air conditioning, cooling for heat sources, and calculation of thermal parameter of enclosure structure. Some experiments are taking for the remove the main heat from electronic. This paper will concentrate on dome seeing improvement, related studies and experiments. The data obtained from calculation and experiments will be used for enclosure design to improve LAMOST dome seeing.

Aspects of the design and experience of the Hobby-Eberly Telescope (HET) were incorporated in the SALT facility design. The characteristics of the local environment were taken into account to ensure a building that is cost effective and functional. The effect of heat from the control room and other warm areas were studied and their locations changed to limit thermal effects. A steel false floor, incorporating forced ventilation and extending around the telescope azimuth pier, was installed. This prevents heat radiating from large concrete surfaces with temperatures potentially higher than ambient. Because site testing (i.e. micro thermal measurements) indicated high turbulence within ~5 m of the ground level, the telescope and pier were raised to improve dome seeing. The SALT site is significantly windy all year round (median velocity = 4.8 m/s), and this was utilized to design better ventilation of the facility using adjustable louvers for natural ventilation. Results of a computational fluid dynamic analysis (CFD) are presented which show an adequate temperature distribution at wind speeds as low as 0.5 m/s. The telescope chamber and dome are build out of insulation panels to ensure low thermal losses during the day when the chamber is air conditioned and thus limit electricity consumption and thermal gradients. Large equipment that emit heat or vibration are housed in a separate utility building 50 m from the telescope in the non-prevailing wind direction in order to limit their effect on the telescope. Vented air from the building is also released at this site.

The Large Binocular Telescope (LBT) under construction on Mount Graham, Arizona is a unique instrument, which supports two 8.4-meter primary mirrors on the same mount. The telescope mirrors will provide a collecting area equivalent to an 11.8 circular aperture plus a diffraction baseline of 22.8 meters. This unique instrument presented new enclosure challenges and configurations in order to accommodate the Owner’s design, telescope operating criteria and budget. The LBT enclosure completed in the summer of 2002 provides useful information on the planning, designing and construction of a telescope enclosure. The use of a team approach by the contractors, engineers, and project office has been successful in maintaining quality construction at a reasonable price. This paper discusses the various systems implemented on the LBT enclosure and the lessons learned during the course of the design and construction.

A long term program to quantify the intrinsic site seeing at McDonald Observatory, using two differential image motion monitors (DIMMs) has been initiated on Mt. Fowlkes where the Hobby-Eberly Telescope (HET) is located. Raw DIMM data are corrected to the zenith and to a uniform 10msec integration time. Nightly median seeing measurements (FWHM) along with the max/min range are presented for 186 nights over the 13 month period between July 2001 and July 2002. A definite seasonal effect is present in the dataset with the median seeing in the spring-summer-fall months (0.93±0.18 arcsec) being significantly better than the winter months (1.24±0.33 arcsec). The measured seeing was better than 0.70 arcsec about 9% of the time. Since DIMM units were operated at ground level these data are not quite lower limits to the site seeing performance. Even so, the seeing of this West Texas continental site at 6,650ft (2,027m) elevation in the Davis Mountains is superior to what has been assumed in the past, based on less direct seeing measurements. Future plans are described for moving a DIMM telescope to a tower mounted, semi-automated observatory to sample the site seeing at an elevation above the ground similar to the HET mirror.

The Hobby-Eberly Telescope (HET) enclosure is receiving a series of modifications to improve dome seeing, including removal of residual heat loads from the optical path, increased insulation of the enclosure, and ventilation of the enclosure ring wall and dome. Analysis indicates that the contribution of dome seeing with the new system will be less than 0.05 arc seconds. The design of the HET enclosure lends itself to very large ventilation openings in the stationary portion of the enclosure also referred to as the "ring wall", with supplementary openings in the rotating dome. The ventilation design implemented has opened approximately 58% of the ring wall, and will open 8% of the dome, in the coming year, in order to achieve natural ventilation of 22 air changes per hour at the minimum design wind velocity of 3.5 mph. A system of ventilation louvers similar in design to the Kitt Peak Observatories 4-meter telescope was determined to be the most practical and cost effective design for use in the ring wall. Conventional off-the-shelf louvers are proposed for the dome, due to constraints in its design. Special considerations for retrofitting an operating facility included a custom hoist mounted on the dome for installation of the louvers (5000lb./ea.), and an inflatable curtain to protect the telescope during foul weather. The ring wall ventilation system has been in full operation since early April 2002 and is part of a program in progress to substantially improve the HET dome seeing.

The SDSS telescope is housed, when not in use, in a roll-off enclosure. This enclosure rolls away from the telescope a distance of 60 feet, leaving the telescope fully exposed for operations. Design considerations for wind and solar loading, thermal venting, conditioning and stability are reviewed. Originally, the enclosure had been constructed to minimize its surface area obstruction to the telescopes field of view. This design feature, however, offered little room to perform engineering tasks during non-operational time. An upgrade to the structure, in the form of raising the roof, was instituted. This improvement greatly enhanced the engineering and testing functions performed on the telescope, thereby increasing operational efficiency and the time allotted to engineering tasks. Problems maintaining and associated with weather sealing, lightning protection, truck wheel alignment, altitude effects on truck controllers and thermal conditioning are examined. Communication and electrical connections between stationary and moving elements of the enclosure are described. Two types of systems, to date, have been used - one a reel and the other a slider system. Advantages and disadvantages of both are examined from the perspective of four years experience.

Based on the successful numerical weather forecasting performed by collaboration between MKWC and Subaru Telescope, we develop a temperature control system of the primary mirror of the Subaru Telescope. Temperature forecast is accurate 80% in 2 degrees. After to start the operation, the temperature of the primary mirror controlled below 1 degree centigrade compare by the ambient night air temperature in over 70% probability. The effect of the temperature control for the improvement of the seeing of Subaru telescope seems to be moderately effective.The median of the seeing size of Subaru Telescope on May 2000 to July 2002 is 0.69 arcsec FWHM. We need further investigation whether the improvement is the result of our successful temperature control system of the primary mirror, or the effect of the annual variation of seeing itself. Thus, we need a long period data for verification the effect of the temperature control.

The AEOS telescope facility was designed for high angular resolution imagery. Part of that design is the inclusion of several air handling systems to maximize dome seeing. Four air conditioning units chill the telescope and dome air to the predicted nighttime temperature. There is a mirror purge system, which prevents moisture from condensing on the mirror by blowing desiccated air into the mirror cell. A laminar air system counteracts the seeing degradation effects of a warm mirror by blowing air across the face of the primary. An hour before sunset the dome is partially opened and outside air is pulled through the telescope truss structure in an effort to remove any thermal differences caused by incorrect cooling. Finally a fan pulls air through the coude' tube in order to remove rising air cells. We present details of each system and the beginnings of our experiments to determine their efficacy. Finally, lessons learned from the systems on the AEOS telescope are presented.

The Southern African Large Telescope (SALT), being erected in Sutherland, South Africa, will be the largest single optical telescope in the southern hemisphere, and the 4th largest telescope in the world, when it is completed in late 2004. The SALT design is based on the Hobby-Eberly Telescope (HET). Deviations from the HET design with respect to the telescope structure, primary mirror truss and tracker beam structure are presented in this paper. Finite element models were generated to perform static, dynamic and thermal analyses on the structures. Despite a significantly heavier payload and increased wind loading requirements, equivalent or improved stiffness characteristics were achieved, without increasing structure mass. Dynamic response analyses were performed to characterize the maximum deflections under dynamic wind loading. Automation of the truss design process, which included the control of the 3-D CAD software, the finite element software, as well as CAM software, with a central computer program, allowed the generation of a full 3-D CAD model, as well as CAM inputs, of a structurally optimized truss, within a few days. Extensive analyses, including Monte Carlo simulations, as well as experimentation, were performed to ensure linear temperature-displacement response of the truss. A methodology was developed, using the complete finite element model, to calculate mirror corrections required to correct for lower order deformations of the primary mirror due to temperature fluctuations in the truss.

The Large sky Area Multi-Object fiber Spectroscopic Telescope is a very special reflecting Schmidt telescope with a 40 m long optical axis between the reflecting Schmidt correcting plate and the spherical main mirror. In the middle is located the spherical focal plane of 1.75 m in diameter. The reflecting Schmidt correcting plate serves not only to correct wavefront by active optics but also to point and track celestial objects by normal tracking with collaboration of the focal plane to form a special mounting and tracking system. In this paper, the operational principle and technical specification of the tracking system is briefed. Design and test measurement as well as driving mode of both the Schmidt plate and the focal plane are investigated with structural calculations and analyses. The paper is closed with the conclusion that the mounting and tracking system is to meet global technical specifications of the LAMOST excellently.

VertexRSI completed the 4.2-meter Southern Astrophysical Research (SOAR) Telescope Mount in 2001. The Mount is now in assembly and test at the site in Chile. This paper will discuss the final mechanical design of the Mount and the implementation of the design requirements during fabrication, factory integration and testing. The final design includes detailed finite element structural analysis, 3-D design models, and precise machining requirements. These requirements were implemented in the fabrication using standard and novel machining approaches. Factory integration proved out the design and fabrication process. The connection of these items with the success of the testing is presented.

Based on its certification testing, the 4.2 Meter SOAR Telescope can be described as one of the most precise pointing instruments in the world, however, this was achieved a little differently than other telescopes. This instrument utilizes gear drives in azimuth, direct drives in altitude, and rolling element bearings on both axes instead of hydrostatic bearings. This combination of features provides a lower initial cost, significantly lower operating costs, simple maintenance, less potential for contaminating both the environment and the optics, less thermal effects and a greater degree of safety. This is achieved by relying on a sophisticated servo control system adapted from much larger radio astronomy instruments and rolling element bearing designs with exceptionally low friction torque. The design approach was not "stumbled upon" but rather performance was predicted from the initial studies, through the proposal, the early design stages, up through the final "as built" configuration. This paper traces the development of the performance estimates through that period.

Under a contract with the GRANTECAN, the Commissioning Instrument (CI) is a project developed by a team of Mexican scientists and engineers from the Instrumentation Department of the Astronomy Institute at the UNAM and the CIDESI Engineering Center. The CI will verify the Gran Telescopio Canarias (GTC) performance during the commissioning phase between First Light and Day One. The design phase is now completed and the project is currently in the manufacturing phase. The CI main goal is to measure the telescope image quality. To obtain a stable high resolution image, the mechanical structures should be as rigid as possible. This paper describes the several steps of the conceptual design and the Finite Element Analysis (FEA) for the CI mechanical structures. A variety of models were proposed. The FEA was useful to evaluate the displacements, shape modes, weight, and thermal expansions of each model. A set of indicators were compared with decision matrixes. The best performance models were subjected to a re-optimization stage. By applying the same decision method, a CI Structure Model was proposed. The FEA results complied with all the instruments specifications. Displacements values and vibration frequencies are reported.

This paper explores the use of direct drive servos in telescopes applications in the quest of standardization key concepts that might push to more reliable and cheaper solutions for future complex motion systems. Considerations related to different PWM Frequencies, Motor Phasing, position feedback, CAN-bus interfaces, etc. A collection of data from the VLT experience is presented showing the particular needs of the modern telescope’s drives. Can an industry standard amplifier meet the telescope specifications, and therefore be easier to maintain and offer a cheaper solution?

Carbon fiber reinforced plastic (CFRP) is a suitable material for space and ground-based telescope structures. CFRP has a high stiffness-over-weight ratio and a low thermal expansion coefficient. Together with aluminum honeycomb, CFRP can form very strong light-weight sandwiched structures. These sandwiched structures, which can support high bending moments and shear forces without much deformation, are used widely in the existing and future large-space or ground-based telescopes. However, some special CFRP-aluminum honeycomb sandwiched structures have shape change problems when the absolute temperature changes. In this paper, some of these thermal shape changes are discussed. The designers of the future large telescopes should be fully aware of the shape change problem of these structures.

The W.M. Keck Observatory is conducting a focused effort to identify and mitigate facility vibrations that significantly affect optimal optical performance. This effort should improve the performance of both Keck adaptive optics systems, the laser guide star, the AO instruments, and the interferometer, and will benefit future high precision instruments. We present our strategy for mitigating vibrations in a large ground-based telescope. Our approach is to establish reasonable confidence in identifying the facility vibration sources that most significantly deteriorate optical performance. For the interferometer we completed vibration surveys that correlate vibrations on the interferometer beam path with direct vibration measurements on the telescope structure and facility. We developed a metric to evaluate the effect of vibrations on the entire interferometer beamline. From our surveys, we prioritized facility components to be addressed, and developed approaches to mitigate key vibrations contributions. Initial results show large local improvements, and global improvements to our vibration environment.

Wind loading is a critical issue for large telescopes and will be even more problematic for proposed future giant telescopes. As the current-generation telescopes were being designed in the 1980s and 1990s, numerous studies were made to understand airflow through the enclosures and wind loading of the telescopes. Now that these telescopes are in operation, it is important to consider what can be learned from them to: (1) verify the assumptions and predictions of previous studies; (2) establish procedures to optimize telescope operation; and (3) guide the design of future extremely large telescopes. With these goals in mind, Gemini Observatory conducted a campaign during the integration of the southern Gemini telescope to simultaneously measure wind velocities inside and outside the enclosure and pressure variations on the (dummy) primary mirror. The data collected in this campaign have been analyzed and results are presented that address these three goals. This paper points out several results that are different from the assumptions of previous studies. It presents a rule of thumb for allowable wind speed around the Gemini primary mirror. Results are shown indicating that the average pressure pattern on the Gemini mirror is primarily produced by airflow around the telescope structure, but that much of the dynamic pressure variation at the mirror comes from turbulence generated by the enclosure. Also described is a strategy for developing realistic wind loading input for simulating the performance of an extremely large telescope, including the spatial and temporal variation of pressure on the primary mirror.

The VST (VLT Survey Telescope) is a 2.6 m class Alt-Az telescope to be installed at Mount Paranal in Chile, in the European Southern Observatory site. The VST is a wide-field imaging facility planned to supply databases for the ESO Very Large Telescope (VLT) science and carry out stand-alone observations in the UV to I spectral range. So far no telescope has been dedicated entirely to surveys; the VST will be the first survey telescope to start the operation in 2004, as a powerful survey facility for the VLT observatory. During the design phase a dynamic analysis of the telescope has been carried out using as inputs the data coming from the structural analysis of the mechanical system. This analysis has been used to build a model of the electro-mechanical system and to give an approximate estimation of the wind loading effect on the axes performance, based on the wind speed spectral model used at ESO.

The VLT Survey Telescope (VST) is a cooperative program between the European Southern Observatory (ESO) and the INAF Capodimonte Astronomical Observatory (OAC), Naples, for the study, design, and realization of a 2.6-m wide-field optical imaging telescope to be operated at the Paranal Observatory, Chile. The VST has been specifically designed to carry out stand-alone observations in the UV to I spectral range and to supply target databases for the ESO Very Large Telescope (VLT). The telescope design, manufacturing and integration are responsibility of TWG and have been carried out on the base of a model of optimized design not only for mechanics but for all telescope subsystems. The paper is an overview on the telescope mechanical design and optimization.

The VLT Survey Telescope (VST) is a cooperative program between the European Southern Observatory (ESO) and the INAF Capodimonte Astronomical Observatory (OAC), Naples, for the study, design, and realization of a 2.6-m wide-field optical imaging telescope to be operated at the Paranal Observatory, Chile. The VST has been specifically designed to carry out stand-alone observations in the UV to I spectral range and to supply target databases for the ESO Very Large Telescope (VLT). The telescope design, manufacturing and integration are responsibility of TWG and have been carried out on the base of a model of optimized design not only for mechanics but for all telescope subsystems. The paper is an overview on the telescope drive system characteristics.

The VLT Survey Telescope (VST) is a cooperative program between the European Southern Observatory (ESO) and the INAF Capodimonte Astronomical Observatory (OAC), Naples, for the study, design, and realization of a 2.6-m wide-field optical imaging telescope to be operated at the Paranal Observatory, Chile. The VST has been specifically designed to carry out stand-alone observations in the UV to I spectral range and to supply target databases for the ESO Very Large Telescope (VLT). The telescope design, manufacturing and integration are responsibility of OAC. The telescope is in Cassegrain configuration and for this reason the primary mirror cell represents one of the most complex telescope subsystems, designed to host a large amount of auxiliary sub-systems and to support a wide field camera. The paper describes the solutions adopted as a result of an integrated optimized optical and mechanical design.

The VLT Survey Telescope (VST) is a co-operative program between the European Southern Observatory (ESO) and the INAF Capodimonte Astronomical Observatory (OAC), Naples, for the study, design, and realization of a 2.6-m wide-field optical imaging telescope to be operated at the Paranal Observatory, Chile. The telescope design, manufacturing and integration are responsibility of OAC. The VST has been specifically designed to carry out stand-alone observations in the UV to I spectral range and to supply target databases for the ESO Very Large Telescope (VLT). The control hardware is based on a large utilization of distributed embedded specialized controllers specifically designed, prototyped and manufactured by the Technology Working Group for VST project. The use of a field bus improves the whole system reliability in terms of high level flexibility, control speed and allow to reduce drastically the plant distribution in the instrument. The paper describes the philosophy and the architecture of the VST control HW with particular reference to the advantages of this distributed solution for the VST project.

I will report on the deformation of the Subaru Telescope primary mirror surface due to wind pressure. The 261 actuators, controlled precisely down to 0.01 N level, together with 3 fixed points maintains the optical figure of the primary mirror. The extra-force exerted by wind pressure, however, pushes the actuator pistons to cause their displacement while not affecting the fixed points. This results in an overall deformation of the primary mirror, which we measured. We first measured the difference in the actuator force of the sensors with and without wind pressure, i.e., with the dome shutter opened and closed. The force were then converted to the displacement of the 261 actuator pistons. The experiment was made under the wind speed of 5m/s with the telescope pointing toward the wind at elevations 30 and 60 degrees. The deformation pattern at EL=30 was triangular with three fixed points protruding, while that at EL=60 was saddle with the left and right pushed back. The value of deformation was ~2um. The patterns were interpreted that the wind pushes the entire mirror surface at EL=30 while it lifts the bottom part up at EL=60.

For the international ALMA project’s prototype antennas, we have developed a high performance, reactionless nutating subreflector (chopping secondary mirror). This single axis mechanism can switch the antenna’s optical axis by ±1.5’ within 10 ms or ±5’ within 20 ms and maintains pointing stability within the antenna’s 0.6” error budget. The light weight 75 cm diameter subreflector is made of carbon fiber composite to achieve a low moment of inertia, <0.25 kg m². Its reflecting surface was formed in a compression mold. Carbon fiber is also used together with Invar in the supporting structure for thermal stability. Both the subreflector and the moving coil motors are mounted on flex pivots and the motor magnets counter rotate to absorb the nutation reaction force. Auxiliary motors provide active damping of external disturbances, such as wind gusts. Non contacting optical sensors measure the positions of the subreflector and the motor rocker. The principle mechanical resonance around 20 Hz is compensated with a digital PID servo loop that provides a closed loop bandwidth near 100 Hz. Shaped transitions are used to avoid overstressing mechanical links.

The WIYN Tip-Tilt Module (WTTM) is an addition to the existing Instrument Adapter System (IAS) providing a high performance optical-NIR image stabilized port on the WIYN 3.5m telescope. The WTTM optical system uses a 3-mirror off-axis design along with a high bandwidth tilt mirror. The WTTM is a reimaging system with 15% magnification producing a 4x4 arcminute field of view and near diffraction limited imagery from 400-2000nm. The optics are diamond turned in electroless Nickel over an Aluminum substrate. The WTTM opto-mechanical assembly was designed and built using the principals of the "build-to-print" technique, where the entire system is fabricated and assembled to tolerance with no adjustments. A unique high performance error sensor, using an internal mirrorlette array that feeds 4 fiber coupled avalanche photodiode photon counters, provides the tilt signal. The system runs under the Real-Time Linux operating system providing a maximum closed loop rate of 3khz. In this paper we report on the successful lab testing, verification of the "build-to-print" technique and on telescope performance of the WTTM.

The paper presents some special, innovative and technological aspects of the secondary mirror mechanism for the GTC 10.8-m telescope, such as: The dual control loop of the hexapod actuators, which provides the GTC M2 alignment system with an absolute accuracy better than a few microns, and a resolution as low as 200 nm. The particular design of the hexapod flexure joints, which ensures frictionless joints without backlash, while effectively limiting the travel of the hexapod to the desired range only. The locking devices, based on an original rotating cam principle, which ensure the safe locking of the M2 support to the hexapod lower plate when the chopper function is not utilized. CuBe flexure parts have been manufactured by Electrodischarge Machining (EDM), and heat treated for maximum strength and fatigue load. A systematic approach to the Reliability, Maintainability and Safety aspects, aimed at ensuring the operational feasibility of the mechanism along its life cycle.

At Kitt Peak National Observatory a, active control of the f/8 secondary mirror on the Mayall, 4m telescope, was installed as phase two of a three phase project improving the telescope's delivered image quality. The resulting changes provide 400 times the previous resolution of control to the existing secondary mirror and its support cell. The redesign and method used to give 100 nanometer control of the secondary's tip, tilt and focus is presented in this paper.

The SUBARU Telescope has four focal positions to allow different types of instruments. At present, there are four different Top Units; three types of secondary mirrors and one primary focus unit. These units have the weight of about 3 tons, and they need to be installed or changed high above in the air, with the telescope in its rest position, namely, pointed to the zenith. In order to carry out this exchange work safely and securely, in already a difficult working condition of high altitude place like Mauna Kea, we developed an automatic exchanger with remote control, called Top Unit Exchanger (TUE).

The progress in development of advanced instrumentation for IR and submillimeter telescopes during the past decades is bringing new structural and logistics challenges to engineers at both the UKIRT and JCMT telescopes. These facilities were designed for instruments much smaller, lighter, and less complex than those currently under construction. This paper describes the ongoing structural changes to the design of both telescopes and innovative approaches to the mechanical interfacing of extremely large and heavy instruments. The design changes and handling schemes these large and unwieldy instruments require would be unthinkable without utilization of advanced 3-D computer modeling and finite element analysis. Examples will be given of particular challenges associated with the handling and interfacing of existing instruments at both facilities as well as the difficulties presented by new generation instrumentation currently under development. The importance of involving facility engineers as early as the conceptual stages of new instrument design and development will be demonstrated.

Based on an unconventional design concept the LAMOST telescope will become the world's most powerful meter-class level ground astronomical optical survey telescope when it is completed. From technical perspective the goal with such a high profile has brought an extraordinary challenge to its control system. For better image quality the telescope's segmented reflecting Schmidt mirror has to be actively controlled by nanometer technique. At the same time the mirror is driven on both azimuth and altitude axes in subarcsecond accuracy for tracking the star. Vigorous study has been done and a number of cutting edge techniques are applied to meet the tough requirements. This paper gives the overview of LAMOST control system, outlines its distributed, real time, reliable and expansible configuration and the simulation approach. The current status of the control system is briefly reported in this paper too.

This paper describes the design of control system of fiber positioning system. The fiber positioning system has more than 4000 fiber units with 2 stopping motor and 2 start position sensor in each unit, and whole units will be assembled at 1.75 meter diameter focal surface of LAMOST, the mechanism and control system have demanding requirements for high precision position control. Detail design, testing and performance evaluation is described in this paper, a special control unit which can control and monitor more than 20 fiber with 1000Hz driving frequency of stepping motor and response start position sensor with one pulse of stepping motor in each fiber unit is set as a CAN bus node, 200 control units combine a can bus real time control system which can control the whole fibers move to new position in 3 minutes. In order to get high precision position in this open loop control unit, a very simple and small sensor is used to eliminate the accumulate errors of mechanism with resetting the start position, and compensation data is measured and set in control software to diminish the mechanical transmission errors. For testing the mechanism and control system, a small fiber positioning system with 19 units have been made.

The Acquisition and Guiding Unit of the Gemini Telescope is able to support two major signal-processing functions: off axis active optics correction, and off axis fast guiding and focus. Both functions are performed by using up to two different Shack-Hartmann wavefront sensors working in the visible (called the Peripheral Wavefront Sensors). In addition to these wavefront sensors, each facility instrument includes its On Instrument Wavefront Sensor, which provides on or off axis fast guiding, and in some cases focus and astigmatism correction. In this paper, we will describe the different wavefront sensors and the results obtained in closed loop in terms of image quality and temporal performance.

Despite the relatively large number of proposed 'extremely large telescopes' very few of them concentrate on the thermal infrared as their main operating wavelengths. An IR-optimized large telescope located in the Atacama dessert at about 5500m altitude, where many atmospheric windows in the mid-IR open up, would be ideal to study astronomical targets that are either intrinsically red or heavily obscured by dust. A large aperture in the order of 15 - 20m requires adaptive optics correction out to λ⩽20 μm with the least possible thermal emission from the instrument itself. Here we discuss a specialized, integrated AO system that provides diffraction-limited performance in the thermal infrared (at λ⩾2.5 μm). This approach is very different from the AO systems proposed for other 10m+ class telescopes. We present the basic concept of such an IR-optimized AO system, based on a 2m chopping adaptive secondary. We derive its technical specifications: configuration, bandwidth, and degrees of freedom show its predicted performance for typical seeing in terms of Strehl ratio as a function of limiting guide star magnitude, wavelength and corrected field-of-view. We also briefly address the science that this AO system/telescope would be ideal for.

This paper describes both the electronics design (ED) and the acceptance control system (ACS) of the Commissioning Instrument (CI) for the Gran Telescopio Canarias (GTC). The CI mainly comprises ten mechanisms accurately positioned by control algorithms, which in turn are programmed according to the CI operation modes. The control system is based on a CANopen protocol and is completely compatible with the GTC control system. CANopen is a serial communication protocol based on CAN bus. The CANopen features allow for the control system high reliability. A Reliability, Availability, Maintainability, and Safety (RAMS) analysis was carried out to guarantee the CI opto-mechanics and electronics performance.

This paper will describe the concerns, parameters and restrictions in the design and construction of the instrument rotator used on the SDSS telescope. The rotator provides support for two 600 Lb. Spectrographs, through all axes motion, without causing harmful radial moments to be translated to its inner ring which supports the mosaic imaging camera. This is accomplished using an outer-inner ring design. The outer ring is a thin-walled box structure incorporating the drive surface and is attached to the inner ring through a steel membrane. This rotator design requires the telescope’s primary support structure to provide final structural integrity. Due to this feature, a special fixture was needed to transport the rotator from the vendor and to install it onto the telescope. Positional accuracy and feedback is provided by an optical tape and read-head system manufactured by Heidenhain and attached to the inner ring. The drive motor was designed to use the same motor as those employed for the other two telescope axes, thus minimizing the spare-parts inventory and maintenance. Its drive pinion is of a pinch design, with the pinion axis parallel to rotator radius. A great deal of attention and planning was required in the construction of the box frame outer ring and the induction heat-treating of the drive surface. Drive surface tolerances were maintained within +/-0.001 inches, and internal stress cracks from heat-treating were minimal.

This paper proposes an optical fiber positioning unit device for LAMOST(Large Area Multi-Object Fiber Spectroscope Telescope), It consists of a central shaft revolving mechanism, and eccentric shaft revolving mechanism relative to central shaft. The central shaft turns round at the range of -180° to +180° and the eccentric shaft turns round at the range of -90° to +90° driving by each control motor. When positioning, the optical fiber end moves on the focal plate throughout, and can never deviate from focal plane. It has simple structure, could be machined and assembled and taken down easily and could be ensured machining practices easily, so could be reduced manufacture costs. The unit sets mechanical electrical zero position detecting device to reduce the accumulate error of multi-positioning. Testing result have demonstrated this new double revolving optical fiber positioning unit device can accord with the demand of LAMOST entirely.

The observation region of fiber positioning unit of LAMSOT is designed as a round area and overlapped each other in order to eliminate the un-observation region and increase the efficiency of the observation. But in such structure, the fiber holders have probability to touch each other during moving to the target images. This paper introduces a method of an observation planning for LAMOST sub-system including 19 fiber positioning units which can diminish the probability of mechanical interference by proper assignment ways and the preparatory processing in which the interference would be detected and eliminated through the retreat algorithm, and the strategy of allocating images and the moving routes of all units are obtained. The computer simulation indicates that this method successfully avoids the mechanical collisions during observations of Sub-system, at the same time, the efficiency of the observation is hardly decreased. This method is definitely valuable to the parallel controllable optical fiber position system of LAMOST which has 4000 fiber positioning units.

SALT, although similar to the Hobby-Eberly Telescope (HET - the prototype for a fixed altitude optical analog of the Arecibo radio telescope), has some significant differences in the optical design. This paper gives an overall description of the SALT optics and a description of the analyses done in order to develop an optical error budget, which satisfies the overall requirements for total image quality. An optical prescription for SALT is presented, including an optical model of the telescope with a segmented primary mirror (PM) array. The design of the spherical aberration corrector (SAC) is summarised, with particular reference to the effects of non-axisymmetric distortion. The concepts for an atmospheric dispersion corrector (ADC), and guidance and focusing (GF) systems, are also discussed. Finally, the primary mirror alignment system (PMAS) concept is presented and the difficulty in controlling the Global Radius of Curvature (GRoC) discussed.

Ceramic mirrors and complex structures are becoming more important for high-precision lightweighted optomechanical applications. Carbon-fiber reinforced silicon carbon (C/SiC) is a composite ceramic material consisting of SiC as its major constituent. Developments over the past 10 years by IABM, ECM, and Astrium GhbH have demonstrated the feasibility and versitility of this ceramic material for different applications. Furthermore, Cesic-a trademark of ECM for C/SiC- allows relatively quick and cheap manufacturing of components because the components can be shaped with conventional tools in a milling and/or drilling process of the greenbody material. Through a joining process and our new development of optical surfaces based on a slurry cladding technology, Cesic allows for a direct up-scaling of structures and optical surfaces to large size applications and systems. The size of the structures and mirrors that can be manufactured is limited only by the scale of the available production facilities, the largest of which currently is 2.4 m in diameter.

The optical performance evaluations for various mirror shapes due to lateral temperature distributions were conducted using the finite element analysis program, SDRC-IDEAS. In this study, bimetallic effects with two different plating materials (nickel and aluminum) were considered for aluminum mirrors and beryllium mirror substrates. Lateral temperature distributions used in this thermal analysis, are cases of linear, quadratic and cubic variations. The optical surface deformations were reduced in terms of Zernike coefficients by the program PCFRINGE. Additionally, corrected surface deformations after piston, tilts, and focus removed were calculated. It was found that the optical performances of bimetallic mirrors strongly depend on the plating material, plating thickness, and the mirror substrate shapes. The results indicate that there does not exist a definitive common rule for the optimum. A detailed analysis as presented herein is generally required to adequately predict the bimetallic effects.

Because of the severe system requirements for the VLTI Auxiliary Telescopes (i.e. mass budget, mechanical stability, image quality and environment), the design and manufacturing of the Primary Mirror Unit required a big effort in FEM computations and a high technology manufacturing process for the primary mirror. Specific tools have been developed for the cell assembly and mirror integration. This paper describes the design and assembly techniques of the M1 unit. A review of the most important techniques used at AMOS for the manufacturing of the lightweighted primary mirror (1.87 m diameter, f#1.44) is described. Final test results of M1 unit are presented to demonstrate the compliance with the allocated sub-system requirements.

We describe the fabrication and testing of the 6.5 m f/1.25 primary mirrors for the Magellan telescopes and the 8.4 m f/1.14 primary mirrors for the Large Binocular Telescope (LBT). These mirrors, along with the 6.5 m MMT primary, are the fastest and most aspheric large mirrors made. Steward Observatory developed special methods to polish and measure these and other fast mirrors. We use a stressed-lap polishing tool to fit the aspheric surface while providing strong passive smoothing, and computer-generated holograms to verify the measurement of up to 1.4 mm peak-to-valley asphericity to an accuracy of 0.01%. The Magellan mirrors are diffraction-limited at visible wavelengths, with surface accuracies of about 20 nm rms on active supports. We are currently polishing the first LBT primary mirror and preparing to make the thin shells for the LBT adaptive secondary mirrors.

The Magellan active optics system has been operating continuously on the Baade 6.5-m since the start of science operations in February 2001. The active optical elements include the primary mirror, with 104 actuators, and the secondary mirror, with 5 positional degrees of freedom. Shack-Hartmann (SH) wavefront sensors are an integral part of the dual probe guiders. The probes function interchangeably, with either probe capable of guiding or wavefront sensing. In the course of most routine observing stars brighter than 17th magnitude are used to apply corrections once or twice per minute. The rms radius determined from roughly 250 SH spots typically ranges between 0.05" and 0.10". The spot pattern is analyzed in terms of a mixture of 3 Zernike polynomials (used to correct the secondary focus and decollimation) and 12 bending modes of the primary mirror (used to compensate for residual thermal and gravitational distortions). Zernike focus and the lowest order circularly symmetric bending mode, known affectionately as the "conemode," are sufficiently non-degenerate that they can be solved for and corrected separately.

The reflecting Schmidt plate M_A of LAMOST is with 5.7m × 4.4m reflecting area and consists of 24 segmented hexagonal sub-mirrors. Each sub-mirror is 25mm in thickness and 1.1m in diagonal. To correct the spherical aberration of the primary mirror, during observation, the aspherical shape of M_A should be changed in every 1.5 minutes. To achieve the good image during observation, the active support system of M_A will not only create the correct off-axis aspherical shape on each sub-mirror, but also maintain the co-focus for all 24 sub-mirrors. This paper presents the studying design with finite element analysis and experiments on the active support system of M_A, including its axial and lateral supports, force actuators, optimization of the stiffness of the force actuator, sub-mirror cell, the mirror support structure etc. There are 30 force actuators and three position actuators, which support each sub-mirror and connected by sub-mirror cell. Total 24 sub-mirror cells located on the top of the M_A main support structure. All force actuators work as both active and passive supports for each sub-mirror. It showed that the support system is complex but should work properly within the optical requirement.

After the installation of the four Unit Telescopes of the VLT in the years 1998 till 2000 more than 1.5 million active optics measurements and corrections have been performed. Since all active optics data are logged together with various environmental parameters (external seeing, temperatures, wind, etc.) extensive statistical studies of the dependence of the optical performance of the telescope on the external parameters can be made. Improvements of the functionality and the performance of the telescopes include the use of a Kalman filter in the Active Optics correction loop and the possibility to adjust actively the plate scale of the telescope.

he author proposes the use of a diffraction grating as a primary collector in a very large ground-based telescope. The grating is to be placed at grazing exodus relative to a secondary receiver and will have considerable length relative to width. Collector areas of square kilometers are being considered. Large collectors pose problems for ordinary telescopes, but with the proposed telescope, the rotation of the earth is the only requisite motion. Other than the earth itself, there are no moving parts. In the course of a night's observation, a plurality of stars within a narrow band of right ascension would yield detailed spectra. We anticipate that while acquiring the spectra of a star, the instrument would also acquire the spectra of any planetary system around it, because the high inherent resolving power of the instrument can measure subtle Doppler shifts, and the collecting area is sufficiently large to detect spectra from planets in the full glare of the star that illuminates them. Where signature spectra are available, planets can by typed, including earth-like planets which can be distinguished by their unique spectra and their implied surface temperature as inferred from orbit diameter. Our study investigates several grating arrangements, types and efficiencies including some using reflection gratings and one with a transmission grating in an evanescent mode. We explore options for grating fabrication and mounting

In LAMOST project, the reflecting Schmidt plate (M_A) and the spherical primary mirror (M_B) are constructed with segmented mirrors. M_A consists of 24 submirrors and M_B consists of 37 submirrors. Three position actuators are mounted on the back of each submirror to support the submirror and maintain the co-focus of the submirrors. The position actuators are the critical components in the system. They must make precise movements under large loads. A set of position actuators for one submirror and its electronics system in the lab will be presented in this paper. The character of one actuator and the networking of handling its position will be described in the paper in detail. Adopt the field bus technology to combine these position actuators into a distributed control system. This paper gives a function description of the distributed system and an implementation and the performance of the experimental subsystem.

LAMOST (The Large Sky Area Multi-object Fiber Spectroscopic Telescope) is a reflecting Schmidt telescope. There are two large segmented mirrors in LAMOST: One is the Schmidt plate M_A, and the other is the spherical primary mirror M_B. The dimension of M_B is about 6.7m×6m and it is face down in 25°. M_B is composed of 37 hexagonal sub-mirrors. During the observation, one should maintain the correct mirror figure for each sub-mirror and co-focus for all 37 sub-mirrors to obtain the good image, even it is an unconventional designed telescope without tracking movement on the primary mirror. This paper presents the design and the finite element analysis for the whole primary mirror support system, which includes the optimization of the mirror support points distribution, the design and the testing of the prototype of M_B sub-cell, the structure analysis and the design of the mirror support truss.

We report current status of active mirror support of Subaru telescope. Total wavefront error we provide for observation is 150-300 nm rms . Elevation dependency of the shape of the primary mirror and wind buffeting effect are shown. We also show a procedure for SH measurements at prime focus with half-cut (D-shape) pick-up mirror.

A system which estimates the global radius of curvature (GRoC) and corrects for changes in GRoC on a segmented primary mirror has been developed for and verified on McDonald Observatory's Hobby Eberly Telescope (HET). The GRoC estimation and control system utilizes HET's primary mirror control (PMC) system and the Segment Alignment Maintenance System (SAMS), an inductive edge sensor system. A special set of boundary conditions is applied to the derivation of the optimal edge-match control. The special boundary conditions allow the further derivation of an observer, which enables estimation and control of the GRoC mode to within HET's specification. The magnitude of the GRoC mode can then be controlled despite the inability of the SAMS edge sensor system, by itself, to observe or control the GRoC mode. The observer can be extended to any segmented mirror telescope. It will be shown that the observer improves with accuracy as the number of segments increases. This paper presents the mathematical theory of the observer. Performance verification data from the HET will be presented.

A sensing and control system for maintaining the optical alignment of the ninety-one 1-meter diameter hexagonal segments forming the Hobby-Eberly Telescope (HET) primary mirror array has been developed by NASA - Marshall Space Flight Center (Huntsville, AL) and Blue Line Engineering (Colorado Springs, CO) and implemented. This Segment Alignment Maintenance System (SAMS) employs 480 edge sensors to measure the relative shear motion between each segment edge pair and compute individual segment tip, tilt and piston position errors. Error information is sent to the HET primary mirror control system, which then corrects the physical position of each segment every 90 seconds. On-site installation of the SAMS sensors, ancillary electronics and software was completed in September 2001. Since that time, SAMS has undergone engineering testing. The system has operated almost nightly, improving HET's overall operational capability and image quality performance. SAMS has not yet, however, demonstrated performance at the specified levels for tip, tilt, piston and Global Radius of Curvature (GRoC) maintenance. Additional systems development and in situ calibration are expected to bring SAMS to completion and improved operation performance by the end of this year.

The Segment Alignment Maintenance System (SAMS) was installed on McDonald Observatory's Hobby-Eberly Telescope (HET) in August 2001. The SAMS became fully operational in October 2001. The SAMS uses a system of 480 inductive edge sensors to correct misalignments of the HET's 91 primary mirror segments when the segments are perturbed from their aligned reference positions. A special observer estimates and corrects for the global radius of curvature (GRoC) mode, a mode unobservable by the edge sensors. The SAMS edge sensor system and GRoC estimator are able to maintain HET's primary figure for longer durations than previously had been observed. This paper gives a functional description of the SAMS control system and presents performance verification data.

The Mirror Alignment Recovery System (MARS) is a Shack-Hartmann based sensor at the center of curvature (CoC) of the Hobby-Eberly Telescope (HET) spherical primary mirror used to align the 91 mirror segments. The instrument resides in a CoC tower next to the HET dome, a location which provides a challenging set of problems including wind shake and seeing from two different domes. The system utilizes an internal light source to illuminate the HET and a reference mirror to provide focused spot locations from a spherical surface. A custom lenslet array is sized to the HET pupil image, matching a single hexagonal lenslet to each mirror segment. Centroids of the HET mirror segment spots are compared to the reference spot locations to measure tip/tilt misalignments of each segment. A MARS proof-of-concept (POC) instrument, tested on the telescope in 2001, utilized a commercial wavefront sensor from Adaptive Optics Associates. The final system uses the same concept, but is customized for optimal performance on the HET. MARS replaces previous burst-antiburst alignment techniques and provides a more intuitive method of aligning the primary mirror for telescope operators. The POC instrument has improved median HET stack sizes by 0.3" EE50, measured at the CoC tower. The current alignment accuracy is 0.14" rms (0.28" rms on the sky), resolution is 0.014", measurement precision is 0.027" rms, and segment capture range is ± 5". With continuing improvements in HET dome ventilation and the addition of software customized for removal of tower motion during measurement, the alignment accuracy is expected to reach approximately 0.04" rms in the final MARS, to be installed in late 2002.

Discontinuities in the wavefront phase or amplitude affect curvature sensor (CS) response. These discontinuities may be the result of an improper alignment of the elements of a segmented mirror in either piston or tip-tilt. We describe the CS response with an analytical approach based on the Fresnel approximation of the diffracted field and show that a CS is capable of detecting misalignment among segments. The response model that we present leads to a fast algorithm for the measurement of segment positions. As an application, we focus on piston co-phasing. The paper concludes with the characterization of the integrated curvature signal, which simplifies the analysis of the CS response to misalignments. The low processing time and principal memory requirements of the algorithm make it suitable for extremely large telescopes (ELTs).

In this paper, we study the ability of a curvature sensor (CS) to measure co-phasing errors in a segmented primary mirror. We study a new fast and low memory-consuming algorithm based on the definition of an integrated curvature signal. This signal results from the integration of the CS response in enclosures matching the shapes of the segments in the mirror. This gives a low number of measurements, equal to the number of segments. The determination of the position of the segments is speeded with an analytical response model, which we formulate in matrix form. In this way, we can make an analysis of the error propagation that is valid for measurement errors or imprecision of the response model. The procedure is well suited to mirrors with a large number of segments, as in the case of ELTs.

Under a contract with the GRANTECAN, the Commissioning Instrument is a project developed by a team of Mexican scientists and engineers from the Instrumentation Department of the Astronomy Institute at the UNAM and the CIDESI Engineering Center. This paper will discuss in some detail the final Commissioning Instrument (CI) mechanical design and fabrication. We will also explain the error budget and the barrels design as well as their thermal compensation. The optical design and the control system are discussed in other papers. The CI will just act as a diagnostic tool for image quality verification during the GTC Commissioning Phase. This phase is a quality control process for achieving, verifying, and documenting the performance of each GTC sub-systems. This is a very important step for the telescope life. It will begin on starting day and will last for a year. The CI project started in December 2000. The critical design phase was reviewed in July 2001. The CI manufacturing is currently in progress and most parts are finished. We are now approaching the factory acceptance stage.

We propose a method for piston errors detection in a segmented surface by means of the classical ronchi test. This consists in comparing the ronchigram fringes frequency of a reference and piston segment. The comparison is developed for the correlation method of the intensity vs pixels curves of the reference and piston segment. The presence of the piston term in a ronchigram is assured experimentally for the shack interferometer, it is by observing the coincidence rings centered type fizeau in each segment. The proposed method is applied to a segmented spherical surface with a two segment mirrors, and resolutions of piston ⩾63 ηm are experimentally obtained.

The Center of Curvature Alignment Sensor (CCAS) was the original instrument installed in the center of curvature (CoC) tower on the Hobby-Eberly Telescope (HET) for aligning the 91 primary mirror segments. The CCAS is a polarization shearing interferometer with HeNe and diode laser sources that illuminate the HET primary mirror with polarized coherent light. Returns from each mirror segment focus back at the CoC and can be viewed on a faceplate at the front of the instrument for coarse alignment of the primary mirror, or sent into the interferometer for fine alignment. Inside the interferometer, Wollaston prisms separate the HET primary mirror image into two polarization components which are spatially shifted by the distance of one mirror segment. This overlaps images of segments with their neighbors to generate interference fringes. The beam is then split into 4 legs, each of which introduces phase shifts to the polarization. Fringe patterns shifted by 0, 90, 180, and 270 degrees are recorded on each leg by a CCD camera. The intensity in each pixel is measured and used in the standard 4-bucket algorithm to calculate the relative phase shift between the two mirror segments, and thus their tip/tilt misalignment. Segment piston is determined from the location of the peak in the fringe contrast function, using all four camera images and light at four laser diode wavelengths. Although the CCAS has recently been replaced with a Shack-Hartmann sensor for mirror alignment on the HET, its operation and performance are described. Under less environmentally challenging conditions, such as laboratory or space-based applications, this instrument could be used for aligning segmented mirrors to high precision.

We present techniques for Fourier analysis of the diffraction-limited optical performance of large-aperture astronomical telescopes. We use combinations of Fast Fourier Transform, Discrete Fourier Transform, and Fourier interpolation algorithms as well as the symmetry properties of the segmented mirrors to achieve full calculation of the diffraction pattern in a computationally-efficient manner. We discuss the implementation and results of these techniques in the context of a 15-meter segmented-mirror telescope design for the Large Atacama Telescope.

The next generation of optical/IR telescopes will require large numbers of co-phased segmented mirrors. Therefore, some form of replication technology is desirable to reduce costs. Electroforming has the advantage that it is a commercially developed technology for replication, and the technology has been widely used for making X-ray mirrors (e.g. XMM-Newton). Composite materials are appealing, since a great deal of development work as been done with composites as well. There are 3 areas that need to be addressed: replication with minimal stress so as to produce a high quality figure; attachment of support of the mirror segment so as to maintain the figure quality; and, thermal control requirements. Here we present a discussion of the requirements that lead us to select replication as the fabrication technology and the advantages of replication. We report on our first results of making a concave mirror and testing support methods of flats.

Methods to limit image degradation due to temperature variations in telescopes include reducing the coefficient of thermal expansion (CTE) of the optical elements. In segmented mirror telescopes, not only does the average CTE have to be as close as possible to zero, but, more importantly, a high level of homogeneity is essential to avoid temperature related changes to mirror figure. The Southern African Large Telescope (SALT) has selected Sitall optical glass-ceramic from the Russian company LZOS for the manufacturing of its 91 primary mirror segments. A detailed specification, including strict requirements for CTE, was developed from basic principles. LZOS, together with the Mendeleev Metrological Institute in St. Petersburg, have developed CTE measuring equipment (dilatometers) to demonstrate that individual segments meet specification. A theoretical analysis of the allowable measurement uncertainty was conducted which accounted for the inaccuracy of the dilatometers, resulting from uncertainties due to sample length, fringe fraction reading and laser wavelength instability. Developments include operating in a dynamical temperature mode to reduce testing time and utilizing computer controlled units to read and process interferograms. Fizeau and heterodyne interferometric methods were implemented in separate dilatometers. CTE measurements of the first batch of SALT segments demonstrate that the material complies with the SALT specification. These results are presented in this paper.

SCHOTT Glas manufactured more than 200 ZERODUR segments for various Telescopes: 84 pcs. 1.900 mm diameter × 76 mm menisci for Keck I and Keck II, 96 pcs. 1.180 mm hexagonal × 56 mm blanks for HET, 42 pcs. 1.870 mm hexagonal × 83 mm blanks for GTC, and produces at present, 40 pcs. 1.100 mm hexagonal × 82 mm blanks for LAMOST. During the production period for the GTC mirror blanks SCHOTT developed improved casting techniques to generate castings with hexagonal shape to realize near net shape processing. This reduces the necessary machining time in a very cost effective manner. Additionally slicing the castings into single blanks reduces the subsequent ceramising time and cost. Results of the important quality characteristics like CTE, CTE homogeneity, internal stress and geometrical dimensions of the GTC blanks will be presented. Finally the upscaling of the present advanced production technique to the needs of the Extremely Large Telescopes will be discussed.

The goal of the Extra Large Telescope Actuator (ELTA) development project was to demonstrate operation of a relatively high stiffness, single stage optical positioning actuator capable of achieving diffraction-limited performance (<10 nm) in the visible optical band for weeks at a time while consuming no electrical power and dissipating no heat. The design challenge was to develop a linear positioning mechanism exhibiting high stiffness, low power, zero backlash, and thermal stability over extended time periods. The key to achieving high resolution, and stability with low power is to eliminate the closed-loop control system that is normally employed to overcome the nonlinearities and hysteresis inherent in some technologies, such as piezoelectric and magnetostrictive transducers. This was accomplished by using the patented elastic transducer developed by Alson E. Hatheway (AEH Inc.) This device consists of two elastic elements; a soft spring and a stiff flexural member. Deflection of the soft spring applies a force input to the stiff flexure, which responds with a proportionally reduced output deflection. To maintain linearity, the displacements, and hence the stresses, developed in both elastic members are kept below the micro-yield strength of the material. The AEH transducer is inherently linear and hysteresis free. The unique design features of this actuator which contribute to its extremely precise motion capability include an electric motor driving a leadscrew through a zero backlash harmonic drive gear reduction. The already fine incremental motion of the leadscrew nut is further attenuated by the elastic action of the AEH transducer, to provide output motion with resolution <10 nm.

Subaru telescope has been commissioned in December, 1998 and received its first light in January, 1999. After that, we concentrated on restoring the initial mechanical misalignments and the bug fixing in control system software. Along with these efforts in the telescope, eight instruments including AO have been commissioned one by one over the next two years. In the end, Open-use of Subaru telescope to the community has started partially in December, 2000 and in a full scale in April, 2002. Here, we report our experience in commissioning and adjusting the telescope mechanics and the control system and also make comments on some important issues. We demonstrate how the telescope was tuned by showing the telescope time allocation table. The detailed report on telescope performance will be discussed in the following talk. We briefly discuss the effect of our unique shape of enclosure to the image size by showing seeing statistics. The detailed discussion is presented elsewhere in this conference. The current status of the eight instruments is also summarized to show our capability in scientific activity. We finally review the current operational system and discuss some future attempts for more efficient operation.

Subaru Telescope has currently achieved the following performances. 1. Image Quality. (1) Subaru Telescope delivers a median image size, evaluated by equipped Auto Guider (AG) cameras, of 0.6-0.7 arcsec FWHM in the R and I-band at all the four foci: Prime (P), Cassegrain (Cs), and tow Nasmyth (Ns). (2) The best image sizes obtained so far are 0.2 arcsecs FWHM without AO in near-infrared (IR), less than 0.1 arcsec FWHM with AO, and 0.3 arcsec FWHM in optical and mid-IR wavelengths. (3) Stable Shack-Hartmann measurement enables one to keep the errors of Zernike coefficients to less than 0.2μm which corresponds to ~0.1 arcsec image size. 2. Tracking and Pointing. (1) Blind pointing accuracy is better than 1 arcsec RMS over most of the sky. (2) Tracking accuracy is better than 0.2 arcsec RMS in 10 minutes. (3) Guiding accuracy is between 0.8 and 0.18 arcsec RMS with 12-18th magnitude guide stars. 3. IR secondary mirror (M2). (1) Chopping performances: typical figures are at 3 Hz, 80% duty cycle with 30-60 arcsec chopping throw. (2) Tip-Tilt performances: Position stability is about 0.030 arcsec RMS for the effective closed-loop bandwidth less than 5 Hz. 4. Others. (1) The reflectivity of the primary mirror has been maintained at higher than 85 and 95% at 670 and 1300 nm wavelengths by regular cleaning with CO₂ ice every two to three weeks. (2) The reflectivity of the blue-side image rotator (ImR) at Nasmyth-optical focus was improved after re-coating of mirrors.

The VLT is a complete new observatory situated at cerro Paranal in the north Atacama desert of Chile. The four 8.2-m telescopes of the VLT are in continuous science operations and are operating with very high efficiency. The operational scenario allows users the options for service or visitor mode observing providing great flexibility to the European astronomical community to fully exploit the telescopes. The interferometric mode of the VLT is already producing scientific results and has demonstrated excellent stability and operability.

Telescopes are built to do astronomy. Often this point is taken to extremes by astronomers demanding access to facilities before they are ready to receive them and often engineers dwell on aspects of a system that have little impact on the final performance of the machine. The right balance may never be found. Doing science early may scoop the competition but doing science more often may be the best long term investment. A systematic approach to commissioning has been adopted at ESO within the VLT project with the end operability and maintainability being a major driver of the activities. In this paper are presented the historical, strategic and problematic aspects of the commissioning of the VLT.

We developed two DIMMs (Differential Image Motion Monitor) for simultaneous seeing measurements at multiple sites. Simultaneous seeing measurements enable us to distinguish temporal variation and site to site variation of seeing, and clarify which site has better seeing. We set the aperture separation of the DIMM at 50 cm for accurate measurements under good (~0.3 arcsec) seeing conditions for Mauna Kea. Our system can also be tuned for moderate to bad seeing conditions by changing the effective focal length of the optics. The frame of our DIMM device is made of CFRP in order to avoid deformation with temperature change and to reduce its weight. We will present the details of our DIMM system and some results of simultaneous seeing measurements at Mauna Kea, Hawaii.

We report an infrared all sky cloud monitor operating at Subaru telescope at Mauna Kea, Hawaii. It consists of panoramic optics and a 10 μm infrared imager. Aspheric metal mirrors coated with gold (sapphire over-coated) are used in the panoramic optics, which is similar to the MAGNUM observatory's cloud monitor at Haleakala, Maui. The imager is a commercially available non-cooled bolometer array. The system is waterproof and (almost) maintenance-free. The video signals from the imager are captured, averaged over 50 frames, subtracted clear-sky frame and flat-fielded in two minutes interval. The processed cloud images are transferred to Subaru observational software system (SOSS) and displayed combined with telescope/targets information and also stored to Subaru Telescope data archive system (STARS). The processed images will be opened on Internet web site.

We conducted the aluminization campaign of the primary mirror of the Subaru Telescope in September 2001. This was the third time with the Subaru's coating facility. The witness samples coated at the same time show reflectance above 91% at 500 nm, the highest of the three coating campaigns. We continue to pursue the film which has high reflectance, high adhesion nature to the glass substratum, and durability with little degradation in time. As part of the effort, we started to compare various evaluation methods of the coating films. The emphasis is on the physical property side, using XPS (X-ray Photoelectron Spectroscopy), SIMS (Secondary Ion Mass Spectrometry), and SEM (Scanning Electron Microscope). We hope to use the findings to improve our coating processes for the Subaru's mirrors and other mirrors. First thing we confirmed is that three oxidization layers exist in the aluminum coatings itself and between the aluminum and the glass substratum. This is caused by the three stage firing in the Subaru's 9 m chamber. The extent of such layers seems to contribute to the adhesion of the film to the glass. Next, we compared the film produced by the conventional evaporation (using 1.6 m chamber at Mitaka, Tokyo) and by the sputtering (using the Tohoku University equipment). The contamination and defects in the film seem to be responsible for the exfoliation, and the reflectance. We will use these physical property evaluations also to optimize the coating process of other coating materials that is suited for the infrared observations.

We would like to present the procedure of how to prepare the primary mirror of Subaru Telescope for the realuminization. The equipment for the coating and its preparation are located at the ground floor of the telescope enclosure. There are two trolleys for carrying the mirror cell and the mirror itself, a mirror lifting jig, a washing facility for the primary mirror (PMWF), the water purification system, the coating chamber and the waste water pit. The PMWF can provide the tap water for initial rinsing, the chemical for stripping the old coating, and the deionized water for final cleaning. It has two pairs of arms that deploy horizontally above the mirror and have nozzles to spray. The arms spin around its center where the rotary joints are connected to the plumbing from storage tanks. Deck above the water arms serve as platform for personnel for the inspection or for scrubbing work. We use hydrochloric acid mixture to remove the old aluminum coating. For rinsing and final cleaning, we use the water through the purification system. The water supply from the nozzles and the rotation of the arms can be controlled from a panel separated from the washing machine itself. After several experiments and improvements in the washing, we have carried out the coating of the 8.3 m primary mirror in September last year. This was the third time, and the reflectivity of the new coating show satisfactory result.

The Starfire Optical Range (SOR) 3.5 Meter primary mirror was installed in 1993 and saw first light in February of 1994. The mirror is a monolithic faceplate backed by a honeycomb structure and coated with bare aluminum oxide. Since the mirror's installation, SOR technicians have adhered to a strict cleaning and care regimen that has proven to be very effective in preserving the optical quality of the coating. This presentation describes the care procedures used by the SOR and presents reflectivity/scatter measurements taken over the life of the coating.

As a further step to improve the excellent tracking performance of the VLT telescopes, the intrinsic errors in the telescope drive systems are analysed. These errors fall into two categories, torque disturbances and sensor errors and they have different impact on the performance. Models for the errors are developed and algorithms for on line adaptive parameter identification are presented. The models can be used to significantly reduce the influence of the errors and also to monitor parameters like friction and unbalance. The VLT servo model is used to test and verify the models and algorithms. It follows a description of the real-time software aspects of the algorithms, which have been implemented for VxWorks-based systems. The software design allows various options for the adaptation of the process coefficients, either running permanently in background, only on demand through maintenance procedures, or fixed off-line modeling based on recorded process data. Finally, real test data are presented.

Commissioning of the two 6.5-meter Magellan telescopes is nearing completion at the Las Campanas Observatory in Chile. The Magellan 1 primary mirror was successfully aluminized at Las Campanas in August 2000. Science operations at Magellan 1 began in February 2001. The second Nasmyth focus on Magellan 1 went into operation in September 2001. Science operations on Magellan 2 are scheduled to begin shortly. The ability to deliver high-quality images is maintained at all times by the simultaneous operation of the primary mirror support system, the primary mirror thermal control system, and a real-time active optics system, based on a Shack-Hartmann image analyzer. Residual aberrations in the delivered image (including focus) are typically 0.10-0.15” fwhm, and real images as good as 0.25” fwhm have been obtained at optical wavelengths. The mount points reliably to 2” rms over the entire sky, using a pointing model which is stable from year to year. The tracking error under typical wind conditions is better than 0.03” rms, although some degradation is observed under high wind conditions when the dome is pointed in an unfavorable direction. Instruments used at Magellan 1 during the first year of operation include two spectrographs previously used at other telescopes (B&C, LDSS-2), a mid-infrared imager (MIRAC) and an optical imager (MAGIC, the first Magellan-specific facility instrument). Two facility spectrographs are scheduled to be installed shortly: IMACS, a wide-field spectrograph, and MIKE, a double echelle spectrograph.

The Hobby-Eberly Telescope (HET) is a fixed-elevation, 9.2-m telescope with a spherical primary mirror and a tracker at prime focus to follow astronomical objects. The telescope was constructed for $13.9M over the period 1994-1997. A number of telescope performance deficiencies were identified and corrected following construction. Remaining problems included: 1) Dome seeing, 2) inadequate initial mirror segment alignment accuracy, and 3) mirror segment misalignment with time. The HET Completion Project was created in May 2001 to attack these problems and to identify and solve the next tier of problems. To address dome seeing, large louvers were installed and in operation by May 2002. Efforts are also underway to eliminate or suppress heat sources within the dome environment. To address segment alignment accuracy, a prototype Shack-Hartmann device, the Mirror Alignment Recovery System (MARS), was built and is in routine use at HET. The Segment Alignment Maintenance System (SAMS) is in early operation and has markedly improved telescope performance. Two Differential Image Motion Monitor (DIMM) telescopes were brought into regular operation in July 2001 to quantify atmospheric seeing at HET. As these improvements have been implemented, telescope image quality has improved significantly. Plans are in place to address additional performance issues.

The 3.5-m telescope at the Starfire Optical Range (SOR), operated by the Directed Energy Directorate of the Air Force Research Laboratory, Kirtland AFB, NM saw first light in February, 1994 and first operation of the adaptive optics in September, 1997. The primary mirror built by Steward Observatory Mirror Lab is spun cast borosilicate, actively supported and temperature conditioned. The telescope mount was designed to smoothly track low-earth-orbiting (LEO) satellites and therefore has different features than most telescopes designed for astronomy. The protective enclosure retracts vertically, leaving the telescope completely exposed, enabling access to rapidly moving targets. The telescope feeds a coude laboratory containing steering mirrors, deformable mirror, sensors for wave front control and target tracking, high resolution cameras, and lasers for beacons and energy projection experiments. This paper summarizes recent operating experiences and provides lessons learned in terms of thermal conditioning, mount control, mirror control, mirror cleaning, optical alignment, and satellite tracking. The operation and performance of the tracking and higher-order wave front compensation to LEO satellites will be presented. Plans for future upgrades will be described.

The National Radio Astronomy Observatory Green Bank Telescope (GBT), the world's largest fully steerable telescope, is now undergoing commissioning and early scientific operation. The GBT has many innovative design features that advance imaging quality, sensitivity, and versatility. These include an unblocked aperture, an active surface, and a six-degree of freedom Gregorian subreflector. The GBT has an advanced laser rangefinder metrology system, which will measure the position of the active surface panels, and also guide the precision pointing of the telescope. Early commissioning results have confirmed the performance of the telescope, and exciting scientific discoveries are already being made. This paper describes the various features of the telescope in more detail, and presents the latest results.

We present the outline and the current status of the MAGNUM automated observation system. The operational objective of the MAGNUM Project is to carry out long-term multi-color monitoring observations of active galactic nuclei in the visible and near-infrared wavelength regions. In order to obtain these observations, we built a new 2 m optical-infrared telescope, and sited it at the University of Hawaii's Haleakala Observatory on the Hawaiian Island of Maui. Preliminary observations were started early in 2001. We are working toward the final form of the MAGNUM observation system, which is an unmanned, automated observatory. This system requirement was set by considering that the observation procedures are relatively simple, and the targets must be observed consistently over many years.

The four 8m VLT telescopes on Paranal are now in full science operation, and they all deliver good results with very small technical downtimes. Of course, many factors are contributing to these results, and also the telescope control software has its share. It has demonstrated to be robust and reliable and also flexible and expandable. In the four years since First Light of the first VLT telescope, this software has been continuously maintained and developed, for improvements on the 8m telescopes but also for use on other telescopes. In addition to the 8m ones, another three telescopes, using applicable parts of the same software, are in operation on Paranal: the 350- mm seeing monitor and two 400-mm siderostats. And the process continues: in the beginning of 2003 the first of three 1.8m Auxiliary Telescopes for the VLT Interferometer will be installed; the control software to 80% being the same as for the 8m telescopes, but with additional devices and control functionality. Another three ESO telescopes on La Silla are also using the same software, as well as two wide field telescopes for Paranal that are now in the design and manufacturing phase. In this development process, and in particular after first installation, we have learned lessons in many areas of software project work. System design and engineering, standardization, tools, testing: these are example areas where there is always room for improvement. Another lesson learned is the importance of the concept of Commissioning, i.e. the work to take the telescope from "integrated" to "working"! What the future of telescope control software will be, that we don't know, but we are working on it! And we try to keep an evolutionary approach, taking advantage of the lessons learned.