This PDF file contains the front matter associated with SPIE Proceedings Volume 7012, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

The GTC (Gran Telescopio Canarias) is an optical/IR telescope, with a 10,4 meter segmented primary, installed at the Observatorio del Roque de Los Muchachos (ORM), at La Palma. Past July 2007 it saw its First Light showing a very promising behaviour. The very good image quality achieved at that an early stage of telescope commissioning is a direct consequence of the quality of its optics, the high performances of its primary mirror control system, and the highly engineered telescope structure and servo system. At present, we are advancing with the telescope commissioning whose first results are presented here. The two Day One science instruments: OSIRIS and CanariCam are being prepared for installation and commissioning on the telescope. Science verification are planned to be initiated by the end of 2008 and regular operation by March 2009.

The Large Binocular Telescope (LBT) Observatory is a collaboration between institutions in Arizona, Germany, Italy, Indiana, Minnesota, Ohio and Virginia. The telescope on Mt. Graham in Southeastern Arizona uses two 8.4-meter diameter primary mirrors mounted side-by-side to produce a collecting area equivalent to an 11.8-meter circular aperture. A unique feature of LBT is that the light from the two primary mirrors can be combined to produce phased array imaging of an extended field. This coherent imaging along with adaptive optics gives the telescope the diffraction-limited resolution of a 22.65-meter telescope. We will describe the scientific results and technical challenges of monocular prime focus imaging starting in Fall 2006. Binocular imaging with two co-pointed prime focus cameras began in Fall 2007. Installation of a rigid (non-adaptive) secondary mirror occurred in Spring 2008 in time for the arrival of the first Gregorian spectrometer. The telescope will use two F/15 adaptive secondaries to correct atmospheric turbulence. The first of these adaptive mirrors is now being tested in Italy, and is planned to be at the telescope by Summer 2009.

Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is an innovative telescope project with both large aperture (effective in 4 meters) and wide field of view (5 degrees) to achieve the large scale spectroscopic survey observation. It is a horizontal meridian reflecting Schmidt configuration realized by an active deformable Schmidt plate. For achieving such an ambitious project with limited budget, both its primary mirror (6.67m × 6.05m) and Schmidt plate (5.74m × 4.4m) are segmented. LAMOST project is expected to be completed before the end of 2008. The assembly and test of whole telescope and 16 spectrographs with 4000 optical fibers in its focal plane is going to be finished in August of 2008. With just its partial aperture, more than 200 optical fibers and one spectrograph, the scientific commissioning has been done and some preliminary results have been obtained. This paper introduces the progress of LAMOST project during 2007 and 2008, and presents the achievement in its technology which is also useful for the future extremely large telescopes.

The Large Synoptic Survey Telescope Project is a public-private partnership that has successfully completed the Concept Design of its wide-field ground based survey system and started several long-lead construction activities using private funding. The telescope has a 3-mirror wide field optical system with an 8.4 meter primary, 3.4 meter secondary, and 5 meter tertiary mirror. The reflective optics feed three refractive elements and a 64 cm 3.2 gigapixel camera. The telescope will be located on the summit of Cerro Pachón in Chile. The LSST data management system will reduce, transport, alert, archive the roughly 15 terabytes of data produced nightly, and will serve the raw and catalog data accumulating at an average of 7 petabytes per year to the community without any proprietary period. This survey will yield contiguous overlapping imaging of 20,000 square degrees of sky in 6 optical filter bands covering wavelengths from 320 to 1080nm. The project continues to attract institutional partners and has acquired non-federal funding sufficient to construct the primary mirror, already in progress at the University of Arizona, and fund detector prototype efforts, two of the longest lead items in the LSST. The project has submitted a proposal for construction to the National Science Foundation Major Research Equipment and Facilities Construction (MREFC) program and is preparing for a 2011 funding authorization.

Using the array of seven 0.6m antennas in Hawaii, we have conducted short observations on several galaxy clusters through the Sunyaev-Zeldovich effect at 3mm wavelength in 2007. The observations were done with a resolution of 6', and we have chosen the low redshift (z=0.09-0.32) massive clusters to optimize detection. Major contamination to the data comes from instrumental offset and ground pickup. We will demonstrate the results based on a simple on source - off source switching observing scheme. In addition, the performance of a wideband analog 4-lag correlator was also investigated.

ASTE is a 10-m submillimeter telescope operating in Atacama desert in northern Chile since 2002 by NAOJ and collaborators. Thanks to the excellent observing condition at the telescope site, ASTE has been producing numerous astronomical results from star forming regions, Galactic center, Magellanic clouds, nearby galaxies, and galaxy clusters. There has been three major improvements during the years 2007-2008: continuum camera "AzTEC", new SIS receiver "CATS345", and a wide-band spectrometer "WHSF". AzTEC is a 144 element bolometer array at 270 GHz, developed by University of Massachusetts and collaborators. The mapping speed reaches 10-30 arcmin²/hr/mJy². CATS345 is a side-band separation (2SB) SIS receiver developed by University of Tokyo and NAOJ. The IF bandwidth is 4 GHz with side-band rejection ratio better than 10 dB. We have achieved the typical system noise temperature of 200-400 K (SSB) within 330-360 GHz, the best value being 150 K (SSB) at the frequency of ¹²CO(J=3-2) at 345 GHz under a typical weather condition. The new spectrometer WHSF employs of an FX type auto-correlator, ultra-high speed sampler, and digital signal transmitter. It can be operated in two modes; 4096 MHz band-width × 2 IFs or 2048 MHz band-width × 4 IFs, both with 4096 channels in spectral resolution.

As the Large Millimeter Telescope (LMT) has continued to progress towards scientific operations, some preliminary commissioning of the telescope control system has taken place. We present the architecture of the LMT control system along with initial commissioning results of the LMT servo and drive system. The LMT azimuth drive system is a wheel-on-track mechanism with sixteen individually driven wheels on a circular track. The elevation drive system consists of two main gear arcs, each driven by two pinions. All twenty of the drives (sixteen in azimuth and four in elevation) consist of a motor and a gearbox. These drives are controlled by a fully digital servo system that is divided into a drive control unit which consists of the servo amplifiers and an embedded PLC that implements torque sharing and safety interlocks, and an antenna control unit that implements the servo control loops and astronomical tracking. The results of the initial commissioning of the LMT servo and drive system include full range motion in azimuth and elevation, azimuth track welding effects, elevation gear rims alignment effects, elevation balance, friction contribution to servo errors, and initial tracking accuracy.

AMOS SA has been awarded of the contract for the design, manufacturing, assembly, tests and on site installation (Nainital, Devasthal site at 2540 mm altitude) of the 3,6 m Optical Telescope for ARIES (Aryabhatta Research Institute of Observational Sciences), Nainital (India). This paper describes the opto-mechanical design of this telescope and presents the solutions adopted by AMOS to meet the specific requirements. The telescope has a Ritchey-Chrétien optical configuration with a Cassegrain focus equipped with one axial port and two side ports. The primary mirror is a meniscus active mirror.

The Hobby-Eberly Telescope (HET) is an innovative large telescope of 9.2 meter aperture, located in West Texas at the McDonald Observatory. The HET operates with a fixed segmented primary and has a tracker which moves the fourmirror corrector and prime focus instrument package to track the sidereal and non-sidereal motions of objects. A major upgrade of the HET is in progress that will substantially increase the field of view by replacing the corrector, tracker and prime focus instrument package. In addition to supporting the existing suite of instruments, this wide field upgrade will feed a revolutionary new integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). This paper discusses the current status of this upgrade.

Las Cumbres Observatory Global Telescope (LCOGT) is redefining the function of robotic telescopes by deploying 0.4 meter telescopes that act as a highly networked intelligent instrument. The 0.4 meter telescopes, (P4) are optimized for quick and accurate object acquisition and tracking. This minimizes response time and enables the leveraging of the instrument. A single P4 can independently execute multiple science programs concurrently or team up with other P4s for deeper or multi-color observations of a single target. The intelligent control software will optimize the observation schedule for each individual telescope and the entire network. LCOGT is deploying 6 networked clusters consisting of four P4s around the world, providing capacity and versatility beyond the classical observatory. Each P4 has zero slippage, no backlash friction systems, and is currently achieving 20 deg/s slewing. Blind pointing is currently 8 arcsec RMS. Using the AG acquisition routine, the drive will have repeatable pointing to within 0.6 arcsec within 12 seconds from anywhere on the sky. Other features include wind buffet correction, rapid thermalization, dual autoguiders, novel scanning flat fielding device, large 20 kg instrument capacity, high speed instrument changer, and a stiff split ring mount.

The eSMA ("expanded SMA") combines the SMA, JCMT and CSO into a single facility, providing enhanced sensitivity and spatial resolution owing to the increased collecting area at the longest baselines. Until ALMA early science observing (2011), the eSMA will be the facility capable of the highest angular resolution observations at 345 GHz. The gain in sensitivity and resolution will bring new insights in a variety of fields, such as protoplanetary/ transition disks, high-mass star formation, solar system bodies, nearby and high-z galaxies. Therefore the eSMA is an important facility to prepare the grounds for ALMA and train scientists in the techniques. Over the last two years, and especially since November 2006, there has been substantial progress toward making the eSMA into a working interferometer. In particular, (i) new 345-GHz receivers, that match the capabilities of the SMA system, were installed at the JCMT and CSO; (ii) numerous tests have been performed for receiver, correlator and baseline calibrations in order to determine and take into account the effects arising from the differences between the three types of antennas; (iii) First fringes at 345 GHz were obtained on August 30 2007, and the array has entered the science-verification stage. We report on the characteristics of the eSMA and its measured performance at 230 GHz and that expected at 345 GHz. We also present the results of the commissioning and some initial science-verification observations, including the first absorption measurement of the C/CO ratio in a galaxy at z=0.89, located along the line of sight to the lensed quasar PKS 1830-211, and on the imaging of the vibrationally excited HCN line towards IRC+10216.

As one of the preliminary research projects of Chinese ELT, 30m RIT--Ring Interferometric Telescope are being simulated and tentatively designed by Yunnan Astronomical Observatory, CAS. The simulations of 30m RIT are mainly included as follows: PSF transform and the image quality at limited photons mode, active control mode of the primary ring mirror, the phasing mode of 30m segmented ring mirror, the turbulent atmosphere and adaptive optics etc. This paper also introduces some tentative design results of 30m RIT, such as the optical design, the conceptual design of the enclosure. The astronomical experiments at seeing limited case and diffraction limited case are introduced in this paper too. A ring aperture mask was put on the entrance pupil of a one meter telescope, real astronomical objects were observed by this "ring telescope" and reconstructed by high resolution imaging techniques such as speckle masking, iterative shift and add methods. The diffraction imaging ability and the full u-v coverage property of a ring aperture were proved by these astronomical experiments.

We present the status of the Sardinia Radio Telescope (SRT) project, a new general purpose, fully steerable 64 m diameter parabolic radiotelescope capable to operate with high efficiency in the 0.3-116 GHz frequency range. The instrument is the result of a scientific and technical collaboration among three Structures of the Italian National Institute for Astrophysics (INAF): the Institute of Radio Astronomy of Bologna, the Cagliari Astronomy Observatory (in Sardinia,) and the Arcetri Astrophysical Observatory in Florence. Funding agencies are the Italian Ministry of Education and Scientific Research, the Sardinia Regional Government, and the Italian Space Agency (ASI,) that has recently rejoined the project. The telescope site is about 35 km North of Cagliari. The radio telescope has a shaped Gregorian optical configuration with a 7.9 m diameter secondary mirror and supplementary Beam-WaveGuide (BWG) mirrors. With four possible focal positions (primary, Gregorian, and two BWGs), SRT will be able to allocate up to 20 remotely controllable receivers. One of the most advanced technical features of the SRT is the active surface: the primary mirror will be composed by 1008 panels supported by electromechanical actuators digitally controlled to compensate for gravitational deformations. With the completion of the foundation on spring 2006 the SRT project entered its final construction phase. This paper reports on the latest advances on the SRT project.

The Infrared Imaging System (IRIS) is a 0.8 m telescope equipped with a 1024×1024 pixels near-infrared camera using a HAWAII-1 detector array. IRIS will be located at the Cerro Armazones Observatory in Chile that is operated by the Ruhr University Bochum jointly with the Universidad Catolica del Norte in Antofagasta. The system is specifically designed to survey star forming regions and to search for deeply embedded variable young stars.

Vibration is becoming a more important element in design of telescope structures as these structures become larger and more compliant and include higher bandwidth actuation systems. This paper describes vibration damping methods available for current and future implementation and compares their effectiveness for a model of the Large Synoptic Survey Telescope (LSST), a structure that is actually stiffer than most large telescopes. Although facility and mount design, structural stiffening and occasionally vibration isolation have been adequate in telescopes built to date, vibration damping offers a mass-efficient means of reducing vibration response, whether the vibration results from external wind disturbances, telescope slewing, or other internal disturbances from translating or rotating components. The paper presents several damping techniques including constrained layer viscoelastics, viscous and magnetorheological (MR) fluid devices, passive and active piezoelectric dampers, tuned mass dampers (vibration absorbers) and active resonant dampers. Basic architectures and practical implementation considerations are discussed and expected performance is assessed using a finite element model of the LSST. With a goal of reducing settling time during the telescope's surveys, and considering practicalities of integration with the telescope structure, two damping methods were identified as most appropriate: passive tuned mass dampers and active electromagnetic resonant dampers.

The four-meter Advanced Technology Solar Telescope (ATST) will be the most powerful solar telescope and the world's leading resource for studying solar magnetism that controls the solar wind, flares, coronal mass ejections and variability in the Sun's output. Development of a four-meter solar telescope presents many technical challenges (e.g., thermal control of the enclosure, telescope structure and optics). We give a status report of the ATST project (e.g., system design reviews, PDR, Haleakalä site environmental impact statement progress) and summarize the design of the major subsystems, including the telescope mount assembly, enclosure, mirror assemblies, wavefront correction, and instrumentation.

The European Solar Telescope (EST) is a project for a large aperture (3-5 meters) ground-based telescope, to be located in the Canary Islands. EST will be optimized for studies of magnetic coupling between the deep photosphere and upper chromosphere. This will require diagnostics of the thermal, dynamic and magnetic properties of the plasma over many scale heights, by using multiple wavelength imaging, spectroscopy and spectropolarimetry. The design of EST will strongly emphasize the use of a large number of visible and near-infrared instruments simultaneously. To achieve these goals, EST will specialize in high spatial and temporal resolution using instruments that can efficiently produce twodimensional spectral information. In this communication, the present situation of the design is outlined, as well as the expected future phases and scheduling.

The solar telescope GREGOR is under construction on the canary island Tenerife. A large effort was made to thermally characterize the telescope during the design phase. The image quality is very sensitive to differences between ambient and structure or main mirror temperatures. Tests with the GREGOR telescope structure and an integrated dummy mirror were made to investigate the distribution and temporal behavior of the temperature of the telescope and main mirror.

The solar submillimeter-wave telescope (SST) is the only one of its kind dedicated to solar continuous observations. Two radiometers at 0.740 mm (405 GHz), and four at 1.415 mm (212 GHz) are placed in the Cassegrain focal plane of the 1.5-m dish at El Leoncito high altitude site, San Juan, Argentina. The aperture efficiencies are close to design predictions: 20% and 35% for 2 and 4 arcminutes beam sizes at 405 and 212 GHz, respectively. The positioner absolute pointing accuracy is 10 arcseconds. Spectral coverage is complemented by ground-based mid-infrared telescopes developed for high cadence observations in the continuum 10 micron band (30 THz), using small apertures and room-temperature microbolometer cameras. Using the system, a new solar burst spectral component was discovered, exhibiting fluxes increasing for smaller wavelengths, separated from the well known microwave component. Rapid sub-second pulsations are common for all bursts. The pulsations onset times of appear to be connected to the launch times of CMEs. Active regions are brighter for shorter submillimeter-waves. Mid-IR bright regions are found closely associated with calcium plages and magnetic structures near the solar photosphere. Intense and rapid 10 micron brightening was detected on active centers in association with weak flares. These results raise challenging difficulties for interpretation.

It was in the years around 1970 that during site-test campaigns for JOSO masts were erected up till 30 m height with sensors at several heights for the measurement of temperature fluctuations. Cornelis (Kees) Zwaan discovered that the fluctuations decrease drastically at heights from about 15 m and upward when there is some wind. The conclusion from this experience was the open telescope principle: the telescope should be completely free in the air 15 m or more above the ground. The Dutch Open Telescope (DOT) was the pioneering demonstrator of the open-telescope technology. Now that larger high-resolution telescopes come in view, it is time to analyze again the principle: (i) the essentials for proper working of the open principle; (ii) the differences with nighttime observations particularly concerning the seeing; (iii) the design consequences for the new generation of high-resolution solar telescopes.

The Atacama Large Millimeter/submillimeter Array (ALMA) is an international radio telescope under construction in the Atacama Desert of northern Chile. ALMA will be situated on a high-altitude site at 5000 m elevation, allowing excellent atmospheric transmission over the instrument wavelength range of 0.3 to 3 mm. ALMA will contain an array of up to sixty-four 12-m diameter high-precision antennas arranged in multiple configurations ranging in size from 150 meters up to ~15 km, and a set of four 12-m and twelve 7-m antennas operating in closely packed configurations ~50m in diameter. The instrument will provide both interferometric and total-power astronomical information on high-energy electrons, molecular gas and dust in solar system, our Galaxy, and the nearby and high-redshift universe. In this paper we outline the scientific drivers, technical challenges and construction status of ALMA.

The Atacama Compact Array (ACA) is an array composed of twelve 7-m dishes and four 12-m dishes. The ACA is designed for use as a part of the ALMA (Atacama Large Millimeter / Submillimeter Array) to provide high fidelity imaging capability for large extended objects. Basic parameters of the array configuration of the ACA were selected based on the analysis of the sensitivity in uv plane for mosaicing observations with the ACA and the ALMA. For detailed design of the sub-array with 7-m dishes (7-m Array), we adopted the compact spiral concept, which realizes higher uv response at the short uv spacings and better sidelobe performance. To satisfy the sky coverage requirement, the north-south elongation is needed. The 7-m Array was designed to have two configurations, one (Inner Array) is a compact spiral array with small north-south elongation (× 1.1) and the other (NS Array) is a dedicated configuration with large north-south elongation (× 1.7). In actual design, inner 6 antenna pads are shared by both configurations because of construction constraints.

The development process of the ALMA project from its first prototype phase to the present one of serial production, has stimulated the development of concepts of innovative engineering and manufacturing design. The technologies adopted such as the large use of composite materials, motorizations without contact (Direct Drive) etc., have allowed to obtain extreme performances with reference to the scientific/environmental context. ALMA technologies represent a new gateway for the astrophysical applications of the future.

The first European ALMA production antenna is in the final stage of manufacturing and pre-assembly. Precommissioning of parts of this antenna will start soon. The series production is partly ongoing or in the final stage of preparation. Design features of the European ALMA antennas w.r.t. to manufacturing, assembly and integration in Europe and on site, the status of the manufacturing works and pre-commissioning are presented. An outlook to the next steps of the realization of the antennas is given.

In the ALMA project, in order to achieve the specification, very important is the use of a metrology instrument able to correct the non repeatable errors. Errors induced by wind or temperature variations inside the structure that are non systematic have to be predicted and corrected by an active system. During design phase, CFD and thermal analyses have been performed in order to identify the whole behaviour of the structure and the relative corrections formulas. Innovative instruments and layout have been studied from the prototype to the production phase.

This paper, presented on behalf of the Large Millimeter Telescope (LMT) project team, describes the status and near-term plans for the telescope and its initial instrumentation. The LMT is a bi-national collaboration between Mexico and the USA, led by the Instituto Nacional de Astrofísica, Optica y Electronica (INAOE) and the University of Massachusetts at Amherst, to construct, commission and operate a 50m-diameter millimeter-wave radio telescope. Construction activities are nearly complete at the 4600m LMT site on the summit of Sierra Negra, an extinct volcano in the Mexican state of Puebla. Full movement of the telescope, under computer control in both azimuth and elevation, has been achieved. First-light at centimeter wavelengths on astronomical sources was obtained in November 2006. Installation of precision surface segments for millimeter-wave operation is underway, with the inner 32m-diameter of the surface now complete and ready to be used to obtain first light at millimeter wavelengths in 2008. Installation of the remainder of the reflector will continue during the next year and be completed in 2009 for final commissioning of the antenna. The full LMT antenna, outfitted with its initial complement of scientific instruments, will be a world-leading scientific research facility for millimeter-wave astronomy.

This paper devotes to the working space analysis of the main positioning system of FAST cabin suspension, a flexible-cable-driven parallel manipulator. The problem formulation is deduced through equilibrium analysis of the cabin platform and suspension cables, which changes subsequently into a nonlinear constrained optimization intending a uniform allocation of the six cable tension force. The analysis verifies the accessibility of focus cabin to the whole focus surface. The optimization investigates the orientation of the focus cabin under equilibrium and the optimal cable forces, as well as elaborates their importance in the finite element modeling of the cable-cabin system and the respective layout designs of the rotator, Stewart stabilizer and capstan motors. In the end, the influences of the tower height and the position of mass center of the focus cabin on the optimization results are discussed.

China has embarked on a project to build the world's largest radio telescope, the Five hundred meter Aperture Spherical Telescope (FAST), in a karst depression in southwest Guizhou Province. The telescope is of a modified Arecibo type. We suggest an active main reflector that is spherical in the neutral state but the illuminated aperture of 300m in diameter would be adjusted into a proper paraboloid such that a simple feed could be used at its focus, since the "spherical correction" has be done on the ground. The feed cabin at the focus is supported and driven directly by cables controlled by computer, which avoids a heavy and expensive feed supporting system. Newly developed method and technology for determining the spatial position of 2400 nodes on the main reflector of the FAST are introduced in this paper. Base on the measurements of the position of node under which the down cable are linked, a loop feedback control enables accurately driving the spherical reflector deformed to paraboloid. The key technique of this implementation is the precise measurement of 2400 nodes. In this article, we introduce the scheme of simplified photogrammetry aiming at no lateral shift situation; we analyse the influence of lateral shift; and considering lateral shift, we propose a scheme using rotation platform plus double-eye camera to accomplish the dynamic measurement of the reflector. The result of analysis and testing shows the feasibility and effectivity of the scheme of measurement.

Reflector surface deformation due to wind loading on the Nobeyama 45-m antenna has been measured with four LED lamps on the surface at r = 20 m and two CCD cameras on the central hub as it rotates in azimuth with elevation angles of 90 and 11 degrees. The side-wind loading of 8.4 m s^-1 caused a tilt of 12 arcseconds and an astigmatic deformation of 0.8 mm. The front- and back-wind loading of 9.9 m s^-1 induced a vertical displacement variation of 2.3 mm. These largescale surface deformation profiles have been compared with those of finite element calculations and coefficients of axial force and yaw moment predicted by a JPL wind tunnel data excerpt.

A wind pressures PSD measured on the Gemini South Telescope was applied to the FEA model of the LSST telescope to determine the RMS motions of the principal optical systems. These motions were then converted to the time domain. The time domain motions were analyzed in the ZEMAX® software to determine the wind induced image degradation. This degradation was shown to be tolerable.

The Wind Evaluation Breadboard (WEB) for the European Extremely Large Telescope (ELT) is a primary mirror and telescope simulator formed by seven segments simulators, including position sensors, electromechanical support systems and support structures. The purpose of the WEB is to evaluate the performance of the control of wind buffeting disturbance on ELT segmented mirrors using an electro-mechanical set-up which simulates the real operational constrains applied to large segmented mirrors. The instrument has been designed and developed by IAC, ALTRAN, JUPASA and ESO, with FOGALE responsible of the Edge Sensors, and TNO of the Position Actuators. This paper describes the mechanical design and analysis, the control architecture, the dynamic model generated based on the Finite Element Model and the close loop performance achieved in simulations. A comparison in control performance between segments modal control and actuators local control is also presented.

The primary, secondary and tertiary mirrors of the Thirty Meter Telescope (TMT), taken together, have approximately 12,000 degrees of freedom in optical alignment. The Alignment and Phasing System (APS) will use starlight and a variety of Shack-Hartmann based measurement techniques to position the segment pistons, tips, and tilts, segment figures, secondary rigid body motion, secondary figure and the tertiary figure to correctly align the TMT. We present a conceptual design of the APS including the requirements, alignment modes, predicted performance, software architecture, and an optical design.

The purpose of the Active Phasing Experiment, designed under the lead of ESO, is to study new phasing technologies and to validate wavefront control concepts for Extremely Large Telescopes. The Active Phasing Experiment is currently tested in the laboratory at the ESO headquarters and will be tested on sky at a Nasmyth focus of a VLT unit telescope at the end of 2008. The test bench contains four different phasing sensors which are tested in parallel to compare them under the same conditions. They have been developed by Istituto Nazionale di Astrofisica in Florenze, Instituto Astrofisica Canarias in Tenerife, Laboratoire d'Astrophysique de Marseille and ESO. It includes also an Active Segmented Mirror which simulates the segmentation of a primary mirror. A non-contact optical metrology has been developed by Fogale Nanotech to control it. The VLT focus and the VLT atmospheric conditions are simulated in the laboratory with a turbulence generator producing a seeing between 0.45 and 0.85 arcsec. Once installed on a VLT unit telescope, the control system of the Active Phasing Experiment will be able to control the phasing of the ASM, but also the guiding and the active optics of the VLT. This proceeding gives a brief summary of the opto-mechanical aspects of the Active Phasing experiment, describes its control system and gives an analysis of the preliminary results obtained in the laboratory.

The out-of-plane degrees of freedom (piston, tip, and tilt) of each of the 492 segments in the Thirty Meter Telescope primary mirror will be actively controlled using three actuators per segment and two edge sensors along each intersegment gap. We address two important topics for this system: edge sensor design, and the correction of fabrication and installation errors. The primary mirror segments are passively constrained in the three lateral degrees of freedom. We evaluate the segment lateral motions due to the changing gravity vector and temperature, using site temperature and wind data, thermal modeling, and finite-element analysis. Sensor fabrication and installation errors combined with these lateral motions will induce errors in the sensor readings. We evaluate these errors for a capacitive sensor design as a function of dihedral angle sensitivity. We also describe operational scenarios for using the Alignment and Phasing System to correct the sensor readings for errors associated with fabrication and installation.

To meet the 10 µm RMS half wavefront error requirement for the 25 m diameter Cornell Caltech Atacama Telescope (CCAT), active control of the approximately 200 primary mirror panels is required. The CCAT baseline design includes carbon fiber aluminum honeycomb sandwich mirror panels. Distortions of the panels due to thermal gradients, gravity and the mounting scheme need to be taken into consideration in the control system design. We have modeled the primary mirror surface as both flat and curved surfaces and have investigated mirror controllability with a variety of sensor types and positions. To study different mirror segmentation schemes and find acceptable sensor configurations, we have created a software package that supports multiple segment shapes and reconfigurable panel sizing and orientation. It includes extensible sensor types and flexible positioning. Inclusion of panel and truss deformations allows modeling the effects of thermal and gravity distortions on mirror controllability. Flat mirrors and curved mirrors with the correct prescription give similar results for controlled modes, but show significant differences in the unsensed flat mirror modes. Both flat and curved mirror models show that sensing schemes that work well with rigid, thermally stable panels will not control a mirror with deformable panels. Sensors external to the mirror surface such as absolute distance measurement systems or Shack-Hartmann type sensors are required to deal with panel deformations. Using a combination of segment based sensors and external sensors we have created a promising prototype control system for the CCAT telescope.

This paper presents a non-contact optical metrology measuring the pistons and tip/tilt angles of the 61 hexagonal segments of a compact-sized segmented mirror. The instrument has been developed within the scope of a design study for a European Extremely Large Telescope (E-ELT). It is used as reference sensor for cophasing of the mirror segments in closed loop control. The mirror shape is also measured by different types of stellar light-based phasing cameras whose performances will be evaluated with regard to a future E-ELT. Following a description of the system architecture, the second part of the paper presents experimental results demonstrating the level of precision: 0.48nm RMS in piston and 0.074 μrad RMS in tip and tilt.

Large segmented mirrors require efficient co-phasing techniques in order to avoid the image degradation due to segments misalignment. DIPSI (Diffraction Image Phase Sensing Instrument) is an instrument developed by IAC, GRANTECAN and LAM. This instrument is being integrated in the Active Phasing Experiment (APE), aimed at testing different phasing techniques for an Extremely Large Telescope. This paper describes the mathematical solution for determining piston and tip-tilt simultaneously from the DIPSI images. A complete set of simulations is included to study the residual errors. Residual errors are bigger when piston and tip-tilt are combined (three degrees of freedom).

One of the major issues in new Extremely Large Telescopes is the phasing of their primary segmented mirror. A cophasing sensor is mandatory to achieve the ultimate resolution of the telescope. Phase diversity (PD) is a light-hardware cophasing technique. In this paper, we show that this technique is suited to segmented pupil instruments, such as the E-ELT.

We present an analytical description of the diffraction halo created by optical aberrations randomly distributed over hexagonal segments of a segmented mirror. We do not restrict ourselves to the piston and tip-tilt errors only, but show that the halo from any type of the aberration can be described in a general form. We also study the ability of the high order adaptive optics to correct for this type of aberrations. These effects are especially critical for application of the high contrast imaging with extremely large segmented telescopes.

The shape correction of the mirrors is a crucial operation to obtain diffraction limited images in actively controlled telescopes. If the mirror is not monolithic, the segmentation errors introduced by piston, tip and tilt of the segments are superimposed on the continuous aberrations. In the case of a sensor based on the measurement of the wave front slopes, like the Shack-Hartmann wave front sensor, an algorithm which allows separating the different contributions is necessary for a proper correction. In the framework of the Active Phasing Experiment (APE) carried out at ESO, we have developed a simple algorithm which can be applied to compute the aberrations and the tip-tilt coefficients using the information obtained with a Shack-Hartmann sensor. It is based on the construction of an orthogonal base in the space of the wave front slope functions. The description of the algorithm and its performance in the cases of low-order aberrations superimposed on tip-tilt misalignment of the segments are reported. A particular application of this technique in the case of the European Extremely Large Telescope (E-ELT) is discussed and the expected upper limits for the residual errors after correction are estimated.

The largest telescopes (ELT) involve a highly segmented primary mirror. The monitoring of the mirror shape use thousands of sensors, located on segment edges, which measure the relative piston, tip and tilt of all segments. Today, telescopes with segmented primary mirrors use capacitance-based edge sensors. Although this technology offers excellent metrological performances, its practical use is limited by the intrinsic sensitivity to humidity, dust and condensation, whose effect exceeds the requirements for future ELTs. Being specialized in both capacitive and inductive metrology, Fogale nanotech has developed a novel concept of edge sensors using the inductive technology, which does not suffer from humidity, condensation, and dust effects. Cost effective sensor with specific layout, associated electronics, demonstrated metrological performance (sub-nanometer resolution and nanometer stability) that outperforms the capacitive concept.

In the framework of the Active Phasing Experiment (APE), four different phasing techniques are tested. The ZErnike Unit for Segment phasing sensor (ZEUS) is integrated on the APE bench. APE has been tested in the laboratory before it will be installed on one of the Nasmyth platform of a Very Large Telescope (VLT) Unit Telescope to perform on sky tests. The ZEUS phasing sensor concept has its origins in the Mach-Zehnder interferometer equipped with a spatial filter in its focal plane. In this paper, the ZEUS phasing sensor is described together with its theoretical background and deployment within the APE experiment. The algorithms and its elements used to reconstruct the wavefront are described. Finally, the preliminary results obtained in the laboratory are presented.

The EELT is a project led by ESO on behalf of its 14 member states. The project is in Phase B (detailed design), a 3-year, 57.2 M activity that will result in a Proposal for Construction by June 2010. The requirements for the basic reference design, starting point for the current phase, were defined through a community process that led to the convergence of earlier concepts into a single European project: a 42m adaptive telescope based on a novel 5-mirror design that is scheduled to have first light in 2017. This paper reports on the status of the Phase B activities, on the basic reference design development, and on the progress of the science case and Design Reference Mission.

The Thirty Meter Telescope (TMT) Project will design and build a thirty-meter diameter telescope for research in astronomy at optical and infrared wavelengths. TMT is a partnership between the University of California, Caltech, and the Association of Canadian Universities for Research in Astronomy (ACURA). The $80 million TMT design and development phase is fully funded and Preliminary Design is in progress. An additional $300 million has been pledged towards early TMT construction which will commence in 2009. We include a high level description of the design of the telescope and its planned adaptive optics and science instrumentation. The schedule of key milestones for completing the design and construction is summarized.

The Giant Magellan Telescope (GMT) is being developed by a consortium of major US and international educational and research institutions. The 25 meter next-generation telescope will be located at Las Campanas Observatory in Chile. The project has completed the conceptual design of the telescope and enclosure and is currently in the Design Development Phase leading up to construction. Various refinements have been made to the telescope structure since the Conceptual Design. These include the modification of the upper truss structure to reduce image blur due to wind shake and the design of a 9 meter rotator for large Gregorian instruments. An integral field spectrograph has been added to the candidate list of first-generation instruments. The primary mirror for GMT consists of seven 8.4 meter diameter segments. The first of the six, highly aspheric, off-axis segments has been cast and generated at the University of Arizona SOML with completion of the mirror expected in 2009. The metrology for polishing the segments is currently being installed in the new test tower at SOML. Verification tests that independently measure the mirror figure have been designed and are also being implemented. This paper summarizes the overall design and recent progress in the technical development of GMT and in characterizing the site.

The baseline design for the enclosure of the E-ELT is based on a spherical dome concept. This dome is tightly fitted to the TRV so that its surface, the enclosed volume and consequently the system overall cost are minimized. The large slit that is required for observation-as compared to the enclosure volume-, much larger than in smaller telescopes, poses a big challenge to the design. This affects the slit covering system design, for which dynamic issues must be carefully considered in order to prevent operation problems, as well as the dome structure and other mechanisms such as the windscreen and the crane, that have to cover a large 45m span. This paper presents a design that solves all these difficulties in both a cost-effective and reliable way. The design work presented in this paper has been performed under contract with the European Southern Observatory.

The design of the calotte enclosure for the Thirty-Meter Telescope is currently in the preliminary design phase. Key aspects of the design include an efficient structural/mechanical form, repetition of components, modular construction, and operational efficiency. This paper includes an overall description of the enclosure design, as well as a description of the major structural and mechanical subsystems. The enclosure incorporates features that influence the thermal and aerodynamic environment of the telescope including ventilation openings and wind deflecting features. Other key considerations of the preliminary design include the constructability and maintainability of a dynamic structure of this scale at a remote mountain site.

FAST is an Arecibo-type antenna with 3 outstanding aspects: the unique karst depression as the site; the active main reflector which corrects spherical aberration on the ground to achieve full polarization and wide band without involving complex feed system; and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. These design features will enable FAST to jumpstart many of science goals, such as HI neutral hydrogen line survey, pulsar survey, largest station in VLBI network, spectral line observations and Search for alien's technologies. The feasibility studies for FAST have been carried out for 14 years, being supported by Chinese and world astronomical communities. Funding for Project FAST has been approved by the National Development and Reform commission NDRC in July of 2007 with a capital budget ~ 600 millions RMB and a project time of 5.5 years from the foundation.

The European Extremely Large Telescope (E-ELT) is a 42-m class optical telescope with a segmented primary mirror composed of 984 segments which is currently being studied by ESO (European Southern Observatory). The segment support system combines a series of mechanical whiffletrees for the axial support, a central diaphragm for lateral support and a torsional constrainer. These elements are fixed to a common moving frame which is actively moved by means of three actuators in piston and tip-tilt in order to keep the whole primary mirror in phase. The moving frame is fixed to the segments subcells, which properly attach the segments to the cell structure, by means of special flexures, allowing large axial alignment capability combined with high lateral stiffness. This paper describes the development of the support system for the primary mirror segments of the E-ELT, which has been specified for a high stiffness and eigenfrequencies, 60Hz for axial modes and 40Hz for lateral ones.

A study is presented of the impact on science data from extremely large telescopes of a transformation of wavelength base for optimization of actuator architecture from 2 200 to 1 250 nm. From the optical path difference (OPD) data for Euro50, we transform to E-ELT OPDs. We compute the corresponding power spectrum, in which we simulate a higher actuator density via high-pass filtering to convert from K to J band actuator-pitch optimization. From the modified power spectrum we derive the correspondingly modified OPDs, PSFs and Strehl ratios. A massive improvement is demonstrated resulting from converting from AO@K to AO@J. This result is followed up by model-based E-ELT imaging in a field in a galactic disc at a distance of 4 Mpc. The improvements in image quality, background and limiting magnitude are very large as are the increases in photometric precision derived from the field imaging. Further, the great science benefit and large opportunities provided by partial AO is demonstrated. In conclusion, while admittedly challenging, pushing AO optimization to wavelengths as short as possible is of prime concern for the science output of ELTs.

Five partners have currently joined a Consortium to develop the Cornell Caltech Atacama Telescope (CCAT.) Included are Cornell University, the California Institute of Technology (Caltech), the University of Colorado at Boulder, the United Kingdom as represented by the Astronomy Technology Centre (ATC), and Canada as represented by the Universities of British Columbia and Waterloo. This consortium has continued work toward the design of the telescope and instrumentation, pursued fund raising, and further developed the science case for CCAT. An Engineering Design Phase is being planned for 2009-2011 with construction planned to begin shortly thereafter. CCAT continues as a wide field (20 arc min) FOV telescope operating from a shortest wavelength of 200µ. Testing has continued near the summit of Cerro Chajnantor in the Atacama Region of Chile above 5600 meters altitude and data indicates significantly lower water vapor in the seeing column than measured at the ALMA site on the plateau below. Work over the past two years has included research on manufacturing methods for optical segments, extensive study of mirror alignment sensing and control techniques, additional concepts for major structures, and further development of instrumentation.

The SKA will have a collecting area of up to one million square metres spread over at least 3000 km, providing a sensitivity 50 times higher than the Expanded Very Large Array, and an instantaneous field of view (FoV) of at least several tens of square degrees and possibly 250 square degrees. The SKA science impact will be widely felt in astroparticle physics and cosmology, fundamental physics, galactic and extragalactic astronomy, solar system science and astrobiology. In this paper, we describe the main features of the SKA, paying attention to the design activities around the world, and outline plans for the final design and phased implementation of the telescope.

Status of the Feasibility Study of E-ELT, the ESO 42m Extreme Large Telescope, with emphasis on the Telescope architecture, manufacturing and erection. The new generation of Extremely Large Telescope, requires the identification of different technologies, in order to improve the stiffness to weight ratio of the structure, to introduce higher damping while maintaining under control the construction and maintenance costs. The identification of different construction technologies and the consequent development of the materials used, may allow to obtain a leading technological instrument able to meet also the most extreme scientific request, able to adapt to the new requests that might be raised along the life of the telescope. The control of the weight of the structure is extremely important for the dimensioning of the auxiliary structures, for energy management, and for the problems related to pre-assembly, disassembly in factory and erection on site.

The PS1 is a wide-field survey telescope which is a prototype for the Pan-STARRS project. It has a 7 square degree field of view, a 1.85-m primary mirror, a 0.9-m secondary mirror, 6 interference filters with 0.48-m diameters, and three corrector lenses with diameters between 0.6 and 0.4-m. The PS1 camera (GPC1) has 0.26" square pixels in a format that includes 1.44 Giga-pixels. The PS1 camera is located on the summit of Haleakala on the island of Maui which has a median seeing of 0.8-0.9". The PS1 telescope has been under commissioning since September 2007. This article describes the mounting and the supports of the PS1 optics as well as the efforts that have been made towards achieving site-limited image quality in the alignment of the telescope optics. We also show here some of the early imaging from this telescope as a function of time during commissioning.

It is now well-known that measurement of field-aberration, and in particular the asymmetric field-astigmatism, is required to break the degeneracy of tip-induced and de-centre-induced aberration that exists when only on-axis misalignment aberrations are considered. This paper discusses the application of the measurement of field-aberrations to the alignment of LBT optics. This application ranges from the use of wide field out-of-focus images to determine corrector tip for the red and blue prime-focus correctors, to the use of data acquired by off-axis Shack-Hartman wavefront sensors to actively reposition the hexapod-mounted primary and secondary mirrors so as to simultaneously remove both de-centre and tip/tilt such that the only remaining field-astigmatism has rotational symmetry about the centre of the detector. Also introduced is a novel method to calculate the misalignment aberrations based on an extension of the plate-diagram analysis. It is shown that this method is readily applicable to the calculation of misalignment aberrations for systems of three-or-more powered mirrors, with almost no more computational difficulty than that of the two-mirror case. Results are discussed, as well as work in progress in this area.

The Large Binocular Telescope (LBT) on Mt. Graham in Southeastern Arizona uses two 8.4-meter diameter primary mirrors mounted side-by-side to produce a collecting area equivalent to an 11.8-meter circular aperture. We describe our use of active optics with the honeycomb primary mirrors to provide focussing, collimation and low-order active wavefront correction for the two prime focus cameras now operating on the telescope. We use a custom IDL program, LBCFPIA, to geometrically analyze extrafocal pupils in order to determine focus and wavefront corrections through third-order spherical aberration. We also describe that section of the telescope control system which manages primary mirror collimation and accepts wavefront correction requests from the instrument. We present active optics results obtained during commissioning of the prime focus cameras and during science observations.

The primary mirror control system (M1CS) stabilizes the 492 segments of the Thirty Meter Telescope primary mirror in the presence of disturbances. Each Primary Segment Assembly (PSA) has three actuators and position sensors that control the piston, tip, and tilt of the mirror segment. Requirements for the PSA position controller are presented, with the main requirements being 10 Newton per micron stiffness below one Hertz, where wind is the primary disturbance. Bandwidths of the PSA position controller of about twenty Hertz, assuming a soft actuator, are needed to meet this requirement. A finite element model of the PSA was developed and used for a preliminary control design. PSA structural modes at 40, 90, and 120 impact the control design. We have studied control designs with different actuators, sensors, and structural filters in order to assess disturbance rejection properties and interactions with the PSA structural modes. The performance requirements are achieved using voice coil actuators with modal control architecture for piston, tip, and tilt. Force interactions with the underlying mirror cell are important, and we present the status of our studies of the control structure interaction effect (CSIE). A related paper presents further analysis of the CSIE and MICS global position control loop.

During the past year the control of the 42m segmented primary mirror of the E-ELT has been studied. This paper presents the progress in the areas of M1 figure control and control hardware implementation. The critical issue of coupling through the supporting structure has been considered in the controller design. Different control strategies have been investigated and from a tradeoff analysis modal control is proposed as a solution addressing the topics of wind rejection as well as sensor noise in the presence of cross-coupling through the supporting structure. Various implementations of the M1 Control System have been studied and a centralized architecture has been selected as baseline. This approach offers maximum flexibility for further iterations. The controller design and main parts of the control system are described.

The TMT mount control system provides telescope pointing and tracking. Requirements include wind disturbance rejection, offsetting time and accuracy, control system robustness, and the magnitude of response at structural resonances. A finite element model of the complete telescope has been developed and the transfer functions used for the control designs are presented. Wind disturbance, encoder, and wave-front-sensor models are presented that are used for the control design. A performance analysis translates the requirements to a required bandwidth. Achieving this bandwidth is important for reducing telescope image motion due to wind-buffeting. A mount control design is presented that meets the demanding requirements by maximizing low frequency gain and using structural filters to roll-off structural modes. The control system analysis includes an outer guide loop using a wave front sensor. Offsetting time and accuracy requirements are satisfied using feed-forward control architecture.

he VLT observatory operated by ESO is located on Cerro Paranal in Chile and consists of four identical 8-m telescopes and four 1.8-m VLTI Auxiliary telescopes (ATs). In order to further improve the tracking axes performance of telescopes regarding wind rejection, different control techniques have been evaluated. Ongoing investigation and studies show that by measuring the acceleration and using that in appropriate control strategy the performance of telescope tracking in face of external perturbation can be improved. The acceleration signal contains the non filtered information (advanced phase compared to velocity and position) of the perturbation load, e.g. wind load. As a result the reaction of the control is faster and hence the perturbation rejection is more efficient. In this paper, two acceleration feedback techniques are discussed and the results of the measurement test on an AT telescope are presented.

The joint U.S. and German Stratospheric Observatory for Infrared Astronomy (SOFIA) Project will operate a 2.5-meter infrared airborne telescope in a Boeing 747SP. Flying in the stratosphere at altitudes as high as 45,000 feet, SOFIA enables observations in the infrared and submillimeter region with an average transmission of 80%. SOFIA has a wide instrument complement including broadband imaging cameras, moderate resolution spectrographs capable of resolving broad features due to dust and large molecules, and high resolution spectrometers suitable for kinematic studies of molecular and atomic gas lines at km/s resolution. The first generation and future instruments will enable SOFIA to make unique contributions to a broad array of science topics. SOFIA began its post-modification test flight series on April 26, 2007 in Waco, Texas and will conclude in winter of 2008-09. SOFIA will be staged out of Dryden's aircraft operations facility at Palmdale, Site 9, CA for science operations. The SOFIA Science Center will be at NASA Ames Research Center, Moffet Field, CA. First science flights will begin in 2009, the next instrument call and first General Observer science call will be in 2010, and a full operations schedule of ~120 flights per year will be reached by 2014. The observatory is expected to operate for more than 20 years. The sensitivity, characteristics, science instrument complement, future instrument opportunities, and examples of first light and early mission science are discussed.

A terrestrial stratospheric telescope is ideally suited for making infrared observations of Venus' night hemisphere during inferior conjunctions. The near-space environment at 35 km altitude has low daytime sky backgrounds and lack of atmospheric turbulence, both of which are necessary for observing Venus' night side at the diffraction limit when Venus is close to the Sun. In addition, the duration of the observing campaign will be around 3 weeks, a time period that is achievable by current long duration flights. The most important advantage, however, will be the ability of a balloonborne telescope to clearly image Venus' night side continuously throughout a 12-hr period (more for certain launch site latitudes), a capability that cannot be matched from the ground or from the Venus Express spacecraft currently in orbit around Venus. Future missions, such as the Japanese Venus Climate Orbiter will also not be able to achieve this level of synoptic coverage. This capability will provide a detailed, continuous look at evolving cloud distributions in Venus' middle and lower cloud decks through atmospheric windows at 1.74 and 2.3 μm, which in turn will provide observational constraints on models of Venus' circulation. The science requirements propagate to several aspects of the telescope: a 1.4-m aperture to provide a diffraction limit of 0.3" at 1.74 μm (to improve upon non-AO ground-based resolution by a factor of 2); a plate scale of 0.1" per pixel, which in turn requires an f/15 telescope for 13 μm pixels; pointing and stability at the 0.05" level; stray light baffling; a field of view of 2 arc minutes; ability to acquire images at 1.26, 1.74 and 2.3 μm; and ability to operate aloft for three weeks at a time. The specific implementations of these requirements are outlined in this paper. Briefly, a 1.4-m Gregorian telescope is proposed, with stray light baffling at the intermediate focus. A three-stage pointing system is described, consisting of a coarse azimuthal rotator, a moderate pointing system based on a star tracker and ALT/AZ gimbals, and a fine pointing system based on analog photodiodes and a fine steering mirror. The science detectors are not discussed here, except to specify the requirement for moderate resolution (R > 1000) spectroscopy.

The site selection for the future European Large Telescope (E-ELT) is a key issue within the European proposal funded by the EC, within the "ELT Design Study" proposal. The organization, working scheme and baseline frameworks are reviewed. For the definition of the working package WP12000 "Site Characterization" important use has been done of previous works in the definition of techniques and tools for the study of the atmosphere above observing sites. We have also taken advantage of the number of data already available which have naturally defined a ranking among the known places which have also been taken as a base line for pre-selecting the candidate sites. The work will last 4 years, started in 2005 and is organized in subtasks whose main objectives are the following: WP12100: To characterize two top astronomical sites (ORM and North-Paranal) and to explore 3 other alternatives (Macon in Argentina, Izana in Spain and Aklim in Morocco) suitable to install an ELT under the best conditions (Dome C is been currently under investigation, and no particular effort will be put in this site, but rather its atmospheric properties will be compared to the above mentioned sites). WP12200 is dedicated to design, build and operate a standard equipment in all the sites and to perform long term campaign. WP12300 will investigate wavefront properties over large baselines (50-100 m) corresponding to the size of the future ELT, as well as the fine characterization of the optical turbulence within the boundary layer.

Las Campanas Observatory has been designated as the location for the Giant Magellan Telescope (GMT). We report results obtained since the commencement, in 2005, of a systematic site testing campaign at LCO. Meteorological (cloud cover, temperature, pressure, wind, and humidity) and DIMM seeing data have been obtained at three potential sites, and are compared with identical data taken at the site of the twin Magellan 6.5m telescopes. In addition, measurements of the turbulence profile of the free-atmosphere above LCO have been collected with a MASS/DIMM. We examine the contribution to the seeing arising from turbulence in the ground layer (defined here as below an altitude of 500 m) through the difference between the turbulence integrals in the full atmosphere (as measured by DIMM) and in the free atmosphere (as measured by MASS). Additionally, we consider photometric quality, light pollution, and precipitable water vapor at LCO.

Coastal mountains at Canada's northern tip possess many of the desirable properties that make the Antarctic glacial plateau attractive for astronomy: they are cold, high, dry, and in continuous darkness for several months in winter. Satellite images suggest that they should also benefit from clear skies for a fraction of time comparable to the best mid-latitude sites, and conventional site-selection criteria point to good seeing. In order to confirm these conditions, we are testing three mountain sites on northwestern Ellesmere Island, in Nunavut. On each we have installed a compact, autonomous site-testing station consisting of a meteorological station, a simple optical/near-infrared camera for sensing cloud cover, and - at one site - a more advanced all-sky viewing camera. The systems were deployed by helicopter and run on batteries recharged by wind (a compact methanol fuel cell is under study as a supplementary power source). Effective two-way communications via the Iridium satellite network allows a limited number of highly compressed images to be transferred. The full-winter dataset is stored at the site on flash-drives, thus requiring a return visit to retrieve, but day-to-day station performance can be assessed using telemetry and a computer model. Based on site-testing results, the plan is to select one site for the addition of a seeing monitor and a small but scientifically productive telescope.

Since November 2004 we measured the optical turbulence (C²_N profiles) with a Generalized Scidar (GS) placed at the focus of the Vatican Advanced Technology Telescope at Mt.Graham, Arizona. The present statistic consists in measurements related to 43 nights covering different periods of the solar year. In this paper we calculate the statistics of the astroclimatic parameters (C²_N, seeing ε , isoplanatic angle θ₀, wavefront coherence time τ₀) and we compare these values with those measured above other top level astronomic sites. All profiles are reduced into a form suitable to be used as inputs for adaptive optics point spread function simulations for the conceptual design of the Laser Guide Star Facility supported by a GLAO system of the Large Binocular Telescope. With GS measurements done observing wide binaries (30-35 arcsec), the turbulence in the first kilometer above the ground is characterized with the vertical resolution (200-250 m) required for the optimization of a 4 arcmin field of view AO system. It is the first time that are published measurements of the optical turbulence vertical distribution above a mid-latitude site with such a high vertical resolution and such a high statistical reliability. On 8 of those nights, employing cross-correlation scintillation maps of wide binaries and the method described in Ref.[1] we characterize the distribution of the optical turbulence in the first kilometer at the extremely high vertical resolution of 20-30 meters.

The Thirty Meter Telescope (TMT) project has been collecting data on five candidate sites since 2003. This paper describes the site testing portion of the TMT site selection program and the process and standards employed by it. This includes descriptions of the candidate sites, the process by which they were identified, the site characterization instrument suite and its calibration and the available results, which will be published shortly.

FriOWL is a site selection tool for large or extremely large telescope projects. It consists of a graphical user interface and a large global climatic and geophysical database, and is directly accessible on the world wide web. A new version (version 3.1) of the software has recently been developed by scientists at the University of Bern (Switzerland) and European Southern Observatory (Germany). The main feature of the new FriOWL database is the inclusion of ERA40 re-analysis data, giving access to over 40 years of long-term climate data. New software tools, programmed in the style of a Geographical Information System, include the capability of resampling layers and time series extraction. A new global seismic hazard layer has been introduced, as well as very high resolution (1km) topographic tiles. Reclassification and overlaying of layers is also possible. Although FriOWL is primarily designed for site selection projects, it can equally be used in other climate studies. It is especially important in the determination of the climatic stability of a potential site, and in the analysis of climatic anomalies and trends. The long-term astroclimatological seeing and photometric statistics for the Paranal and La Silla observatories can be used to validate FriOWL. A case study of ESO Paranal using FriOWL reveals that the deterioration in seeing conditions since 1998 is co-incident with a strong increase in 1000 hPa geopotential height to the south-east of the observatory; there may be a link with the Interdecadal Pacific Oscillation.

Consistently superb observing conditions are crucial for achieving the scientific objectives of a ground based telescope. For observations at submillimeter wavelengths, choosing a site with very little atmospheric water vapor is paramount. In northern Chile, the high Andes near San Pedro de Atacama are among the highest and driest places on Earth. At the 5000 m Chajnantor plateau, long term measurements have demonstrated observing conditions are excellent for submillimeter astronomy. Even better conditions prevail on higher mountain peaks in the vicinity. For the CCAT, we have selected a candidate site at 5612 m near the summit of Cerro Chajnantor. Radiosonde measurements, meteorological data, and measurements of the 350 Consistently superb observing conditions are crucial for achieving the scientific objectives of a ground based telescope. For observations at submillimeter wavelengths, choosing a site with very little atmospheric water vapor is paramount. In northern Chile, the high Andes near San Pedro de Atacama are among the highest and driest places on Earth. At the 5000 m Chajnantor plateau, long term measurements have demonstrated observing conditions are excellent for submillimeter astronomy. Even better conditions prevail on higher mountain peaks in the vicinity. For the CCAT, we have selected a candidate site at 5612 m near the summit of Cerro Chajnantor. Radiosonde measurements, meteorological data, and measurements of the 350 μm transparency all indicate submillimeter observing conditions are consistently better at the CCAT site than at the plateau. transparency all indicate submillimeter observing conditions are consistently better at the CCAT site than at the plateau.

Seeing stability is an important criterion of site characterization. Two sites, with the same seeing statistics, could in principle differ in their temporal stability and hence have their observatories perform differently. Temporal variability can, however, be defined in several ways, all of which may determine the performance of the observatories in different manner. In this paper, we propose three methods to measure variability each focusing on different applications: Selection (maximization of observation time), Image quality (seeing variation within a given integration time) and finally Scheduling (prediction of seeing fluctuation on a given time scale). We apply these methods to the seeing of the TMT candidate sites to determine their stability properties.

We have recombined turbulence profiles from MASS and SLODAR at Paranal Observatory using a new grid of atmospheric layers defined on the basis of the comparison between the MASS and SLODAR weighting functions. A statistical analysis of the relation between the total Paranal DIMM C_n², the ground layer C_n² and the free atmosphere C_n² is presented. Taking into account the height of the VLT Unit Telescopes we have recalculated the seeing skipping the atmosphere below that height, obtaining an estimation of the real turbulence affecting science at the Very Large Telescope and its evolution from January 2005 to June 2007.

One of the main tools used in the TMT site testing campaign is the turbulence profiler MASS. We describe empirical investigations and a side by side comparison of two MASS systems which were performed in order to identify the accuracy of MASS turbulence data and its dependence on the instrument calibration. The accuracy of the total seeing delivered by the TMT MASS systems is found to be better than 0"05. The combination of MASS and DIMM allows to observe the seeing within the first few hundred meters of the atmosphere and can be used to investigate possible correlations with meteorological parameters measured close to the ground. We also compare the detection of clouds and cirrus by means of MASS data (LOSSAM method) with measurements of the thermal emission of clouds using a net radiation sensor. These methods are compared with the visual cloud detection using all sky cameras.

Light pollution can create difficulties for astronomers attempting to observe faint objects in the night sky. Light from a local small town can be just as intrusive as light from a large city in the distance. As the population of the Earth increases, light pollution will become more of a problem, even in remote areas. The Thirty Meter Telescope site testing program has measured light pollution at the candidate sites by using all sky cameras; an analysis procedure enhances the all sky camera images to make the determination of the effects of the light pollution. This paper summarizes the light pollution analysis procedure and current results, which are that light pollution is currently unimportant for TMT to select a site for the final telescope location.

All Sky Cameras were deployed at all Thirty Meter Telescope (TMT) candidate sites. The images gathered by these cameras were used to assess the cloud statistics for each site. We describe two methods that were developed to do this, a manual method based on inspection of blue and red movies, and an automated method based on photometric analysis of the images.

Dome C in Antarctica is a particular astronomical site when considering the optical turbulence conditions. From the first winterover campaign performed in 2005 at Dome C, the set of 34 meteorological balloon profiles has been analyzed. The meteorological balloons were equipped with microthermal sensors used to sense the vertical profile of the optical turbulence intensity C²_n. The C²_n median profile, mean temperature and mean horizontal wind speed are given. The C²_n median profile is characterized by a very strong and thin turbulent surface layer. The surface layer height is defined. The median outer scale profile at Dome C is computed using the Tatarski definition. The von Karman outer scale is also deduced. The integrated parameters as Fried parameter r₀, coherence time τ₀, isoplanatic angle θ₀ and the spatial-coherence outer scale L₀ used to define astronomical site quality, are computed at 8 m above the ground and above the turbulent surface layer.

We present the Gattini project: a multisite campaign to measure the optical sky properties above the two high altitude Antarctic astronomical sites of Dome C and Dome A. The Gattini-DomeC project, part of the IRAIT site testing campaign and ongoing since January 2006, consists of two cameras for the measurement of optical sky brightness, large area cloud cover and auroral detection above the DomeC site, home of the French-Italian Concordia station. The cameras are transit in nature and are virtually identical except for the nature of the lenses. The cameras have operated successfully throughout the past two Antarctic winter seasons and here we present the first results obtained from the returned 2006 dataset. The Gattini-DomeA project will place a similar site testing facility at the highest point on the Antarctic plateau, Dome A, with observations commencing in 2008. The project forms a small part of a much larger venture coordinated by the Polar Research Institute of China as part of the International Polar Year whereby an automated site testing facility called PLATO will be traversed into the DomeA site. The status of this exciting and ambitious project with regards to the Gattini-DomeA cameras will be presented.

Over a decade of site testing in Antarctica has shown that both South Pole and Dome C are exceptional sites for astronomy, with certain atmospheric conditions superior to those at existing mid-latitude sites. However, the highest point on the Antarctic plateau, Dome A, is expected to experience colder atmospheric temperatures, lower wind speeds, and a turbulent boundary layer that is confined closer to the ground. The Polar Research Institute of China, who were the first to visit the Dome A site in January 2005, plan to establish a permanently manned station there within the next decade. As part of this process they conducted a second expedition to Dome A, arriving via overland traverse in January 2008. This traverse involved the delivery and installation of the PLATeau Observatory (PLATO). PLATO is an automated self-powered astrophysical site testing observatory, developed by the University of New South Wales. A number of international institutions have contributed site testing instruments measuring turbulence, optical sky background, and sub-millimetre transparency. In addition, a set of science instruments are providing wide-field high time resolution optical photometry and terahertz imaging of the Galaxy. We present here an overview of the PLATO system design and instrumentation suite.

As Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project is going to be completed in 2008/2009, and Five hundred meter Aperture Spherical Telescope (FAST) have been approved by Government in 2007, and the site survey, led by the National Astronomical Observatories of CAS, in west China, and in Antarctica, have been carried through in recent years, the Chinese astronomical community started to think about the next large astronomical facility which should be proposed and started to be built in next 10 years. A 30m aperture sub-millimeter telescope (TSMT) with an active reflector is suggested in this paper. To extend the observation band to far infrared wave length in 0.2mm, the technology developed in large optical telescope like LAMOST for segmented primary mirror is applied in the segmented reflector of this sub-millimeter telescope, but with much lower requirement in accuracy comparing with the 30m extremely large optical telescope. In this presentation, the optical system design, technologies related to the segmented active reflector, telescope structure design and others are described.

In Antarctica the cold and dry air is expected to provide the best observing conditions on the Earth for astronomical observations from infra-red to sub-millimeter. To enjoy the advantages in Antarctica, we have a plan to make astronomical observations at Dome Fuji, which is located at inland Antarctica. However, the harsh environment is very problematic. For example, the temperature comes down to as low as-80 degree Celsius in winter, where instruments designed for temperate environment would not work. In this context, we have developed a 40 cm infra-red telescope, which is dedicated for the use even in winter at Dome Fuji. In designing the telescope, we took account of the difference of the thermal expansion rate among materials, which were used for the telescope. Movable parts like motors were lubricated with grease which would be effective at -80 degrees. Most parts of the telescope are made of aluminum to make the telescope as light as possible, so that it makes the transportation from seacoast to inland and assembling at Dome Fuji easier. We also report the experiment that we have done at Rikubetsu (the coldest city in Japan) in February 2008.

The Antarctic Cosmic Web Imager (ACWI) is a dedicated 2m-class telescope specifically designed to discover and map resonance UV line emission from the Intergalactic Medium (IGM) and to explore the low surface brightness universe. IGM mapping will provide a new measurement of large-scale structure and the distribution of dark matter over a large and unique range in overdensity. The South Pole provides a location with (1) a target elevation that is constant during observation hence sees constant airmass (2) the lowest measured extinction of any ground based site (3) a low and constant ecliptic elevation and hence zodiacal emission away from the target location and (4) long duration nights yielding stable sky and instrument properties enabling the required accurate sky subtraction. These factors combined imply a sky background that is the most stable of any ground-based site, a requirement for this particular science case where the subtraction of sky background, rather than the image quality, must be exquisite. We present the baseline instrument design that is catered to perform this science case only and is not a general purpose instrument, increasing robustness and reliability.

Submillimetre astronomy is the prime technique to unveil the birth and early evolution of stars and galaxies in the local and distant Universe. Preliminary meteorological studies and atmospheric transmission models tend to demonstrate that Dome C might offer atmosphere conditions that open the 200-μm atmospheric windows, and could potentially be a site for a large ground-based telescope facility. However, Antarctic climate conditions might also severely impact and deform any telescope mirror and hardware. We present prerequisite conditions and their associate experiments for defining a large telescope facility for submillimetre astronomy at Dome C: (1) Whether the submm/THz atmospheric windows open from 200 μm during a large and stable fraction of time; (2) The knowledge of thermal gradient and (3) icing formation and their impact on a telescope mirror and hardware. This paper will present preliminary results on current experiments that measure icing, thermal gradient and sky opacity at Dome C. We finally discuss a possible roadmap toward the deployment of a large telescope facility at Dome C.

What is a good astronomical site? It must be cold, dry, stable, dark. There is one site on Earth that qualifies : Antarctica. To make the best use of these characteristics, we propose a Wide-field (0.5-degree in diameter) High-resolution (~0.3 arcsec using GLAO from the ice), IR (0.8-5 μm) 2.4-m TElescope (WHITE). WHITE will be dedicated to carrying out surveys: a deep extragalactic field over a few square degrees, a survey of the Magellanic Clouds. By adding one more year, WHITE would be able to add one kilo-degree survey.

Since Chinese scientific expedition team first arrived Dome A in 10, Jan., 2005, meteorological data have been obtained from this highest point of the Antarctic Plateau. It is likely that Dome A can be the best site for ground-based astronomy. Chinese astronomy community, led by Chinese Center for Antarctic Astronomy, is part of an international effort to survey Dome A for astronomical observations, and has built 4 small telescopes (CSTAR) which have been installed at Dome A in 2008. We report here a more ambitious goal: three Antarctic Schmidt telescopes (AST3) with aperture 50 cm each and the modified Schmidt system (about half shorter tube comparing with normal one) are being constructed, and will be installed for observation at Dome A in Jan., 2010. AST3 will be used for the discovery and exploration of astrophysical transients. This paper presents the technical configuration, design of these Schmidt telescopes, and study on technical challenges for telescope at such a special place with extremely environment on the earth.

This paper will discuss analysis and design of large ground based telescopes for seismic hazard. Seismic hazard is an important issue for both the observatory and the telescope structure. Properly defined seismic specifications are vital. These specifications should include performance objective that matches performance levels and probabilistic based hazard levels for operational and survival conditions. The paper will discuss specific tools that utilize results of existing seismic hazard assessment programs and can be used for initial seismic assessment during site selection. In the final stage of site selection, site specific probabilistic seismic-hazard studies that account for local geological settings and active faults should be used. The results of these site specific studies usually include response spectra and time history records in horizontal and vertical directions for operational and survival conditions. Different methods to analyze the telescope structure for seismic loadings, such as, equivalent static analysis, response spectrum analysis, linear and nonlinear time history analysis, are discussed. Devices that mitigate seismic forces and/or deformations are also presented.

The Giant Magellan Telescope (GMT) is a 21.5-meter equivalent aperture optical-infrared ELT to be located in Chile. It is being designed and constructed by a group of U.S. and international universities and research institutions¹. The concept design of the telescope structure was summarized in an earlier SPIE paper² and described in greater detail in the GMT Conceptual Design Review document³. The structure design has matured during the current Design Development Phase. Important among design improvements has been optimization of the secondary truss with the goal of significantly reducing telescope pointing errors due to wind loading. Three detailed structural changes have resulted in calculated pointing error reductions of ~30%. The changes and their contributions to the improved performance as well as other tested features are discussed. Additional refinements to the structure include the instrument mounting system, with a stationary folded-instrument platform plus Gregorian Instrument Rotator utilizing hydrostatic bearings. More detailed features, such as revised C-ring bracing to improve instrument access, are described.

The Thirty Meter Telescope (TMT) project has revised the reference optical configuration from an Aplanatic Gregorian to a Ritchey-Chrétien design. This paper describes the revised telescope structural design and outlines the design methodology for achieving the dynamic performance requirements derived from the image jitter error budget. The usage of transfer function tools which incorporate the telescope structure system dynamic characteristics and the control system properties is described along with the optimization process for the integrated system. Progress on the structural design for seismic considerations is presented. Moreover, mechanical design progress on the mount control system hardware such as the hydrostatic bearings and drive motors, cable wraps and safety system hardware such as brakes and absorbers are also presented.

This paper describes the photogrammetry method as a mean to measure the deformation of the 6-meter carbon fiber reinforced plastic (CFRP) Platform of the AMiBA interferometric array telescope installed at the Mauna Loa Observatory, Hawaii. The Platform was surveyed at a series of elevation, azimuth and polarization angles. Photogrammetry demonstrates that the deformation of the Platform is not only gravity-induced but also due to the Hexapod mount actuator. The measurement results verify the predictions of the Finite Element Analysis (FEA).

Technologies of modern optical telescopes with large primary mirror are based on adaptive optics. These telescopes operate with many small mirror segments, so that all the segments work as a large piece of a reflective curved plate, i.e. a paraboloid. Each mirror segment is independently attached to a support structure via adjustable warping harnesses. A support structure is required to be extremely rigid in order to maintain the reflective surface. This paper describes the conceptual approach for the design of such support structures. A system proven to fulfill these requirements with efficient structural material use is a node-and-bar system, so-called space frame. The rules for geometry of space frame structures are based on the system of the five 'platonic solids': The edges of the conceptually assembled solids can be replaced by the bar members of a space frame to achieve maximum stiffness. This conceptual approach is demonstrated with examples in the paper, by illustrating the determination of the geometry and examining the deformation due to the telescope rotations during operation. This paper also demonstrates design solutions for other issues relevant to space frame geometry, such as effects of gradient thermal load and redundancy of the structures.

The Large Binocular Telescope (LBT) is an international collaboration, with partners from the United States, Italy, and Germany. The telescope uses two 8.4-meter diameter primary mirrors to produce coherent images with the combined light along with adaptive optics. The correct functioning and optimum performance of the LBT is only achieved through a complex interplay of various optical elements. Each of these elements has its individual vibration behaviour, and therefore it is necessary to characterize the LBT as a distributed vibration system. LINC-NIRVANA is a near-infrared image-plane beam combiner with advanced, multi-conjugated adaptive optics, and one of the interferometric instruments for the Large Binocular Telescope (LBT). Its spectral range goes from 1.0 μm to 2.45 μm, therefore the requirements for the maximum optical path difference (OPD) are very tight (λ/10 ~ 100 nm). ¹ During two dedicated campaigns, the vibrations introduced by various actuators were measured using different kinds of sensors. The evaluation of the obtained data allows an estimation of the frequency and amplitude contributions of the individual vibration sources. Until the final state of the LBT is reached, further measurements are necessary to optimize and adapt the equipment and also the investigated elements and configurations (measurement points and directions, number of sensors, etc.).

The VST (VLT Survey Telescope), a 2.6 m class Alt-Az telescope in installation phase on Cerro Paranal in Northern Chile, at the European Southern Observatory (ESO) site, is provided with a distributed control system based on electro-mechanical actuators, aimed at implementing the main mirror active optics. Due to the requirement of dissipated power reduction under the mirror, a regulated power bus has been chosen, avoiding the use of voltage regulators mounted on the actuators control board. Because the parallel connection of the all control boards power lines makes this solution critical from the point of view of cabling drop voltage and fault propagation, a Power Distribution System (PDS) provided with remote monitoring and control capabilities has been designed. The PDS configuration is based on several Power Distribution Boxes (PDBs), connected in two separate benches. The harness accommodation was estimated by means of 3D CAD, to evaluate the length of the single power connections. The cabling drop voltage was verified by means of PSpice simulation. The single PDS bench has been provided with drop voltage remote sensing function for all the power supply voltages, while the single PDB has been provided with control and monitoring electronics to disconnect via tele-command the faulty control boards and to monitor in real time voltages and current consumption.

The Earthshine telescope project is a collaborative effort between Lund Observatory (LO) in Sweden and The Institute of Meteorology in Demark (DMI) with the purpose of constructing one or more robotic telescopes to record the albedo of the Earth over a long time. The objective is to measure long-term development of the global cloud coverage and reflectivity for climate modeling. A 1% change in the Earth's albedo will result in an average temperature change of 0.5 K of the Earth, calling for high precision of the albedo measurements. This poses strict demands on the telescope design, in particular with respect to suppression of straylight. The paper describes our proposed optical and mechanical design of the Earthshine telescope, and presents a preliminary straylight analysis of the design.

The Department of Astronomy and Astrophysics (DAA) of the Pontificia Universidad Católica de Chile (PUC) operates a small observatory at Santa Martina hills located in the outskirts of Santiago. Despite the close distance (about 30 km) from the centre of a very large metropolitan area, the observatory offers excellent conditions in terms of number of clear nights and relatively good conditions in terms of light pollution and image quality. The observatory is mostly used for didactic purposes, however we are evaluating scientific applications as well.

We describe the optical design of a sky survey system comprised of small aperture telescope tube assemblies mounted on a common semi-equatorial frame with a single polar axis. It is the first ground-based instrument to create a map of transients down to optical m=17 by imaging a fixed-declination strip of the sky on a nightly basis. The system is fully remotely automated and physically robust. The mount tracks the sky using a motion controller, drive motor, and a laser rotary encoder. The prototype configuration is suited to house up to 6 telescopes on the current mount and is easily expandable to accommodate up to 30 telescopes which would enable full sky coverage if one system each were placed in the Northern and Southern Hemispheres¹.

The Gemini twins were the first large modern telescopes to receive protected silver coatings on their mirrors in 2004. The low emissivity requirement is fundamental for the IR optimization. In the mid-IR a factor of two reduction in telescope emissivity is equivalent to increasing the collecting area by the same factor. Our emissivity maintenance requirement is very stringent: 0.5% maximum degradation during operations, at any single wavelength beyond 2.2 μm. We developed a very rigorous standard to wash the primary mirrors in the telescope without science down time. The in-situ washes are made regularly, and the reflectivity and emissivity gains are significant. The coating lifetime has been extended far more than our original expectations. In this report we describe the in-situ process and hardware, explain our maintenance plan, and show results of the coating performance over time.

The Pan-STARRS project is planning to build a suite of four telescopes (PS4) on the summit of Mauna Kea at the site of the current University of Hawaii 2.2-m telescope. These telescopes will have the goal of surveying the entire sky visible from a single site in 5 colors (g, r, i, z, and y) on the time scale of approximately 1 week at a spatial resolution limited primarily by the quality of the site. To accomplish this task each of these four telescopes will be equipped with a Giga-Pixel camera, a camera shutter, and a 6 filter mechanism. A prototype telescope for this project (PS1) that includes all of these subsystems is already under going commissioning. The project is currently involved in developing the Environmental Impact Statement that is required to build the PS4 array of telescopes. We give an overview here of the scientific goals, the instrumentation package, the telescope design, and the enclosure design for the PS4 system.

To study short stochastic optical flares of different objects (GRBs, SNs, etc) of unknown localizations as well as NEOs it is necessary to monitor large regions of sky with high time resolution. We developed a system which consists of wide-field camera (FOW is 400-600 sq.deg.) using TV-CCD with time resolution of 0.13 s to record and classify optical transients, and a fast robotic telescope aimed to perform their spectroscopic and photometric investigation just after detection. Such two telescope complex TORTOREM combining wide-field camera TORTORA and robotic telescope REM operated from May 2006 at La Silla ESO observatory. Some results of its operation, including first fast time resolution study of optical transient accompanying GRB and discovery of its fine time structure, are presented. Prospects for improving the complex efficiency are given.

The current status of the University of Tokyo Atacama 1.0m telescope project being constructed at the summit of Co. Chajnantor (5,640m) in Atacama, Chile, will be presented. This is an optical/infrared telescope at the world's highest site. A precipitable water vapor (PWV) amount of 0.4 to 1.3 mm at the summit, much lower than that of 0.9 to 2.8 mm at Mauna Kea, Hawaii. provides excellent atmospheric transmission from the near- to the mid-infrared wavelength. Seeing and weather conditions are confirmed to be suitable for infrared observations at the summit. The telescope is an f/12 Ritchey-Chrétien type with a field of view of 10 arcmin. The telescope is installed in a 6-m dome and controlled from an operation room in a container separated from the dome. The operation room will be directly connected to a base support facility in San Pedro de Atacama by a wireless LAN and a satellite link. A power generator and solar panels are equipped for a main and a back-up power supply, respectively. The ANIR near-infrared camera and the MAX38 mid-infrared camera are equipped on the Cassegrain focus. This telescope will start operation at the beginning of 2009, and will be operated remotely from the base facility in the near future.

By study of the classical testing techniques (such as Shack-Hartmann Wave-front Sensor) adopted in testing the aberration of ground-based astronomical optical telescopes, we bring forward two testing methods on the foundation of high-resolution image reconstruction technology. One is based on the averaged short-exposure OTF and the other is based on the Speckle Interferometric OTF by Antoine Labeyrie. Researches made by J.Ohtsubo, F. Roddier, Richard Barakat and J.-Y. ZHANG indicated that the SITF statistical results would be affected by the telescope optical aberrations, which means the SITF statistical results is a function of optical system aberration and the atmospheric Fried parameter (seeing). Telescope diffraction-limited information can be got through two statistics methods of abundant speckle images: by the first method, we can extract the low frequency information such as the full width at half maximum (FWHM) of the telescope PSF to estimate the optical quality; by the second method, we can get a more precise description of the telescope PSF with high frequency information. We will apply the two testing methods to the 2.4m optical telescope of the GMG Observatory, in china to validate their repeatability and correctness and compare the testing results with that of the Shack-Hartmann Wave-Front Sensor got. This part will be described in detail in our paper.

The Dark Energy Camera will be comprised of 74 CCDs with high efficiency out to a wavelength of 1 micron. The CCDs will be read out by a Monsoon-based system consisting of three boards: Master Control, CCD Acquisition, and Clock boards. The charge transfer efficiency (CTE) is closely related to the clock waveforms provided by the Clock Board (CB). The CB has been redesigned to meet the stringent requirements of the Dark Energy Survey. The number of signals provided by the clock board has been extended from 32 (the number required for 2 CCDs) up to 135 signals (the number required for 9 CCDs). This modification is required to fit the electronics into the limited space available on the imager vessel. In addition, the drivers have been changed to provide more current. The first test result with the new clock board shows a clear improvement in the CTE response when reading out at the higher frequencies required for the guide CCDs.

We will present aspects of the installation, commissioning, software development, and early operation of several new robotic telescopes: 1) the 1.2-m MONET/South telescope at Sutherland/ZA, the second Halfmann telescope for the MONET telescope network (the other telescope has been in operation at McDonald Observatory in Texas since early 2006); 2) a siderostat for a 0.5-m vacuum tower telescope for the new physics building of the Georg-August-Universitat Göttingen; and 3) new developments for smaller (down to 0.5m) aperture telescopes. Special emphasis will be given to drive technology: using torque motors we adjust maximum slewing speeds of 10°/sec as standard. Although sufficient for most projects we are investigating even faster slewing speeds.

The Laser Service Enclosure (LSE) is an environmentally controlled ISO 7 clean room designed to house, protect and provide environmental control for the Gemini South multi-conjugate adaptive optics laser system. The LSE is 8.0 meters long, 2.5 meters wide and 2.5 meters high with a mass of approximately 5,100 kg. The LSE shall reside on a new telescope Nasmyth platform named the Support Structure (SS). The SS is a three-dimensional beam and frame structure designed to support the LSE and laser system under all loading conditions. This paper will review the system requirements and describe the system hardware including optical, environmental, structural and operational issues as well as the anticipated impact the system will have on the current telescope performance.

Seismicity induces ground vertical and horizontal displacements that could affect the image quality obtained by telescopes in a similar fashion than atmospheric turbulence. In this work, we study the effect of local seismicity relative to atmospheric turbulence upon the image quality of astronomical observations at El Teide observatory, Canary Islands. Three different aspects of seismicity are studied, namely regional seismicity (that is compared with other astronomical sites), seismic noise and possible resonances between seismic noise and the structure of telescopes.

The derived heat loads from thermal models are used to size the equipment that controls exterior enclosure seeing for the Advanced Technology Solar Telescope. These loads are highly dependent on the radiative properties assumed for the surface coatings of the enclosure. The properties of traditional white coatings and paints are known to degrade with time as they are exposed to the elements, but not by how much or how quickly. The solar reflectance and thermal emissivity of coatings considered for use on the enclosure, in a weathered condition, are not readily available from coatings manufacturers or in the scientific literature. The results from a one-year test of nine different coatings that were weathered at the summit of Haleakala on the island of Maui, Hawaii are reported and discussed.

Measuring magnetic fields in the solar corona requires a large aperture telescope with exceptionally low levels of scattered light. For internally-occulted coronagraphs the main source is scattering from dust or microroughness on the primary lens or mirror. We show refracting primaries offer significantly lower levels for both sources. To observe magnetic fields in the solar corona with scientifically interesting spatial and temporal resolutions, a 1 meter aperture or larger is required. For a long time such large-scale refractors have been deemed impractical or impossible to construct due to gravitational deformation of the lens. We present the results of finite-element and optical analyses of the gravitational deformation, stress-induced birefringence, and absorptive heating of a (see manuscript)1.5 meter f/5 fused silica lens. These studies demonstrate the traditional objections to large refractors are unfounded and large refracting primaries have unique capabilities.

This communication reviews the participation of the Instituto de Astrofísica de Canarias (IAC) in the design of the European Solar Telescope. Apart of being the coordinator institution of the whole project, and, as such, responsible for the project managing, the IAC leads several tasks like overall instrument definition or characterization of the atmospheric turbulence profile with height or the definition of adequate detectors. More in particular, the IAC will design and build two long-base SHABAR (SHAdow BAnd Ranger), instruments to measure medium-altitude seeing. The IAC is also responsible for the design, together with other institutions, of the design of grating spectropolarimeters suitable for multiwavelength high spatial and spectral resolution.

The Advanced Technology Solar Telescope (ATST) project plans to implement thermal control of the primary mirror using jet impingement of temperature controlled air on the backside of the meniscus mirror. This technique will be used to minimize temperature rise of the optical surface due to coating absorption, minimizing mirror seeing effects. The performance of this system has been evaluated using numerical modeling techniques and weather data recorded at the proposed observatory site. To aid in the design of the M1 thermal control system for the ATST, a prototype test bed was designed, fabricated and tested. This paper reviews the progress and results of this development program.

Turbulence, which may exist along an optical path inside a telescope or laboratory setup such as the Dunn Solar Telescope observing room, can negatively impact the imaging performance at the final detector plane. In order to derive requirements and error budget terms for the Advanced Technology Solar Telescope (ATST) we performed interferometric measurements with the goal to determine the amount of aberrations introduced by the air mass through which the beam propagates and characterize temporal and spatial frequencies of these aberrations. We used a He-Ne laser interferometer to measure aberrations along a 50m and 33m, collimated 150mm diameter laser beam. The experiments were performed with both vertical and horizontal beam propagation. We investigated the impact on the amount of self-induced turbulence of the difference in temperature between the top and the bottom of the optical laboratory, the impact of heat sources, such as electronics racks, and the effect of a laminar air flow applied to parts of the beam path. The analysis of the interferograms yields values of the rms wave front aberrations excluding tip/tilt in the range of 1.45nm/m - 2nm/m (@632nm) for the vertical beam propagation and between 0.8nm/m - 1.6nm/m for the horizontal beam. The spatial spectrum of the turbulence tends to decay faster than Kolmogorov turbulence. This is true, in particular, for the horizontal beam path. The temporal frequencies are on the order of a few Hz (<10Hz).

The Multi-Application Solar Telescope (MAST) is a 50 cm diameter class telescope to be installed on the Udaipur Solar Observatory's Island on the Lake Fatehsagar in Udaipur, India. It is dedicated to solar observation. The telescope is designed, manufactured, assembled and installed on-site by the belgian company AMOS SA for the Udaipur Solar Observatory (USO), an academic division of the Physical Research Laboratory (PRL) in India. Despite its limited size, the telescope is expected to be competitive with respect to worldwide large and costly projects thanks to its versatility regarding science goals and also thanks to its demanding optomechanical and thermal specification. This paper describes the optomechanical and thermal design of this telescope and presents solutions adopted by AMOS to meet the specific requirements. The optical configuration of the telescope is based on an afocal off-axis gregorian combination integrated on an Alt.-Az. mechanical mount, with a suite of flat folding mirrors to provide the required stationary collimated beam.

From the first application on the VLT Telescopes till today, the linear motor identifies the best solution in terms of quality/cost for any technological application in the astronomical field. Its application also in the radio-astronomy sector with the ALMA project represents a whole of forefront technology, high reliability and minimum maintenance. The adoption of embedded electronics on each motor sector makes it a system at present modular, redundant with resetting of EMC troubles.

The azimuth track of the Green Bank Telescope did not perform as designed. Relative movement of components was noted during construction; in addition, fretting of the base plate and wear plate faying surfaces, fatigue cracking of the wear plates, fatigue failure of wear plate fasteners, and deterioration of the cementitous grout layer occurred at a rapid pace during the first few years of operation. After extensive failure analysis, a new system of components was designed and fabricated, and installation of the components was performed during 2007 (Symmes, Anderson, and Egan, "Improving the service life of the 100m Green Bank Telescope azimuth track", SPIE 7012-121). The highlights and lessons learned during the fabrication and installation phases are described herein. This information will benefit any organization performing a similar replacement, and may be helpful in new installations as well.

The NRAO Green Bank Telescope (GBT), located in Green Bank, West Virginia, is supported by 16 steel wheels which rest upon a composite steel and concrete Azimuth Track, 210 feet (64 meters) in diameter. From the start of observing in February 2001, the Azimuth Track design presented an operational problem for NRAO. By the spring of 2001, slippage of the top plate on the base plate was causing hold-down bolt failures. In July 2002, wear between the top and base plates (fretting) had become evident around the entire track circumference. NRAO engineers took immediate action to reduce both the track slippage and wear problems. But in January 2003, cracks were discovered in two adjacent top plates; by 2006 the top plates were cracking at a rate of almost one a month - an alarming rate given the design service life of 20 years. This paper will summarize the engineering analysis efforts that were subsequently conducted to assess the root cause of the GBT track degradation problem. We will also discuss a trial modification section that was installed in June 2004. Finally, we will discuss the design solution that was developed to remedy the track performance problem.

The National Astronomical Observatories of China (NAOC) plan to build a 500m radio telescope in southern China [1]. The telescope has a fixed but active main reflector, and large sky coverage is achieved by moving the receivers on a focus surface 160m above the main reflector. The paper describes recommended design concepts for the cable system, the drives and the cabin mechanisms, which position and point the receiver platform. The simulation study, which is basis of the presented results, was executed by engineers of the Technical University Darmstadt under a contract of NAOC in cooperation with two visiting engineers of NAOC and lead by the author [2]. The analysis results and end-toend simulations itself are described in more detail in two other contributions to this conference [3], [4].

The Shack-Hartmann Phasing Sensor (SHAPS) has been integrated in the Active Phasing Experiment (APE) at ESO. It is currently under test in the laboratory. The tests on sky are foreseen for the end of 2008, when APE will be mounted at the Nasmyth focus of one of the VLT unit telescopes. SHAPS is based on the Shack-Hartmann principle: the lenslet array is located in a plane which is optically conjugated to the Active Segmented Mirror (ASM) of APE and is composed of two types of microlenses, circular and cylindrical, which give information about the wavefront slope and the piston steps, respectively. This proceeding contains a description of SHAPS and of the algorithms implemented for the wavefront reconstruction and for the phasing. The preliminary results obtained during the laboratory tests are discussed and compared with the theoretical predictions. The performances of SHAPS at the VLT and at the European Extremely Large Telescope (E-ELT) are estimated.

The construction of extremely large telescope is only possible with a segmented primary mirror. The phasing of the primary mirror due to its size and its number of segments is a main concern at the European Southern Observatory. The European Southern Observatory has developed a test bench called Active Phasing Experiment to study new phasing technology and new telescope control system. The key subsystem of this experiment is a scaled down Active Segmented Mirror (ASM) composed of sixty-one hexagonal segments of seventeen millimeters side to side. Each hexagonal mirror can all be controlled in piston, tip and tilt. The integration of this jewel piece of opto-mechanic started after the successful results obtained with the manufacturing of a prototype composed of only seven modules.

The construction of ELT primary mirrors requires the integration of a hundreds of segments.^{1, 2} A frequent substitution of some segment is foreseen allowing the primary alumimization. Mechanical integration has to reduce residual piston errors up to the capture range of optical cophasing sensors. Enlarging this range, will relax the mechanical integration requirements, speeding up meaningfully the integration operations. In this work we tested the performance of the Wavelength Sweeping Technique³ (WST): a cophasing technique that allow a large piston capture range, with any need of initial calibration. To apply the WST is necessary couple a Liquid Crystal Tunable Filter (LCTF) to a phasing WaveFront Sensor (WFS). In laboratory we measured segment edge steps on a MEMS-DM applying the WST to the PYramid Phasing Sensor4 (PYPS). We measured 72 wavefront phase steps from 0.5 to 3μm with an accuracy of less than 0.2μm. With numerical simulations we inquired the possibility to propagate WST edge step measures to cophase a segmented mirror. To do this we realized a cophasing algorithm and we compared its performace in different observing environments. The algorithm converges in 3 ÷ 5 iterations and all the residual edge steps on the mirror are in the capture range of high resolution cophasing techniques.

PYPS is the pyramid wavefront sensor for the phasing and alignment of segmented mirrors developed in the framework of the Active Phase Experiment (APE). In this paper we will present the PYPS opto-mechanical design, and report the experimental results obtained in the Arcetri laboratories prior to its integration in the main APE bench. A piston-correction closed loop was performed under the presence of emulated turbulence (D/r0=33 @ 700nm and V/D=1.9Hz), achieving a final piston error of 10 nm rms in wavefront. Two filtering techniques were developed to average out faster the atmospheric disturbance reducing the required co-phasing time by two orders of magnitude. We will also present the first experimental results obtained with a synthetic interaction matrix attaining a final piston error of the same order of magnitude.

The design of the future Extremely Large Telescopes (ELTs) is currently under way. The presence of two segmented mirrors in the optical train has been considered to be of high risk due to the additional challenge of phasing and aligning a telescope having two segmented mirrors. Nevertheless this double segmentation could be a feature of the E-ELT where the optical train will contain a segmented primary and possibly a segmented M4. In this paper we will present some preliminary studies based on numerical simulations demonstrating that with the pyramid wavefront sensor it is possible to control piston, tip, and tilt errors of two segmented mirrors in the same optical train simultaneously.

Currently, a number of astrophysical institutes all over the world are working on the design of Extremely Large Telescopes (ELT). Due to the enormous size of the primary mirror these telescopes make use of segmented mirrors. These segments have to be positioned with respect to each other with nanometer accuracy in spite of all kind of external disturbances such as wind loads, thermal loads, deformation of the base frame, varying orientation with respect to the field of gravity, etc. Janssen Precision Engineering (JPE) developed a revolutionary position actuator called the HiPAC which is able to fulfill the demanding requirements for this kind of actuators. The actuator is based on an integrated system of a pneumatic actuator, an electric voice coil and smart control strategy and has the following features: high positioning accuracy performance due to play-free and frictionless actuation; high reliability and maintenance free operation due to flexure-based frictionless guiding; system behavior is constant in time, because no parts affected by wear are used in the actuator; low cost, because no highly accurate machined parts required to reach high end performance; the position actuator acts as an integrated vibration isolator which isolates the segmented mirrors from external vibrations induced in the telescope frame; In this paper the design, simulation and measurements of the HiPAC actuator will be presented.

The SAMS (Segment Alignment Measurement System) is a capacitance-based edge sensing solution for the active alignment of the 10m SALT segmented primary mirror. Commissioning and calibrating the system has been an ongoing task in an attempt to counteract the unfavourable response of the sensors to high humidity conditions and high dust levels. Several solutions were implemented and tested including real-time feedback systems and the application of corrective functions. In parallel with the continuing efforts to improve the performance of the capacitive sensors, we have also been testing a prototype inductive sensor developed by Fogale Nanotech that is of a very similar flexible plate construction. In this paper we present the results obtained and performance gains achieved thus far with the capacitive edge-sensing system as well as a performance comparison of the Fogale inductive sensor to the capacitive edge sensor.

The Large Sky Area Multi-Object Spectroscopic Telescope (LAMOST) is one of the major national projects still under construction in China, which obtained first light in the July 2007. It has two key fundamental technologies, combined thin mirror active optics and segmented mirror active optics, and fiber positioning. This paper introduces briefly the characteristic of the LAMOST active optics wavefront sensing theory, which is very important, and the unique for all the existing telescopes equipped with active optics technology. During the past days, there are many active optics progresses taken place during the LAMOST alignment. Some onsite sensing results are given to show you the wavefront sensing progress and to verify this developed method, which is now successfully adopted and implemented in LAMOST active correction. Finally some conclusions are reached upon the current wavefront sensing method.

We discuss a transmission primary objective grating (POG) telescope that is nearly flat to the ground with its secondary components buried below ground in a protected environment that enjoys a controlled atmosphere. Temperature gradients can be held steady by sealing this enclosure. End-to-end ray paths need not be interrupted by spiders or other structural support elements. Unlike mirror and lens telescopes, this layout is intrinsically off-axis. Light diffracted from a POG at a grazing angle can be collected a few meters below the POG, and the substructures do not require a deep excavation, as would be required for buried on-axis mirrors such as a zenith tube. The POG principle can take advantage of the rotation of the earth to acquire spectra sequentially, so active tilt and rotate axes are not necessary during observations. The POG aperture is extensible as a ribbon optic to kilometer scale at a linear increase in cost, as compared to other choices where infrastructure grows as the cube of the telescope size. The principle of operation was proven in miniature during bench tests that show high resolution spectra can be obtained at angular resolutions equal to seeing. Mathematical models of the underlying relationships show that flux collection increases with increased angles of grazing exodus even as efficiency decreases. Zemax models show a 30° field-of-view and the capacity to take spectra of all sources within that very wide field-of-view. The method lends itself to large apertures, because it is tolerant of POG surface unevenness.

This paper describes a preliminary engineering design for the European Extremely Large Telescope (E-ELT) enclosure. The sheer size of the E-ELT enclosure has provoked an engineering led design approach to re-assess and resolve some conventional telescope enclosure design issues. By drawing on other large scale movable structure design experience, the proposed engineering solution fulfils the design requirements both technically and economically. Throughout the study the design approach has attempted to minimise development risks and maximise reliability of the movable systems wherever possible. All the key elements of the enclosure design are discussed. Emphasis is, however, placed on describing the unusual aspects of the design, which include: a unique system of nested panels for opening the viewing slot; and a curved gantry crane giving extensive coverage of the telescope and enclosure. The paper also proposes a possible construction method, and addresses the specific requirements associated with fabricating and maintaining a large movable structure located at high altitude.

The CTIO V. M. Blanco 4-m telescope is to be the host facility for the Dark Energy Survey (DES), a large area optical survey intended to measure the dark energy equation of state parameter, w. The survey is expected to use ~30% of the telescope time over 5 years and use a new 520 megapixel CCD prime focus imaging system: the Dark Energy Camera (DECam). The Blanco telescope will also be the southern hemisphere platform for NEWFIRM, a large area infrared imager currently being commissioned at the Mayall Telescope at KPNO. As part of its normal cycle of continuing upgrades and in preparation for the arrival of these new instruments, the Blanco telescope control system (TCS) will be upgraded to provide a modern platform for observations and maximize the efficiency of survey operations. The upgraded TCS will be based on that used at the SOAR telescope and will be a prototype of the TCS to be used by LSST. It will be optimized for programmed and queued survey observations, will provide extended real-time telemetry of site and facility characteristics, and will incorporate a distributed observer interface allowing for on- and off-site observations and real time quality control. Hardware modifications will include the use of absolute tape encoders and a modern servo control and power driver systems.

In a modern telescope the Azimuth (AZ) and Altitude (ALT) Axes have to perform a very accurate pointing and tracking. The tracking of celestial objects is a critical operation, during which the telescope axes have to compensate the earth rotation, allowing a stable image integration on the scientific instrument CCD. To accomplish this goal, the two axes control system is provided with state of the art encoders and tachometers, for position and speed feedback, together with motors controlled in torque preload, to avoid backlash effect. The closed loop control system is based on an axes Local Control Unit (LCU), based on VME Computer. In this paper the AZ and ALT Axes Control System of the VST (VLT Survey Telescope) is described. The VST is a 2.6 m class Alt-Azimuthal Survey Telescope in installation phase at Cerro Paranal in Northern Chile, at the European Southern Observatory (ESO) observation site. The VST Telescope was designed and implemented by I.N.A.F., Osservatorio Astronomico di Capodimonte. Nowadays the AZ and ALT axes mechanics and the related control system have already been accepted by ESO, shipped to Chile and integrated in Paranal.

The Hydrostatic Bearing System (HBS) control hardware of the VST (VLT Survey Telescope), a 2.6 m. class Alt-Az telescope in installation phase at Cerro Paranal in Northern Chile, at the European Southern Observatory (ESO) site, is aimed at controlling all the devices present in the HBS pumping station and at monitoring the pressure values in the different points of the plant. The HBS control system is based mainly on a Local Control Unit (LCU) mounted in the HBS control cabinet and connected to the plant by means of proper I/Fs. A distributed pressure and temperature acquisition system, based on General Purpose (GP) acquisition boards, is also present. A local interlock chain and related enabling signal for the Azimuth Axis interlock chain have been implemented to avoid fault propagation in case of lack of delivery pressure. In the present paper all technical details concerning the control and monitoring of the HBS subsystem are given.

Heidenhain position tape encoders are in use on almost all modern telescopes with excellent results. Performance of these systems can be limited by minor mechanical misalignments between the tape and read head causing errors at the grating period. The first and second harmonics of the measured signal are the dominant errors, and have a varying frequency dependant on axis rate. When the error spectrum is within the mount servo bandwidth it results in periodic telescope pointing jitter. This paper will describe an adaptive error correction using elliptic interpolation of the raw signals, based on the well known compensation technique developed by Heydemann [1]. The approach allows the compensation to track in real time with no need of a large static look-up table, or frequent calibrations. This paper also presents the results obtained after applying this approach on data measured on the SOAR telescope.

The paper discusses one direct drive telescope experiment bed (DDTEB), which is designed to simulate the modern telescope tracking system. The main task is to find the problem and the reliability which might be met in the real direct drive tracking system of the telescope and how to handle them. More information and experience will be acquired and accumulated to use the direct drive technology in the telescope complex motion system of Chinese telescope in the future.

Segmented primary mirrors dominate the current generation of 10m class telescopes as well as the designs for the next generation of Extremely Large Telescopes (ELT's). The complex nature of these telescopes is demonstrated by the long time periods associated with their commissioning and the difficulty of performing high precision optical alignments. However, additional tools to provide in situ measurements of their optical alignment can be provided by making use of the individual mirrors of a segmented primary; with the ability to move in six degrees of freedom, the individual mirrors can be deployed to trace multiple optical paths through the telescope. In this paper we describe how it is possible to use the segments themselves to create a number of Hartmann masks that allow focus and other aberrations to be measured using a standard imaging camera rather than a dedicated wavefront sensor. The Southern African Large Telescope (SALT), with a primary mirror composed of 91 1m segments, is used as an example. The segments were arranged to create eight Hartmann masks to measure the optical alignment. Through imaging data obtained at the telescope, the sensitivity of this method to changes in focus along with aberrations inherent in the system is demonstrated through Zernike polynomial fits to the observed patterns. Finally, we present simulations of possible patterns for use on future ELT's.

Astronomical balloon-borne telescopes have the potential to improve seeing over ground-based telescopes, but are compromised by their instability. A one-meter telescope in the Earth's stratosphere could achieve diffraction-limited seeing superior to the performance of any ground-based telescope in optical or UV wavelengths. If the stability issues could be addressed, such a telescope could be used for a variety of scientific purposes, including high- resolution optical imaging, or infrared imaging of targets that are usually precluded from ground-based systems, such as Jupiter, Saturn or Venus. An image stabilization system was developed with the goal of maintaining the position of the image to within 0.1 arcseconds on the focal plane during image acquisition. This effort requires both deriving an error signal and applying that error signal to a corrective element. Using a control loop with an optical reference provides a greater bandwidth than an inertial reference and improves control of high frequency vibrations. The control feedback signal was generated by monitoring the position of an image using a lateral effect cell. A fine steering mirror was used as a diagonal flat to control the position of the image and correct for small disturbances in pointing. To evaluate the system, vibration was induced in a synthetic image and the resultant motion of the image measured. The system was implemented and tested on a 14-inch f/10 Schmidt-Cassegrain telescope. Large disturbances were attenuated by a factor of 10-100, with a noise level of less than 2 arcseconds on the test telescope.

We describe the balloon-borne telescope (69cm aperture) for the project Tera-GATE (THz observation with GaAs photoconductors and a balloon-borne TElescope) aiming at the THz astronomical observations. THz region is the last frontier left not well explored and we are planning to have multiband photometric observations covering the wavelength from 50 to 300 microns and get completed SED data for some Young Stellar Objects in this band. The telescope, we are constructing, has image stabilizing system which cancels out pointing error (up to about 0.3 degrees) of the balloon gondola, and enables us to take a long exposure needed for highly sensitive observations. We will show the structure of the telescope, cold stop design, and characteristics of the image stabilizing system.

We describe the optical design of balloon-borne telescope with an image stabilizing secondary mirror which correct the pointing error of the attitude control system and enable a long-time exposure. We adopted a Cassegrain-like two-mirror system, and investigated the best mirror surface figure by surveying Conic constant (K) of the primary mirror from -1 to 0, where the secondary mirror is a high order aspheric surface to cancel spherical aberration at each K. In the small pointing error region, the classical Cassegrain system (K=-1) provides a wide field of view. However, in the large pointing error region, systems with large K provide a wide FOV. For λt (target wavelength) =50µm and 69cm aperture, a spherical primary system has acceptable optical performances when we assume the pointing error around 0.3 degree.

The Stratospheric Observatory For Infrared Astronomy, SOFIA is a unique aircraft with the telescope optics exposed to extreme environment in the open port of a Boeing 747SP. The aircraft with the integrated telescope was transferred last year to the NASA Dryden Flight research Center in California and, in December 2007 successfully completed its first closed door test flight with the telescope systems in operation. The first open door flights are planned in the second half 2008, the first early science flights are to follow in spring 2009. The telescope is equipped with several design features, such as a vibration isolation system, a flexible body control system and - potentially - active mass dampers, to handle excitations in different frequency ranges. We present a progress report and describe the recent achievements as well as the status of the telescope. We also provide an update of the SOFIA pointing system, and the planned in-flight tests.

The commercially-available Boltwood Cloud Sensor couples a sky-facing non-imaging thermopile operating in the 8-14 micron range with an ambient air thermometer, to determine the relative sky temperature, and thus indicate the presence of cloud. A Boltwood sensor was installed on the Liverpool Telescope's weather mast on La Palma in the Canary Islands in September 2006 in order to investigate its response to both thick and thin cloud at both low and high (cirrus) levels. An additional aim was to investigate the detectability of calima (Saharan dust) that is occasionally blown over the islands. In this paper we present the results of our investigations, presenting correlations between the observed temperature differential and photometricity as determined from the observation of photometric standard stars, and give some useful "rules-of-thumb" for others considering using such devices.

A thermal model of the Discovery Channel Telescope (DCT) was used to estimate the contribution of major sources of local seeing; shell seeing, dome seeing and mirror seeing. The model simulates a dynamic equilibrium over several day/night cycles taking into account the morphology of the facility, diurnal insolation and radiation to the night sky, local air temperature and humidity swings, wind and air flow through the facility, and infiltration from warm spaces within the facility. The model confirmed that the well ventilated design of the DCT facility will virtually eliminate dome seeing, but that shell seeing and mirror seeing could be major contributors to local seeing. These can be mitigated by the choice of an appropriate exterior coating, and by cooling the primary mirror.

The LSST project has acquired an all sky IR camera and started to investigate its effectiveness in cloud monitoring. The IR camera has a 180-degree field of view. The camera uses six filters in the 8-12 micron atmospheric window and has a built in black body reference and visible all sky camera for additional diagnostics. The camera is installed and in nightly use on Cerro Pachon in Chile, between the SOAR and Gemini South telescopes. This paper describes the measurements made to date in comparison to the SOAR visible All Sky Camera (SASCA) and other observed atmospheric throughput. The objective for these tests is to find an IR camera design to provide the survey scheduler with real-time measured conditions of clouds, including high cirrus to better optimize the observing strategy.