The Institute for Astronomy at the University of Hawaii is developing a large optical synoptic survey telescope system; the Panoramic Survey Telescope and Rapid Response System. Pan-STARRS will consist of an array of four 1.8m telescopes with very large (7 square degree) field of view, giving it an etendue larger than all existing survey instruments combined. Each telescope will be equipped with a 1 billion pixel CCD camera with low noise and rapid read-out, and the data will be reduced in near real time to produce both cumulative static sky and difference images, from which transient, moving and variable objects can be detected. Pan-STARRS will be able to survey up to ≈6,000 square degrees per night to a detection limit of approximately 24th magnitude. This unique combination of sensitivity and rate of area coverage will open up many new possibilities in time domain astronomy. A major goal for the project is to survey potentially dangerous asteroids, where Pan-STARRS will be able to detect most objects down to 300m size, much smaller than the km size objects accessible to existing search programs. In addition, the Pan-STARRS data products will used to address a wide range of astronomical problems in the Solar System, the Galaxy, and the Cosmos at large. Here, we first outline the Pan-STARRS science goals and describe the survey modes needed to support these. We then describe the design and performance goals, the data processing pipeline, and we review the basic data products. Finally, we present results from simulations that demonstrate Pan-STARRS' capability for detecting potentially hazardous asteroids.

Programmes driving ELT design are discussed. The nature and evolution of circum-stellar shells and planetary discs are attractive, while the small angular sizes place basic properties, asymmetry and warps, beyond VLT capability. An ELT is neeed to reveal the conversion processes shell - disc - planets, planetary systems, Earth-like planets, habitability and life signatures. Formation and evolution of massive stars are dicussed as are stellar rotation and shape, surface spatial and temporal resolution and evolution. Stellar clusters are discussed as probes of galactic evolution, resolving CMDs for Virgo and Fornax cluster galaxies. High-resolution studies of AGNs are discussed as are supernovae with bearing on early star formation, galactic activity and cosmology. Finally, the requirements defined from the prime science drivers are confronted with technical realities.

We present an overview of the science case for a 50-100m Extremely Large Telescope. This was the subject of a meeting in Marseilles, France in November 2003, attended by about 50 European astronomers. Four key scientific themes were identified by the participants: terrestrial planets in extra-solar systems; stellar populations across the Universe; building galaxies since the darkest ages; the first objects and re-ionisation structure of the Universe. Although by no means an exhaustive list of science areas in which ELT will have a great impact, these cases provide examples where an ELT can make a dramatic advance in our understanding of the Universe around us. This paper describes these highlighted science themes and the challenging demands they place on ELT performance. See http://www-astro.physics.ox.ac.uk/~imh/ELT/ for more information, including the full list of participants in this work.

We describe the scientific case and design challenges for an innovative large submillimetre telescope (LST). LST is proposed to have a diameter of at least 30m, operate in the wavelength range from 0.2 - 1mm and will have a wide field-of-view. The submillimetre region allows us to probe objects during formation - i.e. the earliest evolutionary stages of galaxies, stars and planets. Being so close to the peak of the cosmic far-IR/submm background and the emission from proto-stellar cores, the 200μm atmospheric window gives access to unique science. The key advantage of LST over other facilities will be in terms of addressing astronomical questions requiring large fields and good angular resolution: such as surveys of entire giant molecular clouds and fields of dusty galaxies at early epochs. For example, such a telescope would resolve all protoplanetary disks out to 100pc, revolutionising our knowledge of star and planet formation, and detect tens of millions of dusty high-redshift galaxies yielding information on formation and evolution of the early universe. Equipped with a state-of-the-art large format bolometer camera, LST would offer a survey (mapping) speed up to 5,000 times that of ALMA, arcsecond resolution at the shortest wavelengths, point-source sensitivities at least 25 times better than any planned submm facility, and confusion limits 10 times lower than any existing single-aperture telescope. The wide-field-of-view and superb image fidelity available from a single-dish will be perfect for large-scale surveys of the submillimetre sky - an ideal complement to new generation interferometers such as ALMA.

The Square Kilometre Array (SKA) is a global project to design and build a new generation radio telescope at metre to centimetre wavelengths. It will have a collecting area of order one million square metres, a sensitivity 100 times higher than the VLA, an instantaneous field of view (FOV) of at least 1 square degree and, in some designs, more than one FOV allowing multiple simultaneous use. It will be an extremely powerful survey telescope with the capability to follow up individual objects with high angular and time resolution. The SKA will reach a point source sensitivity of 10 nano-Jy in 8 hours of integration, and a maximum resolution of 1 milli arcsec at 20 GHz with excellent imaging capability at all resolutions and frequencies. The SKA science impact will be felt in astro-particle physics and cosmology, fundamental physics, galactic and extragalactic astronomy, and solar system science. Technological innovation, closely paralleling commercial IT developments, is key to the design concepts under investigation and to the cost goal of USD1000/m2. The selection of technologies for the SKA is scheduled in early 2008. A number of possible locations for the telescope are under investigation with a choice scheduled in early 2006. Construction of the array will take most of the next decade.

I describe the procedures used during the different phases of site testing for astronomical telescopes, that is, during the pre-selection of candidate sites, on-site testing (site selection), the site decision itself and characterization of the telescope site once the decision has been made. Many of the important parameters for astronomical night-time telescopes and some of the methods that can be used to determine these parameters are described. There appear to be no fundamental differences between the methods used for telescopes in the 5 to 10 meter range and telescopes with diameters larger than 10 meters, although specific differences certainly exist.

Selection of an ideal site for the new generation of Overwhelmingly Large (OWL) telescopes is dependent on many climatological and meteorological parameters. Among these are cloud cover, atmospheric humidity, aerosol content, air temperature, airflow direction, strength and turbulence. Even relatively minor changes in weather patterns can have a significant effect on seeing conditions. A composite climatological database has been designed and built for the site selection task at the Department of Geosciences, University of Fribourg, Switzerland. The database is mainly composed of ECMWF and NCEP-NCAR reanalysis data at a global resolution of between 1° and 2.5° latitude / longitude. Using a Java based interface, codenamed "FriOWL", and programmed in the style of a Geographical Information System, all of this relevant information can be interrogated in order to find the best possible sites for the new telescope. Perhaps the most important variable in site selection is the interaction between air-flow and topography, as atmospheric turbulence greatly affects the image quality produced by the telescope. Global climate is changing and it will continue to do throughout the 21st century. Therefore, it is important to ascertain the effect of global warming on potential sites. An ideal site in today’s climate may not prove ideal within 20 to 50 years. It is therefore planned to update the database with future climate data, using output from global climate models. High resolution modeling of the critical parameters at preferred sites under future climates is also planned.

The ESO OWL site survey plan includes the analysis of the astronomical quality of the Atlas mountains in Morocco. In this paper we are presenting the first long time measurement of optical turbulence at Oukaimeden site. For this work we built an instrument called ADIMM for an Automated Differencial Image Motion Monitor, and we use it to the measure the optical turbulence at the Oukaimeden Site. We are describing the instrument and reporting the first results obtained after six month of working on this project. The results of night-time seeing measurements carried out during the period from Jun 14 up to October 01 2003 are presented. The median and mean values of the seeing for the entire period of observations are respectively 0.75" and 0.84". This work was organized in the framework of contract Num.69651/ODG/02/9005/GWI between the European Southern Observatory (ESO) and Astrophysics and Physics of High Energy Laboratory of the Faculty of Sciences, Cadi Ayyad University (LPHEA).

The location of the Advanced Technology Solar Telescope (ATST) is a critical factor in the overall performance of the telescope. We have developed a set of instrumentation to measure daytime seeing, sky brightness, cloud cover, water vapor, dust levels, and weather. The instruments have been located at six sites for periods of one to two years. Here we describe the sites and instrumentation, discuss the data reduction, and present some preliminary results. We demonstrate that it is possible to estimate seeing as a function of height near the ground with an array of scintillometers, and that there is a distinct qualitative difference in daytime seeing between sites with or without a nearby lake.

Climate diagnostic archives appears to be a very useful tool for astronomical site assessment. These climatological databases combine data from meteorological archives for different data sources (radiosoundings, satellites, etc) and meteorological models to derived any parameter at a particular selected location. Although the products from climate diagnostic archives are heavily constrained by observational data, a rigorous control of data quality, analysis and cross comparison needs to be performed before the method becomes extensively used for site characterisation. In this talk we present an statistical analysis of winds, an important parameter for site characterisation, using in-situ measurements (ground level and balloon data) and data derive from climate diagnostic archives. The cross-comparison of results obtained from the two set of data allow us to propose some restrictions in the use of climate diagnostic products for site characterisation.

We combined aerosol index measurements of TOMS/Nimbus-7 and Earth Probe observations with CAMC visual extinction over La Palma from 1984 to 1997, to investigate the possibility to calibrate TOMS data in terms of astronomical extinction. The results show that the correlation of the two sets of data is quite good for extinction values greater than about Av = 0.2 mag./airmass. A detailed analysis reveals that the satellite aerosol index is indeed sensitive to the desert dust, but does not show evidence of the extinction contribution of the volcanic smoke due to the Mt. Pinatubo eruption which affected astronomical observations in 1992-1993. This calibrated aerosol index is then used to investigate the number and distribution of dusty events over the astronomical site of Oukaimeden, Morocco. We find a remarkable correlation of the extinction over the two sites. Finally we study the long term variability of the extinction over the region including Oukaimeden and La Palma, and we conclude that there is some correlation with the Northern Atlantic Oscillation.

The first of the Unit telescopes of the VLT has now been in operation for 5 years. The complete array has been producing scientific results since 2001 and the VLTI has in the past few months celebrated common user status with MIDI on the Unit telescopes. With the first of four auxiliary telescope already on site and VST and VISTA in construction, Paranal observatory is rapidly reaching maturity. Combining the power of these facilities with service observing and full user support the VLT is already having a significant impact on astronomy. In this paper we review our operations and present some metrics of what we believe is success.

The Subaru Telescope has been stably operated with high image quality since common use began in December 2000. We have updated the following items in order to achieve further improvement of observation efficiency, image quality, and tracking. 1. High reflectivity of mirrors. The reflectivity of the primary mirror has been maintained, yielding 84% at 670 nm by regular CO₂ cleaning (every two to three weeks). We successfully carried out the silver coating of the Infrared secondary mirror in April 2003 without over-coating. The reflectivity has been maintained at greater 98% at 1,300 nm. 2. Image Quality. Subaru telescope delivers exceptional image quality {a median image size of 0.6 arc-second FWHM in the R-band as taken by Auto-Guider Cameras at all four foci; Prime, Cassegrain, and two Nasmyth. We optimized parameters of the servo control system of the Elevation servo, reducing the amplitude of 3{8 Hz vibration mode of the telescope and improving image quality when using the Adaptive Optics (AO) system. 3. Acquisition Guiding. Dithering time was shortened by updating the control software. The slit viewer camera for HDS and the fiber bundle for FMOS are available for acquisition guiding in addition to Auto-Guider Cameras. 4. New instruments. We are developing a new prime focus unit for FMOS and will start functional tests in 2005. Moreover, we have started to prepare new interfaces and facilities for FMOS and the new 188 element AO natural/laser guide star system. The focus switching time will be shortened by updating the hardware of the IR and Cassegrain Optical secondary mirrors from September 2004, reducing it to 10 minutes to switch the focus between Cassegrain and Nasmyth foci.

The Hobby-Eberly Telescope (HET) is a fixed-elevation, 9.2-m telescope with a spherical primary mirror and a tracker at prime focus to follow astronomical objects. The telescope was constructed for $13.9M over the period 1994-1997. A series of extensive engineering upgrades and corrective actions have been completed recently, resulting in significantly improved delivered image quality and increased operational efficiency. The telescope's Spherical Aberration Corrector (SAC) optics were recoated with a highly reflective and durable broadband coating at Lawrence Livermore National Laboratory. The software mount model that maintains optical alignment of the SAC with the 11-m primary mirror array was recalibrated and improved. The acquisition and guiding optics for both the High Resolution Spectrograph (HRS) and the Low Resolution Spectrograph (LRS) were reworked and improved, allowing for better focus and SAC alignment monitoring and control. Recoating of the primary mirror segment array was begun. Telescope images of 0.82 arcseconds have been recorded for sustained periods in preliminary testing following the engineering upgrade, an improvement of 50% over previous best performance. Additional engineering upgrades are scheduled to consolidate these performance gains and to continue improving delivered image quality, throughput, and telescope operational efficiency. The HET is now capable of the science performance for which it was designed.

Originally commissioned in 1979, the Multiple Mirror Telescope was a highly innovative and successful facility that pioneered many of the technologies that are used in the new generation of 8 to 10 m class telescopes. After 19 years of operations the MMT was decommissioned in March of 1998: the enclosure was modified, the optics support structure was replaced, and a single 6.5-meter primary mirror was installed and aluminized in-situ. First light for the new MMT was celebrated on May 13, 2000. Operations began with an f/9 optical configuration compatible with existing instruments. Work has continued commissioning two new optical configurations that will serve a suite of new instruments: an f/15 deformable secondary mirror and adaptive optics facility that has obtained diffraction-limited images; and an f/5.4 secondary mirror and refractive corrector that provides a one-degree diameter field of view. The wide-field instrument suite includes two fiber-fed bench spectrographs, a robotic fiber positioner, and a wide-field imaging camera.

The NRAO Robert C. Byrd Green Bank Telescope is a new 100 meter radio telescope that is now in routine astronomical operation. This paper gives a status report on astronomical performance, operational capabilities, development plans, and early scientific highlights. The telescope is now in regular operation to frequencies of 50 GHz, which achieves the base design goal of the facility. Both the surface and pointing accuracies allow good performance at that frequency. The active surface of 2004 movable panels is in regular use at all frequencies above ~8 GHz and significantly improves both gain and diffraction beam shape at high and low elevation angles. Receivers exist at most primary observing frequencies ranging from ~290 MHz to 50 GHz. A 256k-channel correlation spectrometer with up to 16 independent inputs is in routine use for spectroscopy. Backends for pulsar observing, broadband continuum, Very Long Baseline Interferometry, and planetary radar reception also exist. An advanced development program for enhancing the performance of the GBT is also underway. This program includes the Precision Telescope Control Project that will extend operation to 115 GHz or 2.6 mm wavelength (see the paper by Prestage and Constantikes in this volume), a 26-40 GHz receiver, a 68-92 GHz receiver, a fast sampling continuum backend built by a Caltech/NRAO collaboration, and a 64-pixel bolometer camera developed by a consortium of UPenn, NASA-GSFC, NIST, UCardiff, and NRAO. Software development projects for enhanced user interfaces and data handling are underway, and plans to implement queue-based dynamic scheduling and remote observing are being developed. The status of these projects and their anticipated scientific impact will be discussed.

Technological advances are changing the nature of VLBI. Disk based recording has already led to sustantial increases in sensitivity and with the advent of new telescopes and data acquisition systems VLBI will start penetrating the micro-Jansky sky. With the employment of fibre based communication networks as the basis for production, real-time VLBI networks will become a reality. This changes the way VLBI is done and removes bottlenecks in operation and scientific exploration. At the output side, fantastic new correlator output data rates and the ability to deal with these via powerful PC clusters promises to expand the typical VLBI field-of-view to scales previously reserved for connected, short baseline interferometers. These developments require new algorithms for user processing, as well as new interfaces to present the product to the users.

e-MERLIN is an upgrade to the MERLIN array of seven radio telescopes spread across England, which will increase its sensitivity by more than a factor or 30. The combination of μJy sensitivity with the 50-mas resolution already provided by the long baselines of MERLIN, will open new avenues of research for e-MERLIN. The huge increase in bandwidth is achieved by replacing the exiting microwave links with new optical fibre connections. To collect and correlate this wide bandwidth, new receivers, IF and sampling equipment, digital and optical transmission equipment and a new wideband correlator are being designed and constructed. This paper summarises the design goals, scientific objectives and implementation of e-MERLIN.

Progress in the conceptual design phase of ESO's OWL 100-m optical and near-infrared telescope is reported, with emphasis on the development of the science case. The Phase A opto-mechanical design is now basically completed, and provides a clean, symmetrical geometry of the pupil, with a near-circular outer edge. We also report about the latest outcome of industrial studies, introduce the essential definition of the wavefront control systems, and outline operational concepts and instruments priorities. Finally, we elaborate on the favorable cost factors associated to the telescope design, its compatibility with low industrial risks, and argue that progressive implementation allows for competitive timescales. In particular, we show that suitable fabrication and integration schemes should accommodate for a start of science operation at unequalled potential and within a time frame comparable to that of smaller designs, while at the same time maximizing R&D time for critical subsystems.

The Euro50 is an extremely large telescope for optical and infrared wavelength with a 50 m primary mirror. It has a segmented, aspherical primary mirror and an aspherical, deformable secondary in a Gregorian layout. A tentative conceptual design exists and has been documented in a study report. Recent activities have concentrated on the science case for extremely large telescopes in the 50 m class and on identification of potential technical "show stoppers". The science case investigation has identified four fields of particular interest. The studies of critical technical issues have concentrated on atmospheric dispersion effects for high-resolution adaptive optics for extremely large telescopes, and on the influence of wind and other disturbances on wavefront control. Wind load on the telescope, the primary mirror and the enclosure has been studied using wind tunnel measurements and computational fluid dynamics. The impact of wind on the total system has been investigated using an integrated model that includes the telescope structure, the primary mirror segment alignment system, the secondary mirror alignment system, and single conjugate adaptive optics using the deformable secondary mirror. The first, tentative results show that wind disturbances may be significant and that the task of correcting for wind residuals may be at least as large for the adaptive optics system as that of correcting for atmospheric aberrations. The results suggest that use of extremely large telescopes for observations of earth-like planets around nearby stars may imply a considerable challenge.

The status of activites on the future planning of the optical and infrared astronomy community of Japan is reported. The community established a working group to draw a concrete plan for ground based telescopes and space missions for the next decades. Reported in this paper are the basic concept developed for extremely large telescope. Some specific areas of related research and development, for instance optical design, new materials for segmented mirrors, new approach to fabricate aspheric segmented mirror, and other engineering activities. These might turn out to be useful for promoting the project. Japan's community is open for international collaborations in these areas.

This telescope has 30m aperture, segmented primary mirror and alt-azimuth mounting. The aspherical primary mirror with f-ratio 1.2 consists of 1122 partial annular submirrors. The optical system includes Nasmyth I and II systems, Cassegrain system, coude system and a wide field of view system. There are four Nasmyth platforms. Two Nasmyth I foci are located on the upper floor and two Nasmyth II foci are located in the lower floor. All Nasmyth I, II and Cassegrain systems use same one secondary mirror, and all are R-C systems. With adaptive optics system, several diffraction-limited observations can be operated simultaneously on Nasmyth II platforms. The wide field of view system has 20 arcmin FOV, can correct atmospheric dispersion and the low space frequency error from primary mirror and atmosphere turbulence. A special rocking chair structure is designed which can realize the horizontal axis on the front of primary mirror. The tolerances of the surface shape and position of submirrors are given. The issues about tip-tilt correction and adaptive optics are discussed. Some formulae on rotating conic surface especially used for segmented mirror are given.

The Giant Magellan Telescope (GMT) is a joint project of a consortium of universities and research institutions to build and operate a 21.5-m equivalent aperture astronomical telescope for use at visible and IR wavelengths. This paper briefly summarizes the science goals for the project and provides an overview of the preliminary telescope and enclosure concepts and site test program. The telescope is a Gregorian design with a fast, f/0.7, primary mirror that allows a compact and stiff mount structure. The 25.3-meter diameter primary mirror consists of six off-axis 8.4-meter circular mirrors arranged in a hexagon around a center 8.4-meter mirror. The Gregorian secondary mirror is adaptive allowing two-mirror, wide-field adaptive optics. Several corrector designs have been studied for wide-field applications and one such design is shown. Instruments being considered for GMT provide a wide range of scientific capabilities. Instruments mount below the primary mirror on an instrument platform. Instrument mounting and servicing provisions are summarized.

The science case for wide fields on ELTs is well developed and justifies the implementation of 20 arc-minute and larger fields-of-view with seeing-limited performance on a 20 to 30-meter telescope. However, the practical implementation of a wide field can prove to be challenging with classical telescope design when low-thermal emissivity performance is also being optimized. Segmented mirrors assemblies need not be full aperture, axially symmetric structures. Space for secondary, tertiary, and quaternary mirror support structures that do not cross the optical path can be achieved with off-axis mirror assemblies. Barden, Harmer, Claver, and Dey described a 4-mirror, 1-degree FOV 30-meter telescope. We take that concept further with an off-axis approach. Three conic mirrors are required to produce excellent image quality in the 1-degree FOV (diffraction limited across the central few arc-minutes, better than 0.3" imaging performance at the edge of the field). A flat quaternary mirror is utilized both as a beam steering mirror to different instrument ports on the lower side of the telescope and as an adaptive mirror for wind-buffeting and possible ground layer AO correction. The final f/2.2 focal ratio allows the use of an echidna-style fiber positioner for very dense target field acquisition. Extreme AO and Ground Layer AO ports can both be implemented as well. Diffraction characteristics may possibly be improved given the lack of a spider mount for the secondary mirror but will be elliptical rather than circular.

We present a design concept for a 16 metre, wide-field, fixed-axis, all-reflective, segmented f/4 Schmidt telescope to take advantage of the unique possibilities of Antarctica for both optical and near infrared astronomy. The design allows observation of all RA/dec's accessible from Antarctica, with tracking times of several hours. Prime and Cassegrain foci are provided, giving plate scales 300-3000microns/", over fields of view 1.5'-0.5°. Diffraction limited, natural guide-star AO-corrected Kdark images are possible over arc-minute sized fields, over 70% of the sky. The sensitivity, resolution, field of view and cost all compare favourably with current or proposed space or ground-based telescopes.

We have proposed to develop a prototype 0.5-meter far-infrared telescope and heterodyne receiver/spectrometer system for fully-automated remote operation at the summit of Dome A, the highest point on the Antarctic plateau. The unparalleled stability, exceptional dryness, low wind and extreme cold make Dome A a ground-based site without equal for astronomy at infrared and submillimeter wavelengths. HEAT, the High Elevation Antarctic Terahertz Telescope, will operate in the atmospheric windows between 150 and 400 microns, in which the most crucial astrophysical spectral diagnostics of the formation of galaxies, stars, planets, and life are found. At these wavelengths, HEAT will have high aperture efficiency and excellent atmospheric transmission most of the year. The proposed superheterodyne receiver system will be comprised of 0.8, 1.4 and 1.9 THz channels which will observe the pivotal J=7-6 line of CO, the J=2-1 line of atomic carbon, and the far-infrared fine structure lines of N+ and C+, the brightest emission lines in the entire Milky Way Galaxy. When combined with the HEAT telescope, the receiver system represents a uniquely powerful instrument for reconstructing the history of star formation in our Galaxy, with application to the distant Universe. The receiver system itself serves as a valuable testbed for heterodyne Terahertz components, using leading-edge mixer, local oscillator, low-noise amplifier, cryogenic, and digital signal processing technologies that will play essential roles in future Terahertz observatories. The proposed study will pave the way for future astronomical investigations from Dome A.

Wide-Field imaging at visible wavelengths with seeing of the order of 0.1-0.2arcsec is believed to be possible from the high Antarctic plateau site of Dome-C by the removal of ground layer effects only. We present a proposal for a 2m-class telescope specifically designed for the science case of short duration (~10s or greater) microlensing events in the crowded central regions of Galactic Globular Clusters and nearby galaxies where the achievement of a spatial resolution of the order of a fraction of arcsec is essential. The philosophy behind the telescope proposal is discussed in detail. It is emphasized that this is a project with a specific unique science goal in mind and not a large scale facility instrument. A preliminary design for the optics, ground layer removal using a deformable secondary and "static" wavefront sensor and telescope structure is presented. In particular, it is shown that substantial simplification in the design can be achieved by having a specific science goal in mind, so reducing the complexity and increasing reliability. Transport and logistics for the successful deployment and operation of the telescope at the Dome-C site are discussed.

A concept is presented for an extremely large high-resolution solar telescope with an aperture of 11 m and diffraction limited for visual wavelengths. The structure of GISOT will be transparent to wind and placed on a transparent stiff tower. For efficient wind flushing, all optics, including the primary mirror, will be located above the elevation axis. The aperture will be of the order of 11 m, not rotatively symmetrical, but of an elongated shape with dimensions 11 x 4 m. It consists of a central on-axis 4 m mirror with on both sides 3 pieces of 2 m mirrors. The optical layout will be kept simple to guarantee quality and minimize stray light. A Coudé room for instruments is planned below the telescope. The telescope will not be housed in a dome-like construction, which interferes with the open principle. Instead the telescope will be protected by a foldable tent construction with a diameter of the order of 30 m, which doesn’t form any obstruction during observations, but can withstand the severe weather circumstances on mountain sites. Because of the nature of the solar scene, extremely high resolution in only one dimension is sufficient to solve many exciting problems in solar physics and in this respect the concept of GISOT is very promising.

Previously the effect of atmospheric dispersion on telescope performance has attracted only relatively little attention. This may be due to the fact that the dispersion effects have been evaluated in relation to the size of the diffraction limited resolution angle of current telescopes, or to seeing limited telescopes. However, since the resolution angle is inversely proportional to telescope diameter, dispersion and dispersion compensation becomes increasingly important for extremely large telescopes (ELTs). In this paper we present a simple model for the dispersion effects in telescopes with adaptive optics (AO). The model addresses the expected loss in Strehl ratio when the atmospheric wavefront error is measured at a wavelength different from the wavelength of observation. Also, the bandwidth over which the correction will be of a given quality is evaluated. Related to AO performance, the consequence of using laser guide stars (LGSs) for probing the atmosphere may be that the measured wavefront error must be rescaled to the wavelength of observation. This places special demands on the AO control loop. Since linear atmospheric dispersion compensation need not cover a larger bandwidth than the AO compensation, an atmospheric dispersion compensator (ADC) can be designed for narrow band operation. As an example of the benefits to be obtained from this, we briefly present the proposed ADC for the Euro50.

During last decade, several concepts for the next generation of telescopes have evolved into well-established projects. The majority of the proposed concepts are Extremely Large Telescopes (ELTs) utilizing the advantages of having an AO system as an integrated part of the main optical system. An adaptive secondary mirror (AS) has become a typical prerequisite for the future ground-based optical telescopes. Recent advances in deformable mirror technology used for AS mirrors show a possibility of developing this technology to the mirrors of larger diameters suitable for integration into ELT main optical systems. An idea of fully adaptive telescope has been proposed for the Arcetri 40-m multi-conjugate telescope. A four-mirror optical system with a 40 m parabolic segmented primary is considered and optimised for such an advanced ELT. It is shown that the proposed system geometry enables to obtain proper optical conjugation for the tertiary and quaternary mirrors, achieving a diffraction limited image quality over 8-arcmin field. The aspects of internal vignetting and re-imaging of laser guide stars are discussed. If the fabrication of adaptive mirrors of a large size is feasible, the proposed four-mirror system will become highly attractive in terms of system compactness and minimized number of mirrors employed in the ELT multi-conjugate AO system.

Presently the ground-based High Energy Stereoscopic System (H.E.S.S.) with 12 m Cherenkov telescopes is used for very high energy gamma ray astronomy. With these telescopes the Cherenkov light which is generated when cosmic gamma rays are absorbed by the atmosphere is collected by the mirror dishes of these optical telescopes and recorded by digital cameras for further examination. This existing H.E.S.S. Phase I system in Namibia erected and operated by the Max-Planck-Institut fur Kernphysik in Heidelberg, Germany, uses four 12 m telescopes arranged in the corners of a 120 m square for best sensitivity. The next step in order to increase the exploitation of the gamma rays in the atmosphere is to use bigger Cherenkov telescopes with a lower threshold and improved sensitivity. In this paper the results of a feasibility study on the design of Large Cherenkov Telescopes with diameters of up to 30 m are presented. The feasibility investigations done by MAN Technologie in Mainz, Germany had to take into account the required mechanical performance, costs, and local fabrication and erection capabilities of the countries in which the telescopes should be erected.

Aperture plane detection of cosmic radio signals can confer several important advantages. The mechanical signal processing of conventional parabolic dish antennas can be replaced by signal processing purely in electronics and software, thereby placing aperture plane array instruments in a regime with decreasing future costs. Aperture arrays using all-sky element antennas also allow multiple, independent, full sensitivity telescopes to be formed in software. The Low Frequency Array (LOFAR) project aims to realize these advantages in a previously largely unexplored frequency domain, 10-240 MHz. Consisting of up to eight shared aperture telescopes operated independently over internet, it will explore the epoch of re-ionization, open the transient radio Universe to systematic study, record ultra-high energy cosmic particles and add a new dimension to solar and space physics research.

The GTC (Gran Telescopio Canarias) is a 10,4 meter segmented telescope currently being integrated at the ORM in La Palma, Spain. It is a partnership between Spain, Mexico and the University of Florida. Main science drivers for the GTC are image quality, operational efficiency and reliability. First light is planned for mid-2005. The GTC Project, initiated in 1996, is well advanced in its integration. Construction started in October 1999. The main building and dome were finished by end 2002 and are now enclosing the assembly work of the telescope structure. All telescope subsystems are finished and in La Palma where the telescope structure keeps growing. The segments of the primary mirror, probably one of the most demanding part of the GTC, have also started to be delivered by the polisher. Three science instruments are starting their integration and are expected to arrive at the telescope well on time. Two second-generation instruments, including one exploiting the future Adaptive Optics capabilities of the GTC, are under development. Preparation for operation and maintenance has started to ensure a smooth transition from construction into the operation phase. The current status of the project and the short term plans are presented here.

The Southern African Large Telescope (SALT) is a 10-m class telescope for optical/infrared astronomy based on the tilted Arecibo design first adopted by the Hobby Eberly Telescope. SALT is being constructed by a consortium consisting of 11 partners from six countries. SALT will enable a quantum leap in astronomical research capability in the African continent, where currently the largest telescope is a modest 1.9-m, dating to the 1940s. The SALT Project was approved in November 1999, the SALT project team started in January 2000, groundbreaking followed in September, the first mirror segment was installed in December 2002, and On-Sky Testing started in October 2003. SALT is due to start operations by 2005. The commissioning instrument has been developed by the South African Astronomical Observatory and the other first-light instrument is being developed by the University of Wisconsin-Madison. The major technical challenges in SALT are the alignment of the 91 identical spherical mirror segments, the position feedback of the prime focus tracker, and the dome seeing associated with large enclosures at a site with large daily thermal cycles. All of these issues were addressed thoroughly during the design phase, and first tests are showing very positive results in all these areas. This paper will summarize the international partnership in SALT and the management and organisation of the project and then address (1) the basic design, with emphasis on the technical challenges (2) the specified performance of SALT, (3) the progress and status of the project, including first light instruments.

The Large Binocular Telescope (LBT) Project is a collaboration between institutions in Arizona, Germany, Italy, and Ohio. The telescope 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 gives the telescope the diffraction-limited resolution of a 22.65-meter telescope. The first of two 8.4-meter borosilicate honeycomb primary mirrors has been installed in the telescope on Mt. Graham in southeastern Arizona. First Light is planned for later this year with one primary mirror and a prime focus imager. The second of the two primaries is being polished at the Steward Observatory Mirror Lab in Tucson and will be installed in the telescope in the Fall of 2005. The telescope uses two F/15 adaptive secondaries to correct atmospheric turbulence.

Development of the 4.1 meter SOuthern Astrophysical Research (SOAR) Telescope is now complete. All baseline systems are in place and extensive commissioning activities have been performed with and without the primary optics installed in the telescope. The facility and dome have been under observatory operations and TCS control for a year of testing and tuning. The altitude over azimuth telescope mount was integrated on the mountain in a rapid 3-month period due to the complete assembly and testing performed at the factory prior to delivery. Early mount testing and successful integration into the Telescope Control System (TCS) without the optical system was accomplished on the sky through use of two separate small aperture telescopes fixed to the structure. One of these, the "feed telescope" was also pivotal in early testing of the calibration wavefront sensor and SOAR optical imager by directing focused light to these separate instruments. The SOAR optical system, with its 4.1 meter clear aperture, 100 cm thick, ULEtm primary mirror, its lightweight ULEtm secondary, and its fast tip tilt ULEtm tertiary has been delivered and installed in the telescope. This system was also assembled as an electrically connected system and individually optically tested under a visible interferometer at the factory enabling rapid integration and a short commissioning period on telescope. In this paper we present the project status, a summary of the commissioning period, and the performance data for the completed telescope and its major components.

The Advance Technology Solar Telescope (ATST) has finished its conceptual design stage, submitted a proposal for construction funding and is working towards a system level preliminary design review later this year. The current concept (including integrated adaptive optics and instrumentation) will be reviewed with concentration on solutions to the unique engineering challenges for a four meter solar telescope that have been previously presented. The overall status will be given with a concentration on near term milestones and impact on final completion targeted in 2012.

The Visible and Infrared Survey Telescope for Astronomy (VISTA) project started in 2000 following a Joint Infrastructure Fund award to a consortium of 18 Universities within the UK. The UK ATC was contracted to manage the project of developing and building the VISTA facility. VISTA is planned to be a 4-m class telescope with the ability to mount both a visible and infra-red cameras, not concurrently. The design has an F/1 primary resulting in some demanding design issues. The project has now entered its detailed design and manufacturing phase. As we have contracted out major items a coordinated approach to the management of budgets, through systems engineering, risks, through risk management, and safety, through the generation of safety cases, had to be generated. These have been developed through the current phase, and control of the interfaces and science requirements has been maintained. The project is further developing the systems engineering and safety management to generate the commissioning plan and the overall safety case. The plan to deliver an effective and safe survey facility to ESO is being maintained.

The United States Air Force Academy in Colorado Springs has obtained a 4m-diameter, lightweight telescope from the Space Based Laser project. Originally designed and constructed for space, this segmented telescope is being reconfigured for use as a ground-based facility - the largest in the world, wholly owned by any single college. The telescope comes fully equipped with both active and adaptive capabilities for segment phasing and wavefront correction. However, the optical design is a Mersenne configuration, and having been constructed for a space environment, it has an extremely thin (17mm) glass primary. We are redesigning the optics (with new secondary and tertiary mirrors) and are designing a mount and truss capable of both sidereal and low-Earth satellite tracking.

Lowell Observatory has initiated the development of a four meter class optical telescope with significant capabilities for solar system and broad spectrum astronomical research. Key to the Discovery Channel Telescope (DCT) is the ability to rapidly switch between 2 degree FOV imaging via a prime focus camera to 30 arc min FOV instrumentation at Ritchey-Chretien (RC) focus. The telescope is to be constructed at approximately 7700 feet altitude, Southeast of Flagstaff, Arizona at a site which has exhibited 0.6 arc sec best quartile seeing. The telescope will feature active optics and alignment capability and the Prime Focus Instrument will feature a Mosaic Focal Plane array of 40 2k x 4k CCDs. The RC instrument payload will be approximately 5000 lbs, allowing either large instruments or suites of co-mounted instruments. This telescope is being developed in partnership with Discovery Communications, Inc. (DCI), who will utilize the DCT and the association with Lowell Observatory to develop educational programming about astronomy and technology. The telescope will be a substantial enhancement to the current capabilities of Lowell Observatory.

Pan-STARRS, the Panoramic Survey Telescope and Rapid Response System, is a project to first develop a single wide field synoptic survey telescope (Pan-STARRS-1) followed by a system of four such telescopes. It is designed to accomplish many of the science goals envisioned by the decadal review for LSST. The primary mission of Pan-STARRS is the detection of potentially hazardous asteroids (PHA), secondary science objectives are a (nearly) all-sky survey, a medium-deep survey, an ultra-deep survey, and studies of transients and variable objects. This paper presents the current status of the telescope design, with emphasis on the optics.

The Liverpool Telescope is a 2.0 metre robotic telescope that is operating unattended at the Observatorio del Roque de Los Muchachos, Spain. This paper gives an overview of the design and implementation of the telescope and its instrumentation and presents a snapshot of the current performance during the commissioning process. Science observations are under way, and we give brief highlights from a number of programmes that have been enabled by the robotic nature of the telescope.

GREGOR is the new 1.5 m solar telescope assembled on Tenerife, Spain, by the German consortium of the Kiepenheuer Institut fur Sonnenphysik, the Astronomischen Institut Potsdam, the Universitats-Sternwarte Gottingen and other national and international Partners. The refurbishment of the building is almost finished. The manufacturing of the telescope structure and the optics is still in progress. After the integration of the new complete retractable dome in July 2004 the telescope structure, optic and post focus instruments will be assembled during the rest of the year. First light is planned during May 2005.

The 8.4m Large Synoptic Survey Telescope (LSST) is a wide-field telescope facility that will add a qualitatively new capability in astronomy. For the first time, the LSST will provide time-lapse digital imaging of faint astronomical objects across the entire sky. The LSST has been identified as a national scientific priority by diverse national panels, including multiple National Academy of Sciences committees. This judgment is based upon the LSST's ability to address some of the most pressing open questions in astronomy and fundamental physics, while driving advances in data-intensive science and computing. The LSST will provide unprecedented 3-dimensional maps of the mass distribution in the Universe, in addition to the traditional images of luminous stars and galaxies. These mass maps can be used to better understand the nature of the newly discovered and utterly mysterious Dark Energy that is driving the accelerating expansion of the Universe. The LSST will also provide a comprehensive census of our solar system, including potentially hazardous asteroids as small as 100 meters in size. The LSST facility consists of three major subsystems: 1) the telescope, 2) the camera and 3) the data processing system. The baseline design for the LSST telescope is a 8.4m 3-mirror design with a 3.5 degree field of view resulting in an A-Omega product (etendue) of 302deg²m². The camera consists of 3-element transmisive corrector producing a 64cm diameter flat focal plane. This focal plane will be populated with roughly 3 billion 10μm pixels. The data processing system will include pipelines to monitor and assess the data quality, detect and classify transient events, and establish a large searchable object database. We report on the status of the designs for these three major LSST subsystems along with the overall project structure and management.

This paper reports a recently started project for a 2-m diameter robotic telescope dedicated to astronomy and education. After a brief recall of SAGAM-REOSC background in this domain, the project will be presented with more details on the telescope optics, mount and control system, the dome, the coating chamber and the weather station.

EOS Technologies has completed four 1.8m telescopes that are to be used in the NASA/JPL Interferometer. The 1.8m telescopes (Outriggers) will form the workhorse of the interferometric system. This paper presents some of the performance data obtained during the Telescope Factory Acceptance Tests showing some of the best telescope performance ever achieved with a telescope of this class.

SUNRISE is a balloon-borne solar telescope with an aperture of 1m, working in the UV/VIS optical domain. The main scientific goal of SUNRISE is to understand the structure and dynamics of the magnetic field in the atmosphere of the Sun. SUNRISE will provide diffraction-limited images of the photosphere and chromosphere with an unpredecented resolution down to 35km at wavelengths around 220nm. Focal-plane instruments are a spectrograph/polarimeter, a Fabry-Perot filter magnetograph, and a filter imager. The first stratospheric long-duration balloon flight of SUNRISE over Antarctica is planned in winter 2006/2007. SUNRISE is a joint project of the Max-Planck-Institut fur Sonnensystemforschung (MPS), Katlenburg-Lindau, with the Kiepenheuer-Institut für Sonnenphysik (KIS), Freiburg, the High-Altitude Observatory (HAO), Boulder, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, and the Instituto de Astrofisica de Canarias, La Laguna, Tenerife. In this paper we will present an overview on the mission and give a description of the instrumentation, now, at the beginning of the hardware construction phase.

The Antarctica Plateau has recently turned out to be the best place on the Earth to perform astronomical infrared observations in the 2-20 um atmospheric windows and beyond, thanks to the extremely low sky background emission, the excellent atmospheric transparency and stability, the virtual absence of winds and the possibility of passively cooling the telescope and its focal plane instruments down to very low temperatures. Dome C, a site jointly exploited by Italian and French scientific teams in the framework of the Concordia project, lays on the Antarctica Plateau at an altitude of 3200m and presents exceptionally cold and dry climatic conditions. In this paper we shall describe the scientific motivations and the technical details of the infrared telescope IRAIT that we plan to put at Dome C starting from in 2005-2006. The IRAIT telescope is an alt-azimuth f/20 reflector, with a 0.8m parabolic primary mirror and a wobbling secondary mirror suitable for the specific techniques of IR observations. It will be equipped with a Near/Mid IR-camera built in Italy .

We present a summary of the Large Millimeter Telescope Project and its present status. The Large Millimeter Telescope (LMT) is a joint project of the University of Massachusetts (UMass) in the USA and the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) in Mexico to build a 50m-diameter millimeter-wave telescope. The LMT is being built at an altitude of 4600 m atop Volcan Sierra Negra, an extinct volcanic peak in the state of Puebla, Mexico, approximately 100 km east of the city of Puebla. Construction of the antenna is now well underway. The basic structure with a limited number of surface panels is expected to be completed in 2005. Engineering acceptance and telescope commissioning are expected to be completed in 2007.

ASTE (Atacama Submillimeter Telescope Experiment) is a project to install and operate a 10-m submillimeter telescope in the high altitude site (4,800 m) in Atacama desert, northern Chile. The project is aimed to explore the southern sky with submillimeter waves as well as to develop and evaluate various instruments and observing techniques. The telescope was shipped and re-assembled in Chilean site in early 2002, including the establishment of the on site infrastructure. Following evaluation of the telescope and receivers, scientific observations such as supernova remnants, galaxies, star forming regions and proto-planetary nebulae, have been carried out since early 2003. The high-precision 10-m antenna was measured to have the surface accuracy of 18.9 mm and the relative pointing accuracy was 1.2" r.m.s. for both azimuth and elevation. The subreflector is equipped with wobbling capability. Several types of receivers have been on board the telescope; the heterodyne-receivers operating at 100, 230, 345, 500 and 800 GHz bands including cartridge-type receivers, as well as a bolometer system covering 350, 650 and 850 GHz. The spectrometer is equipped with an XF type digital auto-correlator with four channels each covering up to 512 MHz with 1024 bins, which leads to 2 GHz coverage. The control system is designed to be capable of remote control from several sites via network connection, from the base facility at San Pedro de Atacama (2,400 m altitude) or even from Japan.

This contribution gives a description of the Sardinia Radio Telescope (SRT), a new general purpose, fully steerable antenna proposed by the Institute of Radio Astronomy (IRA) of the National Institute for Astrophysics. The radio telescope is under construction near Cagliari (Sardinia) and it will join the two existing antennas of Medicina (Bologna) and Noto (Siracusa) both operated by the IRA. With its large antenna size (64m diameter) and its active surface, SRT, capable of operations up to about 100GHz, will contribute significantly to VLBI networks and will represent a powerful single-dish radio telescope for many science fields. The radio telescope has a Gregorian optical configuration with a supplementary beam-waveguide (BWG), which provides additional focal points. The Gregorian surfaces are shaped to minimize the spill-over and the standing wave between secondary mirror and feed. After the start of the contract for the radio telescope structural and mechanical fabrication in 2003, in the present year the foundation construction will be completed. The schedule foresees the radio telescope inauguration in late 2006.

The Expanded Very Large Array project has the top-level goal of enhancing the performance of the Very Large Array by an order of magnitude or more in all areas: sensitivity, frequency coverge, spectral resolution, and spatial resolution. The project is being implemented in two, overlapping phases: Phase I, which began in 2000 and will finish by 2012 addresses all new capabilities except spatial resolution, and Phase II, which will improve tenfold the spatial resolution, and which is planned to begin in 2006, and finish by 2013. Progress in Phase I is very good, with first light and first fringes having been achieved, and tests of the new hardware and software now underway. A proposal for funding Phase II has now been delivered to the National Science Foundation. A critical component of the project is the new correlator, being designed and built by the Canadian Herzberg Institute of Astrophysics at the DRAO in Penticton, BC Canada. This new advanced correlator will be delivered beginning in late 2008. First shared-risk science with the early portions of the correlator will be done in late 2007.

The Discovery Channel Telescope (DCT) is a joint venture between Discovery Communications and Lowell Observatory. The telescope will have a 4.2-meter clear aperture, active primary mirror working at F/1.9. Two observing stations are presently planned; a Ritchey-Chretien focus some two meters behind the vertex of the primary mirror and a prime focus featuring a wide-field optical corrector (WFOC) with a two-degree field of view. The Ritchey-Chretien focus will be used for a variety of optical and near infrared imaging and spectroscopic instrumentation while the prime focus will be largely used as a survey tool to search for near-earth and Kuiper belt objects, for example. In order to take advantage of sub-arc second seeing at the DCT site, a stringent set of requirements has been placed on the two foci. The requirements are for the full-width, half-maximum (FWHM) image of a point source to be less than 0.20 arc second at the Ritchey-Chretien focus over a 21 arc minute field and less than 0.27 arc second at prime focus in each of six filter bands including a very broad band for survey purposes. This paper describes the optical design of the field correctors at the two foci. Particular attention is paid to the WFOC. This state of the art device poses a number of optical challenges which are discussed here, as well as mechanical challenges which are discussed elsewhere.

The Stratospheric Observatory For Infrared Astronomy (SOFIA) houses a 2.5-m infrared telescope in a Boeing 747SP aircraft. It will be operated at high altitudes above the atmospheric water vapor. The telescope is of Cassegrain type in a so-called Nasmyth configuration with a VIS and an IR focus. The 2.7-m primary mirror is a monolithic element of Zerodur with a milled honeycomb structure on the backside. Despite of its size, it has a high stiffness (approx. 160 Hz 1st natural frequency) and a mass of approx. 885 kg only. The mirror support structure is a lightweight structure made from CFRP panels and profiles, bonded and riveted together with metallic inserts and joints. The mirror mounting by dedicated flexures provides a very stiff but nevertheless isostatic mounting of the mirror in the support structure (first natural frequency around 70 Hz). The secondary mirror is made from SiC with a very high 1st natural frequency of approx. 2 kHz allowing noise-suppressing chopper operation without image distortions. The tertiary mirror assembly is implemented as a dichroic beam splitter providing the IR Nasmyth focus for the scientific instruments and as a fully reflective mirror providing the VIS Nasmyth focus for tracking purposes. The paper describes the optical system with its subassemblies, their tested as-built performance as well as the predicted extrapolated overall image performance. The integration of the primary mirror assembly into the aircraft will be shown. The further integration and alignment steps, planned for summer 2004, will be explained.

The Allen Telescope Array, originally called the One Hectare Telescope (1hT) [1] will be a large array radio telescope whose novel characteristics will be a wide field of view (3.5 deg-GHz HPBW), continuous frequency coverage of 0.5 - 11 GHz, four dual-linear polarization output bands of 100 MHz each, four beams in each band, two 100 MHz spectral correlators for two of the bands, and hardware for RFI mitigation built in. Its scientific motivation is for deep SETI searches and, at the same time, a variety of other radio astronomy projects, including transient (e.g. pulsar) studies, HI mapping of the Milky Way and nearby galaxies, Zeeman studies of the galactic magnetic field in a number of transitions, mapping of long chain molecules in molecular clouds, mapping of the decrement in the cosmic background radiation toward galaxy clusters, and observation of HI absorption toward quasars at redshifts up to z=2. The array is planned for 350 6.1-meter dishes giving a physical collecting area of about 10,000 square meters. The large number of components reduces the price with economies of scale. The front end receiver is a single cryogenically cooled MIMIC Low Noise Amplifier covering the whole band. The feed is a wide-band log periodic feed of novel design, and the reflector system is an offset Gregorian for minimum sidelobes and spillover. All preliminary and critical design reviews have been completed. Three complete antennas with feeds and receivers are under test, and an array of 33 antennas is under construction at the Hat Creek Radio Observatory for the end of 2004. The present plan is to have a total of about 200 antennas completed by the summer of 2006 and the balance of the array finished before the end of the decade.

The NRAO Robert C. Byrd Green Bank Telescope (GBT) is a 100m diameter advanced single dish radio telescope designed for a wide range of astronomical projects with special emphasis on precision imaging. Open-loop adjustments of the active surface, and real-time corrections to pointing and focus on the basis of structural temperatures already allow observations at frequencies up to 50GHz. Our ultimate goal is to extend the observing frequency limit up to 115GHz; this will require a two dimensional tracking error better than 1.3", and an rms surface accuracy better than 210μm. The Precision Telescope Control System project has two main components. One aspect is the continued deployment of appropriate metrology systems, including temperature sensors, inclinometers, laser rangefinders and other devices. An improved control system architecture will harness this measurement capability with the existing servo systems, to deliver the precision operation required. The second aspect is the execution of a series of experiments to identify, understand and correct the residual pointing and surface accuracy errors. These can have multiple causes, many of which depend on variable environmental conditions. A particularly novel approach is to solve simultaneously for gravitational, thermal and wind effects in the development of the telescope pointing and focus tracking models. Our precision temperature sensor system has already allowed us to compensate for thermal gradients in the antenna, which were previously responsible for the largest "non-repeatable" pointing and focus tracking errors. We are currently targetting the effects of wind as the next, currently uncompensated, source of error.

Shack-Hartmann wavefront sensors have been commissioned and are now in routine use at both of the optical foci (f/9 and f/5) of the converted MMT. Both units are of moderate resolution with 14x14 square apertures across the pupil for f/5 and 13x13 hexagonal apertures for f/9. They share a common software interface that fits a set of 19 Zernike polynomials to the wavefront errors. Zernike focus and coma are corrected by moving the secondary mirror, third order spherical by a combination of secondary motion and primary bending, and the rest by primary bending alone. In this paper we will describe the two wavefront sensor systems and how they have performed thus far.

This paper describes the design and summarizes the performance of the recently completed SOAR telescope Active Optical System (AOS). This system is unique in that it uses a thin, solid 4.3-meter diameter ULE lightweight meniscus primary mirror only 100 mm thick. The figure of the primary mirror surface is controlled with 120 electro-mechanical actuators that are force feedback controlled. The telescope is calibrated against the sky using a calibration wave-front sensor; as this calibration progresses, feedback forces, initially set from finite element analysis predictions, are replaced with sky database look-up tables. The system also includes a 0.6-meter diameter secondary mirror articulated by a hexapod for real-time optical alignment of the telescope, a 0.6-meter class tertiary mirror that also works as a 50 Hz tip tilt corrector to compensate for atmospheric turbulence and a rotary turret mechanism for directing the light to either of two nasmyth or three-bent cassegrain instrument ports. An operation control system interfaces with the telescope control system and each of the hardware assemblies. The paper provides an overview of the design of each assembly as well as summarizes results of performance testing the system.

Dispersed Fringe Sensing (DFS) is an efficient and robust method for coarse phasing of segmented primary mirrors (from a quarter of a wavelength up to the depth of focus of a single segment, typically several tens of microns). Unlike phasing techniques currently used for ground-based segmented telescopes, DFS does not require the use of edge sensors to sense changes in the relative heights of adjacent segments; this makes it particularly well-suited to the phasing of space-borne segmented telescopes, such as the James Webb Space Telescope (JWST). In this work we validate DFS by using it to measure the pistons of the segments of one of the Keck telescopes; the results agree with those of the Shack-Hartmann based phasing scheme currently in use at Keck to within 2% over a range of initial piston errors of ±16 μm.

The ALMA telescope will be an interferometer of 64 antennas, which will be situated in the Atacama desert in Chile. Each antenna will have receivers that cover the frequencies 30 GHz to 970 GHZ. This frequency range is divided into 10 frequency bands. All of these receiver bands are fitted on a cartridge and cooled, with bands 1 and 2 at 15K and the other 8 are SIS receivers at a temperature of 4K. Each band has a dual polarization receiver. The optics has been designed so that the maximum of the optics is cooled to minimize the noise temperature increase to the receivers. The design of the optics will be shown for each frequency bands. Test results with the method of testing on a near field amplitude and phase measurement system will be given for the first 4 frequency bands to be used, which are bands 3 (84-116 GHz), 6 (211-275GHz), 7 (275-375 GHz and 9 (600-702 GHz). These measurements will be compared with physical optics calculations.

The National Astronomical Observatory of Japan has constructed a prototype 12-m antenna of the Atacama Compact Array to evaluate its performance at the ALMA Test Facility in the NRAO VLA observatory in New Mexico, the United States. The antenna has a CFRP tube backup structure (BUS) with CFRP boards to support 205 machined Aluminum surface panels. Their accuracies were measured to be 5.9 m rms on average. A chemical treatment technique of the surface panels has successfully applied to scatter the solar radiation, which resulted in a subreflector temperature increase of about 25 degrees relative to ambient temperature during direct solar observations. Holography measurements and panel adjustments led to a final surface accuracy of 20 m rms, (weighted by 12dB edge taper), after three rounds of the panel adjustments. Based on a long term temperature monitoring of the BUS and thermal deformation FEM calculation, the BUS thermal deformation was estimated to be less than 3.1 m rms. We have employed gear drive mechanism both for a fast position switching capability and for smooth drive at low velocities. Servo errors measured with angle encoders were found to be less than 0.1 arcseconds rms at rotational velocities below 0.1 degrees s-1 and to increase to 0.7 arcseconds rms at the maximum speed of the 'on-the-fly' scan as a single dish, 0.5 deg s-1 induced by the irregularity of individual gear tooth profiles. Simultaneous measurements of the antenna motion with the angle encoders and seismic accelerometers mounted at the primary reflector mirror edges and at the subreflector showed the same amplitude and phase of oscillation, indicating that they are rigid, suggesting that it is possible to estimate where the antenna is actually pointing from the encoder readout. Continuous tracking measurements of Polaris during day and night have revealed a large pointing drift due to thermal distortion of the yoke structure. We have applied retrospective thermal corrections to tracking data for two hours, with a preliminary thermal deformation model of the yoke, and have found the tracking accuracy improved to be 0.1 - 0.3 arcseconds rms for a 15-munites period. The whole sky absolute pointing error under no wind and during night was measured to be 1.17 arcseconds rms. We need to make both an elaborated modeling of thermal deformation of the structure and systematic searches for significant correlation among pointing errors and metrology sensor outputs to achieve the stable tracking performance requested by ALMA.

There are a number of millimeter wave antenna projects being formulated and in later planning stages. DSN, ALMA, SKA are three examples. Each is critically dependant, in part, on economical, precise, thermally stable antenna assemblies. This paper describes the incorporation of apparently diverse technologies, that when assembled judiciously, produce a near optimum solution to this problem. Involved are new forms of composite materials, the application of special coatings, derived from outside of the aerospace industry, fabrication techniques, also drawn from commercial industry but occasionally applied in aerospace, and an aggressive, economy-driven design philosophy. A description of a novel reflector design that is being developed for the JPL DSN Antenna Array Project is presented. The design is low cost, producible, and meets the performance specification of the DSN program with application to numerous other millimeter wave antennas. The most significant performance requirements for DSN are as manufactured and operational surface accuracy (thermal stability) for a 12-meter aperture antenna operating at Ka band. The design is particularly specific to a unique manufacturing process that is the assemblage of materials, material form, and processing technologies. Also presented are related subscale articles that have been produced to demonstrate the technology and RF performance.

The surveying speed of large reflectors can be increased by one or two orders of magnitude when the focal fields are sampled with a dense phased array. In a dense array consisting of a large number of antenna elements (100 up to 1000), multiple beams can be synthesised and steered electronically. This collecting and manipulating of the entire electric field in the focal plane creates the possibility of a simultaneously improvement in the efficiency of existing telescopes and open up wide fields-of-view. This paper will describe the first results of the EU project FARADAY. The approach chosen in FARADAY is to use a Vivaldi array of 72 antenna elements configured in 8x9 grid. The analogue beamformer, integrated with the antenna array, syntheses beams by using for example 3x3 elements combined in three rings, where each ring is given a specific weight factor. The number of beams has been limited to two in this demonstrator project. Further more we will explore the possibilities and limitations of the large-scale use of Focal Plane Array's, in particular for the fourteen 25-meter reflectors of the Westerbork Syntheses Radio Telescope (WSRT).

We look at anticipated science results achievable with QUaD, a ground-based experiment to measure the polarization of the CMB from the South Pole, and describe the features that will enable it to measure this weak polarized signal. We show that QUaD can make a high resolution measurement of the polarization signals on small angular scales. This will lead to tighter constraints on the key cosmological parameters and could also put new limits on the inflationary model.

The formation, shaping and evolution of galaxies are processes of high interest but poorly known. This is true also for our closest galactic neighbours. Of key importance is a representative sample of all major types of galaxies with solid evolutionary parameters. Stellar clusters are excellent probes of galactic evolution, albeit so far useful at smaller distances only, mainly due to the limiting effects of image crowding. With Extremely Large Telescopes (ELTs) with full adaptive optics (AO) and near diffraction limited performance, the effects of image crowding will be drastically reduced. Thus, the excellence of clusters of stars as evolutionary probes can be extended out to cosmological distances. We have studied this extension. With data on the Strömgren uvby system, based on direct measurements taken from the literature, we synthesised an open test cluster as well as a galactic background field. The cluster was embedded in the background and located at distances between one and 500 Mpc. y and b data were measured with a 50 m ELT, reduced and analysed, out to 20 Mpc for individual cluster members and between 10 and 500 Mpc for the properties of the integrated cluster. Based on individual stellar data, colour-magnitude diagrams (CMDs) and luminosity functions (LFs) were constructed and studied for age parameters. For the integral cluster data, we studied the cluster colour index (b-y). We conclude that with a 50 m AO ELT, turn-off point (TOP) determination in CMDs provide ages of excellent quality out to 8 Mpc, of high quality out to 16 Mpc and of reasonable quality to 20 Mpc. At this distance level, the luminosity function provides good support. The integral colour, (b-y), as an age parameter for the clusters, can be determined with high precision out to at least 300 Mpc and with somewhat reduced accuracy to 500 Mpc. Thus, using a 50 m ELT and observing stellar clusters, we can study evolutionary parameters of galaxies out to 20 Mpc and obtain age parameters out to around 500 Mpc from the Sun.

The Infrared Radiometer for Millimetre wavelength Astronomy (IRMA) is a compact, light weight, low cost, low maintainance water vapour monitor, with an accuracy that enables it to be used to correct the phase distortions caused by atmospheric water vapour in millimetre wavelength interferometers. The IRMA III prototype is a major improvement on earlier versions of IRMA, with an emphasis on simplicity and reliability. We present results of tests conducted on the Smithsonian Millimeter Array (SMA) telescope on Mauna Kea in February 2004. The test campaign involved using three IRMA III devices with the SMA to provide phase correction information for improving the quality of the astronomical interferometric data.

The Thirty Meter Telescope (TMT) site testing team are developing a suite of instruments to measure the atmospheric and optical characteristics of candidate TMT sites. Identical sets of robotically operating instruments will be placed at each candidate site. The fully developed system will comprise of a combined MASS/DIMM. a SODAR, tower mounted thermal probes and a portable DIMM. These instruments have overlapping altitude coverage and provide a measure of the C²_n profile from the ground up with sufficient resolution to make conclusions about the ground layer and high altitude turbulence characteristics. The overlapping altitude coverage is essential to ensure consistency between these very different instruments. In addition to checking for consistency in the overlap regions, procedures are being used to cross check between instruments, i.e. the calculation of the isoplanatic angle from both the MASS and DIMM and that the integrals of the C²_n profiles from the MASS, SODAR and 30m tower gives the same r₀ value as measured by the DIMM. We discuss a variation of the traditional DIMM system in which we employ a continuous drift mode readout technique giving a maximum of nearly 300 samples per second. Findings of our major equipment testing campaigns and first field deployment are presented that demonstrate our progress in developing a rigorous approach to site testing.

In the United States an Environmental Impact Statement can easily take two years and cost more than one million dollars. This paper summarizes the experience gained from carrying out the Environmental Impact Statement of the Magdalena Ridge Observatory. Methods are given to avoid difficulties and manage time, cost, and communication for a successful conclusion.

To properly characterize the atmospheric properties of a site for a future large telescope or interferometer, it is insufficient to measure quantities, such as the full-width at half-maximum of a stellar image, that have been integrated over the entire atmosphere. A knowledge of the turbulence distribution as a function of height is necessary, since this affects the ease and degree to which adaptive optics systems can improve the telescope’s resolution. Furthermore, some astronomical measurements, such as narrow-field differential astrometry at microarcsecond precision, depend critically on the amount of turbulence high in the atmosphere (up to 20km). In order to obtain the necessary site-testing data at remote sites such as those on the Antarctic plateau, we have designed a robust and reliable instrument based on an 85 mm refractive telescope, a gimbal-mounted sidereostat mirror, and a Multi-Aperture Scintillation Sensor (MASS). The instrument uses the spatial structure of single-star scintillation to measure vertical turbulence profiles from 0.5 to 20km. The MASS system is designed to operate completely autonomously throughout the Antarctic winter. It also has potential applications at existing observatory sites for quantifying the turbulence characteristics of the atmosphere in real-time.

Ionospheric phase errors degrade high-resolution radio images below 100 MHz, and they differ significantly from the tropospheric errors which dominate at high frequencies. The ionosphere is so high (~400 km) and the VLA primary beam is so wide (~0.2 rad) that the intersection of the beam with the ionospheric screen is larger than the "isoplanatic patch" size, a phase coherent region on the sky. Antenna-based calibration techniques developed at higher frequencies cannot be used because ionospheric phase errors vary significantly across the field-of-view of each antenna. This paper describes the "field-based calibration" technique adopted for the 74 MHz VLA Low--frequency Sky Survey (VLSS) being made with the 10 km "B" configuration. This technique is useful for a range of array sizes but fails on baselines longer than the linear size of the isoplanatic patch, a few 10s of km at 74 MHz. Implications for designing larger low-frequency arrays are discussed.

Here we analyse 168 optical turbulence profiles made at nine different locations worldwide by means of free flight balloons equipped with instrumentation. Optical turbulence outer scales L_o, as well as coherence outer scales ℓ_o are derived for the different locations and taking into account the contribution of the surface layer [0, 50m], the boundary layer [0, 1km] and the free atmosphere [1km, 30km]. Noticeable changes are found between the different locations, mainly due to the boundary layer contribution. The free atmosphere contribution seems almost the same for each site. There is a very good coherence between the outer scale derived by us and that measured using the Generalized Seeing Monitor (GSM) technique.

We present results of an extended campaign to test astronomical and environmental qualities of the intended site for the Discovery Channel Telescope, located at 2361m elevation near Happy Jack, AZ. A semi-permanent test station has been in operation since January 2003, consisting of a Differential Image Motion Measurement (DIMM) system and a weather station. Median seeing derived from DIMM measurements for January 2003 - May 2004 on 117 separate nights was 0.84 arcsec, with a first-quartile average of 0.62 arcsec. A wind sensor array deployed on a 12.2m tower is used to characterize air flow over the site. We find that ground induced turbulence becomes more prevalent below the 7.3m level. The Lowell DIMM system has also been run adjacent to the WIYN telescope for simultaneous comparative seeing measurements. Absolute correlations of DIMM seeing with WIYN image quality were good over two nights' observing under a range of environmental conditions.

We have been taking weather data at the location of the Subaru Telescope since 1999. We have also obtained the environmental data on many points in the telescope enclosure and on the telescope structure. Based on those, we will report the statistics of weather data and environmental condition around the Subaru Telescope as well as correlations among them. The statistics of nighttime clear sky ratios at Subaru Telescope site is presented. We have been gathering seeing data since the First Light of the Subaru Telescope in 1999, and we found a clear seasonal variation of the seeing size defined by FWHM method. A strong correlation between seeing sizes and wind velocities/directions is reported.

Institute of Astronomy, University of Tokyo is now planning to build a 6.5-m optical-infrared telescope in Atacama, Chile. This project is called "Univ. Tokyo Atacama Observatory (TAO)", and the site evaluation is now under way. As a part of this evaluation process, we started an investigation to compare the astronomical seeing at Atacama with that at Mauna Kea. Here, we report preliminary results of seeing measurements at several sites in Atacama, carried out on October 2003. In order to separate the temporal and site-to-site variation of the seeing, we used two sets of Differential Image Motion Monitors (DIMMs), each of which has two pairs of 7.4 cm sub-apertures with 20.5 cm separation. Three sites were investigated; the point near the TAO weather station (4,950m), the summit of Cello Chico (5,150m) and the point at 5,430m altitude on Cello Toco. Simultaneous measurements were carried out for three half nights out of four half nights measurements. Although the amount of our data is very limited, the results suggest following: 1) Seeing becomes better and more stable as time passing to midnight (eg. From 0."7 to 0."4 at V-band). 2) Higher altitude sites show better seeing than lower altitude sites.

Since summer 2001, dust pollution of the air is regularly measured through a particle counter at the Telescopio Nazionale Galileo (TNG) located at the Roque de los Muchachos Observatory (La Palma - Canary Islands). Canary Islands are normally interested by a dominant atmospheric circulation with NE winds. Depending on their strenght, and their exact direction, winds may bring with themselves small to large amount of dust from the Sahara desert, with important consequences on the transparency of the sky. Meteorological satellites gave us some impressive examples of such these phenomenon. We show here the results of trying a correlation between dust-pollution data and the nightly atmospheric extinction measured at other telescopes. While the transparency is mostly affecting the astronomical work, other effects like changes of air temperature and humidity are clearly visible; for this reason dust-pollution data are also compared with the weather data recorded at the TNG meteo tower.

In this paper we undertake an attempt to take into account the effect of the underlying terrain (including mountainous terrain) in the regions of location of astronomical receivers on the variance of the image jitter for extraterrestrial objects. It is shown that taking into account the underlying terrain it is possible to achieve a good agreement between theoretical and experimental data that deviate significantly from the well-known theoretical secant law.

Satellite data measuring aerosols over the Canary Islands need to be correctly interpreted in accordance with the spatial resolution and spectroscopic channels used. In situ data are still a necessary reference for calibrating and interpreting the aerosol index provided by different spectrometers onboard satellites. Most of the airmass flux component arriving at the Canarian Archipelago comes from the North Atlantic Ocean and consists of sea aerosols, i.e. absorbent chloride in the UV which does not affect the extinction in the visible range. African dust intrusions affect the western and eastern Canary Islands differently. Moreover, the presence of a stable inversion layer and the sharp orography of the western islands (La Palma at Tenerife) produce different mass flux patterns in the low (mixing) layers closer to the sea and in the median-upper (or free) troposphere layer. The aerosol index provided by the TOMS (Total Ozone Mapping Spectrometer) is one of the most widely accepted products to detect the daily aerosol content. On the other hand, several techniques have been developed in situ to characterize the presence of dust locally at the Canarian Observatories. In particular, a parameter related to sky transparency, the atmospheric extinction coefficient, has been measured at the Roque de los Muchachos Observatory (ORM) on La Palma since 1984 by the Carslberg Automatic Meridian Circle Telescope (CAMC). In situ aerosols are also available for the Teide Observatory (OT) on Tenerife, from 1986 onwards. In this work we compare aerosol index data of TOMS/Earth Probe observations and atmospheric optical extinction coefficient from CAMC in the period 1996-2004. A preliminary comparison of both techniques (in situ and remote) is discussed in this paper, showing there is no linear correlation between the aerosol index and the extinction coefficient. Here, we present an interpretation of different situations arising and discuss critically the correct interpretation of the aerosol index and images provided by the TOMS in accordance with the dust presence over the Observatories.

A tower and access platform were fabricated and erected for the Hobby-Eberly Telescope (HET) Differential Image Motion Monitor (DIMM). The 5 meter high tower exhibits a fundamental frequency of 43 Hz. The cost of the tower system, including access platform and enclosure was $12K US. The enclosure includes a unique application of an off-the-shelf truck accessory that serves as a shutter. The enclosure is ventilated, and incorporates a windshield to reduce vibrations that have proven problematic in the Meade Telescopes used for the DIMM system.

The Canada-France-Hawaii Telescope was modified with the addition of a chilled glycol cooling system to support Wide-field instrumentation. This paper outlines the design and lessons learned during implementation of this major system addition to the Observatory. Our research indicated that different Telescopes used a variety of approaches and there were many options in the commercial market that requires careful selection for use in a Telescope environment. We wish to share our valuable experience with future designers of cooling systems for instruments on large and small Telescopes alike.

The 74 MHz system on the National Radio Astronomy Observatory's Very Large Array (VLA) has opened a high-resolution, high-sensitivity window on the electromagnetic spectrum at low frequencies. It provides us with a unique glimpse into both the possibilities and challenges of planned low-frequency radio interferometers such as LOFAR, the LWA, and the SKA. Observations of bright, resolved radio sources at 74 MHz provide new scientific insights into the structure, history, and energy balances of these systems. However many of these scientifically motivated observations will also be critical to testing the scientific fidelity of new instruments, by providing a set of well-known standard sources. We are also using the 74 MHz system to conduct a sky survey, called the VLA Low-frequency Sky Survey (VLSS). When complete it will cover the entire sky above -30 degrees declination, at a 5σ sensitivity of 0.5 Jy/bm^-1, and a resolution of 80" (B-configuration). Among its various uses, this survey will provide an initial grid of calibrator sources at low frequency. Finally, practical experience with calibration and data reduction at 74 MHz has helped to direct and shape our understanding of the design needs of future instruments. In particular, we have begun experimenting with angle-variant calibration techniques which are essential to properly calibrate the wide field of view at low frequencies.

The Dutch Open Telescope (DOT; http://dot.astro.uu.nl) on La Palma is a revolutionary open solar telescope, on an excellent site, on top of a transparent steel tower, and uses natural air flow to minimize local seeing. The aim is long-duration high-resolution imaging with a multi-wavelength camera system. In order to achieve this, the DOT is equipped with a diffraction limited imaging system and uses the speckle reconstruction technique for removing the remaining atmospheric turbulence. The DOT optical system is simple and consists currently of a 0.45m/F4.44 parabolic mirror and a 10x enlargement lens system. We present our plans to increase the aperture of the DOT from 0.45m to 1.4m. The mirror support and telescope top shall be redesigned, but telescope, tower, multi-wavelength camera system and speckle system remain intact. The new optical design permits user selectable choice between angular resolution and field size, as well as transversal pupil shift introducing the possibility to use obstruction free apertures up to 65cm. The design will include a low order AO system, which improves the speckle S/N substantially during moderate seeing conditions.

We present the final opto-mechanical design of the Large Binocular Telescope (LBT) Acquisition, Guiding and Wavefront Sensing Units (AGW-units) together with the laboratory test performance of the units. The units will be installed at the LBT shortly after this conference, at several of the different Gregorian focal positions available. Each AGW-unit consists of a probe with a camera and a wavefront sensor located in front of the science instrument. The probe can move in two axes allowing it to patrol a field off-axis to the science field. A dichroic beam-splitter on the probe transmits the blue light to the acquisition and guide camera and the red light is reflected into a Shack-Hartmann wavefront sensor. The guide camera is equipped with a 2.5x focal reducer giving a field of view of 28"x28" on a 512x1024 frame-transfer CCD. The 12x12 sub-pupil wavefront sensor uses a micro lenslet array made using an ion-exchange technique on a flat substrate with diffraction limited performance.

During the last four years of operations, low technical downtime has been one of the relevant records of the Paranal Observatory. From the beginning of the Very Large Telescope (VLT) project, European Southern Observatory (ESO) has considered the implementation of a proper maintenance strategy a fundamental point in order to ensure low technical down time and preserve the Observatory's assets. The implementation of the maintenance strategy was based on the following aspects: - Strong maintenance sense during the design stage. Line Replacement Unit (LRU) concept, standardization and modularity of the Observatory equipment - Creation of a dedicated team for Maintenance - The implementation of a Computerized Maintenance Management System After four operational years, the result of these aspects has exceeded the expectations; the Observatory has been operating with high availability under a sustainable strategy. The strengths of the maintenance strategy have been based on modern maintenance concepts applied by regular production companies, where any minute of down time involves high cost. The operation of the actual Paranal Maintenance System is based mainly on proactive activities, such as regular inspections, preventive maintenance (PM) and predictive maintenance (PdM) plans. Nevertheless, it has been necessary to implement a strong plan for corrective maintenance (CM). The Spare Parts Strategy has also been an important point linked to the Maintenance Strategy and CMMS implementation. At present, almost 4,000 items related to the Observatory spare parts are loaded into the CMMS database. Currently, we are studying the implementation of a Reliability Centered Maintenance (RCM) project in one of our critical systems The following document presents the actual status of the Paranal Maintenance Strategy and which have been the motivations to implement the established strategy.

From a preliminary study on the project of a Large Antarctic Telescope for the Concordia Station at Dome C, two qualifying points seem important to be emphasized: a) the first point is to think of a large diameter Telescope, able to achieve high angular resolution measures, in the sub-arcsec range in the mid-ir, that the science, especially that concerned with star forming phenomena, is strongly requiring, using in this way a sensitivity limit never reached before which is amplified by the exceptionality of the site exploited. b) The second point, also related to the site, is to realize a non-conventional instrument with the highest degree of simplicity in the structure design, in the configurations, in the telescoped control and in the measuring modes, as to face the extreme conditions imposed by a space-like environment such as Dome C and also in order to cut costs. Furthermore the idea is to assure the use of such an instrument at wavelengths higher than the mid-ir region, to which the telescope is principally devoted, thus expanding the interest of the astronomical community for Antarctic Astronomy. In the design phase the optimized configurations assuring the possibility to observe in the near-mid- and far-ir and in the sub-mm range, will be selected, obtaining the particular optimized structure by making some modifications that could be implemented in Antarctica during the summer season. Every configuration will permit to have the optimized conditions to observe at different wavelengths and for different types of measures (imaging; polarimetry; spectrscopy; large or small fields of view, etc.) giving priority in some cases to the highest angular resolution or to the highest sensitivity, or to largest field of view. Some example will be given about technical solutions expected for the near and mid-ir in the light of the present and future possibilities in these domains.

In late 2003 the Isaac Newton Group of Telescopes (ING) successfully completed the commissioning of a set of new CCD Autoguider and Television cameras on the 4.2m William Herschel Telescope (WHT). These new multi-purpose heads are built around E2V CCD4720 and CCD5710 frame-transfer detectors fitted with integral Peltier coolers. These new cameras use the same type of CCD controller and Data Acquisition System (DAS) as all of ING’s CCD science cameras and Infrared arrays. These multi-purpose heads have replaced a diverse set of older and difficult-to-maintain Television and Autoguiding systems. The approach of using the same DAS + controller for all cameras at ING greatly aids their maintainability. This paper looks at the reasons for developing the cameras, takes a detailed look at the design and examines existing and possible future applications.

Cost data for ground-based telescopes of the last century are analyzed for trends in the relationship between aperture size and cost. We find that for apertures built prior to 1980, costs scaled as aperture size to the 2.8 power, which is consistent with the previous finding of Meinel (1978). After 1980, 'traditional' monolithic mirror telescope costs have scaled as aperture to the 2.5 power. The large multiple mirror telescopes built or in construction during this time period (Keck, LBT, GTC) appear to deviate from this relationship with significant cost savings as a result, although it is unclear what power law such structures follow. We discuss the implications of the current cost-aperture size data on the proposed large telescope projects of the next ten to twenty years. Structures that naturally tend towards the 2.0 power in the cost-aperture relationship will be the favorable choice for future extremely large apertures; our expectation is that space-based structures will ultimately gain economic advantage over ground-based ones.

The "phase A" of the opto-mechanical design, which started in 1997, is now basically completed. It provides a clean, symmetrical geometry of the pupil, with a near-circular outer edge. The modular design of the mechanical structure is built on the size of the hexagonal segments, provides a perfect match with the optical elements and allows production at reasonable costs. This paper is a summary of the various design iterations. A discussion is devoted to the evaluation of the design assumptions and principles which have been set at the beginning of the study, and to their validity after the completion of this first phase. This includes a discussion about specific aspects whose criticality had been under- or overestimated, and the methodology applied to define system and sub-system requirements. Finally, we present a summary of the present and future activities, which are mainly devoted to sub-systems definition.

The LOw Frequency ARray (LOFAR will observe at 20-200 MHz. At those frequencies, large ionospheric phase variations distort the observed brightness distribution. Fortunately, the imahe may be stabilized for long integrations by using bright radio sources in the sky. The downside is that LOFAR fields will be very crowded, which presents calibration challenges of its own. This is especially true for the bright and extended sources that enter via the relatively high sidelobes of the LOFAR station beams. An extra complication is that these beamshapes vary rather strongly in frequency and time. Altogether, LOFAR will require much more processing than existing radio telescopes, and has only just become possible with the new generation of computers. Even so, new processing techniques like 'peeling' had to be developed to speed things up by several orders of magnitude.

We describe the active support system for the 8.4 m LBT primary mirrors and the use of this system to optimize the mirror figure in the lab before installation in the telescope. We figured the mirror, mounted on passive supports, to an accuracy of 18 nm rms surface after subtraction of spherical aberration and several flexible bending modes that would be corrected with the active supports. After installing the mirror on its active supports, we optimized the 160 support forces based on interferometric wavefront measurements and a finite-element model of mirror bending. We verified the accuracy of the model and determined a scale factor-the model is stiffer than the real mirror-by measuring a number of bending modes using forces calculated from the model. We then optimized the forces to obtain an accuracy of 28 nm rms surface. The optimization included correcting 200 nm of spherical aberration (Zernike coefficient of surface error) with a maximum correction force of 26 N.

Atmospheric dispersion and differential refraction will lead to a non-neglectable light loss varying with wavelength across the field of view during the integral time of multi-fiber spectral observation. These effects will be more severe in telescopes with large field of view such as the Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST). We have calculated the light loss due to atmospheric refraction for LAMOST. To improve the efficiency, we could move individual fiber to correct its 5000 A monochromatic displacement during observation, the best number of this kind of track should be balanced between the displacement correction and the fiber positioner error. We have calculated the best track number by monte-carlo simulation for different declination field and different position of the field. Also we have derived the fiber positioner error tolerance from simulation.

This paper describes the development of a 3-stage cryogenic low noise InP HEMT amplifier for ALMA Band 3 receivers. A detailed design is given using Hughes 0.1 μm low noise InP HEMTs for producing a low power dissipation amplifier, < 9 mW. The amplifier design uses a hybrid circuit in order to provide the flexibility for optimizing the active devices and passive components. The optimal impedance matching for low noise and low input return loss were obtained by computer aided simulation to achieve 5 K noise temperature, 36 dB gain, flatness ±1 dB and -10 dB input return loss at 12 degrees Kelvin in the 4-9 GHz band. The amplifier will be used as a cold IF preamplifier with a SIS mixer in the Band 3 receivers now being constructed for the Atacama Large Millimetre Array (ALMA).

The Southern African Large Telescope (SALT), currently being erected in Sutherland, South Africa, will be the largest single optical telescope in the southern hemisphere, and the 4th largest telescope in the world, when it is completed in late 2004. The SALT design is based on the Hobby-Eberly Telescope. The prime focus payload design presented structural and layout challenges, since four instruments had to be accommodated in a restricted space envelope, combined with mass budget constraints. In addition, the secondary optics (spherical aberration corrector, atmospheric dispersion compensator), moving baffle/pupil mask and guidance system form part of the complete assembly. To adhere to the mass budget and stiffness requirements the major structural components were manufactured from sandwich panels (foam core and carbon fiber skins). A volume that is actively cooled houses all electronics to prevent image degradation as a result of heat build-up. In addition to supporting closed loop guidance by means of four guidance probes (one per instrument bay) the payload also supports active focus control. All components have been manufactured, good progress has been made on the integration and the aim is to have the payload functional in 2004.

The details of the design and the achieved performance of the recently completed primary mirror assembly for the SOAR telescope are described in this paper. The mirror is unique in that it uses a solid 4.3 meter diameter ULE lightweight meniscus primary mirror only 100 mm thick. The ULE substrate weighs approximately 3200 kg. The figure of the primary mirror surface is controlled with 120 electro-mechanical actuators that are force feedback controlled. Details of the design of the 4.1 meter clear aperture F=1.75 active primary mirror are presented. The figure control actuators are force controlled to correct aberrations induced by thermal and elevation changes affecting the telescope. A Calibration Wavefront Sensor provides input data to generate lookup tables used to develop the force commands at all zenith angles and temperatures. During the design development phase of the program the mirror was analyzed using NASTRAN finite element modeling. During optical metrology testing the ability to accurately induce shapes into the mirror surface including Zernike polynomials was compared to the NASTRAN predictions. Details of the results of this testing will be presented including the magnitude of force to impose specific Zernike polynomial shapes and the fidelity of the resulting shapes compared to the analysis.

On completion by the end of 2004 the Southern African Large Telescope (SALT) being erected in Sutherland, South Africa, will be the largest single optical telescope in the southern hemisphere. This paper addresses the process of designing, building and demonstrating a high performance primary mirror system for SALT that meets the overall telescope requirements. Throughout the process consideration was given to the fact that SALT is budget sensitive, which required careful allocation of funds among the various subsystems, innovative designs, and using COTS components where possible. The process delivered subsystems with a very high cost-performance ratio.

The design of the Southern African Large Telescope (SALT), which is based closely on the Hobby-Eberly Telescope (HET) at the University of Texas but includes advances incorporating lessons learned from HET, is briefly reviewed. The flowdown of requirements from the optical error budget to the primary mirror control subsystems is presented. The techniques and algorithms used by the Center of Curvature Alignment Sensor (CCAS) to measure segment tilt and piston and estimate the global radius of curvature of the primary are discussed in detail. The steps in the process that allows CCAS to capture and identify segments misaligned by more than 70 arcsec and bring them into alignment with residual errors less than 50milli-arcsec is fully described. Next, the hardware and software designs of CCAS are presented, as well as the results of laboratory performance testing. CCAS has been installed and integrated with the primary mirror control system. Performance results of the integrated system over a range of environmental conditions will be shown. Finally, the overall results of this project are summarized and suggestions for future improvements presented.

As part of a major enhancement, designated e-MERLIN, to its MERLIN array of radio telescopes there is a need for new feed designs to cover 4GHz to 8GHz band, for large paraboloid dishes (up to 76 m etres diameter) operating in both prime-focus and cassegrain configurations. The requirement, in each case, for good return loss and constant beam width across an octave band, presents a set of difficult challenges. The feed designs for e-MERLIN are introduced here. The prototypes of the prime-focus feeds and the e-system corrugated horn feed have been designed, manufactured and tested, both in the laboratory and on the respective telescope. The complete corrugated horn for the Cambridge telescope will shortly be manufactured and measured.

The SOAR Telescope, near completion on Cerro Pachon - Chile, will carry Instrument Support Modules (ISMs) mounted at the two Nasmyth foci. Each ISM has three focal stations and is capable of making rapid instrument changes between them. Both ISMs also carry a Comparison Lamp System (CLS), guider and an acquisition camera, which are shared between the three instruments. One ISM supports IR instruments. The other is used for "Optical" instruments operating at wavelengths below 900nm. Beam steering mechanisms direct light from the SOAR science field or the CLS to the instrument in use. In the IR-ISM, light is sent to the lateral ports by dichroic mirrors which reflect IR and transmit wavelengths from 400-900nm to the guider. In the Optical-ISM, light is directed to the lateral ports by the use of first surface pick-off mirrors. Guiding is done off-axis. During operation, both ISMs can be rotated by 360° and must carefully control differential flexure between the guider and focal planes. A method of accurate relative flexure measurement has been developed where the ISM is rotated on its handling cart while carrying instrument mass simulators which reproduce its nominal payloads. In this paper, the ISM and its support sub-modules are described. Results of flexure measurements and tests of the CLS are provided.

The SUNRISE telescope is part of a balloon-borne instrument for spectro-polarimetric high-resolution observations of the solar atmosphere, to be flown 2007/2008 in the Antarctic summer stratosphere. It is a 1-m UV-VIS Gregory type telescope, operating close to the VIS diffraction limit. The telescope has a steel central frame and a lightweight CFRP trusswork structure with Serrurier properties, providing proper alignment of the optical elements over the varying eleva-tion angle. Mechanisms allow a fine adjustment of the optics. Aberrations caused by residual deformations of the stiff silicon carbide (Cesic) primary mirror are lowered by a dedicated offset in the secondary mirror polish (imprint). The telescope is subjected to the changing heat loads caused by the sun and earth radiation, necessitating measures to provide thermal conditions suitable for high-performance observations. Adequate preliminary solutions for an effective baffling are outlined.

We present results from a study of the performance of the MMT thermal system. The 6.5-m MMT primary mirror consists of a borosilicate honeycomb structure that is thermally controlled with a forced-air ventilation system. We will give an overview of both the measurement and control systems. Our goal is to define an algorithm for control of the ventilation system such that the primary mirror temperature closely tracks ambient while minimizing thermal gradients. Future work will include a study of correlations between the thermal state of the primary mirror and both seeing and wavefront errors. The thermal system is currently controlled by the telescope operators, but the results from this work will assist in fully automating the system.

The 4.2 m Discovery Channel Telescope requirements create interesting challenges for the Mount mechanical and control system design. The wide field of view survey telescope incorporates two operational foci: prime focus and cassegrain, either one must be available during any night's observing. The mission for observing requires fast slewing / offsets between each exposure with fast settling times to maintain the mission requirements. The prime focus arrangement includes a dedicated camera on the spider assembly and the cassegrain configuration includes a secondary mirror at the spider assembly with a dedicated instrument located at the cassegrain focus. This requirement challenges the design team to incorporate a prime focus / secondary mirror flipping mechanism within the secondary spider. The configuration requires a substantial prime focus and cassegrain payload with long focal distances creating a large inertia on the altitude axis. These are a few of the interesting challenges that are presented in this paper along with the design, trade-offs of different solutions, and the recommended design for the telescope Mount.

The NASA Outrigger Telescope Project is a ground-based component of NASA's Navigator Program. The proposed project would utilize four to six 1.8-meter telescopes with co-rotating domes configured as an interferometer. One of the project’s scientific goals is the detection of exoplanets, which would be accomplished with long baseline narrow-angle astrometry. This astrometry mode would be able to detect Uranus mass planets up to 60 light years away. The requirements of narrow-angle astrometry, both technically and operationally, levy requirements on the telescopes and enclosures, including, for example, wavefront quality, pivot stability, and slew speed. This paper will describe these requirements and how they were achieved in the design. It will also discuss the testing and verification of these requirements. Actual telescope performance as tested at EOS Technologies is presented elsewhere in these proceedings.

Active optics is the most difficult part in LAMOST project. Especially for the segmented reflecting Schmidt plate Ma, in which both segmented mirror active optics and thin mirror (or deformable mirror) active optics are applied. To test and optimize the thin mirror active optics of Ma, and to approach the reality of operating environment of the telescope, an outdoor experiment system has been established. This experiment system is also a 'small LAMOST' with one sub-mirror of the primary mirror Mb and one sub-mirror of the Schmidt plate Ma, and with full scale in spacing (40 meters) between Ma and Mb. many parts of LAMOST were tested in the experiment system except segmented mirror active optics. Especially for force actuators, thin mirror support system, friction driving of the alt-azimuth mounting and its control system, wave front test along such a long optical path. This paper presents the experiment system, research and developments, and some experiment results.

In 2002 the method of thermal control within the HET enclosure was dramatically changed by the installation of 300 square meters of ventilated area to the stationary walls below the rotating dome. During the month of July 2003 a nightly study of the airflow was undertaken at the HET. While dome seeing has shown substantial improvement, this study revealed a number of counter intuitive flow modes which indicate that additional seeing improvements can be achieved by selective ventilation of the HET dome above the ring-wall. Additional study of dome seeing revealed substantial sub-cooling of the dome skin. Measurements of the skin temperature of the un-insulated dome revealed night-time cooling of local ambient air by as much as 3.6° C. An investigation of coating alternatives resulted in the application of aluminum foil tape, which reduced the temperature drop to 0.3° C. Presently, the performance of the HET (as low as EE50=0.8 arc-seconds) is not thought to be limited by dome seeing.

Since 1999 the National Telescope Galileo (TNG) is offering observative nights to the astronomical community. With the aim of increase the efficiency of the telescope and minimize downtime many changes have been done from the original project. Recently it has been taken the decision to completely renew the electronic hardware and software of the active optics system, essencially based on VMEs and on the obsolete transputers processors. From the optical point of view some important modifications have also been implemented in order to allow the off-axis Shack-Hartmann analisys. Also the CCD cameras and their controllers have been redeveloped and the whole control software has been ported to a new architecture to by-pass the VMEs system and directly interact with the actuators and the CCD controllers.

The Discovery Channel Telescope (DCT) is a project of Lowell Observatory in conjuction with the Discovery Channel to design and construct a 4.2-meter clear aperture telescope and support facility on a site approximately 40 miles southeast of Flagstaff, Arizona, USA. The site is an undisturbed mountain top at an altitude of 7800-feet. Design and construction of the telescope enclosure includes all of the site utilities, access road to the site along with the fixed base enclosure, telescope pier and rotating dome structure. The details covered in this paper are the decisions and rationale of the DCT enclosure conceptual design completed by M3 Engineering & Technology Corporation (M3).

The SOFIA telescope has a silicon carbide secondary mirror and a six degree-of-freedom secondary mirror mechanism. Each of these high-technology items represents a single-point failure mode, because both are essential for operation of the observatory, and neither has a spare. Reduced-performance, relatively inexpensive “backup” hardware can enable a large fraction of the planned SOFIA science observations, and so can help to assure a highly reliable flight program. Accordingly, we have developed an aluminum secondary mirror and derived design requirements for a backup secondary mirror mechanism that will meet minimum performance needs.

Alignment of the segmented telescopes requires an accurate phase measurement at the segment borders using an optical sensor. We develop such a sensor based on the Mach-Zehnder interferometer. The operation of this system was previously demonstrated in computer simulation and through the detailed theoretical analysis. In this paper we show the results of the laboratory experiment, which confirms the main predictions we have made. The close loop control for optical phasing of segmented mirrors, analogous to the one with the use of the edge sensors, is also described and illustrated.

We present here a novel concept for achieving real-time super-resolution ground-based imagery for small aperture telescopes. We explore the combination of existing stacking and registration software in conjunction with real-time equation based Data Models. Our research indicates that for anisoplanatic imagery, a real-time video/software enhanced analog to conventional speckle imaging is possible. This paper highlights the technique and theory for creating such a system.

SUNRISE is a 1m solar telescope for the visible and near UV wavelength range. It will be flown in long duration stratospheric balloon flights in Antarctica, with a first scientific flight in 2007. In this paper, we describe the development of a wave-front sensing system that will be used for the automatic in-flight alignment of the SUNRISE telescope and for high-precision tracking. The system is based on the principles of an adaptive optics system. A 19-element wavefront sensor is used to determine low order aberrations of the telescope, including defocus and spherical aberrations. The correction is achieved by controlling the position of the telescope secondary and a focusing mirror in closed-loop. In addition to these quasi-static aberrations, the system will also measure image motion with a dynamical range of at least 30 Hz and with a precision of about 0.005 arcs. To this end, the image displacement measured in all sub-apertures is averaged and used as tip-tilt correction signal. This signal will feed a second closed-loop system that drives the tip-tilt mirror assembly. The tip-tilt mirror unit is designed as a dual-stage system that consists of a slow component with a large range of 60 arcs and a fast component with high bandwidth.

A new membrane mirror is capable of imaging in the infrared and visible for astronomical imaging. The development of the membrane mirror has the order-of-magnitude aperture size increase or weight reduction for large aperture ground based telescopes. The membrane mirror is reproducible at a fraction of the time and cost as compared to glass equivalent size. It also requires a considerable mass and cost reduction of the telescope mount as compared to conventional size equivalent mounts. The membrane mirror has overcome the problems of near edge distortion when stretched that has been a limiting factor until now. Further more, the surface problem of having an oblate spheroid has been overcome now by deepening the centre thereby creating a parabola through active central distortion of the figure. Because there is no active system to produce pattern surface distortion, the ratio of thickness and size has resulted in a stable surface with diffraction limited results in the infrared. Research is continuing on to develop an upgradeable mirror with visible range diffraction limited results. A unique interesting feature of the mirror for astronomy is optional variable focal or N focal lengths. Because it is used as a direct imager focussing can also be accomplished through precision vacuum control. This unique adaptability of the mirror creates multiple telescope applications. Another interesting feature is the option of using the mirror as an off axis system in a telescope. An example of this configuration is in a Gregorian system.

We describe the process of retrofitting an existing Raven telescope with enhanced optical and detector improvements that enable the system autonomously to collect color photometric data. Since it is a commercial system, it provides a low-cost approach for the study of man-made satellites, stars, asteroids, and other space objects. The system upgrades include filter capabilities, a Charge-coupled Device (CCD) camera system, a robust mount, and replacement of the existing telescope with one of larger aperture. Raven systems are not new to the realm of contributing sensors in tracking man-made satellites, and our program represents a logical increase in performance and capabilities as new commercial items have become available. Therefore, this current Raven Signatures Testbed is the latest evolution of such small, lightweight, remote, autonomous systems. This telescope will increase the productivity of the Satellite Signatures Program at the Air Force Research Laboratory by increases in observation time and by enabling remote operations along with autonomous data collection and storage.

The point spread function of a segmented aperture is seriously affected by the misalignment of the segments. Stringent requirements apply to position sensors and their calibration. The Active Phasing Experiment (APE) will be a technical instrument aimed at testing possible phasing techniques for a European Giant Optical Telescope (EGOT) in a representative environment. It will also integrate simultaneous control of segmented and monolithic, active surfaces. A mirror composed of 61 hexagonal segments is conjugated to the primary mirror of the VLT. Each segment can be moved in piston, tip and tilt and can be controlled in open or closed loop. Three new types of Phasing Wave Front Sensors dedicated to the measurement of segmentation errors will be tested, evaluated and compared: a modified Mach-Zehnder sensor developed by the LAM and ESO, a Pyramid Sensor developed by Arcetri, and a Curvature Sensor developed by IAC. A reference metrology developed by FOGALE will be added to measure directly the deformation of the segmented mirror and check the efficiency of the tested wavefront sensors. This metrology will be based on a synthetic wavelength instantaneous phase stepping method. This experiment will first run in the laboratory with point-like polychromatic sources and a turbulence generator. In a second step, it will be mounted at a Nasmyth focus of a VLT unit telescope. These activities are included in a proposal to the European Commission for funding within Framework Program 6.

The Point Spread Function (PSF) or star test is one of the main criteria to be considered in the quality of the image formed by a telescope. In a real system the distribution of irradiance in the image of a point source is given by the PSF, a function which is highly sensitive to aberrations. The PSF of a telescope may be determined by measuring the intensity distribution in the image of a star. Alternatively, if we already know the aberrations present in the optical system, then we may use diffraction theory to calculate the function. In this paper we propose a method for determining the wavefront aberrations from the PSF, using Genetic Algorithms to perform an optimization process starting from the PSF instead of the more traditional method of adjusting an aberration polynomial. We show that this method of phase recuperation is immune to noise-induced errors arising during image aquisition and registration. Some practical results are shown.

Acquisition is defined as identification for a fixed target in the related field of sight (FOS), while tracking means the sway of the telescope's axis of sight (AOS). The automatic acquisition and tracking is a process in which the operating way of the telescope should be switched from guiding to automatic tracking. There are some kinds of method to improve the acquisition and tracking ability for fast moving targets: to extend the acquisition and tracking FOS with memory and storage information of the sensor system; the multimode control to improve the dynamic property of the servo system; to choose an opportune time for acquisition and tracking; to select the control regulator parameter in every working states. If the processor of the CCD sensor can temporarily remember and save the information of the target before it moves out of the FOS, correspondingly, the FOS may be extended. The data forecast technology is used to store the target information. The automatic interception experiments are carried out to verify the control strategy.

The Chinese ever-ambitious project of 30 meter-class telescope, Chinese Future Giant Telescope (CFGT), has brought about an extraordinary challenge for the control system's robustness. Various severe factors that we have never experienced before, will impact on our considerations for the control system. With the practice in our ongoing LAMOST project plus an investigation and a reasonable prediction the paper tries to deal with, at very preliminary stage, the control system configuration in general and a number of extreme difficulties in particular, such as the drive system and analysis of wind torque disturbance rejection, etc.

We are constructing an 8 by 8 bolometer camera, as a 90 GHz facility instrument for the 100 m Green Bank Telescope (GBT). The bolometers use transition-edge-superconducting (TES) sensors read out with a time-based SQUID multiplexing system. The receiver will be one of the first astronomical instruments to use such detectors. Our TES bolometers require cooling below 290 mK. To obtain these temperatures we use He3 and He4 sorption refrigerators that cycle from a two-stage pulse-tube cryocooler. The He3 stage has an operating temperature of 252 mK and a hold time of 77 hours with a 10 microwatt load. A combination of the large collecting area of the GBT and the low noise of the detectors will enable us to map 15 arcsecond by 15 arcsecond areas of sky to 200 microJansky in one hour.

We present the architecture and the characterization results of a Master Laser prototype that can be used to distribute a phase-coherent millimeter wave reference within the Atacama Large Millimeter Array. This source is obtained by frequency-locking a 1556-nm narrow linewidth DFB fiber laser to a two-photon transition in rubidium 85 at 778 nm after second harmonic generation in a non-linear waveguide crystal. The prototype yielded an absolute wavelength of 1556.210 843 nm, a stability of 2x10^-12 at tau = 1 s, a linewidth of 2 kHz over 1 ms, a coherence of 40% at 50 km over 1 ms, and a RIN below -145 dBc/Hz for f>10 MHz. Using this laser, the transmission of an 18.6 GHz reference over 10 km of fiber was achieved with a residual phase fluctuations lower than 0.22 degrees RMS (33 fs RMS) over 10 s.

The second decade of the third millennium AD will hopefully see a new generation of ground-based telescopes, from 20- to 100-m in diameter, that will open a completely new window on the Universe. Here I review the scientific as well as technological drivers that underlie the new projects, looking at how they interact in pushing the limits of the parameter space and in driving the design requirements, and at some of the challenges they bring. As one may expect, much of the preparatory work, both design and industrial, is largely "concept independent", indicating that synergy rather than competition is the way forward (as it is already seen from the various collaborations that have been forming in the past year). While one should not underestimate the technical challenges, the promising result of many studies so far is that the only clearly identified show stopper seems to be funding.