We describe a mission concept for the SEQUOIA instrument, which would carry out the first wide-field, far ultraviolet, photometric all-sky survey. SEQUOIA will image the astronomical sky in the 912-1050 angstrom spectral region to a limiting magnitude of 19.5^m over a one degree field of view with a spatial resolution of less than 30 arc seconds. This mission was proposed to the USRA STEDI program in late 1994, and has been designed as a low cost, fast-track program for launch within 3 years. The spacecraft bus is being provided by Orbital Sciences Corporation (Dulles) and since the entire payload weighs less than 100kg, it can be launched using either a Minuteman or Pegasus rocket.

Since 1990 the Edison program has studied designs for large, long-lived IR space telescopes incorporating intensive use of radiative cooling supplemented by mechanical refrigeration. This approach, which is now generally accepted as the most likely route to achieving large aperture and long lifetimes, led to proposals to ESA in 1993 and 1994 for a 1.7m observatory telescope operating at < 20 K as a Medium-sized mission and a Cornerstone, respectively. Extension of these ideas and the application of newer technology now indicate that a Cornerstone budget and an Ariane 5 launcher could accommodate mid- to far-IR telescopes of up to perhaps 3m aperture and/or achieve telescope temperatures of a few K--thereby attaining the full long-wavelength performance of cryogenic missions--in robust designs able to maintain their performance levels (i.e. low optics temperatures) for many years. These designs, too, have potential applications as the individual elements of spatial interferometers, for example, for searching for extrasolar terrestrial planets.

This paper presents a conceptual design of a next generation large space telescope. A 8-m aperture telescope orbiting Earth at an altitude of 134,000 km would offer dramatic improvements over the Hubble Space Telescope (HST) in sensitivity, resolution, spectral range (1.2 micrometers - 40 micrometers ), sky coverage, and viewing efficiency. The proposed design is characterized by an effective solar shield, inflatable space-rigidized bottom sunshade, lightweight actively controlled primary and secondary mirrors, lightweight telescope shell, and relatively low overall mass (near HST mass). Initial thermal analysis indicates that very low- mirror temperatures can be achieved by purely radiative-cooling schemes, thereby allowing to extend spectral operating range to mid-IR wavelengths. The design presented assumes that research and development over the next decade should make it feasible to: 1) satisfy requirements for the telescope pointing accuracy and stability, autonomous mirror surface control, large format detectors with small size pixels, and cryocooler's long life, and 2) incorporate artificial intelligence into the spacecraft systems to provide extensive autonomy and fault detection/correction ability.

We present an instrument design for imaging spectroscopy in the far ultraviolet (FUV, 912- 1250 angstrom) and the extreme ultraviolet (EUV, 100-912 angstrom). The design consists of a collimator and telescope to collected light, an aberration corrected planar holographic grating placed directly in the converging beam of the telescope, a transfer mirror, and a microchannel plate detector. The design provides spatial on the order of 10 arc seconds and is limited by telescope blur and detector resolution, not by grating-induced aberrations. The spectral resolution is approximately 1000 for point sources and greater than 30 for diffuse objects which uniformly illuminate the 10 arc minute collimator.

The Space Telescope Imaging Spectrograph is a second generation ultraviolet and visible light spectrograph being developed by NASA for installation on the Hubble Space Telescope during the planned 1997 servicing mission. The current schedule calls for the instrument to be completed in the spring of 1996, with an extensive period of functional, environmental, and calibration tests during the summer. A calibration plan has been developed to ensure that the basic performance characteristics of this versatile instrument will be verified and documented before launch, and that the necessary operational and data reduction databases will be adequatley populated. Our strategies to measure the radiometric sensitivity, flat-field response, dispersion relations, resolving power, scattered light, slit functions, and other properties are described. As the execution of the calibration program is still over a year away (at the time of the conference at which this paper was presented), discussion and suggestions from the engineering and scientific communities will be welcomed.

The MSTI-3 sensor package is a three band imaging telescope for military and dual use sensing missions. The MSTI-3 mission is one of the Air Force Phillips Laboratory's Pegasus launched space missions, a third in the series of state-of-the-art lightweight sensors on low cost satellites. The satellite is planned for launch into a 425 Km orbit in late 1995. The MSTI- 3 satellite is configured with a down looking two axis gimbal and gimbal mirror. The gimbal mirror is an approximately 13 cm by 29 cm mirror which allows a field of regard approximately 100 degrees by 180 degrees. The optical train uses several novel optical features to allow for compactness and light weight. A 105 mm Ritchey Chretien Cassegrain imaging system with a CaF₂ dome astigmatism corrector is followed by a CaF₂ beamsplitter cube assembly at the systems first focus. The dichroic beamsplitter cube assembly separates the light into a visible and two IR channels of approximately 2.5 to 3.3, (SWIR), and 3.5 to 4.5, (MWIR), micron wavelength bands. The two IR imaging channels each consist of unity power re-imaging lens cluster, a cooled seven position filter wheel, a cooled Lyot stop and an Amber 256 X 256 InSb array camera. The visible channel uses a unity power re- imaging system prior to a linear variable filter with a Sony CCD array, which allows for a multispectral imaging capability in the 0.5 to 0.8 micron region. The telescope field of view is 1.4 degrees square.

This paper sets out to describe the utilization of an unmanned lighter-than-air vehicle as a sub- orbital airborne mission platform for the deployment of space technology telescopes allowing innovative space quality astronomy to be conducted. The paper describes how a low cost airship of relatively simple design can be produced that will be capable of operating in an unmanned remotely piloted mode from a base, fly to a pressure altitude, shut down engines, and operate in a free balloon stage for the period of experimental research. It will be shown that ballooning will allow the platform to be completely free from vibration, and in conjunction with high altitude and polar weather conditions minimize perturbation caused by weather. This paper outlines the technical features of the airship, the projected mission interfaces and the modus operandi of Airship delivery, ground base and missions operations, and final recovery.

The Polar Stratospheric Telescope payload will be the prototype of a diffraction limited, large space telescope and will fly in the stratosphere to validate a number of new technologies that future large space telescopes will require. The telescope is a 6-m diameter, sparsely-filled array comprised on one 1.8-m and six 60-cm mirrors. Each mirror is a segment of an f/1.2 primary. The mirrors have an unequal spacing around the circumference which optimizes spatial coverage of the u,v plane. The mirror segments are coaligned and cophased by a combination of internal metrology and re-imaging of the pupil onto a small active mirror for the correction of piston and tilt errors. The telescope will be flown during the winter in a polar region where the tropopause is a factor of two lower than at lower latitudes, making the stratosphere accessible to tethered aerostats. The telescope is suspended approximately 100 m below a tethered aerostat flying at an altitude of about 12 km. The telescope body is stabilized gyroscopically with two reaction wheels, and fine guidance of the line of sight is provided by a fast steering mirror. The telescopes primary mirrors are at the ambient temperature of 190 to 220 K, and internal baffles and relay optics are cooled to 160 K to minimize the instrumental background in the near infrared.

The tropopause, typically at 16 to 18 km altitude at the lower latitudes, dips to 8 km in the polar regions. This makes the cold, dry, and nonturbulent lower stratosphere accessible to tethered aerostats. Tethered aerostats can fly as high as 12 km and are extremely reliable, lasting for many years. In contrast to free-flying balloons, they can stay on station for weeks at a time, and payloads can be safely recovered for maintenance and adjustment and relaunched in a matter of hours. We propose to use such a platform, located first in the Arctic (near Fairbanks, Alaska), and then later in the Antarctic, to operate a new technology 4-meter telescope with diffraction-limited performance in the near-IR. Thanks to the low ambient temperature (200 degrees K), thermal emission from the optics is of the same order as that of the zodiacal light in the 2 to 3 micron band. Since this wavelength interval is the darkest part of the zodiacal light spectrum from optical wavelengths to 100 microns, the combination of high resolution images and a very dark sky make it the spectral region of choice for observing the redshifted light from galaxies and clusters of galaxies at moderate to high redshifts.

A description is presented of a sparse aperture telescope system designed to automatically control piston and tilt errors of the optical wavefront. The main thrust of this project is to design a satellite with a sparse aperture optical system payload. In order to reduce risk, this project also includes a laboratory demonstration of the ability to automatically phase the two segments of the sparse primary, common secondary optical telescope. By simulating the degradation of fringe visibility due to disturbances, an error budget has been created to determine the payload and laboratory experiment design requirements. With a fringe visibility system goal of 0.5, the error budget allocates 0.72 visibility to both subaperture phasing and common mode tilt. The purpose of the ongoing laboratory experiment is to validate the automatic phasing control system. A 1/4 scale design of the flight telescope and full scale equivalents of the phasing control system were built for the laboratory test. The tilt control loops have demonstrated the required 100 Hz bandwidth, and the ability of the piston algorithm to sense a change in optical path difference has also been demonstrated.

The Hubble Space Telescope (HST) High Speed Photometer thermal engineering data acquired over its three and one-half year mission provides some insights into the flight thermal environment and long term trends that are not apparent when viewed over short time scales. The flight thermal environment of the HST was less severe than expected, but seems to be warming at a rate between 1.0 and 1.3 degrees C per year.

This paper gives an update on the performance of the faint object camera following the highly successful installation of the corrective optics in COSTAR during the servicing mission. We review the effect that COSTAR has had on the point spread function and detector quantum efficiency, and discuss the improvements in our knowledge of sensitivity, PSF variations, camera distortion, and nonlinearity. The status of the f/48 relay, which has been successfully turned on a number of times, is reviewed.

We present the design, characterization, and flight performance of a sounding rocket instrument developed to address unanswered scientific questions regarding the extreme ultraviolet emissions of the star (epsilon) Canis Majoris (Adhara). The payload consists of an off axis parabolic telescope feeding a standard Rowland circle spectrograph and provides between 2 and 4 cm² of effective area at the short and long wavelength ends of the bandpass, repectively. The spectrograph has a resolution of approximately 800 and covers the wavelength range 600 - 919 angstrom. In this paper we discuss specifics of the optical and mechanical design and present results from the initial calibration. The payload is presently scheduled for launch from Woomera, Australia, in the fall of 1995.

The wide field planetary camera was launched onboard the Hubble Space Telescope in April 1990 and returned to earth during the HST first servicing mission in December 1993. We report on the ongoing examination of the returned hardware. In particular, a significant decline in performance at UV wavelengths in the exterior optics has been found and studied. This appears to be the result of polymerization of molecular contamination on the external optics by UV light reflected off the Earth's atmosphere. Some conlusions from a partial disassembly of the instrument and an examination of its filter elements are presented. We also discuss the effects of radiation on the CCD detectors during their stay in orbit. Radiation damage increased the numbers of hot pixels over time but had no other discernible effects on the performance of the CCDs.

The primary calibration standards for the focal plane structure (FPS) of the Hubble Space Telescope (HST) played a major role in the on-orbit corrections to the telescope during its first servicing mission. Conventional metrology tooling and techniques as well as electronic theodolite metrology system methods were applied to verify the predicted on-orbit positions of the replacement instrument interfaces, latches, and static mechanical envelopes. This paper will discuss the opto-mechanical calibration tooling that was used to develop a high fidelity mechanical simulator of the Aft Shroud region of the HST, and review the processes that were used at NASA Goddard Space Flight Center to verify that the replacement scientific instruments would fit into the flight FPS.

The Stratospheric Observatory for Infrared Astronomy is a planned 2.5 meter telescope that will be installed in a modified Boeing 747 aircraft and operated at altitudes above 40,000 feet. The telescope requires a primary mirror with an areal density of less than 70 kg/m² which can operate at elevations from 15 degrees to 70 degrees, and reach thermal equilibrium at -40 degrees C in less than 2 hours. A passive lightweighted monolithic primary mirror design with no active figure control has been shown to be a key element in meeting these requirements. A comparison of mirror designs using alternate mirror materials will be described.

We present designs for the application of holographically corrected solutions to standard problems in ultraviolet astrophysics. These designs offer advanced aberration control that allows for improved performance, and improved operational ease compared to other aberration reduction schemes. One of these designs has been successfully produced, and performs according to predictions.

A modular user-friendly computer program for the modeling of grazing-incidence type x-ray optical systems has been developed. This comprehensive computer software GRAZTRACE covers the manipulation of input data, ray tracing with reflectivity, and surface deformation effects, convolution with x-ray source shape and x-ray scattering. The program also includes the capabilities for image analysis, detector scan modeling, and graphical presentation of the results. The utilities have been developed to interface the predicted mirror structural and thermal distortions with the ray-trace. There is no commercially available (or published) program tailored for the analysis of grazing-incidence type optical systems. The GRAZTRACE program has the analysis and graphics capabilities similar to those of the standard design and analysis programs (CODE V and SYNOPSYS) for normal-incidence optical systems. This software is written in FORTRAN 77 and runs on a SUN/SPARC station. An interactive command mode version and a batch mode version of the software have been developed. The application of GRAZTRACE for the image modeling of AXAF-I (Advanced X-ray Astrophysics Facility-Imaging) telescope is also discussed.

Near-net-shape replication and ion beam figuring technologies were investigated for chemical vapor deposited (CVD) SiC to fabricate high performance, glancing incidence Wolter Type I x-ray mirrors. Small scale CVD experiments were performed on graphite mandrels to demonstrate replication of SiC shells that closely matched the design of the XMM 40th shell at 1/16th scale. The SiC shells were successfully separated from the graphite mandrels and then machined to the required dimensions. Ion beam figuring as a final fabrication step was investigated on Wolter Type I replicated SiC surfaces. Angular sputtering yields and surface roughness evolution with material removal were found to be sufficiently well behaved to favor ion beam figuring as a means of performing the final figuring step. The CVD-SiC fabrication technology for the x-ray telescopes as developed above appears scaleable. Finally, analysis of a single element CVD-SiC telescope, modeled after the AXAF-S 26th shell showed telescope deflections and weight to be 2.23 and 2.77 times less, respectively, than for a nickel replicated shell of the same dimensions.

We present the latest developments on the concept of space adaptive optics coronography. We review the principle of deformable mirror used to suppress the scattered light in a 'dark hole' region around the optical axis. We describe the main limitations of this concept. A description of the experiment which has been built at JPL and its first results are given.

NINA is the first of three telescopes of the Russian Italian Mission (RIM), devoted through the detection of cosmic rays to the study of galactic and extragalactic astrophysical phenomena. The detector of RIM-1 mission consists of 16 double sided silicon strips. The use of silicon technology is space applications has severel advantages thanks to its low consumption, high signal to noise ratio, low dead area, and no use of gas refueling systems. Indeed these detectors and the electronics used comes from balloon cosmic ray research carried out by the Wizard collaboration in the past years. NINA will be placed in a 700 km polar orbit on the Russian Resource-01 n. 4 satellite by the end of 1996. Solar and galactic cosmic ray nuclei from Hydrogen to Iron in the 10-100 MeV/n region will be studied. In addition to the physical goals, which include the study of anomalous component nuclei inside and outside the radiation belts, technological aspects of this low cost (1.5M dollars) mission will be equally important to the development of the following two steps of RIM mission: PAMELA and GILDA missions--devoted to antimatter and gamma ray research respectively--will make extensive use of the research and development performed with NINA.

Space-based interferometers dedicated to wide-angle astrometry would dramatically increase the accuracy of angular measurements fundamental to a wide range of astrophysical problems. The proposed Global Astrometric Interferometer for Astrophysics, a continuously rotating instrument comprising two or three interferometers, will reach the 5-20 (mu) as level on more than 35 million objects. The necessary wide field-of-view for such a precision could be obtained with a Fizeau interferometer. We propose a design for a 2.6 m baseline interferometer with two 0.5 m apertures, and overal dimensions compatible wiht the size of the Ariane V payload shroud. It has approximately 1 degree diffraction limited field-of-view. The response of the optical system to small perturbations on each optical element is given in terms of fringe visibility, which is shown to depend only on subaperuture spot separation.

A description of the main results of a theoretical study on the required power and coils to drive a large ferrimagnetic liquid mirror are briefly sketched and discussed. A number of possible options are evaluated and a case-study for the International Space Station Alpha is also given.

Rosetta is a cornerstone mission of ESA to have a roundez-vous with a periodic comet, namely Wirtanen P/1991 XVI. A basic instrument of its payload is an imaging system to observe this object both with a narrow and wide angle camera: during the approach phase, Rosetta will orbit around the comet and the two cameras will map the surface of the comet nucleus and the jets. In this paper a possible design for the wide angle camera is described: this solution adopts an all-reflecting, unobstructed three mirror configuration that permits to have a approximately equals 19 degrees X 17 degrees field of view with a F/3.2 aperture, with an optical quality of better than 80% geometrical encircled energy inside 150 microradians. The detector is a 2048 X 2048, 12 X 12 micrometers ² pixel CCD, possibly coated with a suitable fluorescent layer to be sensitive also in the ultraviolet spectral region (above 120 nm). We also describe a possible option, namely to have an add-on spectroscopic channel for obtaining spectral information in the UV region from 120 nm to 240 nm, along a slit keeping a spectral resolution of R approximately equals 500 over at least two degrees.

We showed that the output of an autocorrelation with a gas spectrum could be triple-correlated to reduce the effects of Gaussian noise. Such processing is directly applicable to a correlation spectrometer but could be applied to other designs. In spite of the added processing, triple- correlating the output of a spectrometer allowed us to generally increase the SNR by over a factor of ten. Even with as few as two measurements good results were obtained.

An influence is considered that profile shape of a relief hologram structure applied upon a primary mirror surface exerts on power and aberration features of a telescope's information and control channels. Expressions are obtained that give possibility to determine the hologram structure relief height being optimal for various symmetric and non-symmetric shapes of the relief profile and to estimate power loss in the information channel caused by this. As a result of these expressions analysis, it is found that from the standpoint of power loss minimization in the information channel the relief profile of symmetric shape is optimal being near-to- sinusoidal shape or near-to-triangular one with porosity of 0.5. Expressions are given, too, describing height and shape influence of the hologram structure profile and variations of these within the primary mirror aperture on aberrations in both information and control channels of a telescope. Basic requirements are formulated that are made for profile shape of the hologram structure applied upon the telescope primary mirror.

Nontraditional IR and submillimeter spaceborne telescope concept basing on blind-type parabolic multi-ring mirror is proposed and discussed. Preliminary results for optimization of mirror parameters by means of computer simulation are presented.

Mirror telescopes are designed. Primary mirrors diameter is from 13 cm to 80 cm, field-of- view is up to 15 degree and speed is up to F/1.2. The back focal distance is rather long and convenient for using large receivers, shutters, and filters. There is the telescope consisting of spherical mirrors only. Another telescope consists of three spherical mirrors and only primary mirror is aspherical one. It is intended to cool some mirrors with liquid helium in the space. It is proposed to use these telescopes for ecological space investigations of the Earth surface in large spectral range. The telescope D equals 80 cm was successfully used in the space.

Principles are discussed of numerical design and simulation of laser telescopes, using phase conjugation technique for compensation of the distortions, introduced by the primary mirror and some other elements. Described are the approaches to the dimensional and aberrational design, as well as numerical evaluation of the system compensational abilities. Several specific systems, in particular, the beam prototype for the space-based ecology monitoring LIDAR system, illustrate the principles discussed.

For the first time was realized the laser telescope (beam director), in which the phase conjugation provides the comprensation for the distortions, caused by the primary and secondary mirrors. Nearly diffraction limited laser beam divergence was realized under the significant disadjustments and disalignments of the segmented mirror.

New device, telescope-interferometer (TI), for astronomical observations is proposed. TI has the main advantage of pupil plane interferometry techniques, namely diffraction-limited resolution, which is twice as much than it may be obtained in the focal plane of telescope of the same aperture. At the same time, proposed techniques has a minimum of all possible distortions introduced under measurements. Main limitation of TI is necessity to scan the object plane. At every instant TI builds an image of one point of object observed only.

The constructional decisions and main technical features for the optical bench of large optical test facility (LOFT) 'vertical', designed for complex testing large space telescopes have been considered in this report. The approaches and results of investigations of vibration-isolated optical bench dynamics by methods of physical and mathematical modeling are presented.

This paper is concerned with the collimator equipment of the large optical test facility (LOTF) 'vertical' designed for testing space telescopes. It is being created in the Research Center 'S.I. Vavilov State Optical Institute' in Russia. The optical scheme and special structural features of the vacuum vertical-type double-mirror collimator will be covered here. This paper deals with technical data and potentials of collimator focal equipment. Estimations of the collimator thermal aberrations caused by temperature fields coming from thermal simulators are put forward.

This article describes the Clementine UV/Visible (UV/Vis) multispectral camera, discusses design goals and preliminary estimates of on-orbit performance, and summarized lessons learned in building and using the sensor. While the primary objective of the Clementine Program was to qualify a suite of 6 light-weight, low power imagers for future Department of Defense flights, the mission also has provided the first systematic mapping of the complete lunar surface in the visible and near-IR spectral regions. The 410 g, 4.65 W UV/Vis camera uses a 384 X 288 frame-transfer silicon CCD FPA and operates at 6 user-selectable wavelength bands between 0.4 and 1.1 micrometers . It has yielded lunar imagery and mineralogy data with up to 120 m spatial resolution (band dependent) at 400 km periselene along a 39 km cross-track swath.