The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite will obtain high spectral resolving power ((lambda) /(Delta) (lambda) equals 30,000) measurements of astrophysical objects in the 905 - 1195 angstroms wavelength region from low-earth orbit. The instrument's high effective area (30 - 100 cm²) and low detector background will permit observations of solar system, galactic, and extragalactic targets that have been too faint for previous instruments at this high resolution. The instrument design achieves both high resolution and high throughput by using four nearly identical optical channels. The optics consist of four normal incidence mirrors, four high density holographically-ruled diffraction gratings, and a pair of large format double delay line detectors. These components are supported by a graphite-composite structure. A commercially-procured spacecraft provides pointing stability of 0.5 arcseconds (1 (omega) ), by using data from a Fine Error Sensor included in the instrument. In early 1995 the FUSE mission was reconstructed to be a lower-cost, PI-class mission. The construction phase began in December, 1995, and launch is scheduled for late 1998. We present a description of the FUSE instrument, including details of the optical and mechanical design, along with an estimate of its on-orbit performance.

We describe the Lyman Imaging Telescope Experiment (LITE) which is a NASA Ultraviolet Astrophysics Branch supported Advanced Mission Concept mission. The prime scientific aim of the LITE mission will be to carry out the first set of very high spatial resolution (0.2 arc sec), wide field of view (10 arc minute), pointed observations in several narrow wavelength bands in the far ultraviolet region of the spectrum (900 - 1600 angstroms). LITE will possess excellent detection sensitivity, such that limiting magnitudes for typical images are expected to be close to that of the HST WFPC II instrument. The proposed far ultraviolet astrophysical studies will encompass the emission of diffuse gas with temperatures in the range 80,000 - 1,000,000 K.

A concept study was performed in 1994 to develop a mission design for a telescope to achieve the highest possible spatial resolution in the 10 - 30 micron range within a $DOL200 million mission cost cap. The selected approach for the resulting Mid-InfraRed Optimized Resolution Spacecraft (MIRORS) concept design utilizes a partially filled five meter aperture. A simple deployment scheme permits this spacecraft to be fit within the volume envelope and mass capabilities of a Med-Lite launch vehicle. Low bandwidth cryogenic actuators, which dissipate no heat once set, will align the optics after on-orbit thermal stability is achieved. Image stabilization, fine point and stray-light control are achieved through use of a novel actuated Offner relay. Image reconstruction techniques developed for IRAS will be used to deconvolve nearly diffraction-limited images at 10 microns (FWHM approximately 0.5 arcsec). A Lissajous orbit about the L₂ sun-earth libration point (sun-earth- L₂ on a straight line) is adopted because its extremely stable thermal environment results in correspondingly high telescope mechanical stability and optical performance. This orbit, combined with a spacecraft configuration which incorporates an inflatable sunshield and a deployable four- stage v-groove thermal shield, enables the optics to radiatively cool <25 K. The large format focal plane will be actively cooled to <8 K by a vibration-free, long-life sorption refrigerator.

POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; and other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the `instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer, as is required when out-of-plane observations are made. An instrument for astrometry, unlike those for imaging, can be compact and yet scientifically productive. The POINTS instrument is compact and therefore requires no deployment of precision structures, has no low-frequency (i.e., under 100 Hz) vibration modes, and is relatively easy to control thermally. Because of its small size and mass, it is easily and quickly repointed between observations. Further, because of the low mass, it can be economically launched into high Earth orbit which, in conjunction with a solar shield, yields nearly unrestricted sky coverage and a stable thermal environment.

A separated spacecraft optical interferometer mission concept proposed for NASA's New Millennium Program is described. The interferometer instrument is distributed over three small spacecraft: two spacecraft serve as collectors, directing starlight toward a third spacecraft which combines the light and performs the interferometric detection. As the primary objective is technology demonstration, the optics are modest size, with a 12-cm aperture. The interferometer baseline is variable from 100 m to 1 km, providing angular resolutions from 1 to 0.1 milliarcseconds. Laser metrology is used to measure relative motions of the three spacecraft. High-bandwidth corrections for stationkeeping errors are accomplished by feedforward to an optical delay line in the combiner spacecraft; low-bandwidth corrections are accomplished by spacecraft control with an electric propulsion or cold-gas system. Determination of rotation of the constellation as a whole uses a Kilometric Optical Gyro, which employs counter-propagating laser beams among the three spacecraft to measure rotation with high accuracy. The mission is deployed in a low-disturbance solar orbit to minimize the stationkeeping burden. As it is well beyond the coverage of the GPS constellation, deployment and coarse stationkeeping are monitored with a GPS-like system, with each spacecraft providing both transmit and receive ranging and attitude functions.

Two versions of a kilometric interferometer with equivalent science capabilities have been studied, one located on the Moon and the other operating as a free-flyer. It has been found that the Moon is not the ideal site for interferometry because of tidal and micro-meteorite induced disturbances, the need for long delay lines and the large temperature swings from day to night. Automatic deployment of the Moon- based interferometer would be difficult and site preparation and assistance by man appear to be essential. The free-flyer would be implemented as a very accurately controlled cluster of independent satellites placed in a halo orbit around the 2nd Lagrange point of the Sun-Earth system. Both versions could attain the required scientific performances and each one needs the same type of metrology control. The free-flyer is intrinsically advantageous because of its reconfiguration flexibility, quasi-unlimited baseline length and observation efficiency (the Moon-based interferometer cannot be operated during the lunar day because of stray light). The free-flyer is better suited for implementation in the near or mid-term future, but the Moon-based version could be considered in the long term when a human presence would permit maintenance and upgrading leading to a longer lifetime with continuous performance enhancement.

The Hubble Space Telescope presents unique possibilities for the detection of extrasolar planets. The enormous difference in light intensity between such a planet and its associated star makes detection of any planetary signal intrinsically very difficult. By deploying an inflatable sphere to act as an occulting disk to eclipse the direct light from the associated star, the technical difficulty of planetary detection is greatly reduced. However, observation periods might need to be restricted to times when the occulting structure is in the shadow of the earth or the moon, since light reflected by this structure would impede the detection of any planetary optical signal. Inflatable structure technologies necessary to implement such an idea have already been proven by the success of Echo I. Detailed analysis of possible orbits for the occulting sphere and its concomitant dimension are presented together with a history of this concept. A highly accurate occulting sphere would also make possible a telescope of truly novel concept, here termed a diffracting telescope. Such a telescope would use the occulting sphere as its objective lens, and would have a resolution limit based on the diameter of that sphere, in analogy with the Rayleigh limit criterion for refracting and reflecting telescopes.

We describe the engineering design and operational concept for a series of three complementary top mounted balloon- borne experiments to measure the Cosmic Microwave Background Radiation anisotropy, culminating in a two week circumpolar flight from McMurdo Station, Antarctica. Each experiment is designed to provide a maximum science return in addition to acting as a pathfinder to the successor flights of top- mounted balloon-borne experiments. The experiment program, named TopHat, will involve the launch and operation of the first far-infrared and microwave telescope flown entirely from the top of a 28 million cubic foot balloon. It utilizes a two axis gimbal pointing system, a one meter Cassegrain optical system with a chopping secondary mirror, and a ³He evaporation cryostat designed to maintain a bolometer detector temperature of 0.25 K for 30 days without cycling. The series of flights will begin with an engineering test flight scheduled for launch in July 1996 from Palestine, Texas, followed by a pointing experiment to be flown from Ft. Sumner, New Mexico in April 1997. A spinning experiment will be launched from Ft. Sumner in April 1998 and Antarctica in December 1998.

The High Throughput X-ray Spectroscopy (HTXS) mission is dedicated to observations at high spectral resolution. The HXTS mission represented a major advanced, providing as much as a factor of 100 increase in sensitivity over currently planned high resolution X-ray spectroscopy missions. This X- ray equivalent of the Keck Telescope will mark the start of a new era when high quality X-ray spectral will be obtained for all classes of X-ray sources, over a wide range of luminosity and distance. With its increased capabilities, HTXS will address many fundamental astrophysics questions such as the origin and distribution of the elements from carbon to zinc, the formation and evolution of clusters of galaxies, the validity of general relativity in the strong gravity limit, the evolution of supermassive black holes in active galactic nuclei, the details of supernova explosions and their aftermath, and the mechanisms involved in the heating of stellar coronae and driving of stellar winds.

The Hard X-Ray Telescope was selected for study as a possible new intermediate size mission for the early 21st century. Its principal attributes are: (1) multiwavelength observing with a system of focussing telescopes that collectively observe from the UV to over 1 MeV, (2) much higher sensitivity and much better angular resolution in the 10 - 100 keV band, and (3) higher sensitivity for detecting gamma ray lines of known energy in the 100 keV to 1 MeV band. This paper emphasizes the mission aspects of the concept study such as the payload configuration and launch vehicle. An engineering team at the Marshall Space Center is participating in these two key aspects of the study.

A lightweight segmented adaptive optical telescope for spaceborne applications is described and details of a hardware demonstration program presented. This program demonstrates, at a 4-meter aperture, a configuration and technologies for large deployable imaging systems. Real-time sensing and control is achieved using a suite of sensors to continuously measure wavefront error and segment phasing. The resulting state vector is operated on by the control algorithms and the resultant optimization commands applied to precision actuators to correct the system wavefront. The demonstrated technologies are discussed, along with details of the space qualifiable hardware configuration. These technologies include: a shearing interferometer wavefront sensor, autonomous hierarchical control sequences, lightweight graphite composite structures, and large lightweight optics.

Very high resolution spatial interferometry requires picometer level 1D metrology, surface metrology and 3D metrology. The absolute distance measurements with accuracies of only 1 part in a million are required due to the careful design of spacecraft like the proposed Stellar Interferometry Mission, carrying high resolution stellar interferometers. An absolute calibration system for the surface gauge described in a previous paper is demonstrated. A self-calibrating absolute metrology system with a repeatability of 2 microns rms over a one-way distance of a meter is demonstrated. The accuracy calibration of this gauge is in progress. An auto-aligning, 3D metrology gauge is constructed using the sub-picometer linear metrology gauge described in earlier papers. Initial test results from this demonstration are presented.

The proposed New Millennium Interferometer consists of three spacecraft separated by up to several kilometers. A heterodyne laser metrology system is proposed to measure the relative distances between the spacecraft. Because diffraction losses for a round-trip measurement are prohibitively large, a two-laser metrology system has been suggested in which each spacecraft has both a laser and a receiver. The system has been successfully demonstrated with a one meter baseline and verified by a conventional single- laser system in a laboratory experiment. The precision was limited by thermal effects in the room environment for time scales greater than one minute. The single-laser system obtained a precision of 3 nm for integration times up to 0.5 seconds. The two-laser system obtained a precision of 20 and was limited by self-interference and electronics noise. The resolution of the two-laser metrology system was (lambda) 30.

The Far Ultraviolet Spectroscopic Explorer (FUSE), currently being fabricated and scheduled for a 1998 launch, is an astrophysics satellite designed to provide high spectral resolving power ((lambda) /(Delta) (lambda) equals 30,000) over the interval 910 - 1180 angstroms. It consists of four co- aligned, normal incidence mirrors that illuminate separate Rowland circle spectrograph channels equipped with holographic gratings and delay line microchannel plate detectors. The FUSE mirrors are rectangular, off-axis paraboloids with stringent reflectivity, imaging, lightweighting, and mechanical requirements. Two mirrors have Al + SiC coatings on Zerodur substrates, and the other two have Al + LiF coatings, also on Zerodur substrates. Important aspects of the optical and mechanical design are discussed, including the surface accuracy specifications at different spatial scales and the micropositioning actuators, which provide submicrometer focus and subarcsecond tip-and-tilt adjustment of the mirrors. Also discussed is the proposed design validation, including the predicted surface deformations induced in the mirrors when they are subjected to various gravitational and metrology mount conditions.

The Advanced Camera for the Hubble Space Telescope will have three cameras. The first, the Wide Field Camera, will be a high throughput (45% at 700 nm, including the HST optical telescope assembly), wide field (200' X 204'), optical and I-band camera that is half critically sampled at 500 nm. The second, the High Resolution Camera (HRC), is critically sampled at 500 nm, and has a 26' X 29' field of view and 25% throughput at 600 nm. The HRC optical path will include a coronagraph which will improve the HST contrast near bright objects by a factor of approximately 10. The third camera is a far ultraviolet, Solar-Blind Camera that has a relatively high throughput (6% at 121.6 nm) over a 26' X 29' field of view. The Advanced Camera for Surveys will increase HST's capability for surveys and discovery by at least a factor of ten.

Shearing interferometric spectrometers can be used for all- reflective, high-resolution (R equals 10⁴ - 10⁶) spectroscopy. The spectrometers can provide simultaneous imaging and be used for both sensitive emission and absorption spectroscopy of diffuse and point sources. Our designs require interaction with only a single optical element to create interference fringes and so can be used in the EUV and FUV (100 - 2000 angstroms) bandpass. Spectral interferometers consume a fraction of the volume required by conventional spectrographs with comparable resolution and consequently provide a promising technique for space missions.

An all-reflective, unobstructed and unvignetted optical design for a wide field of view (12 degree(s) squared) camera is described. The camera is obtained by two sections of conical surfaces and allows an efficient stray light rejection, in order to detect faint gaseous features in the neighborhood of the comet nucleus against its bright body. Very good optical performances are obtained with a 2048 X 2048 CCD array detector allowing more than 90% of the encircled energy into a single 12 micrometers squared pixel over the whole detector area. Distortion is kept to a few percent allowing a backup operation of this camera for navigation purposes. Also an add-on option of an off-Rowland quasi-stigmatic spectrograph is described. The optical design is such that this spectrograph is fed by a plane mirror mounted on the camera filter wheel, and the spectrum is sent on the same CCD detector of the imaging mode in a similar way. Thus a very low resource additional spectroscopic option is obtained. This channel mounts a 4 degree(s) length entrance slit, and permits to obtain a very good spectral and spatial resolution.

Our current knowledge of production and destruction of light elements in astrophysical processes suggests that deuterium is produced during Big Bang nucleosynthesis and destroyed when cycled through stars. Primordial deuterium abundance can be determined by measuring the D/H ratio in a variety of astrophysical environments with different degrees of chemical evolution: the D/H ratio of unprocessed material directly gives the primordial value, while the ratio in processed material is expected to be lower and consistent with the predictions of galactic chemical evolution models. Here we focus our attention on deuterium abundance determinations of chemically processed material such as the interstellar gas in our Galaxy. Up to now, most of the determinations of deuterium abundance have been performed in the solar system or in local interstellar clouds. However, the overall accuracy of the measurements in local clouds is still insufficient to probe evolutionary trends. New D/H measurements in clouds at different locations in our Galaxy would be necessary to establish this issue, while interstellar measurements in nearby galaxies would give further constraints on the deuterium evolution in different galactic environments. With this goal in mind we have evaluated the capability of the Lyman channel of the SPECTRUM UV Rowland spectrography in determining deuterium column density in distant interstellar clouds. Three packages have been used to obtain realistic predicted spectra and to derive `observed' column densities: (1) the MIDAS package `CLOUD', to generate theoretical interstellar absorption profiles; (2) the `Synth' package developed in the IRAF environment by two of the authors to simulate spectroscopic observations of point sources obtainable with an astronomical spectrograph, (3) the FITLYMAN package inside the Lyman context of MIDAS to derive `observed' column densities from predicted spectra. The minimum exposure times, t_min, required to obtain a approximately 0.1 dex accuracy in the `observed' column densities, were derived by varying the input interstellar hydrogen column density. As a result, we show that the Lyman channel of the SPECTRUM UV Rowland spectrograph is up to the task of deriving accurate H and D column densities of low and medium column density interstellar clouds while it fails for N(HI) >= 10²¹ atoms cm^-2.

This paper describes a low-mass, (approximately 1.2 kg) low- power (approximately 1.5 watts) ultraviolet telescope- imaging spectrograph which covers the wavelength range 65 - 165 nm with a spectral resolution of 0.5 nm. The instrument is an evolution of the EUV channel of the Ultraviolet Imaging Spectrograph for the Cassini mission in which the mechanical structure, detector electronics, and logic electronics were modified in order to significantly reduce mass and power. It has a novel combination of optical coatings which maximize its throughput for wavelengths greater than 115 nm but still provide significant sensitivity at the shorter wavelengths. The instrument design is optimized to meet the 1-A atmospheric science objectives of the Pluto Express fly-by mission, but it is also suitable for observing the outer atmospheres of other planets including earth.

The second servicing mission for the Hubble Space Telescope (HST), scheduled for early 1997, will be the first change in the spectroscopic capabilities of HST since its initial deployment. The Space Telescope Imaging Spectrograph (STIS) is a multipurpose instrument covering the far ultraviolet (FUV) through near infrared spectral range. It acquires spectra at several spectral resolutions, which facilitates observations at many distances and brightnesses. STIS will replace both of the first generation spectrographs, the Goddard High Resolution Spectrograph and the Faint Object Spectrograph. This will allow the addition of a Near- Infrared Camera. STIS required the development and testing of many high quality diffraction gratings, including several very difficult echelles for the FUV. The methods and results of this grating development program are presented. The results serve as a snapshot of industry capabilities for producing high quality spaceborne diffraction gratings.

In this paper, a CCD position detection system for measuring the displacements and deformations of structure is introduced. This measurement method is based on the position detection technique of digital images. A bright spot is fixed on the object measured and imaged to the target of CCD camera by a telescopic lens. The CCD target converts the optical information into equivalent electric signal. The video frequency signal is digitized into an array of 512 X 512 pixels by the analog-to-digital converter and then transmitted into the microcomputer. The computer controls the data acquisition system performs image processing and detects the position of spot. Comparing the position with original position of spot, the displacement of object is obtained. By using high accurate position detection software the accuracy of detection is up to 0.01 mm in 6 m distance between the object and the observation point, the distance can extend to 100 m and farther.

Two mirror systems with zero spherical aberration are examined. Special kinds of two mirror systems are investigated. They can be used in X-ray or UV spectral regions. A few new fast aplanatic systems are described. Some systems can not be found using Seidel and Gauss optics. Systems can be used for fast telescopes, spectrographs, radio-telescopes, light-collectors etc. Design of the Big Space Telescope is discussed. It will be launched in 1999.

The possible element of telescope optical system with the composite aperture can be two-mirror system, consisting of two confocal paraboloids (Mersen system). This system is an aplanatic anastigmat for infinite target. Its obvious deficiency is the image field curvature. The ways of its elimination are defined by the application of optical system. The possible versions of their constructive realization are considered.

To correct spherical aberration of a spherical mirror the apochromatic meniscus lens may be used. The linear observation of light beams is taken as a set parameter. The location of meniscus lens, concerning spherical mirror and its radiuses correction are taken as corrective parameters. In this case the dependence of parameters, determining the sphere of meniscus system existence, was received. The meniscus lens was received on the condition of aplanatic correction of aberrations. The transformation of this corrector in a two component system leads to the original construction of the optical scheme. The versions of a practical application of the received lens design were considered.

A dynamic analysis of a flexure support system for a one- meter primary mirror in a space telescope is presented. It is assumed that the primary mirror is held by a three-point flexure support at the back surface. The design study is to be conducted with three different power spectral density functions (PSDF) and four different sized support systems. Mechanical responses of the mirror to each PSDF are to be examined. Using the finite-element analysis program, MSC/NASTRAN, the maximum root-mean-square values of the bending stress and the axial stress in the flexure system due to the launch loads are calculated. As a result, the stiffness and the strength of the flexure in the vertical (optical axis) and tangential directions to accommodate the launch loads are discussed.

The relationship between the performance of a partial correction adaptive telescope using laser guide stars and the star brightness is discussed. The laser energy requirements for Rayleigh guide star as well as sodium guide star are presented in cases where the diameter d of a subaperture of the telescope is larger than the atmospheric coherence length r₀ and the residual rms phase error across the subaperture is larger than 0.63.

The Calibration Database System for the Hubble Telescope is a system for calibration data reception, data processing, cataloging, archiving, and delivery to Space Telescope's ground system calibration pipeline and to public on-line archives. A description of this system and access to the calibration data is now available through the Internet on the World Wide Web. The data consists of spectral standards, stellar and galaxy atlases, and the calibration reference data from the five science instruments on Hubble. The calibration data of the instruments; cameras, spectrographs, and the fine guidance sensor; are used to correct for such properties as field flatness, distortion, and sensitivities, among others. Descriptions of the database system, the data, and the web site will be presented here.

New advanced photonic instrumentation previously developed for photonically controlled phased array antennas/radar work, is proposed for astronomical applications. The proposed adaptive optics approach is to use these remotely located photonic phase, time delay, and amplitude control modules for wavefront correction and optical beamforming for astronomical applications, particularly where fiber remoting can lead to larger observation apertures and/or signal processing gains. Scenarios using our photonic instrumentation such as solar wind sensing using radio frequency antenna arrays and fiber-linked optical telescope arrays are highlighted.

The 1-m STARS telescope was one of the five candidates for the coming ESA medium size (M3) mission. Based on the very compact Triply Reflecting Telescope concept, the STARS telescope provides diffraction limited image performance over a large field of view (+/- 0.75 degree(s)). Two different focal plane instruments, the Astero Seismology Detector and the Activity Line Monitor observe simultaneously in different wavelength bands in the range from 110 to 750 nm. Within the frame of an ESTEC conducted phase A study, the optical, mechanical, and thermal design of the complete telescope assembly including the accommodation on the service module has been investigated. A stiff and lightweight hexapod trusswork structure with struts from carbon fiber reinforced composites has been worked out as the most advantageous concept with respect to mass, opto- mechanical, and thermal properties. The major issues were the maintenance of an axial distance stability of +/- 10 micrometers between primary and secondary mirror as well as the fulfillment of certain thermal requirements for the two scientific instruments (Activity Line Monitor and Asteroseismology Detector). The finally chosen concept has a fully reflective optical design with higher order aspheric optical surfaces, a passive thermal design, is extremely lightweight (< 190 kg), and has a high stiffness (all eigenfrequencies are above 60 Hz). For the optics, a simpler approach with only conical reflective surfaces and an additional refractive correction element has been investigated.

This advanced steering mirror design combines large angular travel with high bandwidth dynamic response and high accuracy. The benefits for space-based interferometry include more commonality between mechanisms, reduced spares inventory, lower procurement costs, and reduced risk. These devices are used for alignment and fine-steering functions in the coherent combination of light from several collectors to independent combiner optics. Since this design can be used for alignment and fine-steering functions, a reduced number of component designs are required for interferometric missions. In some cases functions can be combined into a reduced number of mechanisms. The steering mirror design achieves this with a simplified electromagnetic actuator configuration having no iron other than the magnets in the magnetic path. Other benefits of the simplified design include: a compact steering mirror envelope that is only slightly larger than the mirror itself, simplified fabrication and assembly, and reduced power consumption. This paper includes the application, requirements and configuration along with performance analyses and verification test data. Analytical models for force, power, thermal, magnetic, dynamic and mass properties as well as various figures of merit are described.

The Calibrated Infrared Source (CIRCE) is a radiometrically calibrated, highly uniform, infrared source for the calibration of the Hubble Space Telescope Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument. The CIRCE output encompasses the entire NICMOS spectral range, from 0.8 to 2.5 micrometers . CIRCE is designed to operate in vacuum, thus allowing calibration of NICMOS under flight- like conditions. CIRCE is the calibration standard for several tests, including: throughput measurement, flat fields, sensitivity, polarizer characterization, and Red Leak Test.

We present the preliminary results of a feasibility study performed by a team of scientists and engineers from NASA, academia and industrial concerns. The candidate concept is a deployable 8 meter diameter telescope optimized for the near infrared region (1 - 5 microns), but with instruments capable of observing from the visible all the way to 30 microns. The observatory is radiatively cooled to about 30 K and would be launched on an Atlas II-AS to the Lagrange Point L2.

This paper describes the design, development and testing of a precision steering mirror used to provide laser pointing in a laser communication link. The mechanism is used to steer a 9 mm output laser beam about two orthogonal axes using an open loop command. The pointing error budget is 13 (mu) rad over the +/- 6.5 mrad pointing region. The mirror is mounted on a 2-axis flexure suspension system and driven by linear actuators. Position sensors measure the mirror position with respect to the base. The drive electronics utilize redundant servo electronics cards. This paper provides a general overview of the mechanism pointing requirements. After the requirements definition, an overview of the hardware configuration is given, followed by critical performance summaries and test results.

We present a concept for a Next Generation Space Telescope with a monolithic 8 X 4 meter primary, optimized for the near infrared region (2 - 5 microns). The observatory is radiatively cooled to about 35 K and would be launched on an Ariane 5 to the Lagrange Point L2.