The design of a multimode IR spectrometer/imager for the ESO VLT is discussed. The system has two cameras optimized separately for the 1-2.5-micron and 2.5-5.0-micron spectral regions, used to either view the on-axis focal plane for direct imaging or to reimage the intermediate spectrum formed by a grating spectrometer whose input slit is located a few arcmin off axis. The characteristics of the imaging and the spectrometry are described, and a diagram of the opticaL layout of the system is presented together with the spot diagrams for the camera objectives and for the combined spectrometer/camera.

The optical configurations adapted for the IR Imaging Spectrometer (IRIS) designed for AAT are described together with the mechanical design of the spectrometer. The direct imaging of IRIS will provide a number of different angular scales and corresponding fields, with remotely controlled field selection amongst a subset of these. With the widest field, each 0.06-mm pixel will be 2 arcsec; with the narrowest field, it will be about 0.1 arcsec square. The IRIS will be used at both the f/15 and f/36 Cassegrain foci, for the wide-field imaging and the spectroscopy, respectively. Diagrams of optical configurations and the mechanical assembly of IRIS are presented.

The optical and the cryogenic designs for IR imagers and spectrographs of the 8-m UK Large Telescope (UKLT) are described. Performance figures for astronomical observations are presented showing that the basic designs can be matched to the range of optical configurations of 3.5 to 10 m telescopes. A diagram of the cryogenic spectrometer for the UKLT showing the layout of optical elements is presented together with schematics of the f/7 imager.

The main features of the Cooled Grating Spectrometer (CGS4), for the United Kingdom Infrared Telescope (UKIRT), are described. The CGS4 for use at 1 to 5 microns is designed to fully utilize foreseeable arrays and to take maximum advantage of the solid imaging detectors. The spectrometer can use low dispersion first order grating in a back-to-back configuration with a high dispersion echelle, giving wavelength resolutions from approximately 1,000 to 24,000.

This paper describes an implementation of a recently developed charge amplifier, called Integration Amplifier, in the UKIRT 7 channel spectrometer (CGS2), resulting in the conversion of the CGS2 from the traditional transimpedance amplifier to a commercial charge integration scheme. Also described is a new data acquisition system; the news system allowed the implementation of a noise reduction algorithm which is a mojor factor in the improved sensitivity of CGS2. The noise reduction algorithm is presented together with a system diagram of CGS2.

This paper describes the near-infrared grism spectrometer and imager (GRIM) designed for use on the Astrophysical Research Consortium telescope. The GRIM system incorporates a wide range of imaging, spectroscopic, and polarimetric capabilities. Attention is given to the mechanical and optical layout of GRIM, the details of the optical design, and the basic components of the remote observing system.

A novel cryogenic grating spectrometer (FCAS) is being designed for observations of volatiles in cometary and planetary atmospheres, and in newly forming planetary systems. The instrument features two-dimensional detector arrays coupled to a high-dispersion echelle by infrared fibers, and will achieve a spectral resolving power of about 40,000. The primary observational platform for this instrument will be the Kuiper Airborne Observatory, but it will also be configured for use at ground-based observatories. Initially, the spectrometer will use a 58 x 62, 1- to 5-micron InSb array. Larger-format IR arrays and arrays of different composition, will later be incorporated as they become available. The instrument will be used in two modes. The first uses a large format IR array in the spectral image plane for the customary one-dimensional spectral-one-dimensional spatial coverage. In the second mode, a massive, coherent bundle of infrared transmitting ZrF4 fibers will be installed after the dispersive element, to reformat the two-dimensional array into an elongated one-dimensional array for wide spectral coverage, allowing multiple lines to be measured in a single integration with high sensitivity. The overall instrument design is discussed, and the system sensitivity is estimated.

the prime focus of the Wyoming Infrared Observatory (WIRO) 2.3-m telescope. The detector is a 64 x 64 element HgCdTe array. A microprocessor-based control board residing on the dewar clocks the CCD multiplexer, controls the double-correlated sampling, and digitizes the detector signal. All voltage levels and clocking sequences can be adjusted by software in real time. The data acquisition computer communicates with the control board over a modified RS-232 link at an adjustable rate (usually 50 kilobaud). This allows virtually any computer to be used for data acquisition with a minimum of difficulty. The optics are optimized for the study of extended sources of low surface brightness, with maximum optical throughput. The f/2 primary is followed by a liquid-nitrogen-cooled Wynne corrector and two cold-filter wheels with a capacity of 12 individual filters and a 90-degree CVF segment. The positions of the lens, the instrument, and the filter wheels are adjusted by stepper motors. The plate scale is 2.06 arcseconds per pixel.

ProtoCAM, a new infrared array camera, has been built for the NASA 3-m Infrared Telescope Facility (IRTF). The camera is built around a 62 x 58 InSb hybrid array and is sensitive throughout the 1-5-micron atmospheric windows. The camera is equipped with standard astronomical filters as well as a full complement of continuously variable filters providing a spectral resolution down to 1 percent. On the IRTF, the platescale is variable real-time from 0.14 to 0.35 arcsec. The camera, the electronics, the software, and the performances are discussed, and some preliminary astronomical results are presented.

This paper describes the design and the performance of the Astrophysical Research Consortium prototype near-infrared camera (pNIC) designed to test focal plane arrays both on and off the telescope. Special attention is given to the detector in pNIC, the mechanical and optical designs, the electronics, and the instrument interface. Experiments performed to illustrate the most salient aspects of pNIC are described.

The Fabry-Perot spectrometer designed for NIR spectroscopic observations on the Balloon-borne Infrared Telescope (BIRT) is described in detail. Particular attention is given to the newly developed frequency switching method used in the BIRT, which is especially suitable for observations of spatially extended emission because the frequency switching mode does not require spacial chopping. Observations are described from two successful experiments conducted in 1988 using the Fabry-Perot spectrometer on the BIRT, in both the spatial chopping mode and the frequency switching mode.

The Japanese-made Balloon-borne Infrared Telescope (BIRT) designed for FIR astronomy is described. The BIRT system includes a 50-cm-diam telescope; an attitude-control system consisting of an attitude stabilization and a pointing and tracking subsystems; the ground support system consisting of four personal-computer systems; and electronics consisting of three small computer systems, servo circuits, power amplifiers, and other small circuits. Between 1985 and 1988, the BIRT has flown eight times, demonstrating that it is able to provide a suitable telescope observations on a stable platform with a long integration time. Structural diagrams of the BIRT overall system, the optical system, and the wobbling mechanism are presented along with a block diagram of the on-board electronics.

The optical design of a high-resolution 2-5-micron IR cryogenic echelle spectrometer which is currently under construction at NOAO is described. Special attention is given to the design and the purpose of the four units into which the spectrometer's optic can be divided: the foreoptics unit, the order-separation filter and slit unit, the echelle-collimator unit, and the camera unit. Optical specifications of each of these units are summarized.

The design of an infrared cryogenic echelle spectrograph for use on the NASA Infrared Telescope Facility is described. The resolving power achieved over the range 1-5.4 microns is 1-40,000 with slit widths of 2.0-0.5 arcsec. The spectrograph is used in a single order with a 30-arcsec-long slit. No cross dispersion is provided because of the small number of orders that can be observed at once and the need to keep the instrument as small as possible. A closed-cycle cooler is used in lieu of cryogens in order to achieve greater reliability and ease of use at the telescope. The optical layout, the design philosophy, the modes of operation, and the construction details are provided.

Results are presented of an evaluation of the first RANICON detector with a Negative Electron Affinity (NEA) photocathode, known as the Red-RANICON. The Red-RANICON offers a photocathode responsive quantum efficiency of about 22 percent from 0.6 - 0.9 micron, yielding a significant improvement in photon counting performance when compared with multialkali (S20) photocathode detectors. The operating characteristics of the Red-RANICON are similar to standard 25-mm active-area RANICONS, with imaging formats of 512 x 512 or 1024 x 1024 pixels. Spatial resolution is currently about 80 microns FWHM and could be improved to 40 microns FWHM with a modest decrease in the photocathode to microchannel-plate gap. The application of the Red-RANICON to high-resolution imaging and other applications requiring excellent temporal resolution is discussed. Future prospects for improving the long-wavelength response and quantum yield are also explored.

The Hughes 20 x 64 Si:As impurity band conduction arrays designed for ground-based and spaceborne astronomy observations is described together with experiments performed at NOAO to test these arrays. Special attention is given to the design and the characteristics of the test system and to the test methods. The initial tests on two columns of one array indicate that the array is easy to operate and performed satisfactorily.

This paper describes the Multiple Mirror Telescope (MMT) facility and discusses the demands placed upon the MMT by observations with the Thermal Infrared Photometer system, with special attention given to the subsequent modifications of the MMT-Photometer facility. It is shown that the MMT-Photometer competes well in sensitivity with similar detector systems currently operating on conventional single-mirror telescopes. The instrument will reach N (10.6 microns) magnitudes of 10 or better in integrations of one hour through a 5.4 arcsec aperture.

This paper describes the optical system and the electronics of a newly developed low-resolution IR spectrograph, designed for ground-based and airborne observations. The spectrograph covers the entire 2.9- to 13.5-micron spectral region simultaneously, without scanning, at a nominal resolving power of 50 and a minimum resolving power of 20. The new spectrograph equals in spectral coverage to circular variable filter spectrometers that contain three filter segments. Because all of the detectors view the source through the same aperture, telescope tracking errors do not result in spectral ambiguities such as those that can arise in scanning spectrometers.

The principles involved in the IR presensitization photography (IRPP) are discussed, and the feasibility of using IRPP in solar IR astronomy is investigated. Images of the solar disk were acquired in the 1- to 2-micron regime, demonstrating that IRPP is a feasible technique for solar imaging. However, in order to use IRPP images for solar research, the image quality needs improvement in terms of resolution and photometric accuracy.

Recent research efforts aimed at optimizing charge-coupled devices (CCDs) after their manufacture to achieve maximum quantum efficiency, wide spectral bandpass, and excellent cosmetics and surface flatness are discussed. Results are presented of a new acid thinning agitation technique which produces very uniform, high-quality surfaces on large area square and rectangular CCDs and 4-in silicon wafers for back illuminated operation. A method of cleaning thinned CCDs before antireflection coating for increased quantum efficiency is also discussed. The results of initial experiments with a new packaging method to mount thinned CCDs while maintaining a very flat imaging surface are presented. This bump bonding mounting technique increases yield due to reduced handling and robust packaging and is expandable to tightly packed large area focal plane mosaics.

This paper describes the structural design and the performance of a CCD camera system developed for use at the prime focus of the 105-cm Schmidt telescope at Kiso Observatory. In this system, the CCD chip is housed in a compact vacuum microchamber holding a Joule-Thomson cryogenic refrigerator, mounted on the plate holder adaptor located at the prime focus of the telescope. A computer controls the CCD driver electronics. Digital image data can be displayed on a CRT and can be saved on a magnetic tape.

The characterization and low light level performance of the TC215-31 CCD is presented. This device has 12 by 12 micron pixels in a 1024 x 1024 format, with an active image area of 1000 x 1018 pixels. The device is evaluated in terms of its linearity, dark current, charge transfer efficiency, and spectral response. The spectral response of this device in the range of 300 nm to 1000 nm is discussed. The structure of the virtual phase pixel is such that half of the area is covered by a clocking electrode, with the uncovered half remaining sensitive to UV light. Thus this device can be useful in the UV provided that special consideration of the sampling is taken into account. Noise characteristics of this device were measured as a function of clock levels, amplifier bias, readout speed, and temperature. The output of this device is unique in that there are two output amplifiers, one for every other pixel. The mean noise of the two output amplifiers is about 20 electrons, with a dark current of 0.016 electrons/sec at -130 C. This device was used as an astronomical imager at the prime focus of a small Schmidt telescope.

A focal reducer which converts the f/13.5 primary Cassegrain beam of the McDonald 2.1 m telescope to f/3.0 is described. The resulting plate scale is 30 microns/arcsec, which is a good match to the resolution of typical CCDs for seeing conditions of about 1 arcsec. The present system uses a SID501 RCA CCD with 30-micron pixels; however, a TI 800 x 800 CCD with 15-micron pixels and other low-noise, small pixel devices will be used eventually. The focal reducer uses primarily reflective optics to provide good sensitivity down to the atmospheric cutoff at 3100A.

The standard CCD used in the camera installed at the Schmidt Telescope has a poor short wavelength response and so all the CCDs are surface coated with a fluorescent dye to partially overcome this problem. In 1988 it was decided that the system's response around 4000 A could be improved further by replacing the FLAIR (fiber linked array image reformatter) fibers with a set of fibers offering superior transmission properties at this wavelength. The introduction of these larger core diameter fibers would have meant, however, accepting a reduction in signal-to-noise as the fibers illuminate more pixels on the CCD. The CCD sequencing was therefore modified to permit pixel binning across the dispersion direction. Recent modifications also provide a detection capability for approximately twice the number of objects, by appending a second CCD detector and correlated double sample processor to the existing sequencer. Both CCDs are operated via a signal controller which can route clocks and video between the detectors and sequencing electronics. Reduction of galaxy data show that FLAIR, combined with a low noise detector, in both single and dual CCD mode, is easily capable of obtaining cross-correlation redshifts in the blue with a high success rate.

The increased number of pixels in CCD sensors has meant a corresponding increase in the time required to read out the sensor with low noise. Therefore two to four readout circuits are now being included on a single CCD. The CCD image can be broken up into sections and moved separately to each readout amplifier, reducing the overall readout time. This creates the need for CCD camera controllers that can control more than one CCD readout at a time. The system architecture of such a controller is described. The two major boards - a digital timing board shared between all the readouts, and a mostly analog readout dedicated one per readout - are discussed in detail. The timing board contains a fast digital signal processor that contains the readout program and timing information in internal memory and updates the CCD clocks at a 10 MHz rate. The performance of the analog cicuitry and a sample readout program described.

The aim of this paper is to show the relevance of the electron bombardment technique of photon counting for astronomical applications, using results obtained both in the laboratory and on the sky with a prototype tube. The potential astronomical applications discussed are in techniques requiring high time resolution, either in an analog or a photon counting mode (wavefront analysis, speckle interferometry, multitelescope interferometry, etc.) and observation of rapidly varying objects. Current prototypes will be used to achieve wavefront analysis in the near future. The first priority in further technical development must obviously be to develop a larger and faster CCD.

A prototype 40-mm-diameter proximity-focused microchannel-plate intensifier intended for photon-counting applications in both ground-based and space astronomy is described. The intensifier described is a sealed-window device and is also well suited to open-window ultraviolet applications in space astronomy. The tube makes use of a combination of an unfilmed curved-channel plate (C-plate), to prevent ion feedback, and a single straight-channel plate, aligned to prevent optical feedback. The tube has excellent cosmetic quality and shows a counting efficiency superior to that of filmed plate devices reported previously, giving an overall detective quantum efficiency at least equal to that of the best four-stage magnetically focussed intensifiers.

Results of charge transfer efficiency and dark current tests for large Reticon and Ford CCDs are given, as well as a description of some experiments to improve the UV quantum efficiency, using a biased flash-gate for thinned CCDs and phosphor overlay for front-illuminated CCDs. The results indicate that large affordable CCDs suitable for astronomical work are now in reach, with excellent charge-handling characteristics, low dark current and readout noise and high quantum efficiency over the 300 nm to 1000 nm wavelength range. With buttable CCDs, whose production is planned for the future, even larger arrays of CCDs will be possible.

A CCD camera controller based on a transputer chip is described which is used for sequencing programmable waveform patterns, including windowed and pixel binning formats. A key feature is the significant reduction in component count over previous systems made possible by the versatility and unique features of the transputer. The outcome of this is that a complete controller for a single-chip CCD camera may be accommodated in a small enclosure on the cryostat used to cool the chip. Alternatively, extra drive cards may be added to the waveform sequencer to drive a multichip camera. The use of the transputer allows the controller to be incorporated naturally into a parallel processing system whereby several cameras can be operated within the telescope environment using simple serial control and data transfer links.

The microchannel plate intensified CCD (MIC) photon counting detector system was developed to replace a common user photon counting detector, the image photon counting system (IPCS), at the Anglo Australian Telescope and at the William Herschel Telescope and the Isaac Newton Telescope at La Palma Observatory. The IPCS incorporated magnetically-focused four-stage cascade image intensifiers. This paper discusses technological aspects of the design and optimization of very high gain microchannel plate image intensifiers for such photon counting systems and particularly the optimization of device detective quantum efficiency.

Microthermals are often used to test for local seeing contributions of sites and inside telescope buildings. There is however a degree of uncertainty in their use. The refractive fluctuations are proportional to the air density fluctuations. But for isobaric changes the fractional air density fluctuations are equal to minus the fractional absolute temperature fluctuations. Whereas for adiabatic changes the fractional density changes are equal to plus 1/(Gamma4) times the absolute temperature fluctuation. The image size contributions are equal to these changes to the 1.2 power. Thus adiabatic changes produce about three times as much image degradation as do isobaric changes. There is a particular susceptibility to adiabatic changes with wave motion affecting seeing in the presence of stable stratification associated with a nocturnal ground thermal inversion. It is recommended that microthermal measures of seeing contribution from sites and telescope facilities should be treated with distrust unless accompanied by simultaneous measurements of pressure fluctuations. In consequence a number of current indicators for the thermal design of large telescopes and their facilities must be considered moot.

The use of closed cycle cryogenic refrigerators in astronomical applications has been limited due to vibration problems. A closed cycle cooler system to cool instruments to about 50 K and the detectors below 20 K has been designed. The design uses two cold heads diametrically opposed to cancel vibration input to both the telescope and the instrument optical system. The use of vibration damping material to isolate the cold heads results in a nominally vibration free system. A reduction in low frequency vibration amplitude approaching three orders of magnitude was witnessed. This has been demonstrated both in the laboratory and while the system was operating on a telescope.

Modern telescopes of the 4m class, such as the William Herschel Telescope, provide astronomers with a rich set of complex instrumentation. The elements of instruments such as those which one might find on the WilT need careful integration and control, using highly software-oriented systems. This approach leads naturally to the concept of common-user observing systems which rely on a well-defined hardware and software infrastructure to provide the user with an easily used tool.

Methods of observing where the observer continually interacts with the on-line system do not always make optimum use of the time available. Given the increasing pressure on observing time, it is now being recognised that both advance planning and greater automation of the observing process are vital in order to increase efficiency. The William Herschel Telescope, where all instruments and detectors are fully computer controlled, offers an ideal opportunity for building tools to help users improve the efficiency of their observing. The Control File system divides naturally into an off-line preparation and verification phase, and an on-line control phase. The off-line software consists of an 'intelligent' editor which allows the preparation of observing scripts which are syntactically correct. These scripts can then be checked and optimised according to pre-determined rules which can, for example, ensure that a minimum number of calibration observations are slotted into the programme and that the overall set of observations are in a sensible order to minimise telescope slewing.

Astronomers using the William Herschel Telescope are able to collect data from CCD and photoncounting systems attached to instruments such as ISIS (triple spectrograph), Taurus (Fabry-Perot spectrograph and focal reducer for direct imaging) and FOS (the Faint Object Spectrograph). Images are collected in the Detector Memory System and from there are transferred into the System Computer, which is responsible for writing the data into an internal, UK Starlink, standard format. A single acquisition process on the System Computer is used to collect data and control the process of acquisition for all observing configurations. During an observation, ancillary information is gathered from other parts of the system and is used as header information for the final archived image. Collection of header information, image data, and information for the observer log is, in the case of ISIS, complicated by the requirement to organise collection independently and in parallel on each of the three detector arms of the instrument. The information collected on the System Computer is archived in an extended FITS format, necessary to allow extensive ancillary data sets to be stored with the astronomical data, and is eventually transferred to the RGO at its UK site for long-term storage. The archive software has been produced in conjunction with the Netherlands Foundation for Radio-Astronomy and allows local and remote query facilities.

The data acquisition and control systems for the William Herschel Telescope use a "mimic" display to present an easily assimilated view of the status of the telescope, its instruments and detectors. This display is specified in a set of data files that can easily be modified to reflect any changes to the system. A mimic description language, developed at the RGO, is used to describe individual "pages" of the complete mimic display. Such pages can represent various levels of complexity, from complete subsystems down to individual mechanisms. Extensive use is made of colour graphics to allow the user to see the state of any item on the display at a glance. The mimic system also uses colour to warn the user of errors occurring in pages which are not currently displayed, and by this means can indicate or even force the display of those pages to which the user should refer as a matter of priority. The mimic display is directly driven by the low-level processes responsible for controlling the instruments and detectors. The location of the information to be displayed is retrieved from globally accessible memory and displayed according to the prescription for that group of items in the mimic description file.

The CCD autoguider detector system for the William Herschel Telescope (WHT) comprises a Peltier cooled, slow-scan CCD camera supported by an MC68020-based VME computer for image processing. The detector is a fluorescent dye coated EEV P8603 CCD chip operated in frame transfer mode. The CCD controller enables a full image to be read out during acquisition, but with windowed readout during guiding so as to permit an increased frame rate. The windowing is controlled by the VME computer, which is also used to calculate the centroid of the guide star and provides a local user interface, displaying images and guider status information. Special attention has been paid to the CCD drive clocks and bias voltages, enabling a very low dark current to be achieved (2 electrons per pixel per second at -35 C) without the need for extreme cooling. Guiding to magnitude 19 on the WHT has been demonstrated during dark time, with an integration time of one second.

The Transputer is a powerful reduced instruction set microprocessor designed for parallel processing machines. It has excellent communication capabilities and requires little by way of support electronics. This makes it suitable in telescope and satellite control systems for both complex functions, such as image handling, and simple functions, such as motor control. We discuss some of the architectural implications in using Transputers as the basis for an integrated parallel processing engine for instrument and telescope control.

The current state of performance of fiber-optic gyroscopes is discussed in relation to the needs of optical telescopes for tracking and setting. The principles of operation of fiber-optic gyroscopes are outlined, as well as their parameters and practical problems associated with telescope applications, such as fringe-shift measurements. Photon shot noise at the output, drift rate, and scale-factor stability are examined. Telescope configurations for an equatorial and alt-azimuth cases are discussed, along with such astronomical applications as tracking, slewing, static telescope, and field rotation. It is concluded that further improvements the fiber-optic gyroscopes will make an encoder scheme based on these devices competitive with conventionally encoded optical telescopes.

A large telescope spends over 70 per cent of its time observing isolated objects on the telescope axis -an excessive waste of the available field of view. This paper describes a CCD camera which images the off-axis light on the William Herschel Telescope whilst an on-axis observer uses the telescope as normal. This enables a major background survey to be performed at minimal cost, and with no additional observing time. The cost of the system is about $150,000; by doubling the use of a telescope which costs $10,000 per night to run it pays for itself within a matter of weeks. Implementing similar systems on the new generation of large telescopes would ensure that the quality of background surveys will automatically keep pace with the advancing telescope technology.

Tunable optical retarders made of liquid crystal material can be built with excellent spatial and angular response. These elements have been used to construct birefringent filters which are electronically tunable. Initial breadboard systems realize passbands similar to interference filters, and filters are planned with sub-Angstrom passband. Any desired wavelength in the tuning range may be selected in a random-access fashion, in a few milliseconds. One of these filters has been successfully used recently to image the solar photosphere in the 1.2 - 1.6 micron range at the McMath solar telescope at Kitt Peak.

The first and second order statistics in a deadtime affected photo counting distribution are analysed. The reduced mean count rate is modeled for paralyzable and nonparalyzable deadtime in a two-dimensional imaging array. In certain limits the derived expressions are shown to agree with previously published results for single element detectors. A simulation is used to demonstrate the effect deadtime has on the speckle contrast and the speckle peak in the autocorrelation function of static laser speckle. The theoretical approach necessary to describe this behavior is also presented.

The process for spincasting 8 meter borosilicate honeycomb mirrors requires us to heat 14 tons of glass in a complex mold to 1170 °C while spinning the entire furnace at 6.8 rpm. After casting, the honeycomb blank must be cooled through the annealing temperature range at 0.2 °C per hour. The glass will be in the furnace for an eight week period. We describe here the computer control system to read the 600 N-type thermocouples and control the 270 8-kilowatt heaters used in the spincasting furnace. The control system uses a proportional — integral — derivative (PID) algorithm to regulate the furnace temperature to a few degrees over the entire casting cycle. Considerable design effort has gone into assuring that a component failure or a control system error does not turn an 8 meter nilrror into an expensive patio ornament. Errors are avoided by four strategic steps: fault avoidance, fault detection, fault containment and fault recovery. Examples are provided in each of these categories. System redundancy begins with three on-board 68000-family VME-bus computers which control overlapping areas of the furnace. Redundancy extends down through the temperature measurement and power control systems with many modular, interleaved, and optically isolated subsystems. Data logging and system monitoring are achieved with a Sun 3/280 workstation running IRAF in the control room. Rotation of the furnace is controlled by two 40 HP DC servomotors with speed regulation to 0.1%. The oven control system contains over 300 circuit cards, dozens of subracks and power supplies, more than 3000 connectors of at least 10 different types. there are more than 20 miles of wire and cable, most with multiple conductors, ranging from fiber optics thinner than a hair to power cables more than an inch thick. Results are presented from a subset of this control system which has been used to cast three 3.5 meter honeycomb mirrors in 1.988 and 1989.

To exploit the potential of submillimeter astronomy, the Submillimeter Telescope (SMT) will be located at an altitude of 3178 meters on Emerald Peak 75 miles northeast of Tucson in Southern Arizona. The instrument is an altazimuth mounted f/13.8 Cassegrain homology telescope with two Nasmyth and bent Cassegrain foci. It will have diffraction limited performance at a wavelength of 300 microns and an operating overall figure accuracy of 15 microns rms. An important feature of the SMT is the construction of the primary and secondary reflectors out of aluminum-core CFRP face sheet sandwich panels, and the reflector backup structure and secondary support out of CFRP structural elements. This modern technology provides both a means for reaching the required precision of the SMT for both night and day operation (basically because of the low coefficient of thermal expansion and high strength-to-weight ratio of CFRP) and a potential route for the realization of lightweight telescopes of even greater accuracy in the future. The SMT will be the highest accuracy radio telescope ever built (at least a factor of 2 more accurate than existing telescopes). In addition, the SMT will be the first 10 m-class submillimeter telescope with a surface designed for efficient measurements at the important 350 microns wavelength atmospheric window.

A submillimeter continuum array instrument being built for the 15-m James Clerk Maxwell Telescope on Mauna Kea, Hawaii is described. The instrument contains 2 arrays, one of 91 pixels optimized for 438 microns and the second of 37 pixels optimized for 855 microns. Both are hexagonally close-packed, with each pixel having diffraction-limited angular resolution. Conical horns and single-moded waveguides are used to couple to the submillimeter beams, minimizing the bolometer background loading. A filter changing mechanism allows operations of the arrays at 350 and 750 microns. Single 'photometric' pixels are provided optimized for operation at 350, 600, 750, 1100, 1400 and 2000 microns. The instrument will have bolometers sensitive enough to reach the photon-noise sensitivity limit at both wavelengths, corresponding to an optical noise equivalent power (NEP) of 1.6 x 10 to the -16th WHz exp -1/2. This is achieved by cooling to 0.1 K, using a dilution refrigerator.

The design and performance of the FOS-2 faint-object spectrograph for the Herschel Telescope at the Observatorio del Roque de los Muchachos are described and illustrated with diagrams and drawings. The FOS-2 has an image scale of 223 microns/arcsec at the slit and features a cryostat-cooled 385 x 578-pixel CCD detector with 22-micron-sq pixels, operating with resolution 1.5 pixels and dispersion 8.73 A/pixel at 460-970 nm (first order) or 4.32 A/pixel at 350-490 nm (second order). The high-efficiency optical system is of the type described by Wynne (1982) and operates in the diverging f/11 Cassegrain beam without a collimator. Overall system efficiency in first order with a 5-arcsec slit has a peak at 16 percent at 700 nm and remains above 1 percent at all wavelengths imaged by the CCD; in second order the peak efficiency is about 3 percent at 490 nm and remains above 1 percent except below 370 nm. The mechanical system, the control and data acquisition procedures, and the data-reduction software are briefly discussed.

The modifications required to construct an echelle spectrograph similar to the UCLES (currently in use on the 3.9-m AAT and described by Walker et al., 1986) for an 8-m-class telescope are discussed in detail and illustrated with diagrams. The design and operational parameters of the UCLES are reviewed, and a direct factor-of-two linear scaling of the UCLES for an 8-m telescope is outlined, with particular attention to a mosaicked CCD detector array and echelle configuration, the relationship between the field rotation problem and the telescope secondary focus ratio, the feasibility of a Littrow layout with prisms in double pass immediately ahead of the echelle, prism mosaics as a low-cost approach to prismatic cross-dispersion, the characteristics and application of the 79 g/mm R4 echelle, and the possible use of white-light pupil imaging, as proposed by Baranne (1972).

The optical designs of three CCD cameras for the Keck Observatory spectrometers are described and illustrated with drawings and diagrams. The 8-element camera for the Low-Resolution Imaging Spectrometer (LRIS) has focal length 12.0 inches, entrance aperture 8.9 inches, and flat FOV diameter 2.93 inches; the camera is color corrected without refocusing over the spectral range 390-1000 nm. For the High-Resolution Echelle Spectrometer (HIRES), a larger and a smaller version of a 30-inch-focal-length camera have been designed. Each camera is color corrected at 310-1100 nm and comprises a single-element corrector, a concave mirror, a contact triplet field-flattening element, and a flat vacuum window. The smaller design, with 28.7-inch entrance aperture and flat FOV diameter 3.15 inches, has been selected for construction.

The optical design and performance of the UCLES echelle spectrograph, installed at the f/37.7 coude focus of the 3.9-m AAT in June 1988, are described and illustrated with extensive diagrams, drawings, photographs, and sample spectra. The UCLES operates at 300-1100 nm with resolution 30,000-115,000 and adjustable collimated beam size; it employs either 31.6-g/mm or 79-g/mm echelle gratings and a train of UV-transmitting fused-silica prisms for cross-dispersion. Also discussed are the focal modifier lenses; the Bowen-Walraven image slicer; the commissioning procedures; and preliminary observations of Zeta Oph, planetary nebulae, and Seyfert galaxies.

The optical design of an f/4 coude echelle spectrograph for the 3.6-m Canada-France-Hawaii Telescope is described and illustrated with drawings and diagrams. The basic configuration comprises a tilted spherical f/20 collimator mirror, a 30-cm 316-g/mm grating near the slit, a paraboloid camera mirror, and a small triplet corrector lens. Two sets of optics are provided, coated for optimal performance in the UV-blue and green-IR regions, respectively, and small remotely selectable variable-wedge grism or grens modules are located in the diverging beam from the slit to the collimator to prevent other orders from overlapping the part of the spectrum being recorded. Consideration is given to the Hartmann mask system, the mosaic grating controls, the collimator and camera mirror turrets, and the detector support.

The optical design and fabrication of a fast f/1.4 prototype camera for the JNLT are briefly described. The f/1 semisolid Schmidt-Cassegrain camera configuration (a corrector lens plus two aspheric mirrors) developed by Nariai and Yamashita (1987) on the basis of third-order aberration theory is adopted, but the design is modified to reduce the number of aspheric surfaces from four to two. Computer-controlled polishing achieved accuracy of 150 and 200 nm for the corrector plate and secondary mirror, respectively. The use of a constant-radial-shearing interferometer to test the Schmidt corrector plate is explained, and it is reported that the assembled camera had MTF of 55 percent for 100 lp/mm when imaging a 5-micron slit placed in the focal plane.

The optical design and performance of the visible/NIR imaging Fabry-Perot interferometers for the 3.6-m CFHT, the 2.2-m University of Hawaii Telescope, and the 3.9-m UKIRT (all at Mauna Kea) are described. The basic configuration combines a high-finesse etalon of free spectral range about 10 nm with a state-of-the-art CCD image-plane array. The criteria considered in selecting the CCDs and etalons are discussed; the quality of the data obtainable is illustrated with sample data (CFHT 658.3-nm emission line profiles of the central region of NGC 1068 and UKIRT B-gamma profiles of the Galactic center); and the instrument calibration and artefact problems are outlined. It is suggested that, while Fabry-Perot devices offer the best visible-NIR performance at present, Fourier-transform and long-slit spectroscopy show great promise for the future, especially in the IR.

The use of a fiber-optic-link CCD-detector Fabry-Perot interferometer (McMillan et al., 1985, 1986, and 1988) to obtain high-accuracy measurements of stellar Doppler shifts at KPNO is described in detail and illustrated with sample data. Particular attention is given to accuracy requirements and techniques for reducing errors, resolution (orders of 50 mA at wavelength 4300 A are separated by 640 mA), CCD sensitivity, observing and data-processing operations, and the control of environmental conditions. Standard-deviation data and statistics on seven solar-type stars are presented in tables, and the time evolution of the radial velocity of Beta Com is shown in a graph.

The use of the University of Wisconsin 15-cm-diameter pressure-scanned Fabry-Perot spectrometer to detect and characterize faint optical emission lines from the Galaxy and the earth atmosphere is described, and a more powerful multichannel spectrometer is proposed. The fundamental principles and advantages of Fabry-Perot instruments are explained; the need for higher throughput is pointed out; the gains possible with a multichannel spectrometer are determined; and test results demonstrating the feasibility of multichannel spectrometry with either photomultiplier or CCD detectors are summarized. It is estimated that a multichannel spectrometer mounted at the Nasmyth focus of a 3.5-m or 8-m telescope would have a beam diameter of 10 or 4 arcmin, respectively, making it possible to probe ionized gas in the disks and halos of galaxies at emission measures less than about 1/cm to the 6th pc and spectral resolution 10 km/sec.

The theoretical principles and technical feasibility of spatial heterodyne spectroscopy (SHS) for astronomical observations are explored. The SHS setup is basically a Michelson interferometer with the mirrors replaced by diffraction gratings; wavelength-dependent Fizeau fringes are recorded and Fourier analyzed to obtain a high-resolution spectrum even at relatively low spatial frequencies. Two all-reflection SHS instruments are described and illustrated with diagrams, and laboratory test results using CCD detectors for both visible and UV measurements are presented, indicating resolving powers of about 75,000 and 70,000, respectively. Also discussed are the advantages and limitations of SHS vis a vis other Fourier-transform spectroscopic methods.

The MIC, a 40-mm intensified microchannel-plate photo-counting detector being developed for the Anglo-Australian, Isaac Newton, and William Herschel telescopes, is described and illustrated with diagrams and sample spectra. The MIC is linked by optical fibers to a fast-scanning CCD detector, and an accurate centroiding technique is applied to yield an effective maximum of 3104 x 2304 10.6-micron pixels, for field-averaged resolution 27 microns FWHM. Applications include high-resolution spectroscopy, especially in the blue, and Fabry-Perot and speckle interferometry.

A prototype microprocessor-based electronic processing system is described which performs the on-line data processing in an image photon-counting detector. The detector head consists of a microchannel-plate intersifier optically coupled to a CCD with rapid-scanned readout. The digitized data are passed to a group of transputers which separate out the events, calculate the event centers to subpixel accuracy and accumulate the results in an image buffer. In the prototype, all processing is done in software for evaluation purposes. This paper discusses the basic design of the system, the centroiding algorithm and fixed patterning correction, and the implications of the results for future systems.

A data-collection system for use in astronomical observations with the resistive-anode detectors (Ranicons) described by Paresce et al. (1979 and 1988) is briefly characterized. Analog signals from the Ranicon pass through 12-bit A/D converters and (along with time information from a digital clock) into a 64-bit FIFO buffer, and the photon positions are calculated by a high-speed arithmetic-logic system capable of an event rate of 30 kHz (so that, by Poisson statistics, only about 21 percent of events will be missed). Results from successful timing tests of the system on the 2.2-m telescope at ESO are presented graphically.

The optical design and operation of the Coravel direct-correlation spectrograph system used to measure stellar radial velocities at the University of Cambridge 36-inch telescope, are described. The optical layout of the Cambridge Coravel is similar to that of the Coravels at the Observatoire de Haute Provence and ESO, comprising an echelle grating and a prism cross-disperser working in double pass. Particular attention is given to the calibration and scanning systems, the collimator-echelle-camera assembly, the mask and mask holder, the microprocessor-controlled photomultiplier detection system, the control and user interface, and the observing procedure. Diagrams, photographs, and sample observational data are included.

A new faint-object spectrograph was designed and built around the capabilities of fiber optics. This instrument, the Norris Spectrograph, is designed exclusively for the Cassegrain focus of the Hale Telescope. There are 176 indpendently positionable fibers, each with an aperture 1.5 arcsec in diameter. These 176 probes cover a field of view of diameter about 20 arcmin. The output ends of the fibers are collimated with a spherical mirror, dispersed using a normal reflection grating, and focused onto a 2048 x 2048 CCD using all-transmissive optics. The peak overall efficiency of the instrument will be in excess of 10 percent.

The design and operation of the automated optical-fiber positioning system used for spectroscopic observations at the Cassegrain focus of the 4.2-m William Herschel Telescope (WHT) at Observatorio del Roque de los Muchachos are described. The system is a modified version of the Autofib positioner for the AAT and employs 64 spectroscopic fibers and 8 guide fiber bundles arranged to form a 17-arcmin-diameter field. The fibers are 1-m-long polyimide-coated high-OH silica, with core diameter 260 microns and outer diameter 315 microns, and a 1.2-mm side-length microprism is cemented to the end of each fiber or (7-fiber) guide bundle. The fibers are positioned one at a time by a pick-and-place robot assembly, and a viewing head permitting simultaneous observation of the back-illuminated fiber and the object it is trying to acquire is provided. This prototype Cassegrain-focus system is being studied to aid in the development of a more accurate fiber positioner for use at the prime focus of the WHT.

This paper describes the Low Dispersion Survey Sectrograph (LDSS-2) currently under construction for the 4.2-m William Herschel Telescope. The instrument is a versatile highly efficient multiobject spectrograph with an 11.5-arcmin field of view. Around 100 objects can be observed simultaneously using multiaperture masks made at the telescope in real-time at dispersions selectable between 10 and 47 nm/mm. By removing the dispersing element, the instrument can act as a focal reducer with a final focal ratio of f/2. This allows the field to be imaged first in order to derive accurate instrumental coordinates for the manufacture of the aperture mask.

Techniques for improving the subtraction of sky background when performing multiobject spectroscopy with fiber-optic-link instruments are examined analytically and by means of numerical simulations. The sky subtraction problems for multislit, long-slit, and fiber-optic spectroscopy are compared; the detrimental effects of fiber misalignment, poor-quality fiber end preparation, stress-related focal-ratio degradation, absorption losses, and connector losses are described; and consideration is given to improvements based on (1) using higher-quality fibers, (2) allowing for wavelength-dependent differences in fiber response, and (3) mimicking the multislit method by allocating more fibers to each object. The effects of vignetting and parameter shifts on computer-simulated spectra are shown in graphs.

Results are reported from design studies of a fiber positioner and dedicated spectrographs for use in multiobject blue-UV spectroscopy at the new 2dF wide-field prime focus of the 3.9-m AAT. The technology of the present 64-fiber Autofib-1 system is being adapted to handle the 400 fibers and multiple spectrographs needed for the 2-deg unvignetted 2dF field; requirements include reconfiguration time 8 sec/fiber with iterative centroiding, position accuracy 0.2 arcsec (10 microns), button diameter 3 mm, and fiber probe freedom + or - 45 deg in theta and 75 percent diameter in R, with multiple crossovers. The spectrograph specifications include high throughput at 100-350 nm, spectral resolving power 5000 or less, efficient collimators, fast camera optics, and ability to resolve spatially all 400 fibers or subsets at different wavelengths and dispersions. Data from tests of fiber focal-ratio degradation are presented in graphs and discussed in detail.

An automated multi-object spectroscopy system (AMOS) is being developed for use on the 3-meter telescope at Lick Observatory. The overall design is compatible with the eventual goal of acquiring up to one hundred spectra simultaneously in a one degree field of view. The speed and accuracy of AMOS preserve the real time decision making and field changing flexibility associated with traditional singlesource observing techniques. AMOS will operate at the 3-meter prime focus and will feed a floor-mounted spectrograph. We describe some engineering design details and the results of laboratory and 1-meter telescope testing of AMOS.

A robot for positioning fiber optics in the focal plane of the Mayall 4-meter telescope has been constructed at Kin Peak National Observatory (KPNO). This fiber actuator device (FAD) will position up to 100 fibers for multi-object spectroscopy over a 45 arc-minute field. The positioner is based upon the AUTOFIB concept which uses magnets to hold the fibers in place. We have incorporated a unique gripping mechanism which allows a TV camera to view both the fiber and sky simultaneously.

The evolution, current status, and planned improvements of the FLAIR fiber-optic-link multiobject spectroscopy system used on the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory are reviewed and illustrated with diagrams and sample spectra. Consideration is given to the original FLAIR system using photographic film to record spectra, the introduction of a slow-scan cryogenic CCD camera in 1986, the problems of focal-surface coverage and sensitivity in the prototype FLAIR, the improved Panache fiber feed and on-chip pixel binning scheme installed in 1988, and the dispersion options offered by the FLAIR-Panache system. The limitations of the present FLAIR configuration are discussed, along with improvements involving (1) the use of a new spectrograph with Schmidt optics for both collimator and camera and (2) advanced plate-holder and positioner systems making it possible to load FLAIR into the telescope in a few seconds instead of an hour.

In this paper, a new type of astronomical optical fiber coupler is described which couples the Cassegrain focus with f-ratio ff16 of the 6Ocm reflective telescope at Purple Mt.Observatory (P?) and the entrance slit of a prism spectrograph located :1n the lab under the observing floor. The single multi-mode, gradient index optical fiber has a length of about 25m, core diameter of 5Omicron, effective NA of 0.2. At both ends of the fiber, GRIN rod lenses with diameter of 1mm are used as f-ratio transverter. Techniques, e.g. the alegnment between fiber and GRIN rod lenses and guiding, are given in detail. Primary experimental observation with this coupler has been carried out and spectra of Lyr are obtained.

An automated fiber optics manipulator that allows the acquisition of up to 10 spectra simultaneously with an existing long slit spectrograph has been placed in operation at the Michigan-Dartmouth-MIT Observatory. Pickoff optics that view mirrors at the fiber probe tips allow visual alignment of the probes on the target objects. This feature eliminates the requirement for subarcsecond astrometry, careful focal plane calibration and highly precise actuator motion.

We have built a laboratory prototype to evaluate the performance of an innovative design of robot for optical fibre placement as part of the design study for the proposed 2° field (2dF)"5 for the Anglo Australian Telescope (AAT). Based on the Autofib-12'4 system operating at the AAT, it uses a new design of gripper to manipulate, and also measure the positions of fibre optic probes. The new design incorporates a CCD TV camera to check on the accuracy of each fibre's position in real time as the fibres are being placed, with any slight adjustment required being made automatically. This automatic error correction will eliminate the need for extensive calibration procedures, and provide the improved accuracy required to work at typical 4m prime focus platescales. Our laboratory prototype exhibits good accuracy (<10pm rms) and reliability and we now intend to use this approach at the prime focus of the William Herschel Telescope (WHT)3. In this paper we report on the overall performance of the new design and assess it's practicality in applications on real telescopes.

A telescope autoguider constructed of unmodified commercially available components for use with the 2.1-m focal reducer at McDonald Observatory is described. The system comprises a thermoelectrically cooled CCD camera with format 384 x 576 pixels, pixel size 23 microns square, readout noise 25 electrons/pixel, and dark current 10 electrons/sec pixel at -35 C; a 50-mm camera lens giving resolution about 1 arcsec/pixel; an IEEE-488 data bus; a MicroVAX 3200 computer workstation; and a serial-to-parallel converter permitting the computer to address the telescope drive system via four trail-rate controls. Also discussed are the top-down C-language programming approach, the data representation, the autoguiding and search algorithms, and ongoing work on the telescope control algorithm. It is suggested that the present system is versatile enough to be applicable to many similar telescopes.

The design of the acquisition and guider (A&G) unit in use on the 4.2-m William Herschel Telescope at Observatorio del Roque de los Muchachos since May 1989 is described and illustrated with drawings. The Herschel A&G system is an enlarged and improved version of the A&G unit for the 1.0-m Kapetyn telescope at the same observatory (Ellis, 1983). Facilities provided include full-field guiding with minimal obstruction for spectrographs and wide-field instruments (using a CCD camera to image the guide star), an acquisition facility, spectrograph slit viewing by reflection, a TV camera with a 6-position filter wheel, lamps for spectral comparison and flat fielding, a full-field (15-arcmin) auxiliary focal position at right angles to the beam, polarization calibrators, two 8-position filter wheels, and two 5-filter filter slides. The A&G unit is housed in a cylindrical steel structure of diameter 150 cm and depth 65 cm; the mechanical operation of the components is briefly characterized.

A three-detector photoelectric photometer system being developed for use on the 46-cm telescope (and on a planned 80-cm telescope) at the Appalachian State University Dark Sky Observatory is described. One (PIN-diode) detector is used to obtain sky brightness, while the other two can be aligned for simultaneous observations of two objects by adjusting the separation and position angle with stepper motors. Fiber-optic image conduits mounted beside the detectors feed a CCD video camera, permitting field acquisition and microcomputer-based control of the stepping motors from the observatory warm room. Consideration is given to the full-field filter system, the detector characteristics, the data-acquisition and control electronics, and the control software. Plans call for initial testing on the telescope in 1990 and operational status in 1991.

This paper describes a commercially available instrument, CASI (Compact Airborne Spectrographic imager), designed for remote sensing. The instrument is capable of medium-resolution multispectral imaging of both local and distant astronomical objects. The instrument employs a GEC UT1O4 CCD to provide an overall spectral resolution of 1.8 nm and a peak quantum efficiency of 10% at 575 nm. The spectral range of the instrument is 450 nm to 900 nm, with 512 active pixels in the spatial imaging direction. Integration times are variable from several seconds down to 10 ms. A fiber optic tap intO the spectrograph slit enables a real-time spectral calibration to be recorded with the data. The results obtained observing several astronomical objects are presented.

We describe a conceptual plan for the development of a comprehensive long duration solar space observatory, the Advanced Solar Observatory (ASO). The ASO is intended to provide solar astronomers with the observational power (spectral, spatial, and temporal resolution, sensitivity, and breadth of wavelength coverage) necessary to address fundamental problems relating to the solar convection zone and activity cycle, the thermal and nonthermal processes which control the transport of energy, mass and magnetic flux in the solar atmosphere, the generation of the solar wind, and the dynamics of the inner heliosphere. The Advanced Solar Observatory concept encompasses three proposed Space Station based instrument ensembles: (i) the High Resolution Telescope Cluster which includes far ultraviolet, extreme ultraviolet and x-ray telescopes, (ii) the Pinhole/Occulter Facility which includes Fourier transform and coded aperture hard x-ray and gamma ray telescopes and occulted ultraviolet and visible light coronagraphs, and (iii) the High Energy Facility which contains neutron, gamma ray and low frequency radio spectrometers. Two other facilities, the Orbiting Solar Laboratory (OSL), which will contain high resolution visible and ultraviolet telescopes on a free-flying platform, and a package of Global Dynamics Instruments will, with the Space Station ensembles, form a comprehensive capability for solar physics. We describe the scientific program of the ASO, current instrument concepts for the Space Station based ASO instrument ensembles, and pians for their accommodation on the Space Station. subject terms: solar atmosphere, soft x-ray, XUV, extreme ultraviolet (EUV), far ultraviolet (FUV), hard x-rays, gamma rays, neutrons

We have developed compact soft x-rayfEUV (XUV), and far-ultraviolet (FtJV) multilayer coated telescopes for the study of the solar chromosphere, corona, and corona/solar wind interface. Because they operate at short wavelengths (4O A < ). < 1550 A), the modest apertures of 40 mm - 127 mm allow observations at very high angular resolution (0.1 - 0.7arc second). In addition to permitting traditional normal incidence optical configurations such as Cassegrain, Ritchey-Chrétien and Herschelian to be used at soft x-ray/EUV wavelengths, multilayer coatings also allow a narrow wavelength band (A/AX -45 - 100) to be selected for imaging. The resulting telescopes provide a very powerful and flexible diagnostic instrument for the study of both the fine scale structure of the chromosphere/corona interface, and the large scale structure of the corona and corona/solar wind interface. In previous papers we have described a new solar rocket payload, the Multi-Spectral Solar Telescope Array (MSSTA) composed of 17 of these compact telescopes. In the present paper, we report on the performance of the 7 MSSTA Ritchey- Chrétien telescopes. Subject terms: Multilayers, XUV, far ultraviolet, solar corona

We describe a space borne solar observatory, the Ultra High Resolution XUV Spectroheliograph (UHRXS), which has been selected by NASA for flight among the initial scientific instruments to be placed on the space station "Freedom". The principal URRXS instruments are nine XUV multilayer Ritchey-Chretien Telescopes covering the spectral range from -70 to -350 A; each telescope is able to isolate line multiplets within a narrow wavelength interval which are excited over a narrow temperature range, providing full disk images of diagnostic quality covering structures in the solar atmosphere ranging in temperature from T .5O,OOO K (He II ). 304 A) to 20,000,000 K (Fe XXIV X 192 A). The XUV images will be recorded on high resolution 70 mm format film, allowing resolutions as high as 0. 1 arc second to be achieved for a 1.O field. The XUV images will be supplemented by; (i) full disk high resolution (O.1") far ultraviolet images in H I Ly a ( 1216 A) and C IV (X 1548/1550 A), (ii) full disk soft x-ray images in 4 bands in the interval ?X 6 -70 A and (iii) electronically recorded high resolution (;v&% >10,000) spectroheliograms in 2 XUV, 1 EUV (.'45O A to 1 100 A) and 2 FUV (-4 100 A to 1600 A) bands. The electronically recorded images will use the Multi-Anode Multi-Channel Array (MAMA) detector. We propose to utilize the resulting data sets to address fundamental problems related to the following solar phenomena: (i) the fine structure of the solar chromosphere/corona interface, (ii) the structure, energetics and evolution of high temperature coronal loops, (iii) the large scale structure and dynamics of the corona, including the solar wind interface, the magnetic filed, and coronal mass ejections, and (iv) solar flares, especially the pre-flare state, the impulsive release of energy, and the evolution of post-flare loops. Subject Terms: solar atmosphere, corona, soft x-ray (XUV), extreme ultraviolet (EUV), far ultraviolet (FUV), multilayer optics

The problem of atmospheric-aerosol-induced aureole effects in astronomical observations of the solar corona is considered theoretically and by analysis of sample data obtained at Sacramento Peak Observatory. Both conventional solar-telescope and coronagraph observations are examined in terms of spectral coverage, spatial resolution, and instrument speed; effects due to the angular size of the sun; and the phase effect of forward scattering on the flying aerosol particles. Graphs, sample images, and a calculated atmospheric-transmission profile based on the AFGL standard model are provided, and the implications of the analysis for image-processing methods are briefly indicated.

This paper will discuss the scientific and technological motivations for cleaning and re-coating optical surfaces, including solar power and thermal control surfaces, in the vacuum of space. Hardware concepts and their associated problems will also be addressed.

The Optical Monitor is a part of the JET-X experiment which will fly on board the Soviet satellite Spectrum-X-Gamma. The reflector is a Ritchey-Chretien with an aperture of 260 mm, and there are two frame transfer CCD detectors. The scientific objectives of the Optical Monitor are observations in the optical and UV bands simultaneously with X-ray, the real time identification of X-ray sources with mv less than or equal to 22 and detection of their variability, the improvement of the post-facto spacecraft attitude reconstruction for the X-ray observations, and the serendipitous mode search for microvariability of the bright stars to develop the research field of asteroseismology. Since long integration times are required for the faint object detection, a dedicated servo loop operating on the secondary mirror is developed for the stabilization of the images against the drift of the satellite.

NASA plans for PAX, a photometric and spectroscopic FUV survey mission utilizing a Small Explorer spacecraft, are summarized. PAX is to perform an all-sky survey to limiting magnitude 18 at 140 and 180 nm, deep surveys of selected areas to 21 mag in the same bands, and a spectroscopic survey of 2 percent of the sky to 18 mag. The PAX telescope parameters include diameter 33 cm, focal length 72 cm, plate scale 0.3 arcsec/micron, focal ratio 2.2, FOV 4.8 deg, and system angular resolution 15 arcsec; the microchannel-plate detector employs CsI/KBr photocathodes and a mosaic wedge-and-strip readout scheme. The principal scientific aim of PAX is to increase by a factor of 100-1000 the number of known galactic nuclei, QSOs, active galaxies, white dwarfs, cataclysmic variables, and evolved stars. The mission should also provide new insights into post-main-sequence stellar evolution, star formation in normal galaxies, the distribution of dust in the Galaxy, and the ionization and large-scale distribution of the intergalactic medium.

UV-photons from an Xe-filled gas scintillation counter are detected with a CsI photocathode coupled to a double stage, low-pressure wire chamber. The high quantum efficiency, (9 pct), of the UV-detector yields a high detection efficiency of both primary and secondary scintillation photons. An energy resolution of 4.1 pct (FWHM) was recorded with 60 keV X-rays, inducing secondary scintillation in 5 bar of Xe; the wire chamber operated at 20 Torr of CH4. The two-dimensional planar localization of UV-photons, combined with the drift time measurement of primary electrons, provides a three-dimensional, multihit, imaging capability of X-ray photon interactions, with a resolution of 2-3 mm (FWHM). The stability of the CsI photocathode under different operation conditions and its sensitivity to exposure to air are discussed.

The optical design of Isophot-S, the low-resolution NIR spectrophotometer for the IR Space Observatory (ISO), is described and illustrated with drawings and graphs of test data. The ISO is to be launched in 1993 as a successor to IRAS for astronomical surveys at 2.5-200 microns. Isophot-S has an aperture of 24 arcsec sq, and the two 64-pixel Si:Ga detector arrays have noise-equivalent power of about 5 x 10 to the -17th W/sq rt Hz at 15 microns, corresponding to 1-sigma 1-sec detection sensitivity 400 mJy for a point source at 12 microns or surface brightness 0.8 mJy/sq arcsec for an extended source. The system comprises two grating spectrometers, one operating at 2.5-5 microns with resolution 40 nm and one operating at 6-12 microns with resolution 90 nm.

Possible optical designs of imaging detectors for the spaceborne Schmidt telescope proposed by Carruthers et al. (1990) are discussed, surveying the currently or potentially available technology. Consideration is given to FUV electrographic detectors of large format (e.g., 120 mm with 10-micron resolution) using CsI photocathodes, the possible extension of the same technology to the mid-UV using Cs2Te instead of CsI, large CCD arrays for the visible and NIR, electron-bombarded CCDs for the FUV and mid-UV, and the data handling and processing requirements of these detectors.

A demonstration-prototype CO2-laser heterodyne spectrometer operating at 9-12 microns and suitable for long-term space missions is described and illustrated with extensive diagrams, drawings, photographs, and graphs of test performance data. The spectrometer has total volume 0.63 cu m, mass 30 kg, and power requirement 60-70 W, compatible with miniature-class Space Shuttle experiment payload specifications. It comprises three modules: (1) an optical front end with reflecting optics, a 2-GHz BW HgCdTe photomixer, and a 0-2-GHz 40-dB RF preamplifier; (2) a local oscillator with an RF-excited waveguide CO2 laser, a 75-percent-efficiency RF amplifier, a stepper-driven grating mode selector, and an etalon stabilized for over 30,000 h of use; and (3) an RF-filter-bank spectral-line receiver with a 25-MHz RF channel, 1.6-GHz IF spectral coverage, onboard instrument control, a serial link to the host computer, and highly integrated design.

Lyman/FUSE, the Far Ultraviolet Spectroscopic Explorer, is a proposed low earth orbit mission to explore the 1OO-16OGi spectra of diverse astronomical sources. The simultaneous design goals of high spectral resolution, high sensitivity, high signal to noise ratio, limited slit imaging capability, wide spectral coverage, compactness, and high stability were a formidable challenge. In the design, a Wolter type II glancing incidence telescope (70 cm aperture, f/1O) feeds two spectroscopic channels. A boresighted fme error sensor is used to point the instrument. In the 4oo-16oc1i range, a 1.84m Rowland circle spectrograph uses five near normal incidence gratings with a common MAMA detector. To achieve acceptable resolving power and limited imaging with a fast telescope, the grating aberrations must be significantly reduced below those obtained with toroidal or ellipsoidal gratings. A modified ellipsoidal grating is used to achieve resolving powers of 30000 in the three high resolution bands covering 91O-125Q. A separate EUV channel will explore the 1OO-35O range with lower spectral and spatial resolution. The throughput in this range is improved by more than an order of magnitude over the Extreme Ultraviolet Explorer (EUVE), when EUVE is operating in its spectroscopic mode. The optical design and results of ray tracing studies are presented, as well as the expected effective area in each channel.

A long-wavelength IR camera which is currently being built for the 10-m Keck Telescope is described, with attentions given to its overall configuration and to the optics, the dewar, the detector, and the electronics. Special consideration is given to the instrument control system and the software architecture for the remote operation of the Keck long-wavelength-camera detector. The instrument parameters and a schematic diagram of the camera are included.

A CCD-based Acquisition TV Camera has been developed at CTIO to replace the existing ISIT units. In a 60 second exposure, the new Camera shows a sixfold improvement in sensitivity over an ISIT used with a Leaky Memory. Integration times can be varied over a 0.5 to 64 second range. The CCD, contained in an evacuated enclosure, is operated at -45 C. Only the image section, an area of 8.5 mm x 6.4 mm, gets exposed to light. Pixel size is 22 microns and either no binning or 2 x 2 binning can be selected. The typical readout rates used vary between 3.5 and 9 microseconds/pixel. Images are stored in a PC/XT/AT, which generates RS-170 video. The contrast in the RS-170 frames is automatically enhanced by the software.

A recently developed indium antimonide high-sensitivity two-dimensional multiplexed medium wavelength infrared (MWIR) hybrid focal plane array (FPA) is described with special attention given to its multiplexer circuit and the detector array. The device parameters and the performance characteristics of the MWIR FPA are presented in tabular form, demonstrating excellent performance. The multiplexer schematic is included together with graphs of quantum efficiency at various wavelengths and mean dark current at various initial biases and temperatures.

Recent advancements in fabrication of near-infrared focal plane arrays are beginning to revolutionize near-infrared astronomy. The University of California Lick Observatory is undertaking a program to exploit these arrays by starting with a singlefilter (K band at two microns)imaging camera to be used at the Sane 3-meter telescope. The detector is a Rockwell 128x128-pixel device, sensitive from 1 to 2.5 microns and employing the NICMOS design. Camera specifications, controlling electronics, calibrations procedures, and device performance in the lab and at the telescope will be presented. Some images of astronomical targets will also be shown.

A 770 x 1152-element CCD camera being developed for use with the ISIS spectrograph on the 4.2-m William Herschel Telescope at Observatorio del Roque de los Muchachos is described and illustrated with diagrams and graphs of test data. The super-grade EEV 88200 CCDs selected for the ISIS red-arm (401-1060 nm) camera have pixel size 22.5 microns square and rms readout noise 3.5 electrons at operating temperature 150 K; peak quantum efficiency of 50 percent is measured at wavelength 650 nm, and the spatial resolution obtained with ISIS is less than 1.2 pixels FWHM. A similar camera is to be constructed for the blue arm of ISIS. Also provided is a brief overview of the CCD controller hardware and software, summarizing the detailed descriptions of Bregman and Waltham (1986) and Bregman and Doorduin (1986).

New YAG lasers have been found as useful machines to generate 2D masks for multi-object spectroscopy. Compared to the punching technique presently under operation in some astrophysical observatories or to the C02 laser capability, the performances are higher in several ways. The cutting accuracy at the edge of slits is greatly increased and can be improved by selecting the number of loop paths. The size of conventional rectangle slits is easily controlled. Another feature of interest is that various type of curvilinear slits can be generated. Presented results have been obtained with the YAG laser machine commissioned by the Canada-France-Hawaii Telescope Corp.

The New Technology Telescope (NTT) installed at the Observatory of ESO, La Silla, Chile, employs a 3.5m active primary mirror and foresees that two instruments are mounted all the time at the Nasmyth foci. Remote observations from Germany will also be possible. The NTT is in many ways a prototype for ESO's Very Large Telescope (VLT), an array of four 8m telescopes now in the construction phase. This applies also to the control/acquisition system software, developed for the NTT, i.e. the software environment where specific control programs for telescope, adapters and instruments are running. Characteristic aspects of this system, which allows simultaneous multi instrument and multi-user operation, are described in this paper. The system is intrinsecally distributed both in hardware (several microprocessors on Ethernet) and in software (CPU independent program communication). System-wide information and complete decoupling of control programs from the user-end are obtained via a central parameters database (Pool) which supports data both on disc and memory, for time critical operations. This allows local and remote users to access in real-time all information on telescope and instruments without directly interfering with control programs. It permits also to have a truly open system with coherent expansion as soon as new modules are added. The distribution of the Pool on many CPUs and remote access methods will allow to develop a portable user-end for the remote use of the NTT and the VLT. This will be implemented on a workstation accomodating the user-end both for image processing and control and will be software configurable to act as a local control console of one or several telescopes and instruments or a remote observing tool useable from several astronomical Institutes in Europe.

A three-color IR photometer suitable for speckle imaging or for traditional fast or slit-scan photometry is described, with special attention given to the photometer's scanning and relay optics, the dewar, the electronics, and the data acquisition and reduction hardware and software. The system is able to acquire sets of object and sky scans on three colors simultaneously, while concurrently performing a Knox-Thompson speckle analysis on the incoming data. The slit-scan photometry operation mode allows observations of objects too faint for speckle imaging. To date, the system was used to observe more than 20 T Tauri stars, several evolved stars, numerous binaries, and G29-38, with good agreement with published and known results for binary observations and those of NML Cyg and IRC + 10216.

Current uses of the MAMA detector which utilize the photon time-tagging capabilities of these detectors are reported. These applications currently include image stabilization by means of post-processing corrections of platform drift and speckle interferometry. The initial results of a sounding rocket experiment to obtain UV images of NGC 6240 and results from speckle interferometry of Neptune's moon Triton are presented.

This paper describes the Cerro Tololo Infrared Spectometer (IRS), a general purpose cooled-grating spectrometer designed for 4-m and 1.5-m telescopes, which was recently upgraded to operate with the Santa Barbara Research Center 62 x 58 InSb array. Special attention is given to the optical and the mechanical designs of the IRS, its data acquisition and instrument control systems, and the operation characteristics of the instrument and the dewar. The updated IRS provides resolutions from about 0.9 micron to 5 microns.