A system study has been conducted to determine performance capability to make observations of members of the Solar System using the Large Space Telescope (LST), which was primarily conceived for stellar observations. 'Ahe study identified the LST capabilities for viewing opportunities considering the LST orbit location, ability to measure available flux at the input to the science instruments and the amount and rate of travel of the telescope line-of-sight (LOS) needed to follow members of the solar system for integrated measurements. The study results show the LST system to have good capability for the collection of solar system data with small additional equipment requirements to the stellar observational application.

This paper is basically a history of the evolution of the astronomical X-ray telescope as designed and engineered at American Science and Engineering, Inc. To that end, certain telescope designs have been selected which represent milestones along the evolutionary path taken by X-ray astronomy during the past few years. The developmental mile-stones presented here have been selected largely on the basis of a steady improvement in resolution paralleled by rather dramatic increases in collecting area.

A high-performance narrow-angle telescope for the visual imaging subsystem of the Mariner-Venus/Mercury spacecraft was designed to provide high-resolution tele vision photography of the planets Venus and Mercury over a spectral band of 350 to 650 nm during the 1973 Mariner mission to the inner planets. The optical system was designed to meet specific performance requirements and tested after fabrication in flight configuration to ensure that the requirements were met. This paper describes the optical requirements of the telescope, the mechanical constraints placed on the design, the resulting optical system, and its performance in flight configuration.

Far-infrared astronomy is a rapidly developing new field where the early small survey experiments are just now being supplemented with larger payloads capable of mapping with good spati 1 resolution and high sensitivity. Balloons provide an ideal vehicle for this work because they are capable of carrying weights up to several thousand kilograms to above virtually all the atmospheric water vapor for flight times of many hours, and at modest expense.

The 91.5-cm (36-in.) airborne infrared telescope installed in a Cl4lA StarLifter as a national IR observatory is described. Emphasis is placed on those features and subsystems which will be used directly in experimen-tation utilizing the telescope system.

The multiple mirror Telescope is a project being carried out by the Smith-sonian Astrophysical Observatory and by the University of Arizona where the Steward Observatory, Lunar and Plane tary Laboratory, and Optical Sciences Center are participating in the project.

A photometric system providing automated telescope control and data gathering recently has been completed at Michigan State University. At present it is possible to do sequential 3-, 4-, or 5-color photometry.

A unique telescope was designed and built for the Go Aard Space Flight Center of NASA, by the Electro-Optical Division of Kollmorgen Corp. The telescope to be used as an laser ranger, is a servo driven 48" altazimuth telescope with the accuracy and precision of a theodolite. Among its salient features are the use of a gas bearing for azimuth rotation and the precision of its rotational axes. Axis wob ble and axis orthogonality are within one arc second. o achieve the frequency response consistent with a high accuracy servo loop, breakaway torque, from all sources, was limited to 20 ft. lbs about both axes. Final tests showed torque about the elevation axis to be 7 ft. lbs. About the azimuth axis, with a rotating mass of 30,000 lbs, the measured breakaway torque was 0.75 ft. lbs.

The primary objective of this paper is to describe the successful fabrication of an image tube which uses a 1024-element self-scanned diode array at its anode to detect imaged photoelectrons. Although only preliminary test results are available, initial operation has indicated that the concept is sound. A brief description of other related devices containing from one to 212 channels will also be given.

The autoguiding of ground-based telescopes has developed relatively slowly over the last thirty years or so, in spite of the existence of exceedingly sensitive photoelectric detectors. Of those based on the mechanical chopping or dissection of the light in a stellar image, there are essentially three types. The first (Ref. 1) entails division of the light at the roof of a right-angled prism or the apex of a pyramid, the second, a rotating knife-edge (Ref. 2), and the third, an elegant development of the latter (Ref. 3), uses a ball bearing rotating inside an annulus.

The predominance of television systems which operate at standard broadcast rates tend to mask several system optimization techniques which can improve performance of nonstandard systems. Astronomical systems, in particular, benefit by use of nonstandard frame rates, line numbers, and a proper balance between exposure time and sensor gain. Resolution and signal-to-noise from a given sensor can be maximized by proper selection of the number of TV lines and the frame time. In addition, the signal-to-video noise for a given TV resolution has a peak value for the video bandwidth picked from sensor and system parameters.

A versatile photon imaging system for use in the 1 - 1800 A wavelength range is described. The Ranicon employs a microchannel electron multiplier plate to convert the incident photons into a charge signal. This charge pulse is proximity focussed onto a large area resistive anode plate equipped with pickup electrodes on its edges. Each i event is located electronically by the ratios of the charges collected at the edges or by the differneces of the signals' rise times. One and two dimensional pictures are built up by storing events digitally (e.g. a core memory) or in analog form (e.g. a storage oscilloscope). A compact laboratory model has been constructed and tested. Operating characteristics and applications of the Ranicon are discussed.

The Sacramento Peak Observatory has developed and placed in operation an array of photodiodes in the focal plane of a high dispersion spectrograph. The diodes record solar phenomena in the 4000 - 11000 Å range. Signals from the diodes are digitized and computer processed into photographs or other output forms in real time. By varying the placement of 32-diode blocks in the spectrograph, any combination of wavelengths may be used in the construction of spectrograms, spectroheliograms, magnetograms and tachograms. Spatial resolutions vary between 1/2 and 2 arcsec with a spectral resolution of up to 0.02 Å. The signal-to-noise ratio for a single observation is limited in most cases by scintillation to 300:1. Several examples of computer processed photograms are given.

The Thermal Image Projector/Recorder (TIPR) is a system of electro-optical devices which convert low-level thermal images to corresponding high-intensity light images for projection on a screen or recording on film. The performance of typical thermal systems is limited for two primary reasons: first, there is spectral incompatibility in that the energy in a thermal photon is too low to directly expose film or release electrons from imaging cathodes; second, the integration of a thermal image over a period of time only tends to smear the image because of the low thermal impedance of thermal-sensitive materials. The TIPR solves the elemental dwell time as does the pyroelectric vidicon by essentially providing an unlimited number of detectors. It solves the image smear problem by rapid chopping of the thermal image radiometrically and the integration of the chopped images. The theory of the TIPR is based on the release of electron images from thermal-sensitive materials through electron field emission from millions of points.

Two spectrometers of the concave-grating (Rowland circle) type, uti-lizing an entrance slit and a micro-channel plate at the focal surface, have been developed. Our primary application at present is to terrestrial and planetary airglow and auroral studies in the far ultraviolet (300-1800 A). The first spectrometer utilizes electronographic recording of the spectral image, with magnetic focusing of the electron output of the micro-channel plate onto electron-sensitive film. A microchannel plate gain of 10 to 100 is used. Resolution is limited only by the channel size of available microchannel plates. The second spectrometer utilizes a two-stage microchannel plate, operating at gains of up to 107, with the output bursts incident on a resistive (106 ohm) strip placed immediately behind the plate. The ratio of the pulse sizes sensed at opposite ends of the strip is used to determine the position along the strip at which it occurred (and hence the corresponding wavelength along the Rowland circle).

Solar radiation in the far infrared (wavelengths 200-10000 arises primarily from the region of the solar atmosphere near the temperature minimum in the low chromosphere (Ref. 1). An accurate specification of the temperature structure of this region of the sun is important for an understanding of the processes of nonradiative energy transport since it is here that departures from radiative equilibrium first become important in the chromosphere. Because of the relatively high opacity of this region, a comparatively large input of energy is required to support a temperature structure here only slightly above the radiative equilibrium value (Ref. 2).

With the advent of modern precision high speed microdensitometers operating under control of general purpose ii-computers, vast areas of research have suddenly beco e available which, until only recently, were largely inaccessible due simply to the constraint of limited available time. The intent of this paper is to present a general discussion of a number of applications for which such a system (one which we are currently using) is suited. Neither is the list of applications exhaustive, nor is our system the last word in this rapidly developing technology. Even so, with consideration of these finite limitations the research capabilities of such a system seem all the more impressive.

A Michelson interferometer-spectrometer utilizing a rapid, continuous scan has been combined with a minicomputer data acquisition system to provide the capability for measurement of spectra containing up to 217 resolution elements at a resolution of 0.5 cm^-1. The instrument has been used at the Coudg' focus of the University of Texas 2,72 meter telescope, Most of the work done to date with the instrument has been in the 1,0 to 1,41 spectral range using a sensitive germanium photovoltaic cell.

The Otraviolet solar radiation from 1000Å up to the atmospheric cutoff at 3000A is of great interest to solar physics. In order to record this spectral region in a form most advantageous to solar physics, the NRL Extreme Ultraviolet Spectrograph was designed with several major goals in mind. Among these were: the most complete spectral coverage possible, and the highest spectral, spatial, and temporal resolution possible. The total spectral coverage of this instrument is about 1000Å to 4000Å, which provides an overlap with ground based observations.

The Harvard College Observatory instrument on the Apollo Telescope Mount (ATM) is a photoelectric spectroheliometer designed to obtain up to seven simultaneouA spectrohRliograms in the range 280 Å to 1340 Å with a spatial resolution of 5 arc sec as well as spectral scans with a resolution of 1.6 Å over the same wavelength range. Because of its large size, this in-strument has a sensitivity far greater than that of any photoelectric extreme ultraviolet (EUV) spectroheliometer flown to date. The instrument has operated correctly since 29 May 1973 and has obtained many thousands of spatial and spectral scans of a variety of solar features. Furthermore, the laboratory photometric calibration has been reestablished in orbit by comparing the response with that of more recently calibrated spectroheliometers flown on sounding rockets in August and December 1973.

The Apollo Telescope Mount Experiment S-056 successfully completed its soft X-ray data gathering mission with the splash-down of the Skylab 4 astronauts on February 8, 1974, The development of the S-056 experiment along with the problems encountered in designing, testing and operating the equipment is-describedherein with an eye to assisting the designers of more sophisticated future instruments.

The high resolution X-ray observations from Skylab provide a view of the structure and evolution of the solar corona. The S-054. X-ray telescope operated successfully. throughout the eight month mission, photo-graphically recording nearly 35,000 images. The telescope is a grazing incidence instru ment (Ref. 1) with spatial resolution of the order of two arc seconds on axis. The total, wavelength range observed by the instrument. is 2 - 60 R.. Crude spectral resolution within this range is achieved by means of a series of six X-ray filter materials. A spectrographic mode of operation, which employs an objective grating, is used to obtain spectra of flare events and selected coronal features. The images produced by the telescope are recorded on film.

Most of the instruments of the Apollo Telescope Mount are satellite-borne because they observe in regions of the electromag-netic spectrum where the telluric atmosphere is opaque. For the coronagraph of the High Altitude Observatory, observing in visible light, this is not so. The structure of the solar corona is obscured from ground-based observations by scattered light in the earth's atmosphere, and observations from space are required to reduce this scattered light to a level which is negligible with respect to the brightness of the outer solar corona.

The resolution achieved by a large, ground-based astronomical telescope is limited by both the perfection of the optical components of the instrument and the distorting effects of the earth's atmosphere as the electromagnetic waves propagate toward the telescope.

Until recently, the fabrication of aspheric profiles or any other optical element of revolution in glass surface was based on the deformation of a reference profile. We are relating briefly the methods used in recent times for the purpose.

We are reporting initial results of near infrared photoelectric area scanning with control, detection, and on-line-processing employing digital techniques. The primary objective of this instrument is to measure separations and color differences of stellar binary systems in an objective and precise manner. We exploit the extraordinary linearity of the PM tube and develop a photon limited system.

The subject of ghost images, glare spots, false light, parasites and veiling glare has been summarized in photographic manuals (Ref 1) and has received wide attention in artistic, commercial and technical photography. In astronomical photography the matter depends entirely upon the astronomer's demands and the problem can be either crucial or trivial..

Various types of designs were stu-died by the author at the Jet Propulsion Laboratory (JPL) for the optics of the high-resolution television camera for the Mariner '69 and '71 missions to Mars. This telescope had to perform over the spectral range 7100-4850A, weigh less than 9. 1 kg (20 lb), and have a rear clear-ance of 38 mm (1. 5 in. ). The goal for this 2° full field, f/2. 5, Ti< 4. 0, 5.08 mm (20. 0 in. ) efl cassegrain system was 40% response at 80 ip/mm; such resolution implied an rms spot size of about O. 00025 in.

An automated microdensitometer is used to obtain a density distribution on a photographic plate. Each density is proportional to a surface departure from ideal at some point on a mirror during its figuring. The departures are obtained by the screen test method developed at Kitt Peak National Observatory, as applied to the 4-meter primary mirror. It is shown that for various screen rotations with the mirror stationary, easily interpreted results are obtained with this density representation. These results are in good agreement with each other. When all the rotated-screen density representations are made on the same photographic plate, one obtains a composite in which areas of greatest agreement are emphasized and areas of scarce surface sampling are complemented.