The Infrared Space Observatory (ISO) will be the first true infrared astronomical observatory in space, operating at wavelengths from 2.5 to 200 micrometers . Launched into a 24 hour orbit, the observatory will be capable of pointing on specific targets for up to ten hours at a time to make observations with a versatile range of instruments including a camera, a photometer, a complement of spectrophotometers and spectrometers with resolving powers ranging up to 20,000 and polarimetric capabilities over a wide spectral range. During its active lifetime of eighteen months, ISO will be used to observe all classes of astronomical phenomena, including solar system objects, stars, the interstellar medium, and galaxies of all kinds out to extreme distances.

The Infrared Space Observatory (ISO), a fully approved and funded project of the European Space Agency (ESA), will operate at wavelengths from 2.5 - 200 micrometers . ISO will provide astronomers with a unique facility of unprecedented sensitivity for a detailed exploration of the universe ranging from objects in the solar system right out to the most distant extragalactic sources. The satellite essentially consists of a large liquid-helium cryostat, a telescope with a 60-cm diameter primary mirror and four scientific instruments. The instrument complement is: an imaging photopolarimeter (2.5 - 200 micrometers ), a camera (2.5 - 17 micrometers ), a short wavelength spectrometer (2.5 - 45 micrometers ) and a long wavelength spectrometer (45 - 180 micrometers ). These instruments are being built by international consortia of scientific institutes and will be delivered to ESA for in-orbit operations. ISO is scheduled to be launched in 1995 and will be operational for at least 18 months. In keeping with ISO's role as an observatory, two-thirds of its observing time will be made available to the general astronomical community.

Spectroscopy is an essential tool in the astronomer's kit, probing the microscopic physics of astronomical objects. The Long-Wavelength Spectrometer (LWS) is one of two complementary spectrometers in the European Space Agency's Infrared Space Observatory (ISO). In this paper, I discuss briefly the scientific considerations which drove the design of the LWS and describe the instrument itself. I then discuss how the instrument works and outline its photometric performance. The measurement of this performance is described in a companion paper at this conference.

The Short-Wavelength Spectrometer (SWS) for ISO operates in the wavelength range from 2.4 to 45 micrometers. It consists of two, almost identical, grating spectrometers that provide resolving powers varying between 1000 to 2000. In the wavelength region from 12 to 45 micrometers a much larger (>20.000) resolution can be obtained with a pair of Fabry-Perot interferometers. This paper describes the design of the SWS.

ISOPHOT is one of four instruments onboard the ESA Infrared Space Observatory scheduled for launch in September 1995. It covers the wavelength range 2.5 micrometers to 240 micrometers with wide and marrow spectral bands. Diffraction limited observations as well as wide beam measurements of faint extended sources are possible. Polarimetric observation can be made over the whole wavelength range. The minimal detectable flux is approximately 10 mJy. The astronomical areas to be addressed range from solar system objects to cosmology.

ISOCAM, the camera of the Infrared Space Observatory, will image the sky at various angular and spectral resolutions in the wavelength range 2.5 to 17 microns. We recall the main steps of the development, leading to the delivery of the flight model to ESA, and we outline some of the scientific programs to which it will be applied.

The Infrared Space Observatory (ISO) is essentially a cooled 60cm diameter telescope with four flocal plane instruments operating at cryogenic temperature. One of these instruments, the Long Wavelength Spectrometer (LWS), offers spectroscopic capability over the wavelength range 43 micrometers to 198 micrometers , with a choice of either a mid-resolving power mode (R approximately equals 200) or a higher resolution mode (R approximately equals 10000). For testing the Flight Model of the LWS, it is necessary to establish many of the operating conditions which will apply when it is operating in space, using a specially constructed calibration facility. These tests have enabled the operating modes of the LWS to be refined, as well as measuring its operational performance and establishing a calibration database. This data will provide the initial calibration for the LWS when operating in-orbit.

Results of the ground test and characterization program show that the performance of the SWS is well within its specifications. The procedures for ground testing and calibration are tuned to achieve commonality with in-orbit procedures. This strategy optimizes the development of data analysis procedures and allows a fast in-orbit check-out and update of the calibration.

The camera of the Infrared Space Observatory was carefully tested and calibrated during two years (1991 - 1992) in the dedicated facility installed at Institut d'Astrophysique Spatiale at Orsay. A large cryostat with high-precision instrumentation was developed, in order to provide an operation environment close to the conditions expected in orbit. The large amount of data obtained allows a thorough investigation of the imaging, photometric and spectral properties of ISOCAM in all its operation modes, leading to the definition of hopefully optimal observing procedures and data-processing algorithms.

A calibration facility simulating the optical and cryogenic environment of the ISO satellite has been built for characterizing the ISOPHOT instrument. This facility uses a commercially calibrated, 900 K--blackbody radiation source and an optics at room temperature to provide an f/15 beam to the instrument which is contained in a LHe-cryostat. The low level infrared flux levels of ISO are obtained by use of a light sealed instrument chamber and cold attenuation filters. The infrared flux can be calculated using the known blackbody emission and the cold calibrated transmission spectra of the filters. The calibration facility further provides a scanning mechanism, a light modulator and filters for polarization measurements and wavelength calibrations of the ISOPHOT spectrometer channels. Electrical support equipment for the instrument operation and software for data archiving and analysis have been customized for this project. The test program comprised a standardized acceptance test for the entire instrument and special tests addressing individual instrument properties. The data obtained contain the photometric sensitivities of ISOPHOT, optimized instrument settings, reference data for the integrated system tests and inputs for the ongoing mission planning.

This paper presents a brief review of mid and long-wavelength (6 micrometers - 200 micrometers ) infrared detector technology used on space borne astronomical missions. Examples of the focal plane designs from the Infrared Astronomical Satellite (IRAS), Cosmic Background Explorer (COBE), Infrared Space Observatory (ISO), and the Space Infrared Telescope Facility (SIRTF) are presented. The major technical innovations considered are low background photoconductors, self-heated amplifiers, Impurity Band Conduction (IBC) detectors, large format arrays, and true cryogenic readout electronics. The impacts of the changing technology base on the kinds of scientific investigations possible are discussed.

This paper describes the status of NASA's Space Infrared Telescope Facility (SIRTF) program. SIRTF will be a cryogenically cooled observatory for infrared astronomy from space and is planned for launch early in the next decade. We summarize a newly modified baseline SIRTF mission and provide and overview of SIRTF's scientific programs.

This paper describes a new mission concept for the Space Infrared Telescope Facility (SIRTF). In this new concept, SIRTF is launched with just enough energy to escape Earth's gravity. This trajectory is equivalent to a 1 astronomical unit (AU) solar orbit with a small drift rate of about 0.1 AU per year away from the Earth. The new concept uses an Atlas IIAS class launch vehicle to place an 85 cm diameter telescope with a 3 year minimum cryogenic lifetime into a solar orbit. There are many advantages of the solar orbit over an Earth orbit. The spacecraft design can be simplified. Communications and operations can be geared to a 24 hour day, although a directional antenna is needed because of the increasing distance from Earth. Additional advantages include the elimination os the need for Earth/Moon avoidance requirements and the ability to view large portions of the sky continuously for weeks or even months.

This paper describes the current design concepts for the three scientific instruments which are under definition study for NASA's Space Infrared Telescope Facility (SIRTF). These instruments, the Infrared Array Camera (IRAC), the Infrared Spectrograph (IRS), and the Multiband Imaging Photometer for SIRTF (MIPS), will provide imaging and spectroscopy from 2.5 to 200 micrometers . Over much of this range their performance will be limited only be natural astrophysical backgrounds in the solar system, and by diffraction. Changes in the instrument complement from the former Titan launched, Earth orbiting SIRTF concept to the present Atlas launched, solar orbiting concept are discussed.

The Cosmic Background Explorer (COBE) satellite carries three instruments to measure the diffuse infrared and microwave background radiation from the early universe, along with more recent diffuse sources. It was developed by NASA's Goddard Space Flight Center and launched by a Delta rocket on November 18, 1989. It has produced the first measurements of structure in the Big Bang and has shown that the primeval heat radiation has a blackbody spectrum to extraordinary accuracy. The three instruments include a Far Infrared Absolute Spectrophotometer (FIRAS) to cover the range from 100 micrometers to 1 cm wavelength with a 7 degree(s) resolution, a Diffuse Infrared Background Experiment (DIRBE) to map the sky from 1 to 300 micrometers with a 0.7 degree(s) resolution in 10 broad bands, and a Differential Microwave Radiometer (DMR) to map the sky at 31.5, 53, and 90 GHz with a 7 degree(s) resolution. The designs of the instruments and spacecraft are described, and the primary results ar summarized.

The COsmic Background Explorer, (COBE), launched on November 18, 1989, made all-sky surveys in the millimeter, sub-millimeter, and infrared bands, with the goal of detecting and studying the Cosmic Infrared Background (CIB), and of making detailed studies of the Cosmic Microwave Background (CMB). Since these backgrounds come to us from redshifts (Zeta) ranging from, a few to 10³, corresponding to co-moving distances of (54 - 360) X 10²⁴ meters, COBE is certainly doing the most remote of all the 'remote sensing' discussed in this session.

The Far InfraRed Absolute Spectrophotometer (FIRAS) was built to measure the spectrum of diffuse emission from 1 to 100 cm^-1, with particular attention to possible differences between the spectrum of the cosmic microwave background radiation (CMBR) and a blackbody spectrum as small as 0.1% of the peak of the CMBR spectrum. The FIRAS has differential inputs and outputs, a full beam external calibrator, a controllable reference blackbody, and a polarizing Michelson interferometer with bolometer detectors. It is operated at a temperature of 1.5 K inside a liquid helium cryostat to suppress instrument emission and improve detector sensitivities. It has an intrinsic frequency resolution of the order of 0.7%, maximum path lengths of 1.2 and 5.9 cm, and a beamwidth of 7 degree(s), and achieved its goals for accuracy and rms sensitivity for νI_ν, which are better than 10^-9 W/cm²sr over the frequency range from 2 to 20 cm^-1.

The Diffuse InfraRed Background Experiment (DIRBE) onboard the cosmic Background Explorer (COBE) was designed to conduct a search for a cosmic infrared background (CIB), which is expected to be the fossil radiation from the first luminous objects in the universe. The instrument, a ten-band cryogenic absolute photometer and three-band polarimeter with a 0.7 degree(s) beam and a wavelength range from 1 - 240 micrometers , scans the sky redundantly and samples half the sky each day. During the ten month lifetime of the cryogen, the instrument achieved a nominal sensitivity on the sky of 10^-9 W/m²/sr at most wavelengths, or approximately 1% of the natural background at wavelengths where the sky is very luminous. The short wavelength bands from 1 - 5 micrometers continue to operate after exhaustion of the cryogen, although at reduced sensitivity. In this paper, we review the design, testing, and in-flight performance of the DIRBE.

The Cosmic Background Explorer (COBE) satellite was launched on November 18, 1989 from Vandenberg Air Force base on a Delta rocket. It carried two superfluid liquid-helium-cooled (LHe) infrared (IR) instruments in a 600 liter dewar, and three microwave radiometers mounted on the outside of the dewar. One of the LHe-cooled instruments is a ten-band photometer covering the spectral range from 1.2 to 240 micrometers - the Diffuse Infrared Background Experiment (DIRBE). A goal of the DIRBE program is to obtain full-sky infrared observations that can be used to model accurately the IR contributions arising from the interplanetary dust (IPD) and the Galaxy. Using such models, the foreground can be removed to expose and underlying extragalactic IR component produced early in formation of the universe. The nature of the IPD IR foreground detected by the DIRBE is found to be quite complex, but amenable to modelling.

The Diffuse Infrared Background Experiment (DIRBE) on board NASA's Cosmic Background Explorer (COBE) satellite has surveyed the entire sky in 10 broad photometric bands covering the wavelength region from 1 to 240 micrometers , at an angular resolution of 0.7 degree(s) (Boggess et al. 1992). the extensive spectral coverage of the DIRBE observations offers an unprecedented opportunity to undertake comprehensive large-scale studies of the content, structure, and energetics of the stellar and interstellar components of the Galaxy. Understanding the Galactic emission is not only a task of scientific value in its own right, but also a necessary step in the accurate extraction of faint cosmological emission from the DIRBE data.

The Differential Microwave Radiometer (DMR) experiment on the Cosmic Background Explorer is in the final year of a scheduled four years of operation to measure large- and intermediate-scale anisotropies in the Cosmic Microwave Background (CMB). The DMR instrument comprises two independent radiometers at each of three frequencies, 31.5, 53, and 90 GHz, where the frequencies were chosen to best separate the CMB from the foreground emissions from galactic dust and electrons. The radiometers switch symmetrically between two beams of 7 degree(s) half-power width separated by 60 degree(s) on the sky, and provide a data set of sky brightness temperature differences that allows the determination of all-sky maps of brightness temperature variations at 7 degree(s) resolution. Data from the first year's operation were used to produce maps of unprecedented sensitivity in which the long-sought intrinsic anisotropies were identified. Three more years of data will ultimately be available to refine the anisotropy measurements.

This paper describes a low cost adaptive optics (AO) instrument that is being built for the f/31 focus of the UH 2.2m telescope. While operating within the low cost constraint, we have tried to maximize the flexibility and usefulness of the instrument, and minimize the impact of the necessary performance compromises. We have used off-the-shelf optical and electronic components wherever possible, and have emphasized simplicity of design throughout the instrument. The UH prototype AO system, on which the 2.2m AO system is based, is described elsewhere, thus the principles of operation of the UH 2.2m instrument will not be described in detail here.

Methodical research of different object and background radiation in the optical range of the electromagnetic spectrum began at the S.I. Vavilov State Optical Institute 60 years ago. These investigations attempted to solve a wide range of problems in atmosphere optics and optoelectronic instruments. The main aim of the investigations is the creation of a data bank network of optical radiation for objects and backgrounds that could be used for Earth and atmosphere monitoring. The experiments are carried out in the field of radiation measurement research, theoretical calculations, elaboration of measuring apparatus, and treatment of experimental data.

The need exists for systems to monitor extraordinary events like fires, technological accidents, volcano eruptions, and regional military conflicts. We have investigated an IR-telescope placed on a spacecraft functioning on a high-elliptical geotrapped orbit. The ground receiver and control stations receive information and work it up.

An infrared (IR) remote sensing system has been built to acquire data on wildland fires. The 'Firefly' project has developed and implemented a system based on the technology and design presented. The Firefly System produces images through smoke that provide near real-time wildland fire detection and mapping information for fire management and suppression.

As one of the four Cornerstones of its scientific program 'Horizon 2000', the European Space Agency ESA is studying a Far Infrared and Submillimeter Space Telescope (FIRST). FIRST will open to astronomical observations the 100 micrometers to 1mm spectral region, virtually unexplored with a sub-arcmin angular resolution. The 3 - 4 m diameter telescope will be diffraction limited at (lambda) equals 300 micrometers or less. The fabrication of a single dish of composite materials is considered as the baseline. The expected life time of this system in orbit is five years or more. The Model Payload, defined in order to allow a realistic system study and an evaluation of the possible scientific return, is composed of two focal instruments. The Multifrequency heterodyne spectrometer will give a very high spectral resolution in the 400 to 630 micrometers wavelength range and around 300 micrometers . The Far Infrared Receiver will be an imaging spectrometer covering the 100 - 400 micrometers range with spectral resolutions ranging from 5 to 10⁴ obtained with a set of Fabry-Perot interferometers and filters. FIRST is expected to give unprecedented information on the physics, chemistry and dynamics of interstellar, circumstellar, planetary and cometary gas and dust. Extragalactic physics and deep surveys of cosmological interest will also benefit from this project.

The second Spatial sPectral Infrared Rocketbome Interferometer Telescope (SPIRiT II), a recently launched sounding rocket experiment, measured the spatial and spectral structure of the LWIR region of the earthlimb. The two primary instruments, a 300-detector spatial radiometer and a 6-detector interferometer-spectrometer, were both housed in a highoff-axis-rejection telescope cooled to liquid helium temperatures. A photometer was used to sense energy input into the atmosphere. Ancillary instruments used to determine pointing direction and to view scene content (both during flight and for postflight data analysis) included an electronic star tracker, a horizon sensor, a low light level television camera, and a celestial aspect sensor television camera. The instrument payload, which was separated from the booster rocket in flight, contained its own attitude control system and performed a preplanned scanning pattern through the earthlimb.

A cryogenic Michelson Fourier transform interferometer-spectrometer (FTIR) was built and flown as part of the second Spatial sPectral Infrared Rocketborne Interferometer Telescope (SPIRIT II) payload. The flex-pivot mirror-translation interferometer was designed to obtain spectral data from 2 to 28 micrometers. Two different scan rates and resolutions were provided: 10 cm^-1 at 2 seconds per scan, and 2 cm^-1 at 10 seconds per scan. A laser reference channel was run antiparallel to the main channel to provide sampling information. The system was calibrated using an infrared calibration system built specifically for SPIRIT II. The payload was launched from the University of Alaska's Poker Flat Research Range on March 28, 1992, and successfully collected auroral emissions data.

A 300 element spatial radiometer was recently flown as part of the SPIRiT II experiment. This instrument, housed in a high-off-axis-rejection telescope cooled to liquid helium temperatures, measured the spatial structure within six LWIR spectral bands of the earth's limb. The radiometer used hybrid multiplexed focal planes with BIB detectors. The use of this technology enabled several enhancements to system performance. New data collection and analysis tools contributed significantly to the development and enhancement of this radiometer. Postflight analysis shows that the radiometer performed well during its sounding rocket flight.

Many experimental measurement goals can best be accomplished with imaging sensors which have high spatial, spectral, and/or temporal resolution. The design and construction of new types of IR imaging systems have become feasible with the availability of reliable, relatively low cost focal plane arrays (FPA's). This paper presents the design and modeling investigations of an imaging grating spectrometer utilizing a 256 X 256 InSb FPA for Earth observing measurements in the 3 - 5 micrometers region. The design includes an optically filtered, radiometric, imaging mode for increased temporal and spatial resolution. Modeling efforts verify the conceptual feasibility and identify practical limitations in sensitivity and dynamic range. The design concepts and performance were verified experimentally by building and testing a prototype imaging spectrometer using commercially available optics, FPA, electronics, and computer equipment. Data is presented which illustrate the simultaneous spectra and spatial measurement features and the versatility of the sensor system. Both the model and the measurement results show the impact of instrument self-emissions, FPA noise, and FPA non-uniformities on the sensor system. In addition, the impact of system dynamic range and FPA pixel integration timing and read-out electronics are discussed.

The potential benefit of combined spectral and spatial imagery in the classification/monitoring study of events and processes has created strong interest in the class of remote sensors identified as imaging spectrometers. The production and commercial availability of low cost, multiplexed two-dimensional FPAs, and fast signal processing hardware and advances in reflective optical engineering have permitted the developments of a second tier of instruments moderate in both performance and cost. When combined with maturing technologies for lightweight, lowcost optical subsystems with glass-like wavefront properties based on Silicon Carbide (SiC), imaging spectrometers compatible with use on small satellites, sounding rockets and unmanned airborne vehicles emerge. Demonstration of this sensor technology in the MWIR will be made via a spectrally versatile concept for monitoring of combustion events occurring in a Learjet microgravity environment.

Infrared focal plane array technology has matured in response to increasing performance demands, both at the device and system levels. Users of these devices are operating then at or very close to their theoretical signal and noise limits. Greater numbers of pixel channels not only force the development of readout multiplexers that can perform a variety of signal conditioning functions, but demand that these sophisticated operations be executed in an ever- diminishing silicon area. We discuss operational options available in today's detectors and readout multiplexers with an overview of some off-chip functions as well.

A modified Twyman-Green interferometer is in use that makes possible wavefront testing of optical filters at any wavelength from 200 to 1100 nanometers. The use of mirrors for collimation and pupil imaging makes the instrument achromatic, and therefore the focus is fixed over the entire bandwidth. The beamsplitter and compensator plates are made of fused silica, and the detector is a UV enhanced CCD tv camera. A tunable monochrometer with a broadband light source permits selection of any wavelength. Fringe distortion, even when the collimating mirror is spherical, is small enough to keep measurement errors within 0.1 wave peak to valley over the 2 by 2 inch aperture.

Potential transmitting materials for the STIS mission are being considered for order sorters, in-flight calibration filters, detector windows and calibration lamps. In this paper we examine the changes in spectral transmission characteristics with radiation dosage during a mission lifetime. A radiation environment for a 593 km altitude, 28 degree inclination orbit, for solar minimum and solar maximum, assuming a spherical shielding of 2 gms/cm² has been assumed. The dosage for protons is 0.392 Krad (Al)/Yr. and 0.217 Krad (Al)/Yr. for solar minimum and solar maximum respectively. To simulate the mission radiation environment Harvard Cyclotron Laboratory (HCL) has been used. Spectral transmission was measured between 210 nm and 3200 nm using a Perkin Elmer Lambda 9 monochromator. Below 210 nm a one meter McPherson vacuum monochromator was used. Transmission curves for all samples were obtained before irradiation and compared for equality in transmission.

Tree-ring data have been used to reconstruct mean seasonal temperature (June - January) at treeline in the Sierra Nevada, California, USA, from 1050 BC to the present. Comparison with a temperature reconstruction from Fennoscandia (A.D. 500 - 1980) indicates that the temperature records are significantly related over the common interval and suggests that both are recording a possible common hemispheric/global temperature signal. The reconstruction shows that temperature has varied in a coherent manner, with alternating periods of warm and cold temperatures over the last 3030-yr. Analysis of the spectral properties of the reconstructed temperature series from the Sierra Nevada indicates that the strongest peak is at 125-yrs, corresponding to a pronounced 127-yr peak found in the 570 B.C. - A.D. 1830 quarter section of the detrended radiocarbon production (Q) record, and an approximately 130- yr peak in auroral observations. The peak also corresponds to the findings of significant power between 123 and 143-yr in six of two climate records reported by Rothlisberger. Analysis of the autocorrelation function of the temperature record for lags up to 2500-years indicates a highly significant peak at 2120-years and a set of related harmonics, similar to the fundamental 2120-yr Hallstattzeit and its harmonics.

We have proposed to build the Wide Field Infrared Explorer (WIRE), capable of detecting typical starburst galaxies at a redshift of 0.5, ultraluminous infrared galaxies beyond a redshift of 2, and luminous protogalaxies beyond a redshift of 5. This instrument will survey about 100 deg² of high Galactic latitude sky at 12 and 25 micrometers , in passbands where 20% of the luminosity from local starbursts is radiated. WIRE will measure the 12 - 25 micrometers color of the starburst galaxies, which is a powerful statistical luminosity indicator. The distribution of starburst galaxy 12 - 25 micrometers colors as a function of flux density will reveal their evolutionary history and perhaps the presence of protogalaxies at high redshifts. During its four-month mission lifetime, WIRE will gather important data on starburst galaxies and amass a catalog exceeding the size of the IRAS Point Source Catalog. WIRE is specifically designed to detect the maximum number of high-redshift starburst galaxies using an extremely small and simple instrument. The 28 cm aperture Cassegrain telescope has no moving parts and a wide 34 X 34 arcminute field of view.

The size of the secondary mirror in a reflecting, on-axis telescope has three effects on the performance of the imaging telescope for detection of very faint objects in the vicinity of bright objects. First, the size, shape, and peak of the side lobes (including the zeroth side lobe) change with the size of the secondary mirror. Second, the amount of collected light decreases in proportion to the area of the secondary mirror. Third, the position of the first zero decreases, effectively increasing the resolution of the optical system as the secondary mirror increases in size. All three effects impact the optimum design of an imaging instrument used for detection of planetary systems around the nearby stars.

A six-feature all-sky star field identification algorithm has been developed. The minimum identifiable star pattern element consists of an oriented star triplet defined by three stars, their celestial coordinates and visual magnitudes. The performance of the star pattern identification algorithm has been verified using software simulation.

A six-feature, all-sky star field identification algorithm has been developed for autonomous navigation. The minimum identifiable star pattern element consists of an ordered star triplet defined by three stars and their celestial coordinates (right ascension and declination). The star field identification algorithm was integrated with the CCD-based star tracker and tested at the Table Mountain Observatory. Real-time star field identification is reported with a CCD-based imaging camera interfaced to SPARC II workstation.