The Space Infrared Telescope Facility (SIRFT) is a one-meter-class, liquid-helium-cooled, earth-orbiting astronomical observatory that will be the infrared component of NASA's family of Great Observatories. SIRTF will investigate numerous scientific areas including formation and evolution of galaxies, stars, and other solar systems; supernovae; phenomena in our own solar system; and, undoubtedly, topics that are outside today's scientific domain. SIRTF's three instruments will permit imaging at all infrared wavelengths from 1.8 to 1200 microns and spectroscopy from 2.5 to 200 microns. The observatory will operate at an altitude of 100,000 km where it will achieve a five-year lifetime and operate with better than 80 percent on-target efficiency. The scientific importance and technical and programmatic readiness of SIRTF has been recognized by the 1991 report of the National Research Council's Astronomy and Astrophysics Survey Committee which recently identified SIRTF as the highest priority major new initiative in all of astronomy for the coming decade.

The Space Infrared Telescope Facility (SIRTF) will contain three cryogenically cooled infrared instruments: the Infrared Array Camera (IRAC), the Infrared Spectrograph (IRS), and the Multiband Infrared Photometer for SIRTF (MIPS). These instruments are sensitive to infrared radiation in the 1.8-1,200 micrometer range. This paper will discuss the three instruments' functional requirements and their accommodation in the SIRTF telescope system.

The Space Infrared Telescope Facility (SIRTF) is the fourth in NASA's series of Great Observatories. It will feature a one-meter class cryogenically cooled telescope. It is planned for a NASA fiscal start for the development phase in 1994 with a launch in about 2001. The launch vehicle will be the new upgraded Titan IV with a Centaur upper stage. The operational orbit will be circular at an altitude of about 100,000 km. The planned mission lifetime is 5 years. This paper addresses the rationale in the selection of the high altitude orbit, the performance of the launch vehicle in delivering the observatory to orbit, other orbit options, and the planned observational modes and capabilities of the observatory. The paper will also address the viewing geometry and viewing constraints affecting science observation, telescope aperture shade design, and spacecraft solar-panel and communication design.

Key requirements and ground systems implementation strategy for SIRTF which presents a significant challenge in the operational phase of the mission are discussed. The facility is aimed at reliably integrating a guaranteed time program, requests from about 200 guest observer teams per year, and observatory maintenance. SIRFT is characterized by the five-year life time due to cryogen boil-off which means that the ground system must be fully operational at launch and must operate with an efficiency and timeliness rarely achieved in previous space missions.

The Space Infrared Telescope Facility (SIRTF) will have three science instruments, the Infrared Array Camera (IRAC) which will obtain multispectral images between 1.8 micron and 26 microns, the Infrared Spectrometer (IRS) which is a set of two dispersive spectrometers covering the wavelength range between 2.5 and 200 microns, and the Multiband Imaging Photometer for SIRTF (MIPS) which is a general-purpose photometric instrument which operates between 30 and 1,200 microns. Taken together, the full wavelength range of these instruments extends from 1.8 micron to 1,200 microns, equivalent to nearly a factor of 700 in photon energy and diffraction limited image size. In addition to supporting this unprecedented spectral and optical coupling requirement, the SIRTF detectors must operate at lower temperatures than previously demonstrated and be optimized for new levels of performance in order to achieve the goals of the science mission. Thus, development of the detector arrays for the SIRTF instruments is one of the most challenging aspects of the instrument development activities.

The Space Infrared Telescope Facility (SIRTF) will be the first true infrared observatory in space, building upon the technical and scientific experience gained through its two NASA survey-oriented predecessors: the Infrared Astronomical Satellite and the Cosmic Background Explorer. During its minimum five year lifetime, the SIRTF will perform pointed scientific observations at wavelengths from 1.8 to 1200 microns with an increase in sensitivity over previous missions of several orders of magnitude. This paper discusses a candidate design for the SIRTF telescope, encompassing optics, cryostat, and instrument accommodation, which has been undertaken to provide a fulcrum for the development of functional requirements, interface definition, risk assessment and cost. The telescope optics employ a baffled Ritchey-Chretien Cassegrain system with a 1-m class primary mirror, an active secondary mirror, and a stationary facetted tertiary mirror. The optics are embedded in a large superfluid He cryostat designed to maintain the entire telescope-instrument system at temperatures below 3 K.

The Space Infrared Telescope Facility (SIRTF) is a 1-meter cryogenic infrared telescope. Stray light is kept below the natural background by restrictions on sun, Earth, and moon off-axis angles; by conservative baffle design; by the use of advanced diffuse black coatings; and by superfluid helium cooling. The aperture stop is located at the primary mirror rather than at the secondary mirror to increase the aperture and reduce the central obscuration. Stray light from off-axis sources is greater with the aperture stop at the primary than with the aperture stop at the secondary, but the modulation of the signal produced by tilting of the secondary mirror for chopping is less. Stray light from telescope thermal emission is lower with the aperture stop at the primary.

An effort is currently being carried out by the Jet Propulsion Laboratory (JPL) to study mission feasibility and to define functional requirements for various subsystems of the Space Infrared Telescope Facility (SIRTF). As a major part of this effort, structural design requirements have been derived based on the stated mission objectives. Design concerns addressed by these requirements include the limits on mass and location of the center of gravity, launch stiffness and dynamic characteristics, design loads and analysis criteria, survivability of the TITAN IV/Centaur launch environment, thermal control for maintaining a near absolute-zero operating temperature, and helium cryogen volume and storage for a five-year mission. To illustrate how the structural design requirements can be met, a point design of the SIRTF flight hardware system was developed, modeled, and analyzed. A description of the key features of this point design, along with pertinent modeling and analysis results, are discussed in this Paper.

SIRTF will require new liquid helium cryogenics and optical technology at liquid helium temperatures to meet the scientific requirements. In particular, it will require a helium cryogenic system operating at 1.25 K with a lifetime of five years. The optical system will require a 1-m mirror operating at 2 K, which is diffraction limited at 3 microns. This paper describes the advances which will be needed and the approaches to be taken.

Thermal systems analysis models were used to design SFHe cooled dewar for the Space Infrared Telescope Facility (SIRTF), a 1 m class cryogenically cooled observatory for IR astronomy. The models are capable of computing both the heat leaks into the dewar and the operating temperature of a SFHe tank. The models are aimed at predicting the ability of the SIRTF cryogenic system to satisfy a five-year mission lifetime requirement and maintain the SFHe tank operating temperature of 1.25 K to provide sufficient cooling for science instruments and the optical system. The thermal models are very detailed and very fast with a typical steady state run of about 20 sec on a VAX minicomputer.

Abstract not available.

SiGe/Si heterojunction internal photoemission (HIP) long wavelength infrared (LWIR) detectors have been fabricated by MBE. The SiGe/Si HIP detector offers a tailorable spectral response in the long wavelength infrared regime by varying the SiGe/Si heterojunction barrier. Degenerately doped p(+) SiGe layers were grown using elemental boron, as the dopant source allows a low growth temperature. Good crystalline quality was achieved for boron-doped SiGe due to the reduced growth temperature. The dark current density of the boron-doped HIP detectors was found to be thermionic emission limited. HIP detectors with a 0.066 eV were fabricated and characterized using activation energy analysis, corresponding to a 18 micron cutoff wavelength. Photoresponse of the detectors at wavelengths ranging from 2 to 12 microns has been characterized with corresponding quantum efficiencies of 5 - 0.1 percent.

Future NASA missions for earth observation and planetary science require large photovoltaic detector arrays with high performance in the long wavelength region to 18 microns and at operating temperatures above 65 K where single-cycle long-life cryocoolers are being developed. Since these detector array requirements exceed the state of current HgCdTe technology, alternative detector materials are being investigated as a possible option for future missions. Advanced growth techniques (e.g., MBE and MOCVD) of column III-V semiconductors have opened opportunities for engineering new detector materials and device structures. The technical approaches under investigation at JPL (with university and industry participation) include: quantum well infrared photodetectors, heterojunction internal photoemission (HIP) photodetectors, type-II strained layer superlattices, and nipi doping superlattices. Each of these options are briefly described with some of their pros and cons. A more detailed description is given for the HIP approach being pioneered at JPL.

The Stratospheric Wind Infrared Limb Sounder (SWIRLS), which measures wind, temperature, and the abundance of O3 and N2O in the stratosphere from earth orbit is selected as one of the complement of atmospheric sounders that will fly on the Earth Observing System B platform series. This paper outlines the SWIRLS investigation and describes laboratory experiments demonstrating SWIRLS wind measurement capabilities.

A Tropospheric Emission Spectrometer (TES) for the Earth Observing System (EOS) series of polar-orbiting platforms is described. TES is aimed at studying tropospheric chemistry, in particular, the exchange of gases between the surface and the atmosphere, urban and regional pollution, acid rain precursors, sources and sinks of greenhouse gases, and the interchange of gases between the troposphere and the stratosphere. TES is a high-resolution (0.025/cm) infrared Fourier transform spectrometer operating in the passive thermal-emission mode in a very wide spectral range (600 to 4350/cm; 2.3 to 16.7 microns). TES has 32 spatial pixels in each of four optically conjugated linear detector arrays, each optimized for a different spectral region.

Lidars using pulsed TEA-CO2 transmitters and coherent receivers have been developed at JPL and used to measure atmospheric backscatter and extinction at wavelengths in the 9-11 micron region. The global winds measurement application of coherent Doppler lidar requires intensive study of the global climatology of aerosol and cloud backscatter and extinction. An airborne lidar was recently flown on the NASA DC-8 research aircraft for operation during two Pacific circumnavigation missions. The instrument characteristics, as well as representative measurement results, are discussed.

An upgraded version of AVIRIS, an airborne imaging spectrometer based on a whiskbroom-type scanner coupled via optical fibers to four dispersive spectrometers, that has been in operation since 1987 is described. Emphasis is placed on specific AVIRIS subsystems including foreoptics, fiber optics, and an in-flight reference source; spectrometers and detector dewars; a scan drive mechanism; a signal chain; digital electronics; a tape recorder; calibration systems; and ground support requirements.

The Atmospheric Infrared Sounder (AIRS) is a facility instrument on the Earth Observing System (EOS). The ability of AIRS to provide accurate temperature and moisture soundings with high vertical resolution depends critically on a very accurate spectral calibration. The routine in-orbit spectral calibration is accomplished with a Fabry-Perot plate with a fixed spacing of 360 microns. This paper discusses design, Signal-to-Noise, and temperature and alignment stability constraints which have to be met to achieve the required spectral calibration accuracy.

The ALIAS instrument is a very high resolution (0.0003/cm) scanning, tunable diode laser spectrometer designed to make direct, simultaneous measurements of NO2, HNO3, HCl, CH4, and either O3 or N2O (including vertical profiles of CH4 and N2O) in the polar stratosphere at sub-part-per-billion level sensitivities over integration times from 3 to 30 s. Unique features include a sample inlet/throttle system designed to achieve near-isokinetic sampling, in PSC events, an in-flight wavelength reference cell rack, mechanical fringe-spoilers, a four-laser/four-detector dewar with 24-hr hold-time operating at a fixed temperature without electrical regulation, and in-flight fast correlation routines for spectral drift compensation prior to spectral addition. Instrument design and test flight results are discussed in the light of ALIAS's role in the Winter 1991 Arctic aircraft stratospheric ozone campaigns out of Fairbanks, Alaska, and Bangor, Maine.

Search for evidence concerning the existence of extrasolar planets will involve both indirect detection as well as direct (imaging). Indirect detection may be possible using ground based instrumentation on the Keck telescope, Imaging probably will require an orbiting system. Characterizing other planets for complex molecules will require a large orbiting or lunar-based telescope or inteferometer. Cryogenic infrared techniques appear to be necessary. Planning for a NASA ground and space-based program, Toward Other Planet Systems (TOPS), is proceeding.

The Firefly project has developed and implemented an infrared (IR) remote sensing prototype system based on the concept presented. The Firefly system produces image through smoke that will provide near real-time wildland fire information for fire management and suppression. The prototype will be tested through the 1991 fire season. Results of the testing will be incorporated into the final system design for operational use at the end of 1992.

Detecting and imaging small wildfires with an Airborne Scanner is done against generally high background levels. The Airborne Scanner System used is a two-channel thermal IR scanner, with one channel selected for imaging the terrain and the other channel sensitive to hotter targets. If a relationship can be determined between the two channels that quantifies the background signal for hotter targets, then an algorithm can be determined that removes the background signal in that channel leaving only the fire signal. The relationship can be determined anywhere between various points in the signal processing of the radiometric data from the radiometric input to the quantized output of the system. As long as only linear operations are performed on the signal, the relationship will only depend on the system gain and offsets within the range of interest. The algorithm can be implemented either by using a look-up table or performing the calculation in the system computer. The current presentation will describe the algorithm, its derivation, and its implementation in the Firefly Wildfire Detection System by means of an off-the-shelf commercial scanner. Improvement over the previous algorithm used and the margin gained for improving the imaging of the terrain will be demonstrated.

The alignment and performance of the optical system for the Pressure Modulator Infrared Radiometer (PMIRR) are described. This limb and nadir scanning instrument will be used for remote sounding of the Martian atmosphere and will be launched on Mars Observer in 1992. The instrument has nine channels distributed over the wavelength range 0.3 to 50 microns and has two pressure modulator cells for water vapor and carbon dioxide.

A focal plane assembly combining hybrid electronic components with passive optical components within a single hermetically sealed package has been designed by Cincinnati Electronics to meet the performance requirements imposed by the Comet Rendezvous/Asteroid Flyby (CRAF) and Cassini Visible and Infrared Mapping Spectrometers (VIMSs). A single line array of 256 InSb photodiodes, accessed by two 1 x 128 multiplexers, provides continuous spectral coverage from 0.85 to 5.1 microns. Intrinsic field-of-view apertures and a unique order sorting filter require critical optical alignment within the hybrid. FPA performance requirements, design approach, and critical issues are discussed.

Progress made in the last ten years in understanding the daytime earthlimb emission around 2.7 microns is reviewed. It is pointed that the solar pumped emission from the earth's atmosphere consists of radiation primarily from carbon dioxide and from water vapor. Radiation from CO2 was the subject of a thorough investigation (Sharma and Wintersteiner, 1985). The radiation from water vapor is studied using the newly developed Strategic High-Altitude Radiance Code, and the results are compared with the SPectral Infrared Rocket Experiment. The next few years should see dramatic progress in the backgrounds models because of the global measurement made by the CIRRIS 1A.

Progress in the ten years since the previous SPIE publication (Kumer, 1981) on the subject of modeling high-altitude non-LTE CO2 4.3 micron phenomena is summarized. Several models have been developed in these years. These models implement improvements in radiation transport, spectral characterization, rate constants, atmospheric models, and numerics. Applications of these models to the three distinct cases of daytime, ambient night time, and aurora are discussed, and compared with applications of the older model. Several new data bases have just become, or will soon become available. The obvious applications of the models to these data will be discussed.

The use of IR technology for solar cell crack detection in the manufacture and inspection of large solar arrays is reviewed. It is concluded that silicon CCD technology was used to develop IR technology for GaAs-on-GaAs at 1.0 micron, and PtSi technology was used to develop GaAs-on-Ge IR technology at 2-2.5 microns. IR crack inspection for the thinner, etched silicon solar cells of large, flexible solar wings was developed to visualize their cracks, because the surfaces of these cells were pitted.

Infrared zoom lens systems have benefited from advances in the state of the art during the past decade. These advances have included extending the zoom range, improvements in performance, reduction of size and weight, and minimizing complexity. The application of these developments to infrared zoom lens design will be presented. The zoom lens systems of several companies active in the field will be reviewed, with some reference to tolerancing techniques for production. Innovative reflective zoom systems will also be considered. Promising future developments will be discussed.

Semiconductor devices must face various space environments ranging from extremely low temperatures in the upper atmosphere to very high temperatures in power systems, and from low levels of ionizing radiation to high levels of neutron irradiation. Pressure varies from atmospheric pressure near the ground to vacuum at high altitudes. The semiconductor materials and devices are affected by the following external mechanisms: temperature, optical radiation, impurities and ionized gases, nuclear radiation, particle bombardment and pressure. This paper will discuss the effects of (gamma) -irradiation and pressure on optoelectronic devices such as related photodiodes, light-emitting diodes, and charge-coupled devices. These effects will be related not only to bulk effects, but also to surface effects.

Range calculations for ladar models or optical communication models may utilize look-up tables for atmospheric transmission. To generate these tables using the standard atmospheric transmission model, FASCODE, would normally require an extensive amount of time spent at a computer. A program, LASTRNM2, has been written using macros, an editor, and a collection of FORTRAN programs to run a personal computer (PC) version of FASCODE in batch mode. LASTRNM2 modifies the input files for FASCODE, runs the program, extracts the transmission value from FASCODE's large output file, performs desired calculations on that value, stores it in a table along with the conditions for the run, and repeats for succeeding positions. Both slant paths and horizontal paths through the atmosphere may be utilized. Essentials of the program will be presented.

Molecules in the atmosphere absorb differently in different spectral regions. In particular, atmospheric moisture affects transmission in certain regions. Results are presented of a study on the effects of atmospheric moisture on temperature discrimination by infrared detectors. Probability of accepting a low temperature object and of rejecting one 1000 K higher was calculated. Detectors were in two bands in the middle infrared (IR) region. Even for transmission distances as short as 100 feet, probabilities were strongly affected by varying temperature and relative humidity.

We discuss the physics and 128 X 128 array imaging performance of GaAs/AlxGa1-xAs n-doped quantum well infrared photodetectors (QWIPs). The device physics of novel p-doped QWIPs which respond to normal incidence radiation of also presented.

A 256 X 256 element platinum silicide monolithic image sensor with a large fill factor has been developed as a high sensitivity infrared image sensor. It is essential to increase the maximum signal charge of the staring infrared image sensor to obtain higher sensitivity. We used the Charge Sweep Device readout architecture and improved operations of the floating diffusion amplifier to increase the maximum signal charge. A 52 X 40 micrometers 2 pixel using a minimum features size of 2 micrometers has a fill factor of 66%. Evaluating the performance of the device, we confirmed the effectiveness of the improved technologies. The measured saturation level is 2.8 X 106 electrons which is determined by the storage capacity of the detector. We estimated from a measurement point at low background temperature that the noise equivalent temperature difference with a f/1.2 optics is 0.036 K at 300 K background.

A medium wavelength infrared (MWIR) staring focal plane array (FPA) technology using Schottky barrier detectors with arrays consisting of 20-micron pixel spacings in a 488 x 640 array format is described. The new 488 x 640 hybrid FPA is a result of an ongoing developmental process that has evolved from a 62 x 58 array to a 488 x 640 array over the past nine years. Reported are the performance goals, design, fabrication, and test results of this high-density hybrid FPA based on PtSi infrared detector technology. The advantages of the hybrid approach include the ease of fabrication, high optical fill factor, compatibility with existing multiplexer technology, and excellent imaging performance. We review past Schottky FPA development and discuss the technical trade-offs of our approach. Also discussed are the design, fabrication, and test results of our most recent Schottky FPA.

The design of a 1st and 2nd generation 640(H) X 480(V) element PtSi Schottky-barrier infrared image sensor employing a low-noise MOS X-Y addressable readout multiplexer and on-chip low-noise output amplifier is described. Measured performance characteristics for Gen 1 devices are presented along with calculated performance for the Gen 2 design. A multiplexed horizontal/vertical input address port and on-chip decoding is used to load scan data into CMOS horizontal and vertical scanning registers. This allows random access to any sub-frame in the 640 X 480 element focal plane array. By changing the digital pattern applied to the vertical scan register, the FPA can be operated in either an interlaced or non- interlaced format, and the integration time may be varied over a wide range (60 microsecond(s) to > 30 ms, for RS170 operation) resulting in a form of 'electronic shutter,' or variable exposure control. The pixel size of 24-micrometers X 24-micrometers results in a fill factor of 38% for 1.5-micrometers process design rules. The overall die size for the IR imager is 13.7 mm X 17.2 mm. All digital inputs to the chip are TTL compatible and include ESD protection.

An infrared imaging system based on a high resolution platinum silicide detector has been developed. The detector is a 486 X 640 Schottky Barrier photodiode array with a CCD readout multiplexer. The imaging system includes signal processing electronics to correct the fixed pattern noise and implements a histogram projection algorithm for automatic gain and offset adjustment and dynamic range compression. The performance of the pattern noise correction has been demonstrated to reduce the residual pattern noise below the image shot noise over a scene temperature range of more than 50 degree(s)C. The effect of optical cross talk in the imager has been examined. The magnitude of the side lobes has been found to be a factor of about 7 X 104 smaller than the central spot.

PACE-I HgCdTe, an industry-leading intrinsic detector technology for developing large, high performance IR focal plane arrays (IRFPAs) in the MWIR (3-5 microns) spectral band, is reviewed. Emphasis is placed on hybrid HgCdTe 256 x 256 IRFPAs and the status of 640 x 480 hybrid HgCdTe FPA.

The current advances in density and performance of 2-D staring IR FPAs are now enabling the development of solid state non-scanning imagers of TV quality. Significant cost reductions with performance improvements are accomplished using these new high density staring arrays. This paper reports on the development of an IR imager using a new system oriented 256 X 256 InSb hybrid FPA. Two-dimensional InSb hybrid FPAs were first reported on in 1978 at the IEDM with papers describing 32 X 32 arrays using indium bumps and CCD multiplexers. This basic technology has progressed to 256 X 256 and large arrays using HgCdTe and InSb detectors. The arrays are still interconnected with indium bumps but rely on improved MOS switched readouts using the latest in CMOS process technology. Significant improvements in performance and operability as well as system implementation have also been made.

A 256 x 256 element InSb array developed for low-background commercial applications is described, focusing on the signal and noise performance and the spatial uniformity of these parameters. The arrays are characterized by high operability, good uniformity, the quantum efficiency close to theoretical, low red noise, and dark currents in the 10 exp -17 amp range.

Abstract not available.

Abstract not available.

The paper deals with the review of the current state of the trends in electronic-optical instrument-making development. It deals with the main theoretical conceptions, material studies criteria and pyroelectric sensors and device operation in astronautics. These instruments and devices were used aboard different vehicles such as artificial Earth satellites, interplanetary unattended stations and long-term orbital stations.

The paper contains a review of works on nonselective thermal radiation detectors, published and discussed in recent years in the USSR: pyroelectrical detectors, detectors based on thermo-elastic effect of quartz, semiconductor bolometers, cryogenic bolometers, opto- acoustical detectors, thermoelectrical detectors. In the USSR all types of thermal detectors are used in various parts of the infrared region. Every two years a scientific conferences on thermal detectors takes place, where authors submit about 70 papers on pyroelectrical detectors, bolometers, thermoelectrical detectors, opto-acoustical detectors, on radiometric devices, optical materials, used in detectors, and on metrology in infrared region. This paper focuses on materials.

An analysis of the basic energy equation which describes the infrared system (IRS) operation is suggested as the basis for the adaptation methodology. First, it is necessary to do a sufficiently complete formula for the IRS figure of merit being adapted as the function of the IRS parameters. Secondly, it is useful to determine both a degree of various parameters influence on the adapted figure of merit and a possible range of its variation. Then it will be possible to evaluate the accuracy of the chosen adaptation method. As a simple example, the parametric adaptation of IRS sensitivity has been considered.

History, technical parameters and applications of Soviet IR imagers are discussed.

The paper considers classes of non-linear inertialess statistical transformations of IR images. The origin of nuclei is attributed to visual perception regularities and to the possibilities of providing modes of constantness or stabilization of the transformed images characteristics.

This paper presents the principles of the use of Fibonacci polynomials and series for construction of nonlinear operators of optical image transformations for the information conformity of their formation and perception processes.

Results of using the standard processing algorithms (spatial filtering, linear and non-linear transformation, histograms, etc.) to enhance the quality of thermograms in infrared NDT are discussed. More sophisticated algorithms have been developed to suppress the emissivity noise and non-uniform heating-cooling effects. In addition, some new approaches to thermal tomography are presented.

This paper describes how the measurement and prediction activities have been integrated to obtain a complete and accurate characterization of a target, even when it is not possible to know a priori part of the prediction code's inputs. We particularly emphasize the meticulous care given to the design and realization of our system for the acquisition of IR signatures of flying air targets. This attenuation was aimed at improving the target's stability in the center of the sensor's FOV, in order to optimize the quality of the data from early on in the acquisition phase, and to allow the use of interframe processing techniques during the elaboration phase. A good level of agreement between the simulated and the measured aircraft signatures is obtained, especially when alterations induced by the imaging radiometer are taken into account.

This paper presents the criteria selected, the physical implementation, and some of the results of a series of simulation tests performed in order to obtain the infrared signature of ships. These results have been compared with data obtained under real conditions. The methodology used can be also applied to other types of targets of interest, such as ground vehicles and buildings, and with more elaborate techniques, in the case in which the target presents hot gaseous effluents.

The electron-beam-addressed membrane light modulator is a computer-controlled display device that allows the production of high-resolution, flickerless, dynamic infrared (IR) scenes. The projector consists of the membrane light modulator and an IR schlieren readout optical train. The light modulator is composed of a high-resolution scanning electron gun, a collector grid, and a special charge-transfer-plate anode onto which is bonded a highly reflective deformable membrane mirror. In a prototype device built at Optron Systems, readout of the system with a Helium-Neon laser operating at 3.39 micrometers has produced IR images with a contrast ratio of 40:1, a resolution of 100 television lines, and a membrane response time of 1 microsecond(s) . The goal of the next-generation device is 256 X 256 resolution elements, 100 Hz frame rate and a contrast ratio of > 100:1. We will describe the operating principles of the device, its performance characteristics, and its applications.

A model is presented for generation of synthetic images representing what an airborne or satellite thermal infrared imaging sensor would record. The scene and the atmosphere are modeled spectrally with final bandwidth determined by integration over the spectral bandwidth of the sensor (the model will function from 0.25 - 20 micrometers ). The scene is created using a computer aided design package to create objects, assign attributes to facets, and assemble the scene. Object temperatures are computer using a thermodynamic model incorporating 24 hours worth of meteorological history, as well as pixel specific solar load (i.e., self-shadowing is fully supported). The radiance reaching the sensor is computed using a ray tracer and atmospheric propagation models that vary with wavelength and slant range. Objects can be modeled as specular or diffuse with emissivities (reflectivities) dependent on look angle and wavelength. The resulting images mimic the phenomenology commonly observed by high resolution thermal infrared sensors to a point where the model can be used as a research tool to evaluate the limitations in our understanding of the thermal infrared imaging process.

This paper presents excerpts from the data that was collected on the Microscan Flir Data Collection (MFDC) program conducted by the Wright Laboratory's Avionics Directorate (WL/AA) and the Royal Signals and Radar Establishment (RSRE). These data items describe the effects that microscanning has on imagery generated with staring flir sensors. The paper also includes a description of the microscan concept, and one of the unique Microscan Flir sensors developed by RSRE. The sensor was characterized in the Infrared Sensor Measurement Laboratory and used to collect imagery at variable sample rates on tactical targets at the E-O Sensor Tower Test Range. The laboratory data was used to demonstrate the effects of microscanning on flir performance parameters and on flir imagery of various periodic and aperiodic test patterns. A sampling of imagery from the tower tests is also presented to demonstrate the effects of microscanning on real world imagery.

Heterojunction GexSi1-x/Si internal-photoemission infrared detectors exhibiting nearly ideal thermionic-emission dark-current characteristics have been fabricated with cutoff wavelengths out to 25 micrometers . Heteroepitaxial p-GexSi1-x layers, degenerately doped with boron to concentrations exceeding 1020 cm-3 in order to obtain high free-carrier absorption, are grown in Si substrates by molecular beam epitaxy. The detector cutoff wavelength, which is determined to first order by the valence- band offset, is tailored by varying the composition of the GexSi1-x layer and can be fine tuned by adjusting such parameters as the doping concentration and growth temperature. High-quality imaging without uniformity correction has been demonstrated in the long-wavelength infrared spectral band for 400 X 400- and 320 X 244-element focal plane arrays consisting of GexSi1-x/Si detectors, which have cutoff wavelengths of 9.3 and 10.5 micrometers , respectively, and monolithic CCD readout circuitry.

In(x)Ga(1-x)As detector linear arrays with 256 and 512 elements have been made for the 1.0-1.7 micron spectrum (x = 0.53) and 1.4-2.6 microns (x = 0.8) with 30 x 30, 30 x 100, and 25 x 500 micron pixel sizes. Room temperature D* values beyond 1 x 10 exp 13 W/cm-sq rt Hz (at 1.7 micron) and 1 x 10 exp 11 W/cm-sq rt Hz (at 2.5 microns) are reported. A 128 x 128 element In(0.53)Ga(0.47)As detector array with less than 1 percent dropouts is also described. High reliability is also reported for these arrays. Future improvements needed include lower-noise multiplexers and the use of zero-bias multiplexers.

A method is presented for the thermal noise reduction in a near room-temperature intrinsic IR photodetector. The method is based on suppression of the Auger generation-recombination processes using the Electro-Magnetic Carrier Depletion (EMCD) of a narrow gap semiconductor. The device is a lightly doped narrow gap semiconductor flake with a high backside surface recombination velocity, supplied with electrical contact and placed in a magnetic field. Due to action of the Lorentz force, most of the device depletes in charge carriers, resulting in suppression of the Auger generation and recombination processes. As a result, the I-V characteristic becomes nonlinear, exhibiting regions of high positive and negative resistance. The thermal noise can be dramatically reduced, leading to a substantial improvement of performance. The ultimate detectivity may be determined either by the background radiation or by the Shockley-Read generation, in dependence on the ratio of the background photon flux to the recombination center concentration. The near-BLIP performance is predicted for 10.6 micrometers (Hg,Cd)Te devices, prepared from high quality materials and operated at 225 - 250 K.

Two recent demonstrations of diffractive optics for uncooled staring 8 - 12 micrometers infrared imagers are reviewed and critically examined. Although each demonstration by itself yielded impressive results, when viewed from a broader system standpoint and considering current state-of-the-art in uncooled detector arrays, it is concluded that there is not a compelling reason to use diffractive elements in current systems. Alternatives are suggested.

Most infrared optical materials exhibit a relatively strong dependence on refractive index on temperature. This dependence is about one or two orders of magnitude more severe than for the optical glasses used in the visual spectral range. As a result, important optical properties of an IR-optical system (e.g., focal length, image plane), change with temperature. This is particularly annoying with FLIRs in aircraft because the necessary refocusing increases the pilot's workload. A method to overcome that problem will be described. It makes use of automatic autocollimation, where the radiation of a special thermal target is passing the optical system twice before hitting the infrared detector. A microprocessor evaluates the detector signals and moves an optical element in such a manner that the image plane of the optical systems always remains on the detector focal plane.

A compact IR zoom telescope with diameter/length = 94/159 mm and magnification from 2 to 6 times at 8-12 microns is designed. Mechanically compensated zoom is adopted. Zooming lens and compensating lens groups possessing three roller followers for each are controlled by the stationary control cylinder on which there are three pairs of cam slots to which six followers are attached. When the outer cylinder having six linear slots is rotated, it will force the followers (i.e., the two lens mountings) to turn, resulting in smoothly turning and moving the two. The effect of air gap between the follower and the slot on backlash in the cam track is eliminated by special design of elastic construction of the roller follower. The image quality examed by MTF testing is satisfactory.

An infrared zoom telescope possessing the lenses made of germanium and working at -10 degree(s) to 40 degree(s)C and at 8 - 12 micrometers has been designed. The main problem to be solved is that the refraction index of Ge changes with the temperature, resulting in decollimation. For the purpose of lower production cost and reduced size and weight, a combination of mechanical passive athermalization by the collimating lens group with manual athermalization by the front lens which is chiefly utilized to focus the object is adopted. The lens mount is made of aluminum alloy. A pair of elements of mechanical passive athermalization, nylon/indium steel, is used to partially compensate the effect of variation of refraction index of Ge and expansion or contraction of aluminum alloy on the distance between the fixed and the collimating lens groups. The manually additional adjustment of the focusing lens, i.e., the front lens, is to partially compensate the distance between the front lens and the second lens group.

Focal plane arrays (FPA) design requirements and the progress made in the development of Schottky-barrier FPAs to provide very large focal planes of high performance are discussed. It is concluded that improvements were made in PtSi, IrSi, and GeSi heterojunction materials. Using material apportionment, the cutoff wavelength can be tailored up to 16 microns to optimize the relationship between satellite-signal and sensor-cooling requirements. At low exposures, sensor readout noise was reduced to 35 rms-electrons, and good charge-transfer efficiencies were demonstrated down to temperatures of 55 K.

A compact thermal video camera with very high sensitivity has been developed by using a self-scanned 128 InSb linear array photodiode. Two-dimensional images are formed by a self- scanning function of the linear array focal plane assembly in the horizontal direction and by a vibration mirror in the vertical direction. Images with 128 X 128 pixel number are obtained every 1/30 seconds. A small size InSb detector array with a total length of 7.68 mm is utilized in order to build the compact system. In addition, special consideration is given to a configuration of optics, vibration mirror, and focal plane assembly. Real-time signal processing by a microprocessor is carried out to compensate inhomogeneous sensitivities and irradiances for each detector. The standard NTSC TV format is employed for output video signals. The thermal video camera developed had a very high radiometric sensitivity. Minimum resolvable temperature difference (MRTD) is estimated at about 0.02 K for 300 K target. The stable operation is possible without blackbody reference, because of very small stray radiation.

We describe an infrared spectrometer system designed for passive, ground-based remote profiling of atmospheric temperature and humidity. This instrument will be useful in atmospheric science, climate, and global change studies. We plan eventually to demonstrate its potential for unattended remote sensing. If successful, the infrared instrument could become a component of an integrated sounding system being designed for next-generation meteorological observations. At the heart of the infrared instrument is a rugged Michelson interferometer which views thermal atmospheric emission between 550 cm-1 and 2000 cm-1 (5.0 - 18.2 micrometers ), with 1-cm-1 spectral resolution. Calculated weighting functions suggest that we should be able to profile temperature with about 200-m vertical resolution, and humidity with about 500-m vertical resolution, in the lower 2 kilometers of the atmosphere. In order to retrieve accurate profiles, absolute radiometric calibration will be necessary. We have constructed two high-emissivity inner-cone cavities which the interferometer will view between atmospheric measurements in order to establish this calibration. We show measured spectra of a clear atmosphere and of cirrus clouds and point out features of these spectra which will be useful in atmospheric profiling.

An infrared staring imaging system in the 3 to 5 micrometers spectral band has been developed by SITP laboratories in China. The sensor utilized is a Pt-Si Schottky-barrier infrared CCD focal plane array. The digital video processing electronics is designed for 32 X 64, 64 X 64, and 128 X 128 pixel formats and contains the elimination of fixed pattern noise and the correction of response nonuniformity in real time and provides the high-quality IR image. The standard TV compatible and portable features are part of the design. In this paper, we describe the design and performance of this prototype system and present some experimental examples of IR imagery. The results demonstrate that the Pt-Si IR CCD imaging system has good performance, high reliability, low cost, and can be suitable for a variety of commercial applications.

This paper will describe the design of a dual band infrared optical system for collecting multiband data through a common aperture. The dual band camera was designed to support the development of multicolor processing techniques for enhanced detection, tracking and identification of air-breathing threats.

An infrared (IR) measurement technique for determining two-dimensional (2-D) and three- dimensional (3-D) microwave field distributions is presented. This IR technique is used to verify predictions made by various numerical electromagnetic (EM) codes. The experimental technique is based on IR thermal measurements of the Joule heating induced in a lossy dielectric or resistive material used as a calibrated IR detection screen when microwave energy is absorbed by the screen. An IR scanning system records the thermal radiation from the screen. The intensity of the microwave field is related to variations in the surface temperature distribution. The detection screen material is of a thin, planar construction and, thus, produces a 2-D map of the microwave field. By moving the screen along the normal to its plane, samples of the 3-D field are obtained. This experimental approach has been applied to several 2-D and 3-D scattering and coupling problems. Comparisons are made between the theoretical and experimental results for various hollow slit cylinder configurations. The advantages, disadvantages and limitations of this IR thermal technique for validation of EM theoretical predictions are discussed.

In order to control organic coating thickness on a steel sheet, two types of coating thickness gauges using a new method and the Brewster angle method have been developed for on-line monitoring. The new gauge has an on-line accuracy of +/- 0.2 micrometers and the Brewster angle method gauge has an on-line accuracy of +/- 0.1 micrometers . A portable oil thickness gauge has been developed to measure the oil thickness easily in various places.

In this paper, the Bidirectional Reflectance Distribution Function (BRDF) and the directional radiance factor are applied to the construction of a universal equation for IR parameter measurement. The ambient radiation is also divided into two parts--the uniformand the nonuniform. The universal equation is also applied to the quantitative error analysis, which will be helpful to perfect and improve the IR devices and measurement methods. It is shown that the theoretical results correspond to the experiment results. Furthermore, the universal equation is also applied to the emissivity measurement to present an active method in which the results are in good agreement with those obtained with the box method.

The design and construction of four extended-area blackbody radiators for field calibration are described, and the special performance features of each are detailed. Emphasized in design considerations is maintenance of uniform thermal profiles on high-emissivity metal plates that operate at temperatures ranging from 40 to 375 degree(s)C. For each of the four versions, individual radiator plate size and uniform blackbody temperature are the critical design parameters. Laboratory test data are presented to establish that each design configuration meets the operating specifications. The data demonstrate that reliable extended-area blackbody radiators can be built for field use at a lower cost than those of currently available radiators.

The present report gives a brief review of the problems one may be faced with in developing selective multicomponent photodetectors for rather a wide wavelength range of electromagnetic radiation--approximately from 0.1 micrometers in the ultraviolet to 50 micrometers in the infrared (IR) spectrum regions. The limits of this range are mainly defined by spectral distribution of brightness of the solar direct or scattered radiation and by the spectrum of thermal radiation of the Earth and objects on its surface.

An optical detector prepared by high Tc superconducting thin film has been discussed. The device has been made from YBaCuO superconducting thin film with zero resistance at more than 80 K on a ZrO2 substrate. A pattern of the device with the dimension of the microbridge is formed through photolithographic process. Electrical contacts are made by evaporating gold or silver with thickness of 0.5 - 1 micrometers . The sample is then placed in a dewar with an infrared window and is cooled by liquid nitrogen. A blackbody source at 800 K is used to measure the responsivity of the detector, and the infrared radiation is chopped at frequencies between 6.3 and 2000 Hz. The detector output with the detectivity larger than 109 cmHz1/2/w and a typical responsivity value as large as 103 V/w is observed on both lock-in amplifier and root-mean-square voltmeter. In addition, the mechanism of optical detection and the methods to improve the sensitivity have been described.

The development of staring infrared focal plane arrays has forced potential users to consider the effect of spatial noise on the performance of infrared sensors. In this work, we varied the amount of spatial noise present in infrared imagery and measured its effect on the value of the minimum resolvable temperature (MRT). A mathematical model for including the effects of spatial noise on image quality is presented and compared to experimental data.

A set of field tests was performed to demonstrate the use of a PtSi camera for airborne applications. The test-data was used to verify the applicability of Tamam's performance model. The sensor was integrated into a Tamam stabilized payload and mounted on a Bell 206 helicopter. Over 30 hours of recorded data was collected from different backgrounds and scenarios. The information analyzed so far was matched with computed results. These results, generated by our 'Detector' program and compared to the test results show good correlation, and thus validate the 'Detector' analysis program.

A study was conducted to (1) determine the feasibility of design and fabrication of a low pass filter with a relatively sharp cut-on at higher wavelengths (i.e. 30-40 microns), using metallic mesh technique; and (2) investigate whether the combination of this filter and a suitable IR detector, as a part of a Lunar Observer (LO) horizon sensor, is capable of detecting radiation emanating from two blackbody sources kept at temperatures simulating space and the surface temperature of dark or lit sides of the moon. Various designs of multilayer metallic mesh filters with different mesh parameters and substrate thicknesses were simulated. Using mesh parameters corresponding to the optimum four-layer filter design, a filter was fabricated on a 6.35 micron thick mylar substrate. The transmission curve of the fabricated filter is very close to what the simulation predicted. Room temperature signal level tests were performed on the combination of filter-detector assemblies. The data obtained from these tests indicate that the assembly can detect temperature differences as low as few degrees K between two black bodies.

A spectroradiometer was modified to test the stability, uniformity, and accuracy of radiance differentials of state-of-the-art FLIR test systems. It is shown that the radiometric tests make it possible to obtain important information which cannot be obtained with conventional contact temperature probes. The output radiance of the FLIR test equipment was measured as a function of time and angle with respect to the collimator optical axis.

Advances in FLIR (Forward-Looking Infrared) technology are threatening to surpass the capabilities of the IR test equipment--the blackbodies and target projectors--used to characterize them. New systems currently under development, such as those using advanced focal plane technology, will provide even greater performance. In response, a new approach to IR target projection has been developed. This approach will allow testing technology to keep pace with the ever-increasing demands of these advanced FLIRs.

In supersonic flight, the JR dome of a missile becomes heated by friction with the air. This heating creates an IR flux that can overload the detector, obscuring the target image created by the onboard JR sensor. The problem is becoming more severe as faster missiles with more sensitive infrared imagers are developed. A new hot Dome Simulator that allows missile designers to simulate these effects in the laboratory has been developed. This device enables improvements in hardware and software to be tested conveniently and inexpensively.

Analytical expressions for the photon radiance and its derivative in the spectral band from 400 to 700 microns are presented in a graphic form as a function of temperature for the cryogenic temperatures from 1 to 8 K. The temperature dependence of photon radiance and its derivative have been applied to a background-limited telescope to determine the temperature tolerances. It is concluded that the application of the background-limited telescope operation concept to the telescope operational requirements results in a reduction in the telescope temperature, i.e., an increase in temperatures for the most components, and a prolonged telescope facility lifetime.

Experimental and theoretical results of photosensitive semiconductor structures as well as the main developments of modern semiconductor photoresistors, photodiodes, including injection ones, based on polycrystalline and monocrystalline materials, multilayer structures and superlattices for visual far infrared spectral range are presented. Performance of multielement photodetectors based on lead chalcogenides, germanium and silicon, AIIIBV compounds, and CMT structures are described.

Instrument equipment and method of remote IR-measurements of sea surface temperature are widely used in the world science and practice.

In 1991, it is a 110 -year anniversary since the invisible radiation discovered in 1800 by British astronomer and optician, F.W.Hershel, was termed "Infrared Rays". This term was introduced for the first time in 1881 by W.Abney. However, it took about 50years more to extend the use of the IR rays outside research laboratories. Primarily, this was due to the unavailability of the radiation detectors which not only could be superior to a conventional thermometer, but could also show high reliability and provide the feasibility to enhance and process weak signals.