Infrared detector applications often require detector sensitive areas that are as closely spaced as possible. In particular, imaging systems often need close-packed detectors in order to increase their resolution. The imaging/resolution performance of two-dimensional arrays may be limited by the fact that the electron-hole pairs created by an optical disturbance (detection) may diffuse long distances from where the electron-hole pair was created. Some results of measurements of crosstalk and out-of-field signals in InSb detectors specially fabricated for these measurements are given herein. The detector arrays were configured in a manner such that the measurements would allow differentiation between electrical and optical (carrier diffusion) crosstalk.

By tailoring process parameters, InSb can be operated at temperatures exceeding 140°K. Recent developments in mechanical coolers have allowed such temperatures to be achieved with increased reliability and much reduced power consumption. The measured performance of InSb cooled to such elevated temperatures is presented.

A 160 x 244 element PtSi IRCCD imaging array is characterized using a conventional approach com-monly reported for visible imagers, introducing as needed, issues specific to IR imagery. Mean-variance data is used to extract two CCD charge transfer efficiencies; one efficiency correspon6 to the charge lost in a transfer and the other efficiency corresponds to the charge partitioning in a transfer. The array is shown to be background limited for pixels close to the output node. A 2-point correction is shown to substantially reduce fixed pattern noise of linear PtSi photodetectors at backgrounds offset from the points of correction. The horizontal and vertical MRT of the array is measured to be 0.02°C at a spatial frequency of 1/6 cycle/mrad. 1/f noise was not observed in the array to 10-1 Hz.

NASA Langley Research Center has initiated several programs to develop space flight and aircraft LIDAR instruments. These instruments will be used for scientific investigation of aerosols and trace gas constituents in the troposphere and stratosphere. Extensive analysis shows that avalanche photodiodes have definite advantages over photomultiplier tubes for given laser wavelengths and return signal amplitudes. For this class of signal returns, avalanche photodiodes have improved quantum efficiency, signal to noise ratio, linearity and overload recovery. These features help minimize the systematic errors caused by the detector. Laboratory measurements of the avalanche photodiodes were conducted to collect data for system performance analysis. This data was used to maximize system signal to noise ratios, and provided electronic and other useful design parameters. Tests were conducted on approximately ten avalanche photodiodes to characterize noise, dark currents, overload, and gain versus bias relationships. This paper presents the results and conclusions of the above analysis.

Present day optical signal processing using acousto-optical (A-0) diffraction is well-known for its inherent ability to perform wideband spectrum analysis on a real-time basis. This type of application requires a high-speed high-dynamic range linear array. In this paper, we describe a novel photodetector which provides an analog voltage of a few volts when the incident radiation intensity varies over a range of seven orders of magnitude. Its principle of operation utilizes the subthreshold effect of short channel MOSFET's, which is normally regarded as a detrimental effect. However, the phenomenon has been exploited in this case to inject excess collected photocharge into a common drain, thus, giving the device its logrithmic response. The detector array consists of 108 photoelements arranged in a linear array. The structure uses an epitaxial wafer construction for low crosstalk characteristics. There are six output registers each consisting of an eighteen-stage CCD and a buffer amplifier. Each of the six output multiplexers runs at a speed of 20 MHz, and since these are readout in parallel, the effective speed of the device is 120 Megapixels/second. The full well capacity is 1.17 million electrons, crosstalk at the second nearest pixel is down-51 dB, the electron sensitivity of the device is 1.2 AV/electron, and the power dissipation of the device is less than 170 mW.

The surface leakage current of Cd0.2 Hg0.8Te photodiodes has been reduced by forming a wide gap epitaxial layer on the surface. CdHgTe double-layers consisting of p-CdxHgl_xTe (x>0.2)/p-Cd0.2Hg0,8Te were grown by liquid phase epitaxy on CdTe substrates. The hole carrier concen 3tration and m 1obility, obtained from van der Pauw Hall measurement at 77K, were 9x1015cm-3 and 6x102cm2V-15-, respectively. The p-n junctions were formed by removing the wide gap layer of 100/i m diameter to reach p-Cd0.2Hg0.8Te followed by the Indium diffusion in p-Cd0.2Hg0.8Te. The R0A products of the photodiode with and without the wide band gap layer were 9.1Q cm ² (λ c=11μ m) and 2.00 cm2 (λ c=10μ m) at 77K, respectively, which confirm the effect of the wide gap layer on the surface leakage current reduction.

The Visual and Infrared Mapping Spectrometer (VIMS), a facility instrument for NASA's Mars Observer mission, has a spectral bandwidth of 0.35 to 5.14 μm. Detection over such a large spectral bandwidth requires the use of two different detector materials. Indium antimonide is the choice for infrared detection, and silicon for the visible/UV region. Indium antimonide's cryongenic operating temperature forces the silicon photodiodes to operate at 77 K also, since both arrays will be within the same focal plane assembly. The VIMS system analysis required quantitative responsivity data for silicon pho-todiodes at 77 K in the band from 0.5 to 1.1 pm. This paper describes the experiment used to measure and compare the responsivities of Si, Ge, and InSb photodiodes and to provide an analysis of the data. The results as applied to the VIMS predicted performance are briefly discussed.

A 1024-element random-access linear photodiode array has been developed for emission or absorption spectros-copy applications. This new array is especially useful in very high contrast intensity conditions. Each element of the array is 25 μm x 2500 μm giving each a slit-like geometry with a 100 : 1 aspect ratio suitable for coupling to monochromators or spectro-graphs. Ten address lines are implemented to select an individual photo-site. Therefore, the array has the flexibility of operating in either random-access or sequential-readout modes. In the case of the sequential-readout mode, the array will detect a photo spectrum with a dynamic range in excess of 10,000 : 1. In the random-access mode, the spectrum infomation can be further enhanced by varying the integration times of each pixel. Other array sizes with 512 and 256 photoelements have also been developed. The device structure, operation, and performance will be presented.

A 2048 x 64 element time-delay-and integration (TDI) charge-coupled optical imaging device has been designed, fabri-cated, and tested. The device is a four-phase, buried-channel CCD structure and is designed for high-speed low-noise imaging (with low illumination in the visible and near-infrared spectral regions). The sensor array is divided into 16 sections of 128 x 64 pixels. Each section has two output structures, one at the top and one at the bottom of the sensor array. The device's serial-parallel-serial structure allows the charge in the parallel CCD shift register to be able to shift either up or down to the top or bottom serial CCD readout register. The readout register, in turn, transfers the charge in sequence to the output amplifier at a frequency of up to 8 Mhz. This high pixel rate combined with the parallel readout structure provides the imager with a maximum line rate of 62.5k lines per second. The high full-well capacity of each pixel (>.6 million electrons) and low noise floor of the output amplifier (<40 electrons rms) yield a dynamic range of more than 83 dB. Typical dark signal and charge-transfer-efficiency off the imager at 25°C are 2nA/cm and 0.99997, respectively. Subject terms: time-delay- and integration (TDI); charge-coupled device (CCD); visible; near-infrared; charge-transfer efficiency; full-well capacity; dynamic range.

This paper discusses a computer model of a staring thermal imaging sensor with respect to spatial nonuniformities. The staring sensor is a two-dimensional array of infrared detectors that is often called a focal plane array (FPA). Microscopic differences in the fabrication of a detector and nonuniformity in the input and output circuits of the charge-coupled device (CCD) can cause spatial nonuniformities across the FPA. Thus an image viewed by such a sensor will be covered with spatial noise for which correction should be made. Since the computer model can generate output images for a staring sensor with spatial nonuniformities, the objective of this paper is to present a computer simulation of the one-point and two-point spatial nonuniformity correction of a staring sensor. The corrections will be performed on flat fields and barcharts with spatial noise. The signal-to-noise ratio (S/N) for the bars and the background will be calculated before and after the correction. In addition, the simulated image after correction will be evaluated by comparing it with an image from a real system. The limits and assumptions of the simulation also will be discussed.

This paper presents alignment test results and scene simulator imagery of a 1 x 1280 element, linear assembly comprised of 5 end-butted modules. Each module consists of a silicon read-out chip, a 256 element, photovoltaic, HgCdTe detector array and a silicon/sapphire carrier. Resistance Area (RnAi) products of 4.2 x 105 ohm-cm² were achieved with the Lift; short-wave (Ac = 2.42 pm), HgCdTe detector array operating at 145K. A detector spacing of 30 μm and an optical area of 23 x 23 μm2 were used. The modules were end-butted with a loss of 4 60μm (4 1 pixel missing) at the butt joints. Sensor components are described and radiometric test results are summarized. Test assembly alignment verification and scene simulation are emphasized.

The NOAO infrared camera was designed for use with the Santa Barbara Research Center (SBRC) 58x62 indium antimonide photovoltaic hybrid array, a device which is sensitive over the spectral range 1-5 microns. There are two versions of the camera design, one of which uses either reflective or transmissive optics, the other only transmissive optics. Both cameras utilize a LN2 radiation shield and cool the detector to the mid 30K region with LHe. The electronics consist of a preamplifier inside the dewar, signal processing electronics, clock drivers, and a digital control unit which generates timing pulses and controls the link to the host computer. These cameras were developed by NOAO in Tucson and are now available for general visitor use at the Kitt Peak National Observatory in Tucson and the Cerro Tololo Inter-American Observatory in Chile.

This paper describes a 256 by 256 HgCdTe hybrid focal plane with a 0.9 to 2.6 μm spectral range. The silicon FET switch multiplexer (mux) is based on previous hybrid work with a 128 by 128 Reticon mux. The high-density device described has a 40 μm pixel pitch vs. 60 gm for the 128 by 128 devices. A read noise of about 1,000 e-has been obtained on developmental hybrid structures, along with full well capacities of about 1 x 10⁶ e-. Preliminary device characterization for the 256 by 256 device, along with the first low-background astronomy test results for the 128 by 128 devices, will be presented.

Features of the design and operation of a dual-multiplexed 64 element linear InSb FPA are presented. The capacitive discharge mode is discussed describing operation of the InSb diodes in both the reverse and forward biased regions. Images produced by mechanically scanning the array are shown demonstrating absence of blooming using this technique.

Within ten years from now, large polar platforms intended to be built by the United States, Europe and Japan are expected to enter into operational service. These platforms will offer significant improvements over the capabilities of current earth observation satellites in terms of mass, power and data rate available to the payload. New instruments must therefore be developed to optimally exploit these capabilities, taking advantage of the last developments in optical systems, data processing and detector technology. The paper describes two such instruments primarily designed for land applications in the frame of the European earth observation preparatory program : a thermal infrared push-broom imager ('[IRI) and a high resolution imaging spectrometer (HRIS). As its name indicates, TIRI is an optical imager specifically designed to work in the 8-12 micron band, split in two spectral channels. Each line of the image being electronically scanned by linear arrays of detectors, no mechanical scanning device is required. Ground resolution is 30 m, with 0.1°K NE T. HRIS is required to provide very high resolution, both spatially (30 m) and spectrally (5 nm in VN1R, 10 nm in SWIR) ; in total, there are 260 spectral channels among which any set of 30 individual channels can be selected for transmission to ground ; low spectral resolution modes are also possible by combining several channels. TIRI and HRIS are large instruments each weighting about 350 kg. Both have a relatively narrow swath width of 30 km, combined with an off-track pointing capability over + 30° from nadir.

Israel Aircraft Industries (IAI) operates a Jet Thermal Signature and Effects Fac ility (MMSEF). The JETSEF facilitates the simulation of the IR radiation emitted by the exhaust system and gaseous plume of a low-f lying aircraft. The flight is simulated by the effect of an external air stream flowing around the exhaust gas jet. The JETSEF complex includes automatic multichannel radiometric and data reduction systems. Furthermore, the JETSEF has a facility for the creation of an aerosol cloud around the exhaust flow produced by the simulator. The IR radiation, corresponding to an afterburn ing engine setting and flight speed of 0,9 Mach, was measured in the 2 to 3 microns, 3 to 4 microns and 4 to 5 microns wavebands. The angular range covered was fram 00 to 90°, where 0° is defined as the tail-on aspect angle. The data were reduced on-line and the measured radiation was stored on an IHNEAT computer, An aerosol cloud was injected into the air stream surrounding the exhaust jet flow. It was found that the IR radiation emitted by the exhaust system and 'gaseous plume was substantially reduced at all aspect angles. A theoretical model has been developed at IAI which describes the passage of IR radiation through an aerosol cloud. The model takes into consideration the absorption, the multiple scattering and the self-emission of the particles in the aerosol cloud. Using this theoretical model, the attenuation of the IR radiation by the aerosol cloud was estimated. Good agreement between the measured and calculated attenuations was obtained.

Thermal infrared data from the Thematic Mapper has been analyzed and methods of calibration developed that can reduce residual error to 0.9K (1 standard deviation). The instrument and its ground calibration and the methods of verifying radiometric performance on orbit are discussed. The substantial data uncertainty caused by the atmosphere is illustrated. The Enhanced TM is being built with an additional window to reduce condensation. Other instruments in preliminary design will have more and narrower spectral bands to expand the applications of radiometric thermal imagery on land and at sea. A detailed procedure for accurate reduction of raw data from the Landsat-5 thermal band is presented.

During the rocket borne experiments flown by the Optical Physics division, we observed: non-linear responses which produces anomalously large values for the low frequency background components, particulate contamination, non-rejected off-axis radiation from the earth and payload, the re-entry wake from the sustainer, exhaust gasses from the ARIES solid motor, condensations in the ACS gas, atmospheric emission above the payload at high altitudes, and an exponentially decreasing background observed at the beginning of three absolute radiometric experiments. All of these phenomena interfere with the measurements and complicate the interpretation of the background of interest. We describe these experiments and discuss the various sources of extraneous signals observed.

The probability of detecting (Pr) a target in a thermal image is an important performance parameter in many ima'6ing systems. The system P depends on many parameters, such as: noise equivalent temperature difference (NETD), instantaneous field of view (IFOV), background characteristics and scanning efficiency. In this presentation the theoretical dependence of Pc on some of the above-mentioned parameters is discussed. Laboratory simulation results as well as some field test results are shown in this paper. 1.

A ten-year update is presented on performance criteria and measurement techniques to evaluate integrating image sensors. The integrating image sensor has an irradiance-sensitive focal plane that continuously monitors the field of view and an electronic mechanism that sequentially reads out the integrated signal on each resolution element. Ten years ago, camera tubes were the integrating imagers of interest; today, staring focal plane arrays have supplanted camera tubes as integrating imagers. The adaptability of the 1978 figures of merit to the new staring devices is reviewed and, when indicated, the figures are modified.

Time delay and integration (TDI) technique has been used in the imaging from moving platforms like satellite and remotely piloted vehicles (RPV) for improving resolution and signal to noise ratio. When the sensor is in motion with respect to the scene being imaged the TDI provides real advantage in the output signal to noise ratio (S/N). The improvement is proportional to the square root of the number of steps of integration. In the present paper authors present the improvement obtained in the S/N ratio by using time delay and integration in the pyroelectric linear imaging arrays. Scanning is performed with the help of a mechanical chopper. The signals from the alternate scans are of opposite polarity. The output of each scan from the array is digitised and stored in a memory. The output from the successive scans are delayed and added in phase. An inverter switch operating in synchronism with chopper inverts outputs of alternate scans and provides a sequence of signals of the same polarity. The signals of opposite polarity from alternate scans are thus also added in phase. Improvement in noise ratio (S/N) obtained is proportional to the square root of twice the number of integration steps. The integration has been performed on a 256 element linear pyroelectric array using 8 and 64 integration steps. The improvement obtained has been experimentally verified in each case.

IR Earth horizon sensors are used for attitude determination of satellites. Simulation of IR horizon and ground calibration are major problems for testing sensors used in low altitude orbits due to geometrical constraints. A large earth simulator and a test facility with a 3500 mm. diameter disc have been developed for the calibration and the qualification of different types of IR earth sensors used on-board Indian Remote Sensing (IRS) satellites. The unique design of the test facility enables the simulation of the satellite altitudes, roll and pitch angles, IR radiation from space and Earth, gradients due to seasonal changes in radiance and thermo-vacuum environments of the sensor under test. The sensor performance can be tested either in open air conditions or under clean vacuum conditions at different temperatures of the sensor. The gradient of the Earth's IR radiation which changes with latitudes and seasons, and the Sun and the Moon interference can also be simulated. A computer based data acquisition system along with the instrumentation is used for controlling and monitoring vacuum, linear and rotary motions, temperature distribution on the earth disc and also for monitoring and recording of the sensor outputs. This paper describes the methodology behind various simulations and the testing involved. The constructional details of the large earth simulator and the alignment of the sensor with respect to the earth simulator are explained. A few of the actual sensor test results obtained are also included.

As part of the Space Station program, NASA is collaborating with the European and Japanese space agencies to develop an unmanned, polar orbiting Earth observing system (Eos) to begin operation in the mid 1990 s Eos will provide, global. measurements with active and passive remote sensors having greater resolution and accuracy than those currently in use. One of the proposed Eos facility instruments, the Lidar Atmospheric Sounder and Altimeter (LASA), is an active remote sensor that offers the possibility of measurements such as the global vertical distributions of aerosols, cloud top heights, atmospheric trace gasses such as water vapor and ozone, and atmospheric temperature and pressure; and the height of the planetary boundary layer (PBL). LASA employs the principles of optical radar (lidar), differential absorption 1 i da r (DIAL), and laser altimetry to provide these measurements with unprecedented resolution. This paper describes the conceptual design of LASA and also describes the conceptual design of one of the experiments proposed for the LASA facility the Eos Atmospheric Global Lidar Experiment (EAGLE).

A high-speed scanning Fabry-Perot interferometer (FPI) has been developed to provide time-resolved spectral data on a pulsed iodine laser operating at 1.3152 Am. The instrument consists of a Fabry-Perot etalon operating in the bull's-eye (Haidinger) fringe mode, combined with transfer optics and a polygon scan mirror for streaking a slit image containing the Fabry-Perot spectrum onto a lead sulfide vidicon camera. The FPI is adjusted for a free spectral range of 0.250 nm in order to detect any or all of the six possible iodine transitions. Spectra with pulse lengths as long as 50 μs can be measured to a resolution better than 500 ns. The instrument is coupled to a personal computer based video frame grabber for data acquisition and analysis.

Usually, the range performance of thermal imagers is predicted by using the static performance model for thermal imaging systems4 from the Night Vision Laboratory NVL. Most range performance models yield results which are quite similar to the results of the NVL-model. Range-performance measurements with different thermal imagers have proved, that the NVL-model must be modified or extended by following points:-cue-identification-aliasing-vertical MRT-moving images - effective MRT

Commercial infrared sources (commonly known as "blackbodies") are useful as reference sources in as much as they emit known amounts of radiation. These sources are usually calibrated by contact temperature sensors (thermocouples), or by a radiometric nulling method. The former method assumes that the radiator emissivity is equal to one; the latter is very time consuming. In this paper we present the following: i)spectroradiometric measurements of a blackbody, which show that the temperature predicted radiometrically agrees with the nulling method calibration within the blackbody calibration accuracy (±2C); ii) analysis of the errors present in the radiometric calibration, which show that an accuracy better than ±2C can be expected from the SR 5000: the SR 5000 is used with an effective temperature software package and an NBS traceable reference blackbody. The analysis can be used to predict the accuracy that can be reached with other radiometers, once their performance parameters are known.

Implementation of robotics into welding is an important step toward higher productivity and better quality control of the fabrication process. However most robots currently perform welding in a "blind" fashion. In order to enhance the intelligence of the robots several sensing techniques such as laser stripping, through-the-arc sensing and infrared thermography have been investigated. Most of these sensing techniques are capable of monitoring only a single welding parameter. However infrared thermography has shown promise to detect several types of impending weld defects. 1,2 The results presented in this paper identify approaches to obtain quantitative relationships to monitor the torch position with respect to the seam of the plates being welded. The asymmetry of the thermal profiles caused by arc misalignment has been quantified into a torch seam error relationship. Two principal comparison techniques have been identified. Averaging methods have been implemented to reduce the noise level in the error signals.

Penetration depth is a key variable, which needs to be controlled to ensure defect-free welds. One of the major problems involved with adaptive control penetration is the lack of suitable variables which can be viewed directly by the sensor. A proposed sensing technique is to relate the invisible variables, such as penetration depth and thickness of the welded steel plates, to visible variables of thermal images. The sensed infrared information was obtained through digital signal process of the thermal images associated with the high temperature of the molten metal pool and its vicinity during the welding process. Quantitative measurements were conducted to find a relationship between visible and invisible parameters. The thickness of plates being welded was varied and the corresponding changes in both penetration depth and surface temperature distributions were studied quantitatively. A least squares method was used to fit the obtained isotherms to an equation of an ellipse. The penetration depth and thickness of the materials being welded were found to be functions of the minor axes and the area of the ellipse for Gas Tungsten Arc Welding (GTAW). The experimental results can be used to achieve adaptive penetration depth control.

Today radiothermometers have a wide variety of applications in non-contact tememperature measurments and begin in use for estimation of heat flow and thermal resistance, in these measurements there are still some problems to be solved, in recent years we have designed a kind of enclosed radiothermometer which can be used for emissivity and temperature measurements simultaneously. Now we have established a mathemetical model of heat flow through building walls . With this model we can use the enclosed radiothermometer to measure the radiation heat flow and thermal resistance. The advantages of the measurements using enclosed radiothermometer are that the emissivity, temperature, heat flow, heat resistance can be measured only by one instrument; the measurement speed is high and the measured surface may not be thermally disturbed.

Indium gallium arsenide (InGaAs) photodetectors have been configured into linear arrays of 30 x 30 micron photodetectors spaced 50 um apart. The devices have typical responsivities of 0.9 NW (86% QE) at 1.3 μm and exhibit room temperature dark currents below 100 pA. A 256 element array has been mounted in a Reticon multiplexer and configured into a PAR optical multichannel analyzer to extend spectral response out to 1.7 urn. Individual InGaAs detectors have been fabricated for response out to 2.2 urn with dark current below 1 uA (-1V) and 50% QE at room temperature.

Indium doped silicon (Si:In) material has been used to fabricate the detector elements for an infrared (IR) radiometer array. The array will be employed in experiments on a spaceborne platform, where a low radiation background (fiDg < 109 cm^-2sec^-1) and a low operating temperature (T < 20 K) is provided. The performance of the Si:In detectors has been characterized prior to the assembly of the array. Test results will be presented for the spectral responsivity, the linearity, the frequency behaviour, the noise equivalent power values and the cross talk.

Earth observation satellites will use linear arrays of a few thousands of pv-CMT-detectors combined with CCDs to scan the surface in the (8-12) μm spectral range in the pushbroom principle. The hybrid approach of large CMT-IRCCDs is based on butting small entities of CMT-submodules with CCD-signalprocessors. According to the high photon background charge suppression techniques have to be implemented in the detector-CCD coupling circuit. CMT-IRCCD engineering models are manufactured, electro-optical results are presented.

On indium doped silicon monolith integrated focal plane arrays with 300 x 200 picture elements were developed. The chip size is 100 mm2, the pixel size 10 μm x 10 μm and the pitch 20 pm in both directions. The picture elements operate with punch through technique (inherent antiblooming) and the read-out structure is a frame transfer design. PtSi Schottky barrier focal plane arrays with 128 x 64 picture elements were developed. To achieve high photoresponse the SBDs are constructed with a thin layer of PtSi separated from an aluminum mirror by a layer of Si3N4. The focal plane arrays show an excellent homogeneity of the responsivity. Quantum efficiencies of several percent are achivied. Test camera systems have been built with PtSi devices and with focal plane array on In doped Si to demonstrate the possibilities of infrared sensors using silicon as the basic material.

The task to observe a thermal scene and to measure its range traditionally requires two devices: - a thermal imager (TI) and - a CO2 laser range-finder (LRF) Simple investigations concerning these two systems exhibit a remarkable degree of commonality between both systems. The thermal imager as well as the CO2 laser range-finder receiver consist of an IR optics, an IR detector and normally a cooling engine. For a couple of years it has been the idea to combine (at least) some of the components of both systems. Looking closer at this idea, there are three areas of special concern: - there is a mismatch between the "instantaneous fields of view (F0V)" of the thermal imaging detector and the laser range finding detector by a factor of about 5 (linear) - due to the scanning inherent in thermal imagers there arises the problem of image motion during the time of flight of the laser pulse - the time constant of the detector of the widely used (US-) Common Module System Thermal Imagers is by far too slow to receive laser pulse radiation undistortedly. Electronic means to overcome this limitation are essential. The following discussion gives some details how to resolve the above mentioned difficulties. Compromises are necessary to overcome these problems.

Laser rangefinders, laser altimeters, laser radars and other laser equipment must at least fulfill the requirements of class III a as defined in the STANAG 3606 (Standard Nato agreement) in order to be eye safe. This class calls out a Nominal Optical Hazard Distance of zero meters thus guaranteeing eye safety for direct observation into the exit pupil of the laser transmitter with the unprotected eye. Some military applications in the Federal Republic of Germany place a more strenuous NOHD requirement, namely 0 meters for intra beam viewing with a 10x50 binoculars. Such a system is described. The performance achieved shows that the class III a requirement need not necessary exclude the use of such a laser for military applications. On the contrary, the measured data of such lasers shows a performance which excells that achieved with the military proven Nd:YAG laser. The eye safe feature plays an important role in respect to training. Namely training can be conducted using the actual laser system without the need for laser simulation techniques thus allowing for real system training. This paper reports on the performance of lasers operating at 0.9 μm, 1.54 μm and 10.6 μm. The laser types used in the three wavelengths are the semi-conductor, the Raman-shifted Nd:YAG and the CO₂ TEA laser respectively. The results show - naturally excluding weapon laser requirements - that eye safe lasers can really fulfill the performance requirements of military systems.

The direct conversion of sunlight into laser radiation might become a process of economic importance. The present report investigates the fundamental question of the energetic efficiencies obtainable with the presently known solid state laser materials. With respect to an optimization it seems advisable to design a combined laser-power plant system where the incident light is splitted into two parts, one of which, whose wavelength being adjusted to the absorption spectra of the special laser crystals, serves as the pumping source of the laser and the other part delivers its energy to a solar dynamic and/or a photovoltaic converter.

Battelle has developed a multispectral LIDAR(Llght Detection And Ranging) for the accurate identification and quantification of numerous gaseous pollutants within a range of a few kilometers in the troposphere. This instrument is using the multispectral differential absorption technique (rapid examination of the atmospheric transmission on several different wavelengths). The main components of this DIAL (DIfferential Absorption Lidar) are a CO2 laser operating in the 9 - 11 μm region with a maximum repetition rate of 300 Hz together with a rapid tuning device forming the transmitter and a conventional 8"-Newtonian telescope with a LN-cooled HgCdTe-detector as the receiver. The whole LIDAR instrument is fully controlled by a 16 bit microprocessor system (68000 CPU). The rapid tuning unit allows to emitt pulse pairs of different wavelengths within 3 ms, and to probe up to 10 wavelength pairs within one second.

The proposed airborne remote sensing instrument LIMES (LIdar Multispectral Earth Observation System) is the combination of an imaging 4 channel laser spectrometer (9.1 μm through 11.2 μm) and a multispectral scanner (11 channels between 0.42 μm and 13.0 μm). This instrument is the successor of the airborne 2-laser profiling instrument DIALEX (DIfferential Atmospheric Laser EXperiment, which was successfully flown over different test sites. The enhanced spectral resolution of the LIMES instrumentation will be used for applications and scientific objectives as there are: Geologic remote sensing (exploration), geologic -geographic remote sensing (mapping), discrimination and identification of surface materials (soils, rocks, vegetation), detection of vegetation anomalies and moisture detection.'

NIR.ATAM ( NATO InfraRed Air T.Arget Model ) is a computer model which predicts IR radiation of an aircraft in its natural surroundings. A special version of NIRATAM enables to treat a hypersonic reentry vehicle. The model takes into account the IR radiation emitted by aerodynamically and internally heated surface, hot engine parts and combustion gas and particles in the exhaust plume. The reflected radiation of the sky and terrain background and the sun on the aircraft surface is calculated. The atmospheric transmission and emission between target and observer and the radiation of a homogenous background in the scene is determined. The spectral response of a sensor is included. The development took place in collaboration with other NATO-countries. The code is of modular structure. One of the major modules (IRMA) , for the hot gas emission calculation, was developed at This paper describes the modules, the major features and shows some typical results. For the "Reentry-Version" the exhaust plume flew field model is replaced by an aerodynamic flow field model which determines the hypersonic flow around the body. A thermal model computes the aerodynamic heating and heat balance of the body by considering the convection , the thermal conduction and the radiative heat loss. A dynamic thermal map of the surface is computed for the course of reentry. The principal model components and steps for &terming the IR-signature are discussed and results for a typical reentry vehicle are presented in the paper. The code is applicable in the spectral range from 2 to 25 μm with 5cm ' spectral resolution. Radiation of gas can be predicted within the temperature range from 100 -- 3000° K . The results are presented as emission spectra and their cumulated integrals. Thermal images are provided in radiance and equivalent blackbody temperature values. The contributions of the different radiation sources are analysed.

Scenes taken by infrared (IR-)cameras show the temperature distribution within a scene in the form of different image half-tones as a chequerboard pattern. The half-tone distribution of the image displayed depends on the intensity of the radiation of the individual parts of a scene and on the momentary transmission conditions of the atmosphere as well as the sensory characteristics of the camera system. This means that one and the same scene, taken with different cameras or at different times, results in different half-tone distributions for the pictures. Therefore, a long-term trainingis required for equipment provided with IR-cameras in order of cover as many weather conditions as possible. This problem is solved by the IR-Scene Simulator.

This paper describes a method to classify targets especially helicopter by evaluating their vibration signa-tures. The mechanical vibrations of the targets are mainly caused by all moving parts ( engines, turbines, gears, etc. ). Different types of targets have different vibration spectra. These were measured in the field by an experimental heterodyne laser radar. The measured signals show type characteristic vibration signatures. These can be evaluated by proper mathematic algorithms so that classification of noncooperative targets is possible.

Acousto-optic signal processing systems require linear detectors arrays with wide dynamic range and fast transient response. In the past, these two characteristics have not successfully been combined into a single integrated detector array with a large number of elements. DALSA's DYNASENSOR detector utilizes an optimized, ion implant doped, profiled MOSFET photodetector specifically designed for wide dynamic range. This detector, originally introduced by DALSA over a year ago, has been redesigned to improve transient response. The new device offers high speed, linear response characteristics at low light levels or short integration times (on the order of 1 microsecond). To achieve the short integration times necessary in acousto-optic applications, the DYNASENSOR has been implemented in a tapped array architecture with eight outputs and 256 photoelements. Operation of each output at 20 MHz yields detector integration times of 1.6 micro-seconds.

This paper gives the development and examples of synthetic nuclear background scenes. These scenes are compared with nuclear test data. These scenes may be used for sensor design and analysis.

Both absolute and differential temperature measurements were simultaneously performed as a function of time for a pixel on a high-temperature, multi-spectral, spatially and temporally varying infrared target simulator. A scanning laser beam was used to maintain a pixel at an on-the-average constant temperature of 520 K. The laser refresh rate of up to 1 kHz resulted in small-amplitude temperature fluctuations with a peak-to-peak amplitude of less than 1 K. The experimental setup to accurately measure the differential and the absolute temperature as a function of time is described.

The most familiar method of star removal for a scanning space surveillance sensor uses a permanent Sky Catalog Comparison in which the location in inertial coordinates of each object above threshold TH is checked against the catalog. If that location has a catalog star, the object is removed. The catalog limit is at a lower threshold, TL, than the threshold of stars to be removed, TH. The primary method proposed here, method A, "Prior Scan Comparison," is similar to the Sky Catalog Comparison, except that the comparison catalog is simply the prior scan at threshold TL. (That small portion of the current scan not viewed on the prior scan uses the following scan for comparison.) The resulting simplicity is significant, inasmuch as just two scans are involved, large amounts of storage and retrieval are avoided, and no catalog updates are required. Since asteroids do not move appreciably in inertial coordinates from scan to scan, asteroids that would leak through the Sky Catalog Comparison method are removed by this method. There are three constraints on the high and low thresholds used by the Prior Scan Comparison method to ensure an acceptable star leakage rate, target detection rate, and target loss rate due to star search boxes. Under extreme conditions, it may not be possible to satisfy constraints simply by adjusting the two threshold values, particularly when the noise has an abnormal, heavy tailed (platykurtic) distribution. Under such conditions, modifications of this algorithm may be necessary. Two such modified algorithms are described as methods B and C. Both are still much simpler than the permanent Star Catalog method.