Proceedings Volume 0430

Infrared Technology IX

Richard A. Mollicone, Irving J. Spiro
cover
Proceedings Volume 0430

Infrared Technology IX

Richard A. Mollicone, Irving J. Spiro
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 9 January 1984
Contents: 1 Sessions, 44 Papers, 0 Presentations
Conference: 27th Annual Technical Symposium 1983
Volume Number: 0430

Table of Contents

icon_mobile_dropdown

Table of Contents

All links to SPIE Proceedings will open in the SPIE Digital Library. external link icon
View Session icon_mobile_dropdown
  • All Papers
All Papers
icon_mobile_dropdown
Three-Dimensional Target Signature Modeling
G. A. Davison, R. S. Dummer, K. M. Reitz
The capability of accurately modeling a wide, range of military targets, in both the RF and IR portion of the spectrum, has become essential for the numerous defense programs associated with tactical weapon sensors and satellite surveillance systems. Advances in computer technology permit the use of precise analytical models early in the development cycle of new sensors. This capability leads to a new class of methods for synthetic sensor performance verification. Having recognized this opportunity Aerojet ElectroSystems Company (AESC) has developed techniques for passive target signature modeling in the 1 to 25 μm region. This paper summarizes the company's approach to passive three dimensional target modeling.
A Local Spatial Correlation Length For Background Modeling
P. K. Mazaika
Radiometric measurements obtained from scanning sensors are useful for deriving one-dimensional spatial statistics of background. This paper introduces a local spatial statistic, the "differential length scale," that is particularly relevant for using the measurements to predict clutter leakage in proposed sensor systems. A method is given for calculating the differential length scale in the presence of measurement sensor noise, and the relationship of the differential length scale to the usual power spectrum length scale is described. Computer simulation experiments show that RMS clutter leakage from two-dimensional images can be predicted within 10% accuracy using only the differential length scale of one-dimensional slices of the image.
Model For Atmospheric Clutter As Seen From A Satellite Platform
George H. Lindquist, Heemook Kwon, A.Robert Nagy Jr.
A model for the atmospheric clutter as seen from above the atmosphere is developed. It utilizes the algorithm and data generally present in atmospheric attenuation codes such as LOWTRAN 5. A weighting function for clutter contributions as a function of altitude and spectral region, and, under the assumption of uniform temperature statistics, a means of comparing expected clutter as a function of spectral region are obtained. Opaque bands in the 4.3 μm carbon dioxide band, the 6.3 μm water band, and the 15 μm carbon dioxide band all show very low expected clutter, while a partially transparent band in the long wavelength wing of the 4.3 μm carbon dioxide bands shows a much larger clutter contribution.
Apparent infrared (IR) Cloud Radiance Model
C. M. Randall, D. D. Little
The infrared radiation from clouds, which results as clouds emit heat and scatter sunlight, is an important consideration in the design of high-altitude sensor systems. The radiation detected by a high-altitude sensor depends both upon the origin and the path of the rays. The purpose of this paper is to show how such variables as the observation angle, the solar zenith angle, the particle scattering angle, the wavelength band and cloud altitude are incorporated into a comprehensive background description, and to illustrate the effect of these parameters on backgrounds. The description uses previously developed models for its separate components.
Evaluation Of Aerosol-Obscured Infrared Imagers
E. R. Craine, M. A. Lancaster, R. M. Ransier
Military infrared devices are vulnerable to a variety of countermeasures which must be qualitatively and quantitatively evaluated to assure effective application of the systems. Because of the high costs of field testing this equipment, attempts to create various environments for simulating battlefield conditions have evolved. We report on progress with a shortened real-world simulator and an instrumented field van used to provide validating real-world data. Both facilities are being used in the presence of obscuring aerosols to study the behavior of infrared imagers in the 2-14 micrometer bands. We discuss the capabilities of the facility and the nature of the measurements involved.
Comparison Of Modelled And Empirical Atmospheric Propagation Data
John R. Schott, Joseph D. Biegel
Airborne measurements of atmospheric transmission and path radiance in the 8-14 μm band were obtained by applying a profile calibration technique to infrared line scanner data. The profile technique involves collecting quantitative thermal infrared images over the same target areas at different altitudes. Calibration of these images to account for atmospheric effects has been demonstrated to yield computed surface tempera-tures within 0.4°C of concurrent kinetic temperature readings. Radiometric propagation models, calibrated with radiosonde data, were also used to generate transmission and path radiance values corresponding to the empirical measurements. This paper contains the results of a comparative analysis of these approaches. Some limitations of the radiometric propagation models are presented. The problems of applying atmospheric propagation models for precise quantitative analysis of satellite images are discussed. An empirical method for precise calibration of single channel satellite infrared imaging systems requiring underflight data is demonstrated and airborne test results are presented. In addition, the potential for a precise calibration approach not requiring underflight data is suggested .
Transmittance Band Model For Atmospheric Nitrous Oxide In The Infrared
Joseph H. Pierluissi, John M. Jarem
The problem of numerically determining the parameters which describe an analytical transmission function for gaseous molecular absorption over an infrared band is addressed. A double exponential described by three absorber parameters and one spectral parameter is proposed as the transmission function. Four numerical methods for the determination of the parameters are briefly discussed, and applied to line-by-line and measured spectra for nitrous oxide (N20) over its three principal infrared bands. A discussion is also presented on a comparison between the line-by-line and the laboratory measured spectra. The model developed with the recommended method reproduced the original data with an overall rms deviation of 1.49%, which is an improvement over a previously reported model. The model parameters at 5 cm -1 intervals for 20 cm-1 resolution transmitt ance calculations throughout the bands, are available upon request in a form compatible with the LOWTRAN code.
The BAMM IIA Radiometer
R. T. Pohlman
The Balloon Altitude Mosaic Measurement (BAMM) IIA Radiometer is designed to make mosaic measurements in either of two modes of operation: the stare or demonstration mode and the radiometer mode. In the stare mode, background suppression and target detection can be demonstrated; in the radiometer mode the incoming energy is chopped to allow absolute measurements to be made. The Noise Equivalent Radiance (NER) in each available spectral band is less than 2.5E-8 W/cm2-sr in the stare mode and less than 1.25E-7 W/cm2-sr in the radiometer mode. The Radiometer is physically divided into two units: the Radiometer Unit and the Support Electronics Unit. The Radiometer Unit contains the optical, detection, and preprocessor sections of the instrument. Ten narrow-band spectral filters in the 2.59 to 5.1 micrometer region are mounted on a wheel and are selectable from the ground. Three telescopes on a turret allow the selection of 50, 200, or 800 meter detector footprints (at the nadir from the 100,000 ft. flight altitude). The focal plane module uses the Grumman-developed Z-dimension technology with 16 x 64 HgCdTe detectors. Included on the module are hybrid CMOS chips containing the signal conditioning circuitry for sample and hold operations, bandpass filtering, and 32:1 signal multiplexing. The second unit, the Support Electronics, supplies control signals, bias voltages, and clock signals. The output lines from the focal plane are converted to digital signals, multiplexed, and formatted for PCM trans-mission to the ground in this unit.
Airborne Imaging Spectrometer: An Advanced Concept Instrument
Clayton LaBaw
The Airborne Imaging Spectrometer (AIS) is a multispectral infrared imaging instrument utilizing a 32- x 32-element mercury-cadmium-telluride detector array to achieve high spatial resolution. A novel optical design provides high spectral resolution, and, in conjunction with the 32-element spatial resolution, makes optimal use of the capabilities of the area array. The experiment requirements and the details of instrument design, implementation, and calibration are presented. The superior resolution, accuracy, and data acquisition rate of this sensor/instrument concept for reconnaissance and geophysical survey is detailed and plans for upgrading/improving the instrument and future applications of this design concept are discussed.
The Thematic Mapper - Instrument Overview and Preliminary On-Orbit Results
Jack L. Engel
The Thematic Mapper (TM) is a second-generation Earth Resources Sensor built for NASA for the Landsat series of spacecraft. The TM was placed in orbit aboard the Landsat-4 space-craft in July of 1982. Its predecessor, the Multispectral Scanner (MSS), has flown on Land-sats 1 through 3 and accompanies the TM on Landsat 4. This paper provides an overview description of the Thematic Mapper, a summary of the TM's performance derived from prelaunch testing and concludes with the presentation of prelimi-nary results of the assessment of on-orbit data. These early results indicate that the per-formance of the Thematic Mapper is consistent with the prelaunch results and the utility of the data is meeting or exceeding expectations. Keywords: Thematic Mapper (TM), remote sensing, Landsat, Multispectral Scanner (MSS), and Earth Resources Sensor.
Large Scan Mirror Assembly Of The New Thematic Mapper Developed For LANDSAT 4 Earth Resources Satellite
Charles John Starkus
This paper reviews mechanical aspects in the development of a large, oscillating scan mirror mechanism that featured a remarkably low level of structural vibration for the impact energies involved in mirror oscillation. Another feature was that energy lost during impact was returned to the mirror by applying torque only during the instant of impact. Because the duration of impact was only about 0.010 second, it was critical that energy losses be minimal since there was not much time to restore them. Solutions to these critical mechanical problems constituted a major milestone in the development of object-space scanning sensors.
Spectral Radiometer For The (AM.OS) 1.6 Meter Telescope
Glen W . Ashley
A LWIR, contrast-mode, spectral radiometer has been installed on the 1.6 meter tele-scope of the DARPA Maui Optical Station (AMOS) Observatory located on Mt. Haleakala, Maui, Hawaii. The instrument covers the spectral range from 3 to 23 micrometers using a pair of Si:As detectors which are cooled to 10°K with a helium based closed cycle refrigerator. Two rotating Circular Variable Filters cover the 3 to 5 and 8 to 14 micrometer atmospheric windows with a 2% spectral resolution. Other wavelengths are covered with fixed filters. Details of the optical and dewar design are presented.
Design And Performance Of The Stratospheric Aerosol And Gas Experiment II (SAGE II) Instrument
N. H. Zaun, L. E. Mauldin III, M. P. McCormick
Design and performance data are presented for the Stratospheric Aerosol and Gas Experi-ment II (SAGE II) instrument, which has been developed for the Earth Radiation Budget Satellite (ERBS). SAGE II is designed to monitor globally the vertical distribution of strato-spheric aerosols, ozone, water vapor and nitrogen dioxide by measuring the extinction of solar radiation through the earth's atmosphere during the ERBS observatory solar occultations. Solar radiation is reflected from a flat scanning mirror into a Cassegrain type telescope, which forms a solar image on the entrance slit of a grating spectrometer. The SAGE II instantaneous-field-of-view (IFOV) is scanned along the vertical solar diameter by the elevation scan mirror. The entire optical system is contained within an azimuth gimbal which tracks the solar radiometric centroid during the data event. This spectrometer, with help from three interference filters, isolates seven spectral wavelengths ranging from 0.385 micrometers to 1.02 micrometers. All seven channels use silicon photodiode detectors oper-ated in the photovoltaic mode. Detector outputs are multiplexed into a serial data stream for readout by the ERBS telemetry system. Each output is sampled 64 times per second and digitized to 12 bit resolution. SAGE II is a third generation instrument following the highly successful SAM II and SAGE programs.
Telescope - Optical System Performance Analysis For The Cryogenic Limb Array Etalon Spectrometer (CLAES) On The Upper Atmospheric Research Satellite
A. E. Roche, P. B. Forney, H. E. Morrow, et al.
This paper presents a first-order performance analysis of the telescope - optical system for the Cryogenic Limb Array Etalon Spectrometer (CLAES), one of several experiments intended for flight on the Upper Atmospheric Research Satellite (UARS). The experiment is based around a solid Fabry-Perot spectrometer which provides spectral resolution of 0.25 cm-1 for atmospheric emission spectroscopy over the 3.5- to 12-μm infrared wavelength range. A solid hydrogen cryostat sized for a two-year in-orbit lifetime provides cooling for the detector array, spectrometer, and telescope optics. The experiment involves the passive measurement of earth-limb radiance over a 10- to 60-km tangent altitude range. The instrument is required to provide near diffraction-limited performance over this 50 km or 1-deg field-of-view, and over the full wavelength range. The optical system must also provide a high degree of off-axis rejection and stray-light control, primarily to suppress intense emission from the earth surface which resides at -0.2 deg off-axis for the 10-km lowest altitude of observation. The optical system consists of a Gregorian telescope and refractive re-imager arranged in the common "z" configuration with folded baffles and no obscuration. The 6-in. telescope primary mirror produces an intermediate focus where the astigmatic image spread is oriented along the horizontal limb direction. This allows for precise location of the field stop and very sharp cutoff of the field below -0.175 deg. The astigmatism and other geometric aberrations are corrected by the secondary mirror which produces an excellent image of the primary, allowing for location of a diffraction control or Lyot stop. The re-imaging lens corrects for field curvature associated with the telescope and produces a flat field at the detector focal plane. Image quality is at the diffraction limit from 3.5 to 10 μm, with a point spread less than 10 percent of the airy disc diameter for example at 5 μm. The airy disc itself is less than 10 percent of a detector vertical dimension at this wavelength. Some chromatic correction remains to be incorporated between 10 and 12μm, where the point spread exceeds the diffraction limit by about 20 percent. The off-axis scattering performance of the telescope is discussed in terms of the mirror scatter coefficient and point source rejection ratio. A mirror bidirectional reflectance distribution function (BRDF) of 1 x 10-4 at 1 deg with a 1/02 roll-off between 1 and 0.2 deg is realizable based on recent measurements. This results in an off-axis radiance term generally small in comparison with the system-limiting noise equivalent radiance (NER = 10-12 W/cm2/sr at 10 μm.) As the observational altitude increases the off-axis term becomes less and less significant.
A Modular Approach To Developing A Large Deployable Reflector
R. Pittman, C. Leidich, F. Mascy, et al.
NASA is currently studying the feasibility of developing a Large Deployable Reflector (LDR) astronomical facility to perform astrophysical studies of the infrared and submillimeter portion of the spectrum in the mid 1990's. The LDR concept was recommended by the Astronomy Survey Committee of the National Academy of Sciences as one of two space based projects to be started this decade. The current baseline calls for a 20 m (65.6 ft) aperture telescope diffraction limited at 30 μm and automatically deployed from a single Shuttle launch. The volume, performance, and single launch constraints place great demands on the technology and place LDR beyond the state-of-the-art in certain areas such as lightweight reflector segments. The advent of the Shuttle is opening up many new options and capabilities for producing large space systems. Until now, LDR has always been conceived as an integrated system, deployed autonomously in a single launch. This paper will look at a combination of automatic deployment and on-orbit assembly that may reduce the technological complexity and cost of the LDR system. Many technological tools are now in use or under study that will greatly enhance our capabilities to do assembly in space. Two Shuttle volume budget scenarios will be examined to assess the potential of these tools to reduce the LDR system complexity. Further study will be required to reach the full optimal combination of deployment and assembly, since in most cases the capabilities of these new tools have not been demonstrated. In order to take maximum advantage of these concepts, the design of LDR must be flexible and allow one subsystem to be modified without adversely affecting the entire system. One method of achieving this flexibility is to use a modular design approach in which the major subsystems are physically separated during launch and assembled on orbit. A modular design approach facilitates this flexibility but requires that the subsystems be interfaced in a simple, straightforward, and controlled manner. NASA is currently defining a technology development plan for LDR which will identify the technology advances that are required. The modular approach offers the flexibility to easily incorporate these new advances into the design.
Infrared Earth/Atmosphere Background Illuminated by Low Grazing Angle Sunlight
R. E. Murphy, A. Fairbairn, R . A . Van Tassel, et al.
A BAMM (balloon altitude mosaic measurements) flight was launched in April 1982 to obtain data on the earth/atmosphere IR background during the early hours of sunrise looking at low angle specular reflections. The data were obtained by a filtered radiometer and an interferometer in the spectral region 2.5 - 5.5 micrometers. The data from the radiometer were processed for their statistical content and for comparison within the passband of the filter with the interferometer. The interferometer data were analyzed for their wavelength spectral content and compared with predictions from LOWTRAN. We have concluded that new features occurred in the SWIR and MWIR under low solar scatter angle conditions which were not found in other flights, in particular, there were several simultaneous solar reflection mechanisms at work and these produced highly variable effects.
High Speed Infrared Charge Injecton Device : Design Considerations
T. Maekawa, Y. Miyamoto, K. Tanikawa, et al.
This paper describes the results of calculation to develop high speed infrared charge injection devices (IRCIDs). The charge injection time dominates the readout frequency of IRCIDs operated by a sequential injection scheme. The behavior of the injected minority carriers are simulated by solving the diffusion equation. The simulation reveals that the high speed device needs a special structure to eliminate the injected charge. Two devices are proposed. One structure is made on thin n-type layer formed by Hg diffusion to a p-type substrate. The p-n junction underlies the charge storage cell and removes the injected charge. The other structure uses an epitaxially grown substrate and utilizes the HgCdTeCdTe interface as recombination layer of the injected charge.
An Integrating IR Detector
D. D. Coon, S. Gunapala, R.P. G. Karunasiri, et al.
We have recently demonstrated a new integrating mode of IR detection which utilizes charge storage in impurity levels rather than in potential wells associated with device architecture as in CID's or CCD' s. The new mode is based on control of impurity-to-band tunneling via an applied field. The impurities are located in the i-region of a p-i-n diode. IR integration is accomplished by field-assisted impurity photoionization which depletes the population of carriers trapped in impurity levels. The field (0.1 to 0.6 volts/pm for Si:P) yields a very small tunneling dark current which permits integration times of up to 12 hours or more. A high field ( > 1 volt/pm for Si:P) pulse causes rapid impurity-to-band tunneling and ejection of the remaining charge after an IR exposure. Readout is accomplished by measurement of the ejected charge. The zero-field photoionization cross section for Si:P has a maximum at 27μm. Using a liquid helium cooled monochromator we have studied the spectral response of this detector. An analysis of the field dependence of photoionization of semiconductor impurities shows agreement between theory and experiment. We therefore feel confident to predict the performance of improved versions of detectors using this mode of detection. We also explore the possiblities of designing large far infrared detector-arrays. Although functionally different from CID's, arrays of these devices could be used as staring arrays in much the same way as CID's are presently used.
Operation Of Integrating Indium Antimonide Linear Arrays At 65 K And Below
Gary C. Bailey, Keith Matthews, Curtiss A. Niblack
The combination of a FET switch non-CCD readout architecture with high-quality mesa photovoltaic indium antimonide detector material has led to high-performance integrating linear imagers in the 1- to 5-pm region. These devices operate in the temperature regime below 100 K and provide very good dark current and responsivity uniformity (±2%). Test data will show performance at 65 K for a 512-element array and 46 K for a 128-element array. Useful integration times of 3600 seconds at 46 K and >12 seconds at 65 K have been achieved. kTC read noise levels of less than 1200 electrons have been measured for both devices.
Optical Processing Technology For Infrared Sensors
Jeffrey L. Nelson
As modern infrared sensing systems become smarter and able to collect more data at faster rates, the complexity of on-board data processing systems becomes greater. While V HSIC and VLSI digital systems offer a great amount of support for the on-board processing, there is a place for optical data processing. This paper discusses one processor architecture which performs several on-board analysis functions optically as well as reduces the data processing load which the electronic digital processing portion must address. The application exemplified is an infrared search and track system with optical processing to support background rejection and moving target indication. Backgrounds to be rejected in this application do not generally exceed the target intensity; that is, the targets are typically as bright as or brighter than the background. Background rejection consists of a spatial filter to eliminate large distributed sources on which a small target is superimposed, and optical image subtraction to remove small stationary targets. Moving target indication is performed with a spatial filter and a wedge detector array. Techniques for target characterization and identification have been developed but will not be discussed in this paper; nor will techniques for ballistic target impact point prediction be presented. One of the more difficult aspects of optical processing is the interconnect between the infrared detector array and the optical processor; candidate technologies for this optical interconnect will be reviewed.
Ultra-Wide Waveband Optics
Thomas H. Jamieson
Optical systems are normally usable over a restricted spectral waveband. A refractive optical system will only transmit radiation over a limited range of wavelengths and it may only produce well color corrected images over part of this transmission band. This paper discusses the design of lens systems for use over the extended waveband from about 0.4 microns to 12 microns, which encompasses the visible, the 3-5 micron mid-infrared and the 8-12 micron thermal wavebands. Discussion is given to the available optical materials including glasses formed by chemical vapor deposition and crystalline materials. The relationships between the refractive and dispersive properties required for wide band color correction are formulated and several designs are described which use two and three optical materials. Some discussion is given to the coatings required for such optics viz. ultra-wide band anti-reflection, mirror and beam splitting coatings. The potential use of this type of optical system is in multi-sensor applications such as dual visual/thermal observation systems perhaps employing staring array technology and/or CO2 laser incorporation.
Small Angle Bidirectional Reflectance Distribution Function (BRDF) at 10 µm
Wallace K. Wong
The Sensor Systems Group (SSG), Inc., has been routinely using a BRDF measurement as an acceptance test for low scatter mirrors for use in high straylight rejection telescopes. Our conventional 10.6 μm BRDF measurement apparatus can characterize a low scatter sample from -5° to -50° off specular using a sampling ΩFOV of 2.2 X 10-4 sr. Recently, this apparatus was modified to allow successful measurement of a 24-inch focal length low scatter off-axis parabola from 0.5° to 5° off specular using a sampling QFOV of 1.2 X 10-5 sr. The measured BRDF data on this particular sample at 0.5, 1.0, 2.0 and 5.0 degrees are 6.5 X 10-4, 2.1 X 10-4, 6.7 X 10-5 and 1.5 X 10-5 per sr, respectively. The test configuration and design issues are described in this paper.
Coupling Efficiency To IR Fiber Optics In The Focal Plane: A Radiometric Analysis
Donald G. Lubnau
A radiometric analysis of the coupling efficiency of focal plane energy to a step-index optical fiber has been carried out using Walther's generalized radiance function Bw(r,s)1 for a small, distant blackbody target imaged by aberration-free optics. A second analysis evaluates the ratio of the coupling efficiency of blackbody radiation directly incident on the focal plane (considered to arise from the telescope environment itself or, approximately, large area Earth background) to that of the distant thermal source. For a range of fiber optics parameters, this ratio is less than unity indicating that to some extent, the fiber acts to discriminate against spatially incoherent radiation.
Photodiode Quantum Efficiency Improvement through Vacuum Surface Effects
N. S. Kopeika, I. Hirsh, E. Hazout
Surface effects stemming simply from photodiode operation in vacuum environment are seen to improve quantum efficiency significantly. This is attributed to desorption of surface impurities and consequent reduction of surface potential, recombination, and Debye length. Effective depletion layer width can also be noticeably affected by free charge redistribution after desorption of surface impurities. Quantum efficiency here in vacuum is greatest at longer wavelengths because of decreased surface depth in vacuum.
Operational Test Considerations For Low Quantity Satellite Systems
R. K. Chadbourne Jr.
This paper discusses the unique considerations of operational test and evaluation for low quantity satellite systems. Traditionally, operational test and evaluation has been on large quanitity systems (e.g., aircraft, missiles, munitions, etc.) where preproduction test articles were available strictly for the test and evaluation. In most cases, this operational test and evaluation supported a production decision. However, in the case of low quantity satellite systems, there are no satellites available strictly for operational test and evaluation. Moreover, in many cases the production decision has been made prior to the operational test and evaluation. With these differences in mind, the Air Force and contractors must cooperate to achieve the goal of the best possible satellite system "in the field" in the least amount of time for the least cost. By appropriate planning and early operational test and evaluation involvement in a satellite program, the Air Force and contractors can achieve this goal.
Infrared Data Analysis With Minimal Computer Resources
Donna M. Winter, Edwin M. Winter
The analysis of infrared and other image data has been traditionally associated with large expensive computer hardware. In this paper, a functioning image processing system implemention based upon an Apple II personal computer is described. The approach offers a low-cost alternative for image processing and infrared data analysis.
Focal Plane Processor Interface Studies For Large Mosaic Focal Planes
James S. Gross
As large mosaic focal planes are developed, the interface with the data processor will become a key design issue. A study has been performed to identify the key parameters that affect the interface design, and to determine their interaction. System parameters, multiplexer design, and reliability considerations were examined to define an optimum multiplexer length for on-focal plane multiplexing and a strategy was developed to determine the optimum number of data lines emerging from the focal plane.
Performance Of A Staring Infrared Mosaic Sensor Against A High Reflectance Background
K. N. Myers
The application of mosaic focal planes to the problem of satellite surveillance has resulted in an increased interest in background clutter. Perhaps the most stressing background, in terms of its sharp radiance gradients and the existence of edges, occurs under conditions of high solar reflection off of clouds. A high reflectance scene, simulated in two spectral bands, was used to study the clutter induced by platform drift and jitter across such a background. Clutter was studied as a function of footprint, drift rate, and RMS jitter amplitude for first and second difference filters. These results were then compared against those derived from a simulated scene representing a more typical cloud background. All results presented are for a synchronous orbit system.
Mosaic System Template Filter Algorithms For Events With Changing Velocities
Laverne Hall
As a part of the ongoing studies for methods to improve signal processing capabilities for mosaic infrared sensor systems, many algorithms for filtering or separating background points from target points have been developed, namely n-order differencing and spatial filters. The need for improved background rejection performance has resulted in several recent innovative approaches, including the template filter algorithm. This paper evaluates the abilities of the template filter algorithm to further eliminate false track points using n-order temporal differencing as an integral part of its logic design for the case of an event of interest with changing velocity. In other words, it evaluates the algorithm's contributions to increased background and noise rejection capability and speed of processing which are very important to today's real-time signal processing systems. Section 1 of the paper gives an introduction and summary of the analysis results. Section 2 covers the logic of the template filter algorithm and the factors affecting its performance. Section 3 gives some of the results of the algorithm evaluation, and Section 4 takes a look at future considerations and implementations or modifications to the algorithm.
CO2 As An Inverse Greenhouse Gas
Sherwood B. Idso
It is a well-known fact that mankind's burning of fossil fuels such as coal, gas and oil has significantly increased the CO2 content of Earth's atmosphere, from something less than 300 ppm (parts per million by volume) in the pre-Industrial Revolution era to a con-centration which is currently somewhat over 340 ppm. It is also fairly well established that a concentration of 600 ppm will be reached sometime in the next century. Atmospheric scientists using complex computer models of the atmosphere have predicted that such a concentration doubling will lead to a calamatous climatic warming, due to the thermal infra-red "greenhouse" properties of CO2. However, my investigation of a large body of empirical evidence suggests just the opposite. Indeed, long-term records of surface air temperature and snow cover data indicate that increasing concentrations of atmospheric CO2 may actually tend to cool the Earth and not warm it. These and other observations of the real world lead to the conclusion that, for the present composition of the Earth's atmosphere, CO2 appears to behave as an inverse greenhouse gas. A mechanism for this phenomenon is suggested; and it is then indicated how enhanced concentrations of atmospheric CO2 may be beneficial for the planet, particularly with respect to the ability of enhanced CO2 concentrations to stimulate plant growth and reduce water requirements.
Thermal Patterns in Ice Under Dynamic Loading
Anatoly M. Fish, Stephen J. Marshall, Richard H. Munis
Heat emission patterns in the infrared spectrum were discovered in ice subjected to cyclic loading. The ice plates used in the tests had a rectangular shape of 13 x 19 cm and a thickness of 2 cm. The plates were frozen to the platen of the testing apparatus to form a cantilever beam and were vibrated over a frequency range from n.5 to 5 kHz at an ambient temperature of -4°C. The surface heat patterns were scanned by two thermal imaging systems with spectral hand passes of 2-5.6 pm and 8-14 μm, and the heat patterns were recorded on Polaroid film and on videotape. The heat emission patterns first appeared at the fixed end of the ice plate and migrated gradually to the free end. The temperature difference between the ends was found to depend on the duration and frequency of excitation. The results of these tests indicate that vihrothermography can have wide areas of practical application in the study of the origin and growth of defects, recrystallization, fatigue, and failure processes in ice.
Detailed Analysis Of 4.3-µm Earthlimb Data
J. B. Kumer, R. M. Nadile, W. Grieder
Spectral earthlimb emission data were obtained 28 September 1977 in the DNA sponsored Spectral Infrared Rocket Experiment (SPIRE) that was conducted by Air Force Geophysics Laboratory (AFGL) personnel, assisted by Utah State University (USU) personnel. Spectral radiance as a function of tangent altitude was obtained for four sunlit and eight dark data scans. This paper presents a detailed analysis of the non-LTE emission mechanisms, and the radiative transfer formulation, that is required to optimally model the 4.3- μm SPIRE data.
Infrared Imaging Techniques To Determine The Bond Integrity In High Density Lap Soldered Printed Circuit Boards
R. Paulson, H. Decker, J. Hodor, et al.
As the electronics world continues to increase in complexity, yet demanding reduced size and higher reliability, the problem of product assurance becomes more difficult. Inspection techniques must keep pace. To accomplish this, infrared techniques have been applied to the non-destructive analysis of high density, multi-layer printed circuit boards and in particular the area regarding the integrity of lap solder bonds. An 8 - 13 micron infrared scanner was used to observe the circuit boards while heat was flowing through the bonds under test. The general procedure was to actively apply heat or cold in some way to the component or to the circuit board and observe the rate of heat flow through the bonded leads. Fast flow indicated a good bond while slow flow a poor bond. All the leads to one component could be done at one glance. Although emissivity variations both from the material's differences and shape presented some problems, five different infrared techniques proved successful as applicable for NDT tests.
Properties And Applications Of Infrared Transparent And Electrically Conductive In2O3 Thin Film
Tze-Chiang Chen, Tso-ping Ma, Richard C. Barker, et al.
High quality infrared (1-12μ) transparent and electrically conductive thin films based on thermally evaporated In903 have been developed. Optical constants of these films have been obtained by the use or an iteration technique, which involves the formulas for multiple transmition and reflection. The details of the film deposition process and the theoretical foundation leading to its development are discussed in this paper. It has been found that the transparency and conductivity of these films is primarily due to high electron concen-tration and mobility. A multilayer design of a bandpass filter has been developed and implemented on ZnS and ZnSe substrates for the wavelength range of 8 to 12 μp. Typical transmittance of 65 to 80% with a film sheet resistance of 20 to 50 Ω/sq. has been achieved. Such a design is applicable to forward looking infrared (FLIR) systems where a window having both high electromegnetic (RF and microwave) shielding effectiveness and good in-frared transparency are required. The properties of these films lend themselves to many other potential applications.
Use Of Monte-Carlo Analysis In Estimating Yields Of Acceptable Infrared Detector Array Modules
Paul E. Thurlow
Production yield of acceptable focal plane infrared (IR) arrays may be minimal when performance specifications are severe. When anticipated yields are orders of magnitude below unity, the ability to estimate yields, and to identify production factors which can improve yields, assumes a particular importance. Since production yields as a function of focal plane array parameters cannot normally be computed analytically, empirical statistical methods must be developed, based primarily on numerical modeling and simulation, and confirmed by available spot-check measurements. This paper describes one method of estimating array yields, using a monte-carlo approach to model individual and combined photodiode performance in a statistical manner.
Thermal Modeling Of The Shuttle Infrared Telescope Facility
H. L. Gier, W. D. Taylor
The Shuttle Infrared Telescope Facility (SIRTF) is a cryogenically cooled telescope in the one-meter aperture class designed for sensing in the infrared from 2-200 pm. This facility is currently planned for multiple missions onboard the Space Shuttle with varying instrument complements. All components of the SIRTF within the field of view of the optics are cryogenically cooled. The baseline primary coolant is supercritical helium which is stored in an external tank and routed through the telescope-cooling the instruments, the optical components and the baffles. For detector cooling below 6K, small reservoirs of superfluid helium (Hell) are provided. The SIRTF was thermally modeled on the SINDA computer program both for steady state and transient solutions. The analysis shows that the baseline configuration has a large capacity for growth in cryogen requirements. A proportional controller model was developed for transient operations. The control system maintained the optics within all prescribed temperature limits except for certain combinations of transients involving a large step change in the power dissipation in the secondary mirror assembly and/or when the primary mirror was assumed to be constructed of quartz. The baseline SIRTF will perform the mission for which it was designed.
Cryogenic Telescope On The Infrared Astronomical Satellite (IRAS)
F. J. Low, C. A. Beichman, F. C. Gillett, et al.
The Infrared Astronomical Satellite (IRAS) has completed an unbiased all-sky survey at wavelengths from 10 to 100 um. The design and performance of the focal plane array is described with emphasis on in-orbit measurements of the sensitivity and stability. In the four broad spectral bands centered at 12, 25, 60 and 100 um the system NEFD values are, in Jy/Hz1/2,0.03, 0.025, 0.046 and 0.21 respectively (Jansky = 1E-26 w/m2/Hz). For point sources, a single scan at the survey rate of 3.8 arcmin/sec yields limiting flux densities at the 3 sigma confidence level of 0.36 , 0.30, 0.39 and 1.2 Jy. The DC stability of the JFET amplifiers and the excellent off-axis rejection of the telescope permit total flux meaurements of extended infrared emission at levels below 1 E 6 Jy/sr. Response of the extrinsic silicon and germanium photodetectors to ionizing radiation is described.
Preliminary Scientific Results From The First Six Months Of The Infrared Astronomy Satellite (IRAS)
B. T. Soifer, C. A. Beichman, J. R. Houck, et al.
The Infrared Astronomy Satellite (IRAS) was successfully launched on 25 January 1983. The goals of this joint US, Dutch, and British project were twofold. The first, and most important, goal was to perform an unbiased all-sky survey at wavelengths of 12, 25, 60, and 100 ,μm to establish the importance of infrared emission in the energy balance of the universe, to map the diffuse emission from the Galaxy and the material in the solar system, and to obtain low resolution spectra of the brightest sources identified at 12 and 25 4m. A second mission objective was to study specific known astronomical objects in more detail to gain higher sensitivity or higher spatial resolution than that achievable by normal survey observations.
Infrared Window Manufacturing Technology
Barry Robinson, Daniel R. Eastman, John Bacevic Jr., et al.
We discuss some new techniques being applied in the polishing, testing and coating of protective windows that function as integral components of high performance infrared sensor systems.
Spin Mount System - A Test System For An Infrared Sensor
Philip Pressel
The spin mount system for testing an infrared sensor assembly is a state-of-the-art test facility in which cryogen (gaseous helium at 5 K) is fed through a unique rotary coupling to a rotating infrared detector. The system is rotationally stable about its spin axis to less than +10 microradians while operating at 1500 rpm in air or vacuum, with cryogen flowing. Optical techniques are used to monitor the dynamic motion of the rotor. The project was sponsored by AEDC, Air Force System Command, USAF, Arnold Air Force Station, TN 27289, under Contract No. F40600-81-C-0015.
Near-Infrared Mapping Spectrometer Optical Subsystem Development and Testing
Steve A. Macenka
The Near-Infrared Mapping Spectrometer (NIMS) is one of the four remote-sensing science instruments of the Galileo Orbiter scientific payload. The NIMS scientific objectives re-quire operating the detector and optical subsystem at cryogenic temperatures. The necessity of assembling, aligning, and testing the optics at room temperature and meeting design speci-fications at the cryogenic operating temperature (130 K) presented a set of challenging technical problems. A systematic approach to the development of athermalized mounts and supporting structures for optical components is described. A technique utilizing the visible spectral range and supplementary ray-trace information for alignment of an infrared instrument is presented. The optical subsystem point-spread function and spatial and spectral resolution were determined at room temperature using selected spectral and spatial targets. Based on thermal-distortion analyses of the structure and mounts, compensators were selected, implemented, and verified at cryogenic temperatures. The selection of the compensator and the overall system performance were verified in a thermal vacuum chamber. Various external and internal calibration targets were used.
System Design Parameter Study For Shuttle Infrared Telescope Facility (SIRTF)
A. J. Mord, M. Bottema, W. P. Devereux, et al.
SIRTF is a high-sensitivity, cooled astronomical telescope operating from 2 to 1000 μm. The techniques used in analyzing the sensitivity of the SIRTF system performance to several technical issues are presented. Lowering the telescope temperature to near 4K is found to produce margin in several areas. A refined observing requirements model relieves the hardware performance requirements, and identifies extended source size/observing strategy as an important system specification. Other major conclusions are presented.
Gamma Ray Irradiated LEDs In Vacuum: Surface Emission And Significant Wavelength Tuning Via Surface States
N. S. Kopeika, S. Hava, I. Hirsh
Wavelength tuning via shallow junction GaAs LEDs as a result of y-irradiation is increased significantly when the irradiated LEDs are operated in vacuum. Vacuum operation is seen to be essentially equivalent to increased y-ray doseage for low irradiation levels as a result of desorptive processes common to both phenomena. They give rise to increased radiative surface recombination photon emission. It is this spectrum which is shifted according to changes in surface potential and forward voltage deriving from alterations in surface state populations. This technique is, in principle, a general technique independent of semiconductor material. It suggests the possibility of wavelength tuning via surface band bending changes deriving from surface electric field changes, as is done with MIS devices. Examination of irradiated diode properties in vacuum and under pressure permits greater insight into the basic nature of surface phenomena long suspected to play a significant role in the diode electronic property changes brought about by nuclear irradation.
Calculation Of Auroral Infrared Earthlimb Spatial Structure Based On All-Sky TV 4278 and 6300 Angstrom Measurements
J. B. Kumer, R. D. Sears, J. E. Evans, et al.
Successive "frames" of the auroral infrared earthlimb may be inferred from successive frame pairs of ground-based TV all-sky auroral data obtained at 4278 (blue) and 6300 A (red). Hence the name Blue Red Input Model (BRIM) is selected to refer to our model for the auroral infrared earthlimb. On a per pixel basis the total column energy deposition may be inferred from the electronically allowed 4278 A N2 (B→X) brightness 4πIB, and a measure of the altitude dependence of the energy deposition from the ratio IR/IB of the 6300-A 0(1D) brightness to the 4278-A brightness. Thus given the altitude dependence of the energy deposition over the entire sky, it is possible to employ the physics of the infrared aurora, as has been determined within the AFGL/DNA scientific community by analysis of data obtained via AFGL/DNA rocketborne infrared experiments, in order to dynamically construct the altitude dependence of infrared emission over the entire sky. The infrared earthlimb images are formed by performing integration of the instantaneous infrared emission along earthlimb viewing lines of sight through the emitting volume. Mechanisms we have considered for auroral infrared emission include vibraluminescence of NO(V) at -2.7 μM, chemiluminescence of CO2(v3) at 4.3 μm, and a prompt emission near 4.3 μm, which may be due to emission by NO+(V)and/or direct electron impact excitation of CO2(v3). Samples of auroral earthlimb radiance, and the corresponding spatial and temporal power spectral densities, which are calculated from 101 successive auroral 4278 and 6300 A all-sky TV images obtained 23 March 1973 over a 30-min interval at Chatanika, Alaska, are presented.