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  • Other Sources  (10,014)
  • EARTH RESOURCES AND REMOTE SENSING  (4,547)
  • SPACECRAFT PROPULSION AND POWER  (2,796)
  • INSTRUMENTATION AND PHOTOGRAPHY  (2,671)
  • Chemical Engineering
  • 2010-2014
  • 1990-1994  (4,642)
  • 1980-1984  (5,372)
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Year
  • 101
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    Using calibrated SAR data (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A number of approaches for calibrating SAR imaging data including data from multipolarization and multifrequency systems developed at the Jet Propulsion Laboratory are discussed. It is shown how calibrated SAR data can be used to improve the understanding of the physical properties of the earth's surface layer and how calibration uncertainties and system noise should be handled by the SAR data user. Examples of calibrated SAR data from the NASA/JPL DC-8 SAR are used to demonstrate use of calibrated data to monitor temporal change and to improve the classification of land cover type.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Synthetic aperture radar; Proceedings of the Meeting, Los Angeles, CA, Jan. 20, 21, 1992 (A93-32508 12-32); p. 224-234.
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  • 102
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    Hot rocket plume experiment - Survey and conceptual design (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Attention is given to a space-borne engine plume experiment study to fly an experiment which will both verify and quantify the reduced contamination from advanced rhenium-iridium earth-storable bipropellant rockets (hot rockets) and provide a correlation between high-fidelity, in-space measurements and theoretical plume and surface contamination models. The experiment conceptual design is based on survey results from plume and contamination technologists throughout the U.S. With respect to shuttle use, cursory investigations validate Hitchhiker availability and adaptability, adequate remote manipulator system (RMS) articulation and dynamic capability, acceptable RMS attachment capability, adequate power and telemetry capability, and adequate flight altitude and attitude/orbital capability.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: In: Optical system contamination: Effects, measurement, control III, Proceedings of the Meeting, San Diego, CA, July 23, 24, 1992 (A93-32476 12-19); p. 2-13.
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  • 103
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    Pressure oscillations in post-Challenger Space Shuttle redesigned solid rocket motors (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 9; 2; p. 217-221.
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  • 104
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    Evaluation of the Munich Method for modeling rocket engine performance (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A new procedure, dubbed the Munich Method, has been proposed recently for the modeling of rocket engine performance. The author of the Munich Method claims it to be an extension and improvement of the thermodynamic procedures used to model rocket engines in the NASA-Lewis chemical equilibrium program. An examination of the Munich Method shows that it contains several flaws. If these defects are corrected then the Munich Method will produce results identical to those generated by the NASA-Lewis Code.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 9; 2; p. 191-196.
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  • 105
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    Modelling, calibration, and error analysis of seven-hole pressure probes (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This report describes the calibration of a nonnulling, conical, seven-hole pressure probe over a large range of flow onset angles. The calibration procedure is based on the use of differential pressures to determine the three components of velocity. The method allows determination of the flow angle and velocity magnitude to within an average error of 1.0 deg and 1.0 percent, respectively. Greater accuracy can be achieved by using high-quality pressure transducers. Also included is an examination of the factors which limit the use of the probe, a description of the measurement chain, an error analysis, and a typical experimental result. In addition, a new general analytical model of pressure probe behavior is described, and the validity of the model is demonstrated by comparing it with experimentally measured calibration data for a three-hole yaw meter and a seven-hole probe.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Experiments in Fluids (ISSN 0723-4864); 14; 1-2; p. 104-120.
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  • 106
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    An airborne system for collecting polarization imagery (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This paper describes a recently completed electrooptical camera flying onboard the NASA ER-2 high altitude aircraft. The device includes a six-position filter wheel which can be fitted with a combination of polarizing and/or spectral filters. An alternate configuration will include a polarizing filter which can be rotated to any angle under computer control. The camera mount in the nose of the ER-2 can tilt forward or aft up to 40 degrees, both for bidirectional reflectance studies and for image motion compensation (the aircraft moves 34 meters between frame acquisitions). The ground resolution is nominally 5 meters from and altitude of 20 km. Spectral responsivity is that of the silicon imaging array (Kodak KAF-1400). Initial data sets were acquired in support of the International Satellite Cloud Climatology Program Regional Experiment of November, 1991, and will be used to study cirrus cloud properties.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Polarization and remote sensing; Proceedings of the Meeting, San Diego, CA, July 22, 23, 1992 (A93-30026 11-35); p. 200-204.
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  • 107
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    The microstrip proportional counter (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Microstrip detectors in which the usual discrete anode and cathode wires are replaced by conducting strips on an insulating or partially insulating substrate are fabricated using integrated circuit-type photolithographic techniques and hence offer very high spatial accuracy and uniformity, together with the capability of producing extremely fine electrode structures. Microstrip proportional counters have now been variously reported having an energy resolution of better than 11 percent FWHM at 5.9 keV. They have been fabricated with anode bars down to 2 microns and on a variety of substrate materials including thin films which can be molded to different shapes. This review will examine the development of the microstrip detector with emphasis on the qualities which make this detector particularly interesting for use in astronomy.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: EUV, X-ray, and gamma-ray instrumentation for astronomy III; Proceedings of the Meeting, San Diego, CA, July 22-24, 1992 (A93-29476 10-35); p. 96-103.
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  • 108
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    Experimental demonstration of a star-field identification algorithm (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A fault-tolerant, six-feature, all-sky star-field identification algorithm has been integrated with a CCD-based imaging camera. This autonomous intelligent camera identifies in real time any star field without a priori knowledge and requires a reference catalog incorporating fewer than 1000 stars. Observatory tests on star fields with this intelligent camera are described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optics Letters (ISSN 0146-9592); 18; 6; p. 402-404.
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  • 109
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    Laser absorption measurements of OH concentration and temperature in pulsed facilities (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA Journal (ISSN 0001-1452); 31; 3; p. 491-498.
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  • 110
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    Progress in laser spectroscopic techniques for aerodynamic measurements - An overview (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA Journal (ISSN 0001-1452); 31; 3; p. 465-477.
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  • 111
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    Aero-optical phase measurements using Fourier transform holographic interferometry (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA Journal (ISSN 0001-1452); 31; 3; p. 426-433.
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  • 112
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    Automated anomaly detection for Orbiter High Temperature Reusable Surface Insulation (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The description, analysis, and experimental results of a method for identifying possible defects on High Temperature Reusable Surface Insulation (HRSI) of the Orbiter Thermal Protection System (TPS) is presented. Currently, a visual postflight inspection of Orbiter TPS is conducted to detect and classify defects as part of the Orbiter maintenance flow. The objective of the method is to automate the detection of defects by identifying anomalies between preflight and postflight images of TPS components. The initial version is intended to detect and label gross (greater than 0.1 inches in the smallest dimension) anomalies on HRSI components for subsequent classification by a human inspector. The approach is a modified Golden Template technique where the preflight image of a tile serves as the template against which the postflight image of the tile is compared. Candidate anomalies are selected as a result of the comparison and processed to identify true anomalies. The processing methods are developed and discussed, and the results of testing on actual and simulated tile images are presented. Solutions to the problems of brightness and spatial normalization, timely execution, and minimization of false positives are also discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Cooperative intelligent robotics in space III; Proceedings of the Meeting, Boston, MA, Nov. 16-18, 1992 (A93-29101 10-54); p. 330-340.
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  • 113
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    On Capaciflector sensor data interpretation using the constrained deconvolution algorithm (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Capaciflector, a capacitive proximity sensor, is being developed by NASA for collision avoidance. Capaciflector provides a single output value as measure of altered base frequency. This value is a characteristic of an external object in the sensor's field of view. An attempt is made to use the Capaciflector for imaging with operating range from 1 to 2 inches. By positional arangement of sensors in a grid pattern and electronic activation of sensors over the grid one at a time an object characteristic image is obtained. The article describes the Capaciflector experimental imaging system and preliminary results obtained by the system.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Cooperative intelligent robotics in space III; Proceedings of the Meeting, Boston, MA, Nov. 16-18, 1992 (A93-29101 10-54); p. 13-24.
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  • 114
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    Exploratory geological analysis of AVIRIS data (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The size and complexity of AVIRIS data sets makes analysis difficult. We present a technique that allows the researcher to rapidly scan the full data set in image form in order to empirically find significant spatial patterns anywhere across the spectrum. Our approach takes advantage of the speed and power of computer graphics workstations to allow real-time, interactive data manipulation and display. Empirical data selection avoids the bias inherent in theoretical selection criteria, and allows discovery of unexpected relationships within the data set. Link Winds, a prototype data analysis system under development, provides the visualization tools used in this study. We are applying this approach to geological studies in the eastern Mojave Desert.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 423-426.
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  • 115
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    Comparison of three atmospheric correction models for a vegetated airborne visible/infrared imaging spectrometer (AVIRIS) scene (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Current atmospheric correction models applied to imaging spectroscopy data include such methods as residual or scene average, flat field correction, regression method or empirical line algorithm, the continuum interpolated band ratio (CIBR) derivation and the LOWTRAN 7 method. Due to the limitations of using residual and flat field corrections on vegetated scenes, three methods will be compared: regression, CIBR derivation and LOWTRAN 7. Field-measured bright and dark targets taken at the time of the 13 April, 1989 AVIRIS overflight of Jasper Ridge, California were used to formulate the regression method atmospheric correction. Using this corrected scene as 'ground truth', the CIBR derivation and the LOWTRAN 7 method with both input models are compared on the vegetated Jasper Ridge scene. Although representing a qualitative approach, this is a first approximation and shows the need for more quantitative analysis.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 413-421.
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  • 116
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    Regional exploration in desert terrains - A guide to the use of Landsat Thematic Mapper imagery (1991)
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    Publication Date: 2011-08-24
    Description: This paper provides a guide for the acquisition, processing, and interpretation of Landsat Thematic Mapper (TM) imagery of desert terrains for use in regional exploration. Sun angle considerations, data quality cautions, noise suppression routines, band selections, data calibration, spectral enhancements, perceptual considerations of displays, and general interpretation guidelines are all discussed as components of an image-information extraction procedure.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 277-285.
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  • 117
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    Utilization of biosensors and chemical sensors for space applications (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: There will be a need for a wide array of chemical sensors for biomedical experimentation and for the monitoring of water and air recycling processes on Space Station Freedom. The infrequent logistics flights of the Space Shuttle will necessitate onboard analysis. The advantages of biosensors and chemical sensors over conventional analysis onboard spacecraft are manifold. They require less crew time, space, and power. Sample treatment is not needed. Real time or near-real time monitoring is possible, in some cases on a continuous basis. Sensor signals in digitized form can be transmitted to the ground. Types and requirements for chemical sensors to be used in biomedical experimentation and monitoring of water recycling during long-term space missions are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Biosensors and Bioelectronics (ISSN 0956-5663); 7; 8; p. 535-548.
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  • 118
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    Selection of LCTV operating curves for input and filter (1992)
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    Publication Date: 2011-08-24
    Description: A liquid crystal television (LCTV) SLM's phase, amplitude, and polarization all influence our selection of operating curves for input and filter. With its continuum of drive voltage, the LCTV permits grey-level control in both locations. Selection of an optimum curve depends on expected variations in signal amplitude, presence of input scene structured noise, and other factors. Using modulators obtained from a commercially available projection LCTV, and with no specifically added input noise present, we have obtained laboratory results in which the ratio of peak intensity to correlator system noise exceeded 100:1. Unfortunately, it was massively inefficient to implement the algorithm which had been developed as the abstract for this paper was submitted. Fortunately, we have quite recently developed two insights that will speed it by several orders of magnitude, and we shall report that result in the future. We will also extend the work to include clutter objects and additive input scene noise.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Optical pattern recognition III; Proceedings of the Meeting, Orlando, FL, Apr. 21, 22, 1992 (A93-28672 10-63); p. 78-82.
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  • 119
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    Power systems for the Mars Environmental Survey (MESUR) Mission (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Mars Environmental Survey Mission (MESUR) is intended to be a low cost, near term mission to study the chemical composition of Martian surface, structure and circulation of Mars' atmosphere, and the structure and dynamics of Mars' interior. To meet the science objectives of the mission, a network of 16 landers will be placed at various latitudes and longitudes of Mars. The paper identifies various options for powering the landers and lists the attributes of each option. The current strategy is to precede the lander launch and deployment with an engineering demo mission called the Pathfinder which would demonstrate the landing strategy and the engineering subsystems. The paper briefly describes the challenges involved in the power system development for the Pathfinder mission.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 1 (A93-25851 09-44); p. 1.313-1.318.
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  • 120
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    Space micro-guidance and control - Applications and architectures (1992)
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    Publication Date: 2011-08-24
    Description: The features and the components of a new microscale guidance, navigation, and control (GN&C) system for future space systems are discussed. An approach is described for the utilization of new microengineering technologies for achieving major reductions in the GN&C system's mass, size, power, and costs. The micro-GN&C system and the component concepts include microactuated adaptive optics, micromachined inertial sensors, fiberoptic data nets with light-power transmission, and VLSI microcomputers. The GN&C system will be applied in microspacecraft, microlanders, microrovers, remote sensing platforms, interferometers, and deployable reflectors.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Sensors and sensor systems for guidance and navigation II; Proceedings of the Meeting, Orlando, FL, Apr. 22, 23, 1992 (A93-28151 10-35); p. 144-158.
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  • 121
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    Commercial applications multispectral sensor system (1992)
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    Publication Date: 2011-08-24
    Description: NASA's Office of Commercial Programs is funding a multispectral sensor system to be used in the development of remote sensing applications. The Airborne Terrestrial Applications Sensor (ATLAS) is designed to provide versatility in acquiring spectral and spatial information and will be a test bed for the development of specifications for airborne and spaceborne remote sensing instrumentation for dedicated applications. This objective requires spectral coverage from the visible through thermal IR wavelengths, variable spatial resolution form 2-25 meters; high geometric and geolocation accuracy; on-board radiometric calibration; digital recording; and optimized performance for minimized cost, size, and weight.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Small satellite technologies and applications II; Proceedings of the Meeting, Orlando, FL, Apr. 21, 22, 1992 (A93-28076 10-12); p. 63-74.
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  • 122
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    Photovoltaic Array Space Power flight experiment plus diagnostics (PASP+) modules (1992)
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    Publication Date: 2011-08-24
    Description: The Photovoltaic Array Space Power Plus Diagnostics flight experiment (PASP+) subsumes twelve solar array modules which represent the state of the art in the space photovoltaic array industry. Each of the twelve modules individually feature specific photovoltaic technologies such as advanced semiconductor materials, multi-bandgap structures, lightweight array designs, advanced interconnect technologies, or concentrator array designs. This paper will describe each module in detail including the configuration, components, materials, anticipated on orbit performance, and some of the aspects of each array technology. The layout of each module and the photovoltaic cells or array cross section will be presented graphically. A discussion on the environmental constraints and materials selection will be included as well as a delineation of the differences between the modules and the baseline array configuration in its intended application.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 1 (A93-25851 09-44); p. 1.295-1.301.
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  • 123
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    Geologic process studies using Synthetic Aperture Radar (SAR) data (1992)
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    Publication Date: 2011-08-24
    Description: The use of SAR data to study geologic processes for better understanding of recent tectonic activity and climate change as well as the mitigation of geologic hazards and exploration for nonrenewable resources is discussed. The geologic processes that are particularly amenable to SAR-based data include volcanism; soil erosion, degradation, and redistribution; coastal erosion and inundation; glacier fluctuations; permafrost; and crustal motions. When SAR data are combined with data from other planned spaceborne sensors including ESA ERS, the Japanese Earth Resources Satellite, and the Canadian Radarsat, it will be possible to build a time-series view of temporal changes over many regions of earth.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Episodes (ISSN 0705-3797); 15; 1; p. 21-31.
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  • 124
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    Measurement of subresolution terrain displacements using SPOT panchromatic imagery (1992)
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    Publication Date: 2011-08-24
    Description: SPOT panchromatic imagery is used to measure subresolution horizontal terrain displacements that are associated with earthquakes, sand dune migration, coastal processes, and glacial motion. The approach is aimed at detecting and measuring surface processes by statistically matching the radiometric patterns in the data that differ spatially in a consistent direction over many pixels. Data obtained from the satellite-derived imagery can facilitate the understanding of natural hazards and the determination of the rates of many environmental processes worldwide.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Episodes (ISSN 0705-3797); 15; 1; p. 56-61.
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  • 125
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    Automated absolute phase retrieval in across-track interferometry (1992)
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    Publication Date: 2011-08-24
    Description: Discussed is a key element in the processing of topographic radar maps acquired by the NASA/JPL airborne synthetic aperture radar configured as an across-track interferometer (TOPSAR). TOPSAR utilizes a single transmit and two receive antennas; the three-dimensional target location is determined by triangulation based on a known baseline and two measured slant ranges. The slant range difference is determined very accurately from the phase difference between the signals received by the two antennas. This phase is measured modulo 2pi, whereas it is the absolute phase which relates directly to the difference in slant range. It is shown that splitting the range bandwidth into two subbands in the processor and processing each individually allows for the absolute phase. The underlying principles and system errors which must be considered are discussed, together with the implementation and results from processing data acquired during the summer of 1991.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1582-1584.
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  • 126
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    Albedo patterns and gypsum generation in the central Namib Desert - Land, sea and air interactions on an arid West Coast (1992)
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    Publication Date: 2011-08-24
    Description: In the central Namib Desert, dune-free surfaces are separated abruptly from a sea of yellow and red sand dunes at the Kuiseb River canyon. The off-white hues of the dune-free area result from anomalously high surficial gypsum enrichment. Satellite imagery indicates that the gypsum surfaces are associated with lower surface maximum temperatures than those of the darker dune surfaces to the south. One of various sources of sulfate for the gypsum bodies is oceanic H2S, supplied to desert land-surfaces by regular fog incursions. Since fog events are widespread along the coast, the question of anomalous gypsum accumulations north of the dune sea arises. Satellite imagery, in conjunction with more detailed handheld photography from the space shuttle, indicates that the penetration of fog inland is significantly greater over the gypsum surfaces than it is over the dunes. It is postulated that the thermal gradient between these surfaces generates a heat low centered over the northern part of dune sea and that this enhances fog and H2S advection on its north side onto the nearby dune-free zone. In such a system, gypsum/caliche surfaces reinforce advection of fog over themselves in a positive feedback mode.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1565-1567.
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  • 127
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    Radiometric gains of satellite sensors of reflected solar radiation - Results from NASA ER-2 aircraft measurements (1992)
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    Publication Date: 2011-08-24
    Description: A method for using congruent aircraft-satellite observations to calibrate a satellite sensor is presented. A calibrated spectroradiometer at an altitude of 19 km above White Sands, NM, is oriented to view White Sands at the satellite overpass time along the same view vector as the satellite sensor. Collected data are transformed into corresponding estimates of sensor band radiance at the satellite (derived from the aircraft measurements), and average count (from the sensor measurements). These are both averaged across the footprint of the spectroradiometer. Results are presented for the evolution of NOAA-11 Advanced Very High Resolution Radiometer (AVHRR) (Bands 1 and 2) gain between November 1988 and October 1990, and for GOES-6 and GOES-7 VISSR/VAS visible bands during the same period. Estimates of uncertainty in the results are presented, as well as ideas for their reduction in future flights.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 802-805.
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  • 128
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    LAI inversion from optical reflectance using a neural network trained with a multiple scattering model (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The inversion of the leaf area index (LAI) canopy parameter from optical spectral reflectance measurements is obtained using a backpropagation artificial neural network trained using input-output pairs generated by a multiple scattering reflectance model. The problem of LAI estimation over sparse canopies (LAI 〈 1.0) with varying soil reflectance backgrounds is particularly difficult. Standard multiple regression methods applied to canopies within a single homogeneous soil type yield good results but perform unacceptably when applied across soil boundaries, resulting in absolute percentage errors of 〉1000 percent for low LAI. Minimization methods applied to merit functions constructed from differences between measured reflectances and predicted reflectances using multiple-scattering models are unacceptably sensitive to a good initial guess for the desired parameter. In contrast, the neural network reported generally yields absolute percentage errors of 〈30 percent when weighting coefficients trained on one soil type were applied to predicted canopy reflectance at a different soil background.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 757-759.
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    Inferring total canopy APAR from PAR bidirectional reflectances and vegetation indices in tallgrass prairie (1992)
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    Publication Date: 2011-08-24
    Description: The fraction of photosynthetically active radiation (PAR) absorbed by a vegetated canopy (APARc) or landscape (APARs) is a critical parameter in climate processes. A grassland study examined: 1) whether APARs can be estimated from PAR bidirectional exitance fractions; and 2) whether APARs is correlated with spectral vegetation indices (SVIs). Data were acquired with a high resolution continuous spectroradiometer at 4 sun angles on grassland sites. APARs was computed from the scattered surface PAR exitance fractions. The nadir APARs value was the most variable diurnally; it provided a good estimate of the average surface APARs at ~95 percent. APARc was best represented by exitance factors between 30-60* forward.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 749-751.
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    The NASA/JPL three-frequency polarimetric AIRSAR system (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The NASA/Jet Propulsion Laboratory Airborne Synthetic Aperture Radar (JPL AIRSAR) system has now completed four flight campaigns. The authors describe the current state of this system and provide insight into how flight seasons are planned for this instrument. The data processors and data products are described. A table containing relevant system parameters is provided.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 649-651.
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    Monitoring of environmental conditions in the Alaskan forests using ERS-1 SAR data (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Preliminary results from an analysis of the multitemporal radar backscatter signatures of tree species acquired by European Remote Sensing Satellite (ERS-1) synthetic aperture radar (SAR) data are presented. Significant changes in radar backscatter are detected. Correlation of these differences with ground truth observations indicate that these are due to changes in soil and liquid water content as a result of freeze/thaw events. C-band observations acquired by the NASA/Jet Propulsion Laboratory Airborne SAR (JPL AIRSAR) instrument demonstrate the potential of a C-band radar instrument to monitor drought/flood events. The potential of ERS-1 for monitoring phenologic changes in the forest and for classifying tree species is less promising.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 530-532.
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  • 132
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    An investigation of the relationship between tree water potential and dielectric constant (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An experiment that has been performed to verify the relationship between the dielectric constant of several tree species and their respective water potentials is described. The water potential, xylem flow and dielectric properties of five tree species were continuously monitored while simultaneously manipulating canopy transpiration and water status. An analysis of the data recorded during these manipulations is presented. Results of this analysis demonstrate a clear coincidence of change in dielectric constant and water status. The implication of this relationship for the utilization of remotely sensed data to study canopy water relations is explored. Preliminary backscatter modeling results demonstrate that the changes in dielectric constant that occur as a result of changes in water status are significant enough to be observable with microwave radar.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 523-525.
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  • 133
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    Radiometric correction of SAR images of varying terrain heights (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The advantages and disadvantages of three different approaches to solving the problem of the radiometric correction of synthetic aperture radar (SAR) images of varying terrain heights are presented. The first approach involves registration of a digital elevation model (DEM) of the terrain to the image, determination of the local elevation and incidence angles, and appropriate radiometric correction. The second approach uses a DEM generated from interferometric SAR data to derive the elevation and incidence angle maps. In the third approach, a monopulse technique is employed to determine the elevation angle only. The relative errors in radiometric correction between these approaches are assessed. Calibration errors are estimated using corner reflectors deployed within some of the scenes imaged by the Jet Propulsion Laboratory airborne SAR (JPL AIRSAR).
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 271-273.
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    Ground support for Space Shuttle earth observations by the NASA environment remote sensing analysis facility (ERSAF) (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The functions and capabilities of the NASA Environment Remote Sensing Analysis Facility (ERSAF) located at the Johnson Space Center are described. ERSAF provides dedicated support to earth-observation activities and Earth-looking payloads conducted aboard the Space Shuttle. This support merges environmental satellite imagery with high-resolution film products and digital imagery acquired aboard the Space Shuttle. ERSAF utilizes several computer systems with specialized software to process and analyze environmental information as well as data acquired from the Space Shuttle. These computer systems and the image analysis capabilities are discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 158-160.
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  • 135
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    The NASA Electronic Still Camera system (1992)
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    Publication Date: 2011-08-24
    Description: The Electronic Still Camera (ESC) project has been implemented in its first form for space shuttle operations. The system is composed of three components: (1) a hand-held battery-operated fully digital and programmable high-resolution camera; (2) a laptop-computer-based playback/downlink unit for onboard image processing; and (3) a ground station capable of receiving shuttle data, processing images, producing hardcopies, and distributing the data and hardcopies to end users. The advantages of the ESC system over film and satellites are discussed, and system specifications are summarized.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 149-151.
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  • 136
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    Relative phase calibration of the NASA/DC-8 three-frequency polarimetric SAR system (1992)
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    Publication Date: 2011-08-24
    Description: Relative phase calibration of radar polarimetry data may be achieved by utilizing the phase information of the receiver calibration tone and knowledge of the antenna path differences among channels measured upon installation of the radar polarimeter. This calibration method does not require any assumptions on the scattering behavior of the scene. This method of phase calibration may be verified by examining the polarization signatures of calibration instruments such as the trihedral corner reflectors.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 104, 105.
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  • 137
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    ESTAR - A synthetic aperture microwave radiometer for measuring soil moisture (1992)
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    Publication Date: 2011-08-24
    Description: The measurement of soil moisture from space requires putting relatively large microwave antennas in orbit. Aperture synthesis, an interferometric technique for reducing the antenna aperture needed in space, offers the potential for a practical means of meeting these requirements. An aircraft prototype, electronically steered thinned array L-band radiometer (ESTAR), has been built to develop this concept and to demonstrate its suitability for the measurement of soil moisture. Recent flights over the Walnut Gulch Watershed in Arizona show good agreement with ground truth and with measurements with the Pushbroom Microwave Radiometer (PBMR).
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 483-485.
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  • 138
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    Dielectric measurement using an open ended coaxial line with an extended center conductor (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Permittivity may be determined by measuring the complex reflection coefficient of an open-ended coaxial line placed in contact with a test sample. This method works best for liquid samples. For the measurement of non-liquid materials problems can arise. A perfect preparation is needed to provide a good contact between the tip and the dielectric medium. At times, the dimension of the sensor cannot be freely chosen, as is the case for the measurement of the dielectric constant of the xylem layer of a living tree. The influence of the installation of the sensor on a tree's water status must be minimized by using a small sensor. In such cases the capacitance cannot be optimized. By extending the center conductor of the open-ended coaxial line, some of these problems can be avoided. This provides an additional tool to tune the capacitance of the sensor by adjusting the length of the extension. Therefore the measurement accuracy can be optimized. The sensor also becomes sensitive to a larger volume. A comparative study of a flush and extended tipped probes shows that the ability to measure the dielectric constant of trees has been notably increased due to the extension of the center conductor.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 443-445.
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  • 139
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    Topographic mapping from ERS-1 and SEASAT radar interferometry (1992)
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    Publication Date: 2011-08-24
    Description: A radar interferometric technique for topographic mapping of surfaces yields a high resolution, globally consistent approach to generation of digital elevation models. The technique is illustrated with maps generated from SEASAT and European Space Agency Remote Sensing Satellite (ERS-1) data. A SEASAT interferometric image of a forested area which includes some unvegetated lava flows is analyzed. An analysis of errors expected from application of the technique to maps generated from ERS-1 data is presented. An orbital scenario for a global mapping mission is outlined.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 387, 388.
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  • 140
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    Measurement and analysis of a small nozzle plume in vacuum (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 9; 4; p. 646-648. Abridged
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  • 141
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    Multispectral thermal infrared mapping of the 1 October 1988 Kupaianaha flow field, Kilauea volcano, Hawaii (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Multispectral thermal infrared radiance measurements of the Kupaianaha flow field were acquired with the NASA airborne Thermal Infrared Multispectral Scanner (TIMS) on the morning of 1 October 1988. The TIMS data were used to map both the temperature and emissivity of the surface of the flow field. The temperature map depicted the underground storage and transport of lava. The presence of molten lava in a tube or tumulus resulted in surface temperatures that were at least 10 C above ambient. The temperature map also clearly defined the boundaries of hydrothermal plumes which resulted from the entry of lava into the ocean. The emissivity map revealed the boundaries between individual flow units within the Kupaianaha field. Distinct spectral anomalies, indicative of silica-rich surface materials, were mapped near fumaroles and ocean entry sites. This apparent enrichment in silica may have resulted from an acid-induced leaching of cations from the surfaces of glassy flows.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Bulletin of Volcanology (ISSN 0258-8988); p. 33-44.
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  • 142
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    The effect of topography on radar scattering from vegetated areas (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This paper shows how the radar scattering from vegetated areas is affected by the topography of the surface underneath the vegetation. It is shown, using a discrete scatterer model, that the dominant scattering mechanism may change drastically when the ground surface is tilted relative to the horizontal. In the case of a horizontal ground surface, total scattering may be dominated by scattering off the tree trunks, followed by a reflection off the ground surface. For a relatively small tilt in the ground surface (about 2 deg from horizontal), the ground-trunk interaction term may be replaced by scattering from the branches alone as the dominant scattering mechanism. We also show that the effect of the topography is more pronounced for scattering by longer wavelengths, and discuss the implications on algorithms designed to infer forest woody biomass and soil and vegetation moisture using polarimetric SAR data. The effect of the topography on the scattering behavior from forested areas is illustrated with images acquired by the NASA/JPL three-frequency polarimetric SAR over the Black Forest in Germany.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 31; 1; p. 153-160.
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  • 143
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    Aircraft laser infrared absorption spectrometer (ALIAS) for polar ozone studies (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: 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.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Infrared technology XVII; Proceedings of the Meeting, San Diego, CA, July 22-26, 1991 (A93-38376 15-35); p. 187-194.
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    Calibration of a synthetic aperture radiometer (1993)
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    Publication Date: 2011-08-24
    Description: Calibration algorithms for a synthetic aperture microwave radiometer are presented. The calibration is geared to Earth remote sensing applications, and is demonstrated on an airborne prototype of thinned array imager. Two approaches to the system calibration are presented; the first utilizes commonly available reference brightness temperature scenes, such as open water, and the second utilizes data collected on the antenna range. Both algorithms yield spatial response information which is cast in matrix form and inverted to obtain the image reconstruction formula. Experimental results are examined, and errors in some reconstructed images are linked to the present prototype antenna design. Algorithms for improving the synthesized antenna pattern side lobe performance are also presented. In one solution, the pattern efficiency is optimized by minimizing the pattern outside a defined beam. In another solution, the patterns are matched to a desired model pattern by the method of least squared errors. Both techniques offer an attractive alternative to aperture weighting.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 31; 1; p. 257-267.
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  • 145
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    Correction-free radiometry on specular spheres for containerless processing in microgravity (1992)
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    Publication Date: 2011-08-24
    Description: An analysis is presented that establishes how correction-free radiance measurements or pyrometry can be performed on targets in furnaces where there may be significant additional radiance from heated furnace walls or from reflecting surfaces close to the target. These configurations are common in microgravity and containerless processing applications where a specular target is radiantly heated in a hot-wall furnace, or inductively heated from the fields arising from nearby closely spaced electromagnetic coils. Proper design requires that the pyrometer does not view any images of the background features in the specular target so that stray radiation will not be reflected into the viewing optics of the pyrometer. To analyze the problem, conventional paraxial optics analysis is shown to be significantly in error. Instead a method of nonparaxial ray tracing, based on the derivatives of the ray paths, shows how the images must be located. This leads to analytical results that can be used to design such systems. The findings are applied to the furnace geometries that are presently being considered for flight in LEO.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 63; 11; p. 5394-5402.
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  • 146
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    Microwave soil moisture estimation in humid and semiarid watersheds (1993)
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    Publication Date: 2011-08-24
    Description: Land surface hydrologic-atmospheric interactions in humid and semi-arid watersheds were investigated. Active and passive microwave sensors were used to estimate the spatial and temporal distribution of soil moisture at the catchment scale in four areas. Results are presented and discussed. The eventual use of this information in the analysis and prediction of associated hydrologic processes is examined.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Advances in Space Research (ISSN 0273-1177); 13; 5; p. 115-118.
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  • 147
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    Quantitative measurement of in-plane acoustic field components using surface-mounted fiber sensors (1993)
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    Publication Date: 2011-08-24
    Description: Extrinsic Fabry-Perot interferometric sensors have been used to obtain calibrated, quantitative measurements of the in-plane displacement components associated with the propagation of ultrasonic elastic stress waves on the surfaces of solids. The frequency response of the sensor is determined by the internal spacing between the two reflecting fiber endface surfaces which form the Fabry-Perot cavity, a distance which is easily controlled during fabrication. With knowledge of the material properties of the solid, the out-of-plane displacement component of the wave may also be determined, giving full field data.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Fiber optic smart structures and skins V; Proceedings of the Meeting, Boston, MA, Sept. 8, 9, 1992 (A93-37326 14-35); p. 144-152.
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  • 148
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    Use of Spectralon as a diffuse reflectance standard for in-flight calibration of earth-orbiting sensors (1993)
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    Publication Date: 2011-08-24
    Description: Spectralon, a commercially available diffuse reflectance material made from polytetrafluoroethylene (PTFE), is being evaluated for the multiangle imaging spectroradiometer (MISR), currently under development for the Earth Observing System. Results of a series of environmental exposure tests indicate that no degradation of the optical properties was apparent following proton bombardment, and stability through UV illumination was satisfactory, provided simple cleaning and handling procedures were implemented. A buildup of several thousand volts of static charge was found to develop while simulating a rare pass through an auroral storm.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering (ISSN 0091-3286); 32; 4; p. 805-814.
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  • 149
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    Development and flight history of the SERT II spacecraft (1993)
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    Publication Date: 2011-08-24
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 30; 3; p. 258-290.
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  • 150
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    Regional studies of the land surface using space-based means (1993)
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    Publication Date: 2011-08-24
    Description: Regional ecological studies are considered in the context of the global change problem. The Kursk-91 international experiment is used to illustrate applications of remote sensing data and data bases of field experiments for assessment of parameters of the state of the soil and vegetative cover and subsequent study of biospheric stability on the basis of regular satellite observations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Issledovanie Zemli iz Kosmosa (ISSN 0205-9614); 2Apr; p. 63-75.
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  • 151
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    Astronaut observations of the Persian (Arabian) Gulf during STS-45 (1992)
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    Publication Date: 2011-08-24
    Description: As a result of the 1991 Persian Gulf war, between mid-January and June 1991, the Persian Gulf was contaminated with an estimated 4 to 6 million barrels of crude oil, released directly into the Gulf from refinement facilities, transhipment terminals, and moored tankers along the coast of Kuwait, and precipitated from oil fire smoke plumes. To assess the environmental impact of the oil, an international team of marine scientists representing 14 nations was assembled under the auspices of the United Nations International Oceanic Commission and the Regional Organization for Protection of the Marine Environment to conduct detailed surveys of the Persian Gulf, the Strait of Hormuz, and the Gulf of Oman, including hydrographic, chemical, and biological measurements. To supplement the field surveys and to serve as an aid in data interpretation, astronauts aboard the Space Shuttle Atlantis photographed water features and coastal habitats in the Persian Gulf during mission STS-45 (24 March to 02 April 1992). The astronauts collected 111 hand-held, color photographs of the Gulf (72 70-mm photographs and 39 5-inch photographs) from an altitude of 296 km (160 n.mi.). The photographs reveal distributions in water turbidity associated with outflow from the Shatt-al-Arab and water circulation along the entire coast of Iran and the Strait of Hormuz, coastal wetlands and shallow-water habitats, and sticks appearing in the sunglint pattern, which appear to be oil.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geocarto International (ISSN 1010-6049); 7; 4; p. 59-68.
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  • 152
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    Earth observations during Space Shuttle mission STS-45 Mission to Planet Earth - March 24-April 2, 1992 (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A description is presented of the activities and results of the Space Shuttle mission STS-45, known as the Mission to Planet Earth. Observations of Mount St. Helens, Manila Bay and Mt. Pinatubo, the Great Salt Lake, the Aral Sea, and the Siberian cities of Troitsk and Kuybyshev are examined. The geological features and effects of human activity seen in photographs of these areas are pointed out.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geocarto International (ISSN 1010-6049); 7; 4; p. 69-80.
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  • 153
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    The simulation of multispectral composite satellite imagery on 8-bit color workstations (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A technique is described which combines up to three channels of imagery into a single 8-bit composite color image. Each image controls a specific color or colors (red, green, or blue) in the resultant color composite image, allowing for improved interpretation of scene characteristics. The technique is a useful tool for the forecaster and satellite image analyst. In addition to providing the capability of displaying multichannel images on an 8-bit desktop color workstation, the technique allows sophisticated image manipulation to be performed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Conference on Satellite Meteorology and Oceanography, 6th, Atlanta, GA, Jan. 5-10, 1992, Preprints (A93-36051 14-47); p. J92-J95.
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  • 154
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    Results from a Si(Li) gamma ray detector stack for future Mars missions (1992)
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    Publication Date: 2011-08-24
    Description: We present Monte Carlo analysis and experimental data from a novel lithium-drifted silicon detector stack for gamma ray spectroscopy instrumentation in future Mars surface landers and other planetary missions. The Monte Carlo analysis shows full energy photopeaks even in the range of about 100 keV to 2 MeV where, in Si, Compton scattering dominates the absorption processes. Laboratory data is shown for an experimental detector stack of four planar Si(Li) devices, each 5 mm thick with an active area 2 cm in diameter. All the experimental data were collected with maximum temperature of the stack at 175 K. Background reduction is achieved by using the detector of the stack closest to the source in anticoincidence. We present a comparison of experimental data from the stack with the Monte Carlo model for Cs-137 (662 keV). Agreement is shown to be good, with a full energy photopeak clearly seen (FWHM about 10 keV). Experimental stack data is also shown for multiple peaks at 511 keV (Na-22) and 662 keV (Cs-137). The peaks are clearly resolved (FWHM 10 keV), and are compared with the results obtained using a 8 percent resolution, 3 in. x 3 in. NaI(TI) device (FWHM about 50 keV).
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); 39; 4; p. 981-986.
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    An Automated Thermocouple Calibration System (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An Automated Thermocouple Calibration System (ATCS) was developed for the unattended calibration of type K thermocouples. This system operates from room temperature to 650 C and has been used for calibration of thermocouples in an eight-zone furnace system which may employ as many as 60 thermocouples simultaneously. It is highly efficient, allowing for the calibration of large numbers of thermocouples in significantly less time than required for manual calibrations. The system consists of a personal computer, a data acquisition/control unit, and a laboratory calibration furnace. The calibration furnace is a microprocessor-controlled multipurpose temperature calibrator with an accuracy of +/- 0.7 C. The accuracy of the calibration furnace is traceable to the National Institute of Standards and Technology (NIST). The computer software is menu-based to give the user flexibility and ease of use. The user needs no programming experience to operate the systems. This system was specifically developed for use in the Microgravity Materials Science Laboratory (MMSL) at the NASA LeRC.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Instrumentation and Measurement (ISSN 0018-9456); 41; 5; p. 702-706.
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  • 156
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    Distributed optical proximity sensor system - HexEYE (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A novel optical proximity sensor system, capable of measuring the distance to the orientation and the discontinuity at a local area of an object surface, was designed and evaluated for robotic applications. The sensor system gets its name, Hexagonal Eye, (HexEYE) from its shape where seven identical hexagonal sensing units were configured hexagonally into a compact geometric structure. The seven sensing units were grouped into multiple combinations of three sensing units to measure the surface orientation as well as surface discontinuity. The distinctive features of HexEYE are an order of magnitude increased in distance sensitivity by optimizing the curvature of a conical mirror, the enhanced measurement accuracy based on multiple levels of sensor fusion, and the compactness in size due to a sensing mechanism based on the Gaussian lens law. A prototype of single sensing unit has been built and was evaluated experimentally.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: 1992 IEEE International Conference on Robotics and Automation, 8th, Nice, France, May 12-14, 1992, Proceedings. Vol. 2 (A93-35501 13-63); p. 1567-1572.
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  • 157
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    Data processing and calibration for tunable diode laser harmonic absorption spectrometers (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Data processing and calibration methods are described for tunable diode laser absorption spectrometers which produce harmonic absorption spectra as raw data for measuring gas mixing ratios down to parts-per-trillion levels at a variety of pressures. The methods, which take advantage of modern computer speed, memory, and data storage capabilities, are applicable to the detection of weakly absorbing gases in quantitative industrial monitoring, in addition to aircraft and balloon atmospheric measurements for which they were designed. Algorithms for calibration and data analysis, including rejection of erroneous spectra, variation of effective integration time, spectral alignment prior to averaging, and plotting and archiving of results, have been tested on actual stratospheric laser spectra recorded by the Aircraft Laser Infrared Absorption Spectrometer (ALIAS) spectrometer in numerous flights of NASA's ER-2 aircraft.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Quantitative Spectroscopy and Radiative Transfer (ISSN 0022-4073); 49; 4; p. 335-347.
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  • 158
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    Evolving SP-100 powerplants via electric propulsion to GEO and lunar orbit (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 9; 3; p. 449-455.
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  • 159
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    Dynamic interferometer alignment and its utility in UV Fourier transform spectrometer systems (1993)
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    Publication Date: 2011-08-24
    Description: Dynamic alignment has been demonstrated as a practical approach to alignment maintenance for systems in the infrared region of the spectrum. On the basis of work done by OPTRA, this technique was introduced in commercial Fourier transform spectrometer systems in 1982 and in various forms is now available from a number of manufacturers. This paper reports on work by OPTRA to extend the basic technique to systems operating in the ultraviolet. In addition, this paper reports the preliminary results of the development of an alignment system using a laser diode in place of a gas laser normally found in dynamic alignment systems. A unique optical system and spatial heterodyne technique allows for achievement of a metrology system with characteristics that fully satisfy the requirements of an ultraviolet spectrometer system.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Ultraviolet technology IV; Proceedings of the Meeting, San Diego, CA, July 20, 21, 1992 (A93-34426 13-35); p. 308-322.
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  • 160
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    High throughput narrowband 83.4 nm self-filtering camera (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Photometric imaging of ionospheric/magnetospheric O II emission at 83.4 nm is a primary objective for mapping the distribution of O(+) ions. However, instrumental sensitivity has been a major barrier to realizing this goal. We report an instrumental design employing a low focal ratio three-mirror camera where the reflecting surfaces act as both narrowband reflection filters at 83.4 nm and as a high quality imaging system. The design includes coatings with reflectances that are relatively insensitive to the angle of incidence of light. The peak reflectance per mirror is more than 60 percent at 83.4 nm with the average reflectance for out-of-band wavelengths of less than 5 percent. The net reflective transmission for the three mirrors is greater than 20 percent with 6.8 nm bandwidth and 0.01 percent maximum transmittance for out-of-band wavelengths. The transmittance at 30.4 nm is 0.03 percent at 58.4 nm 0.05 percent, and at 121.6 nm 0.004 percent. When used with an open microchannel plate detector, contamination by H Ly-alpha is essentially eliminated. With this spectral purity and effective elimination of major contributors to background contamination noise, a signal-to-noise ratio (excluding detector noise) of 10 is achievable for a 0.01 R signal in 8.8 seconds for the full 6 deg field-of-view.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: EUV, X-ray, and gamma-ray instrumentation for astronomy II; Proceedings of the Meeting, San Diego, CA, July 24-26, 1991 (A93-34376 13-35); p. 234-244.
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  • 161
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    Characteristics of a high pressure gas proportional counter filled with xenon (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The characteristics of a conventional cylindrical geometry proportional counter filled with high pressure xenon gas up to 10 atm. were fundamentally investigated for use as a detector in hard X-ray astronomy. With a 2 percent methane gas mixture the energy resolutions at 10 atm. were 9.8 percent and 7.3 percent for 22 keV and 60 keV X-rays, respectively. From calculations of the Townsend ionization coefficient, it is shown that proportional counters at high pressure operate at weaker reduced electric field than low pressure counters. The characteristics of a parallel grid proportional counter at low pressure showed similar pressure dependence. It is suggested that this is the fundamental reason for the degradation of resolution observed with increasing pressure.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: EUV, X-ray, and gamma-ray instrumentation for astronomy II; Proceedings of the Meeting, San Diego, CA, July 24-26, 1991 (A93-34376 13-35); p. 20-27.
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  • 162
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    Remote sensing of submerged vegetation canopies for biomass estimation (1993)
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    Publication Date: 2011-08-24
    Description: The visible bands of the Landsat Thematic Mapper (TM) sensor were used in an empirical assessment of seagrass biomass on shallow banks near Lee Stocking Island in the Bahamas. The TM bands were transformed to minimize the depth-dependent variance in the bottom reflectance signal. Regression analyses were performed between the transformed bands and field measurements of seagrass standing crop (above-ground biomass). Regression equations using spectral data accounted for up to 80 per cent of the variability in seagrass biomass. The unexplained variance was ascribed to variations in bottom sediment color.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 14; 3; p. 621-627.
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  • 163
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    On-orbit characterization of electric propulsion on LEO satellites (1992)
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    Publication Date: 2011-08-24
    Description: Utilizing commercial or military satellites as testbeds for subsystems is a potential platform for small devices. Electric propulsion is a viable and upcoming subsystem that is of high interest to planetary mission engineers as well as commercial satellite developers. It is proposed that by incorporating small lightweight electric propulsion devices onto small satellites as external or 'bolt-on' experiments, an increase in the number of flight opportunities can occur. Specific problems are spacecraft body interaction, contamination effects, thermal interface problems, power conditioning control electronics, and propulsion feed system interfaces.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: In: Space Congress, 29th, Cocoa Beach, FL, Apr. 21-24, 1992, Proceedings (A93-25276 08-12); p. 7-7 to 7-17.
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  • 164
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    Error analysis of combined stereo/optical-flow passive ranging (1991)
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    Publication Date: 2011-08-24
    Description: The motion of an imaging sensor causes each imaged point of the scene to correspondingly describe a time trajectory on the image plane. The trajectories of all imaged points are reminiscent of a flow (e.g., of liquid) which is the source of the term 'optical flow'. Optical-flow ranging is a method by which the stream of two-dimensional images obtained from a forward-looking forward-moving passive sensor is used to compute depth (or range) to points in the field of view. Another well-known ranging method consists of triangulation based on stereo images obtained from at least two stationary sensors. In this paper we analyze the potential accuracies of a combined optical flow and stereo passive-ranging system in the context of helicopter nap-of-the-earth obstacle avoidance. The Cramer-Rao lower bound is developed for the combined system under the assumption of an unknown angular bias error common to both cameras of a stereo pair. It is shown that the depth accuracy degradations caused by a bias error is negligible for a combined optical-flow and stereo system as compared to a monocular optical-flow system.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Surveillance technologies; Proceedings of the Meeting, Orlando, FL, Apr. 2-5, 1991 (A93-27712 09-35); p. 259-267.
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  • 165
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    Theory and operation of a three-gate time-of-flight velocity analyzer (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Theoretical considerations and test results are presented for a new-type velocity analyzer for incident fast neutral particles, positive ions, and negative ions. Velocity analysis is carried out by means of a pulsed, three-gate time-of-flight (TOF) technique capable of eliminating alias velocities (harmonics) to sixth order. In addition the design and operation are presented of a four-element ion lens system, with small spherical and chromatic aberrations, suitable for interfacing a large-diameter ion beam from the TOF section with a subsequent mass analyzer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 64; 2; p. 470-476.
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  • 166
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    High Tc bolometer developments for planetary missions (1991)
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    Publication Date: 2011-08-24
    Description: A simple polishing technique was developed for thinning the LaAlO3 substrates for high-quality Tc bolometer films, and thus reducing their heat capacity. A 150-ms bolometer was made on a LaAlO3 substrate with a 5-Hz D* value of 1.5 x 10 exp 8. It is shown that passive temperature stabilization is adequate for operation at the transition. There remained excess noise at the transition, but this noise appears to be of nonbolometric origin.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Superconductivity applications for infrared and microwave devices II; Proceedings of the Meeting, Orlando, FL, Apr. 4, 5, 1991 (A93-27243 09-33); p. 166-173.
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  • 167
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    Passive range sensor refinement using texture and segmentation (1991)
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    Publication Date: 2011-08-24
    Description: Electrooptical sensors provide a covert way of computing range during helicopter flight. The optical flow-based computation of range provides range information only in certain distinguishable parts of the image. The regions where range information is available can be increased by performing texture analysis and object segmentation in the image. This paper reviews some of the literature on texture segmentation methods with a view towards applying them to images containing both man-made and natural objects at varying ranges. Two algorithmic approaches are given and their application to a real image is demonstrated. Results indicate that it will be necessary to combine several different texture measures and methods in a hierarchical way in order to achieve an object segmentation which is useful in enhancing range information.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Sensors and sensor systems for guidance and navigation; Proceedings of the Meeting, Orlando, FL, Apr. 2, 3, 1991 (A93-27043 09-19); p. 178-189.
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  • 168
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    Temporal averaging of phase measurements in the presence of spurious phase drift - Application to phase-stepped real-time holographic interferometry (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A technique that compensates for low spatial frequency spurious phase changes during an interference experiment is developed; it permits temporal averaging of multiple-phase measurements, made before and after object displacement. The method is tested with phase-stepped real-time holographic interferometry applied to cantilever bending of a piezoelectric bimorph ceramic. Results indicate that temporal averaging of the corrected data significantly reduces the white noise in a phase measurement without incurring systematic errors or sacrificing spatial resolution. White noise is reduced from 3 deg to less than 1 deg using these methods.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 32; 2; p. 147-154.
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  • 169
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    Remote spectral identification of surface aggregates by thermal imaging techniques - Progress report (1991)
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    Publication Date: 2011-08-24
    Description: The NASA Thermal Infrared Multispectral Scanner (TIMS) has been successfully used for the remote identification of a variety of soil and aggregate deposits in vegetated areas of two states. Over three million cubic meters of gravel deposits were identified from the imagery during a two year period. Verification was accomplished by ground reconnaissance using drilling machinery and by ground instrumentation. The method has been used to differentiate between fine and coarse grained soils, and gravel deposits. The deposits were found to have been naturally sorted according to grain size by depositional processes, providing each deposit with distinct spectral qualities. It was found that the masking effects of relatively dense vegetation were largely overcome by using imagery acquired at higher altitudes above terrain than 9000 meters, due to loss of resolution of the finer detail. The mechanics of image resolution are discussed, a method of data analysis used is described, and sample spectral signatures are illustrated.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Earth and atmospheric remote sensing; Proceedings of the Meeting, Orlando, FL, Apr. 2-4, 1991 (A93-24176 08-42); p. 358-369.
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    Determination of water surface temperature based on the use of Thermal Infrared Multispectral Scanner data (1992)
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    Publication Date: 2011-08-24
    Description: A straightforward method for compensating Thermal Infrared Multispectral Scanner (TIMS) digital data for the influence of atmospheric path radiance and the attenuation of target energy by the atmosphere is presented. A band ratioing model useful for estimating water surface temperatures, which requires no ground truth measurements, is included. A study conducted to test the potential of the model and the magnitudes of the corrections for atmosphere encountered is presented. Results of the study, which was based on data collected during an engineering evaluation flight of TIMS, indicate errors in the estimate of the surface temperature of the water fall from +/- 1.0 C for uncorrected data to +/- 0.4 C when data have been corrected according to the model presented. This value approaches the noise-limited thermal resolution of the sensor at the time of the flight.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geocarto International (ISSN 1010-6049); 7; 3; p. 3-8.
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  • 171
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    Determination of microwave vegetation optical depth and single scattering albedo from large scale soil moisture and Nimbus/SMMR satellite observations (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The single scattering albedo and optical depth of typical savanna vegetation in Botswana (Africa) have been determined by inverse modelling using satellite observed microwave signatures and surface soil moisture. Soil emissivity was modelled using a multi-layer radiative transfer model. The study is based on large scale surface moisture data and Nimbus/SMMR 6-6 GHz and 37 GHz dual polarized brightness temperatures over a 3-year period. As compared to the optical depths, the derived single scattering albedos displayed only minor seasonal variations, whereas the values fit well within the range reported in the literature from laboratory and field experiments. Both 6-6 and 37GHz optical depths were found to be significantly related to NDVI-values derived from NOAA/AVHRR.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 14; 10; p. 1875-1886.
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  • 172
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    Electric propulsion - An evolutionary technology (1993)
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    Publication Date: 2011-08-24
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Acta Astronautica (ISSN 0094-5765); 29; 9; p. 651-665.
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  • 173
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    Specularly modified vegetation indices to estimate photosynthetic activity (1993)
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    Publication Date: 2011-08-24
    Description: The hypothesis tested was that some part of the ecosystem-dependent variability of vegetation indices was attributable to the effects of light specularly reflected by leaves. 'Minus specular' indices were defined excluding effects of specular light which contains no cellular pigment information. Results, both empirical and theoretical, show that the 'minus specular' indices, when compared to the traditional vegetation indices, potentially provide better estimates of the photosynthetic activity within a canopy - and therefore canopy primary production - specifically as a function of sun and view angles.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 14; 9; p. 1815-1823.
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  • 174
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    Linear mixing model applied to coarse spatial resolution data from multispectral satellite sensors (1993)
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    Publication Date: 2011-08-24
    Description: A linear mixing model was applied to coarse spatial resolution data from the NOAA Advanced Very High Resolution Radiometer. The reflective component of the 3.55-3.95 micron channel was used with the two reflective channels 0.58-0.68 micron and 0.725-1.1 micron to run a constrained least squares model to generate fraction images for an area in the west central region of Brazil. The fraction images were compared with an unsupervised classification derived from Landsat TM data acquired on the same day. The relationship between the fraction images and normalized difference vegetation index images show the potential of the unmixing techniques when using coarse spatial resolution data for global studies.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 14; 11; p. 2231-2240.
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  • 175
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    On the use of passive microwaves at 37 GHz in remote sensing of vegetation (1993)
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    Publication Date: 2011-08-24
    Description: Recently, a number of studies have investigated the use of the 37 GHz channels of the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) for vegetation monitoring and for studying synergisms between the SMMR and the NOAA Advanced Very High Resolution Radiometer (AVHRR). The approaches are promising but raise a number of issues concerning interpretation of the results, specifically on the relative effects of vegetation and other surface and atmospheric characteristics on the observed signal. This article analyzes the 37 GHz Microwave Polarization Difference Temperature (MPDT) in terms of its sensitivity to surface and atmospheric parameters. For this, a radiative transfer model is used which indicates some limitations of the MPDT index and suggests the importance of accounting for atmospheric effects in the data analysis. An alternative approach to the MPDT, including lower SMMR frequencies than 37 GHz, is discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 14; 10; p. 1931-1943.
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  • 176
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    Micro-displacement fiber sensor using two-frequency interferometry (1991)
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    Publication Date: 2011-08-24
    Description: A He-Ne Zeeman laser has been utilized as a two-frequency light source in a Michelson-type micro-displacement fiber sensor. A polarization maintaining fiber has been installed in the sensing arm, which facilitates flexibility and allows the sensing region to be remotely located. This fiber sensing arm is arranged to replace a quarterwave plate component. The fiber sensor system has a resolution of half a micrometer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Fiber optic and laser sensors IX; Proceedings of the Meeting, Boston, MA, Sept. 3-5, 1991 (A93-53103 23-35); p. 146-151.
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  • 177
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    Fiber-optic thermometer using Fourier transform spectroscopy (1991)
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    Publication Date: 2011-08-24
    Description: An integrated-optic Mach-Zender interferometer is used as a Fourier transform spectrometer to analyze the input and output spectra of a temperature-sensing thin-film etalon. This configuration provides a high degree of immunity to the effects of changes in the source spectrum, and it readily permits the interrogation of a number of different sensors using a single spectrometer. In addition, this system has a potentially low cost because it uses optical communications hardware that may in the future be manufactured in large quantities.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Fiber optic and laser sensors IX; Proceedings of the Meeting, Boston, MA, Sept. 3-5, 1991 (A93-53103 23-35); p. 64-71.
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  • 178
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    Using image pyramids for the visualization of large terrain data sets (1991)
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    Publication Date: 2011-08-24
    Description: Viewing terrain data from various remote sensors in three dimensions has proven to be a valuable tool for scientists in understanding a variety of problems. A technique is presented for using image pyramids in such visualization of large terrain data sets, providing up to two orders of magnitude performance enhancement over simpler techniques, while at the same time eliminating false high-frequency information, which causes animations to sparkle.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Imaging Systems and Technology (ISSN 0899-9457); p. 157-166.
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  • 179
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    Balloon-borne submillimeterwave stratospheric measurements (1993)
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    Publication Date: 2011-08-24
    Description: A new remote sensing instrument, the Submillimeterwave Limb Sounder, has been developed to simultaneously measure ClO, HCl, O3 and HO2 from high altitude balloon and aircraft platforms. The instrument is a double sideband heterodyne radiometer measuring atmospheric thermal emission spectra near 640 GHz from the Earth's limb. The instrument was flown in April and October, 1991 and in February, 1992 on high altitude balloon platforms over the southwestern United States.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Optical methods in atmospheric chemistry; Proceedings of the Meeting, Berlin, Germany, June 22-24, 1992 (A93-51501 22-35); p. 433-440.
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  • 180
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    Effect of trapped ions in a gated time-of-flight apparatus (1993)
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    Publication Date: 2011-08-24
    Description: A three-mesh gate is used in a time-of-flight (TOF) apparatus to analyze the velocity of positive ions. Test results and a theoretical description are presented of an effect arising from trapping ions between meshes of a two-gate TOF velocity analyzer. The entrapped ions produce a side peak in the TOF spectra corresponding to faster ions. The onset and relative height of the side peak is dependent on the gating voltage and risetime of the pulsing electronics, while the relative intensity depends upon the velocity being sampled and the ratio of the gate width to duration.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 64; 7; p. 1754-1757.
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  • 181
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    Calibration of the forward-scattering spectrometer probe - Modeling scattering from a multimode laser beam (1993)
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    Publication Date: 2011-08-24
    Description: Scattering calculations using a detailed model of the multimode laser beam in the forward-scattering spectrometer probe (FSSP) were carried out using a recently developed extension to Mie scattering theory. From this model, new calibration curves for the FSSP were calculated. The difference between the old calibration curves and the new ones is small for droplet diameters less than 10 microns, but the difference increases to approximately 10 percent at diameters of 50 microns. When using glass beads to calibrate the FSSP, calibration errors can be minimized by using glass beads of many different diameters, over the entire range of the FSSP. If the FSSP is calibrated using one-diameter glass beads, then the new formalism is necessary to extrapolate the calibration over the entire range.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Atmospheric and Oceanic Technology (ISSN 0739-0572); 10; 4; p. 518-525.
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  • 182
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    An evaluation of short-wave-infrared (SWIR) data from the AVIRIS and GEOSCAN instruments for mineralogical mapping at Cuprite, Nevada (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An evaluation was performed on SWIR (2000-2400 nm) data from two airborne remote sensing systems for discriminating and identifying alteration minerals at Cuprite, Nevada. The data were acquired by the NASA Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) and the GEOSCAN Mk II multispectral scanner. The evaluation involved comparison of processed imagery and image-derived spectra with existing alteration maps and laboratory spectra of rock samples from Cuprite. Results indicate that both the AVIRIS and GEOSCAN data permit the discrimination of areas of alunite, buddingtonite, kaolinite, and silicification using color composite images formed from three SWIR bands processed with either the decorrelation stretch or a log residual algorithm. The laboratory spectral features alunite, kaolinite and buddingtonite could be seen clearly only in the log residual processed AVIRIS data. However, this does not preclude their identification with the GEOSCAN data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geophysics (ISSN 0016-8033); 56; 9; p. 1432-1440.
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  • 183
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    The Airborne Ocean Color Imager - System description and image processing (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Airborne Ocean Color Imager was developed as an aircraft instrument to simulate the spectral and radiometric characteristics of the next generation of satellite ocean color instrumentation. Data processing programs have been developed as extensions of the Coastal Zone Color Scanner algorithms for atmospheric correction and bio-optical output products. The latter include several bio-optical algorithms for estimating phytoplankton pigment concentration, as well as one for the diffuse attenuation coefficient of the water. Additional programs have been developed to geolocate these products and remap them into a georeferenced data base, using data from the aircraft's inertial navigation system. Examples illustrate the sequential data products generated by the processing system, using data from flightlines near the mouth of the Mississippi River: from raw data to atmospherically corrected data, to bio-optical data, to geolocated data, and, finally, to georeferenced data.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Imaging Science and Technology (ISSN 8750-9237); 36; 5; p. 423-430.
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  • 184
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    Unified Navier-Stokes flowfield and performance analysis of liquid rocket engines (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 9; 5; p. 678-685.
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  • 185
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    Fourier transform spectrometry for fiber-optic sensor systems (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An integrated-optic Mach-Zehnder interferometer is used as a Fourier transform spectrometer to analyze the input and output spectra of a temperature-sensing thin-film etalon. This type of spectrometer has an advantage over conventional grating spectrometers because it is better suited for use with time-division-multiplexed sensor networks. In addition, this spectrometer has the potential for low cost due to its use of a component that could be manufactured in large quantities for the optical communications industry.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Integrated optics and microstructures; Proceedings of the Meeting, Boston, MA, Sept. 8, 9, 1992 (A93-49456 21-35); p. 127-136.
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  • 186
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    Two-mode elliptical-core weighted fiber sensors for vibration analysis (1992)
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    Publication Date: 2011-08-24
    Description: Two-mode, elliptical-core optical fibers are demonstrated in weighted, distributed and selective vibration-mode-filtering applications. We show how appropriate placement of optical fibers on a vibrating structure can lead to vibration mode filtering. Selective vibration-mode suppression on the order of 10 dB has been obtained using tapered two-mode, circular-core fibers with tapering functions that match the second derivatives of the modes of vibration to be enhanced. We also demonstrate the use of chirped, two-mode gratings in fibers as spatial modal sensors that are equivalents of shaped piezoelectric sensors.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Distributed and multiplexed fiber optic sensors; Proceedings of the Meeting, Boston, MA, Sept. 4, 5, 1991 (A93-49426 21-35); p. 53-66.
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  • 187
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    U.S./CIS eye joint nuclear rocket venture (1993)
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    Publication Date: 2011-08-24
    Description: An account is given of the significance for U.S. spacecraft development of a nuclear thermal rocket (NTR) reactor concept that has been developed in the (formerly Soviet) Commonwealth of Independent States (CIS). The CIS NTR reactor employs a hydrogen-cooled zirconium hydride moderator and ternary carbide fuels; the comparatively cool operating temperatures associated with this design promise overall robustness.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Aerospace America (ISSN 0740-722X); 31; 7; p. 28-30, 35.
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  • 188
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    Hydrogen no-vent fill testing in a 34 liter (1.2 cubic foot) tank (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Experimental results of no-vent fill testing with liquid hydrogen in a 34 liter stainless steel tank are presented. More than 40 tests were performed with various liquid inlet temperatures, inlet flowrates, initial tank wall temperatures, and liquid injection techniques. Maximum pressure within the receiver tank was limited to 0.207 MPa (30 psia), and fill levels equal to or exceeding 90 percent by volume were achieved in 40 percent of the tests. Three liquid injection techniques were employed; top spray, upward pipe discharge, and bottom diffuser. Effects of each of the various parameters on the tank pressure history and final fill level are evaluated. The final fill level is found to be indirectly proportional to the initial wall and inlet liquid temperatures and directly proportional to the inlet liquid flowrate. Furthermore, the top spray is the most efficient no-vent fill method of the three configurations examined. The success of this injection method is primarily due to condensation of the ullage vapor onto the incoming liquid droplets. Ullage condensation counteracts the tank pressure rise resulting from energy exchange between the fluid and the warmer tank walls and from ullage compression.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: In: Advances in cryogenic engineering. Vol. 37B - Proceedings of the 1991 Cryogenic Engineering Conference, Univ. of Alabama, Huntsville, June 11-14, 1991 (A93-48578 20-37); p. 1257-1264.
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  • 189
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    Hydrologic applications of SAR derived soil moisture (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The MACHYDRO-90 was a multi-sensor aircraft campaign conducted to study drainage basin hydrology and the role of soil moisture in defining hydrologic characteristics and patterns. The results from the synthetic aperture radar (SAR) are presented. Data were collected over a period in which the soil conditions changed from dry to wet and then through a drying period which was close to ideal. Radar backscatter data are compared to detailed soil moisture samples taken to define soil moisture gradients within a watershed. The analysis also includes 40-MHz bandwidth SAR data, which provide very high spatial resolution. It is shown these data can be interpreted for hydrology and their application to hydrologic modeling is discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1741-1743.
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  • 190
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    Mapping sub-tropical vegetation using multi-frequency, multi-polarization SAR data (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: In 1990 the NASA/JPL airborne synthetic aperture radar DC-8 (Airsar) was flown over an area in northern Belize and the surrounding countries of Guatemala and Mexico. The three-frequency polarimetric radar signatures of a variety of natural areas have been extracted, and many have a unique radar signature. Scattering mechanisms which may explain these signatures and results of an image classification technique are presented.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1686-1689.
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  • 191
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    Atmospheric effects on the NDVI - Strategies for its removal (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The compositing technique used to derive global vegetation index (NDVI) from the NOAA AVHRR radiances reduces the residual effect of water vapor and aerosol on the NDVI. The reduction in the atmospheric effect is shown using a comprehensive measured data set for desert conditions, and a simulation for grass with continental aerosol. A statistical analaysis of the probability of occurrence of aerosol optical thickness and precipitable water vapor measured in different climatic regimes is used for this simulation. It is concluded that for a long compositing period (e.g., 27 days), the residual aerosol optical thickness and precipitable water vapor are usually too small to be corrected. For a 9-day compositing, the residual average aerosol effect may be about twice the correction uncertainty. For Landsat TM or Earth Observing System Moderate Resolution Imaging Spectrometer (EOS-MODIS) data, the newly defined atmospherically resistant vegetation index (ARVI) is more promising than possible direct atmospheric correction schemes, except for heavy desert dust conditions.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1238-1241.
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  • 192
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    Modeling and measurement of microwave emission and backscattering from bare soil surfaces (1992)
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    Publication Date: 2011-08-24
    Description: A multifrequency ground-based radiometer-scatterometer system working at frequencies between 3.0 GHz and 11.0 GHz has been used to study the effect of soil moisture and roughness on microwave emission and backscattering. The freezing and thawing effect of the soil surface and the changes of the surface roughness due to rain and erosion are reported. To analyze the combined active and passive data, a scattering model based on physical optics approximation for the low frequency and geometrical optics approximation for high frequency has been developed. The model is used to calculate the bistatic scattering coefficients from the surface. By considering the conservation of energy, the result has been integrated over a hemisphere above the surface to calculate the emissivity. The backscattering and emission model has been coupled with the observed data in order to extract soil moisture and surface roughness.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1190-1192.
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  • 193
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    An examination of the assumptions in the POLCAL cross-talk removal algorithm (1992)
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    Publication Date: 2011-08-24
    Description: The POLCAL crosstalk removal algorithm is based on the statistical properties of the image background and does not need any corner reflector or active radar calibrator deployed in the scene. The advantage of being able to remove the crosstalk contamination without using external calibration targets gives rise to the consideration of algorithms based on clutter statistics in polarimetric synthetic aperture radar (SAR) images in more detail. The basic assumption of the POLCAL procedure is the decorrelation of copolarized and cross-polarized backscatter, which is valid for natural targets with azimuthal symmetry. This assumption and others regarding the properties of the imaged surface are examined. An improved version called POLCALII is presented, and its performance is compared with POLCAL.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1171-1173.
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  • 194
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    The effect of topography on radar scattering from vegetated areas (1992)
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    Publication Date: 2011-08-24
    Description: It is shown how radar scattering from vegetated areas is affected by the topography of the surface underneath the vegetation, and that by the use of a discrete scatterer model the dominant scattering mechanism may change drastically when the ground surface is tilted relative to the horizontal. In the case of a horizontal ground surface total scattering may be dominated by scattering off the tree trunks, followed by a reflection off the ground surface. It is shown that for a relatively small tilt in the ground surface the ground-trunk interaction term may be replaced by scattering from the branches alone as the dominant scattering mechanism. The effect of the topography is more pronounced for scattering by longer wavelengths. The implications for algorithms designed to infer forest woody biomass and soil and vegetation moisture using polarimetric synthetic aperture radar (SAR) data are discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1132-1134.
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  • 195
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    KUREX-91 - A USSR/US study for global climate processes in steppe vegetation (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Researchers use satellite remote sensing of the earth's reflected and emitted radiation as correlated indices of the variables they measure on the ground or within the atmosphere. The Kursk 1991 Experiment (KUREX-91) was conducted to develop capabilities for monitoring global change, and to understand how the earth's land-surface vegetation and atmospheric boundary layer interact. The experiment enabled scientific interactions between the international participants, and comparisons of instruments and data. Intensive ground measurements were coordinated with helicopter, aircraft and satellite data acquisitions.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1035-1038.
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  • 196
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    Temporal decorrelation in repeat pass-radar interferometry (1992)
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    Publication Date: 2011-08-24
    Description: Correlation in pass-to-pass, interferometric radar can be degraded by thermal noise, lack of parallelism between the radar flight tracks, spatial baseline noise, and surficial change. The effects of decorrelation due to thermal noise can be easily evaluated and removed, while those due slight angular changes between flight tracks are negligible for data acquired using near-repeat orbits. Empirical results obtained using images of Death Valley confirm that as the baseline increases, the overall correlation decreases due to spatial baseline noise. It is shown that areas of Cottonball Basin in Death Valley remained unchanged over the three-week period for which data was obtained, while a heavily forested area in Oregon exhibited significant temporal decorrelation. Lava in central Oregon also appeared to decorrelate. The results demonstrate that generation of height maps of heavily vegetated areas using pass-to-pass interferometry is practical, provided that the time between passes is at most several weeks.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 941-943.
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  • 197
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    Acoustic composition sensor for cryogenic gas mixtures (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An acoustic sensor useful for the determination of the composition of a gaseous binary mixture in cryogenic liquid spills has been characterized. One version of the instrument traps a known mixture of helium and nitrogen at ambient temperature in a tube which is interrogated by sonic pulses to determine the speed of sound and hence the composition. Experimental data shows that this sensor is quite accurate. The second version uses two unconfined microphones which sense sound pulses. Experimental data acquired during mixing when liquid nitrogen is poured into a vessel of gaseous helium is presented. Data during transient cooling of the tubular sensor containing nitrogen when the sensor is dipped into liquid nitrogen and during transient warm-up when the sensor is withdrawn are also presented. This sensor is being developed for use in the mixing of liquid cryogens with gas evolution in the simulation of liquid hydrogen/liquid oxygen explosion hazards.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Advances in cryogenic engineering. Vol. 37B - Proceedings of the 1991 Cryogenic Engineering Conference, Univ. of Alabama, Huntsville, June 11-14, 1991 (A93-48578 20-37); p. 1453-1460.
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  • 198
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    Spectral vegetation indexes and the remote sensing of biophysical parameters (1992)
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    Publication Date: 2011-08-24
    Description: Combinations of remotely sensed data from different spectral bands have been combined into spectral vegetation indexes (SVIs) and used to determine biophysical parameters. The characteristics of two-band SVIs made up of visible and near-infrared reflectances are examined. Two canopy reflectance models, a turbid media model and a geometrical model, are used to study the effects of different canopy structures on the measurement of leaf area index and the fraction of photosynthetically intercepted active radiation.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1017-1019.
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  • 199
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    Phase difference statistics related to sensor and forest parameters (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The information content of ordinary synthetic aperture radar (SAR) data is principally contained in the radiometric polarization channels, i.e., the four Ihh, Ivv, Ihv and Ivh backscattered intensities. In the case of clutter, polarimetric information is given by the four complex degrees of coherence, from which the mean polarization phase differences (PPD), correlation coefficients or degrees of polarization can be deduced. For radiometric features, the polarimetric parameters are corrupted by multiplicative speckle noise and by some sensor effects. The PPD distribution is related to the sensor, speckle and terrain properties. Experimental results are given for the variation of the terrain hh/vv mean phase difference and magnitude of the degree of coherence observed on bare soil and on different pine forest stands.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 779-781.
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  • 200
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    Cyclops - The JPL AIRSAR synoptic processor (1992)
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    Publication Date: 2011-08-24
    Description: Capability for synoptic, or wide-area, SAR processing has been added to the JPL Aircraft Synthetic Aperture Radar System (AIRSAR) by means of the CYCLOPS synoptic processor. Polarimetric requirements have been relaxed so that a single node in the system can process SAR data with a throughput of three channels in 3.75 hours. Each channel consists of five minutes of full-range-swath data chosen from the twelve available AIRSAR polarization channels. Processed data consists of 16-look, 16-meter resolution imagery with a swath size of 60 km. The processor fully utilizes the available Doppler bandwidth and provides processing options for range migration correction, zero-Doppler deskew, frequency registration, and radiometric correction. The detected-power output product is scaled so as to provide sigma zero radiometric calibration.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 652-654.
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