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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 433 records · Page 24
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NASA NTRS1987

The line integral approach to radarclinometry

Advances over previous work in radarclinometry (Wildey, 1984 and 1986) are proposed, including incorporation of a more exact treatment of the dependence on terrain orientation of the solid angle of integration of the microwave specific energy comprising individual pixel power, and the integration of the theory in the cross-ground-range direction. The local curvature hypothesis, making possible formulation of the theory in terms of a line integral, is expanded to include the possibilities of local cylindricity, local biaxial ellipsoidal hyperbolicity, and least-squares local sphericity. It is suggested that the banding noted in topographic maps which are produced on the basis of variation in the proportioning between curvature assumptions may be due to the lack of radiometric calibration.

Wildey, Robert L.↗
NASA NTRS1987

Digital cartography of the planets - New methods, its status, and its future

A system has been developed that establishes a standardized cartographic database for each of the 19 planets and major satellites that have been explored to date. Compilation of the databases involves both traditional and newly developed digital image processing and mosaicking techniques, including radiometric and geometric corrections of the images. Each database, or digital image model (DIM), is a digital mosaic of spacecraft images that have been radiometrically and geometrically corrected and photometrically modeled. During compilation, ancillary data files such as radiometric calibrations and refined photometric values for all camera lens and filter combinations and refined camera-orientation matrices for all images used in the mapping are produced. The system is designed to aid in the following: access to and utilization of spatial data returned by planetary spacecraft; coregistration of cartographic image and topographic elevation models with geological, geophysical, and geochemical databases; and the design and preparation of both standard and custom map products. A major goal of the project is to publish the DIMs on compact computer-compatible media such as digital-optical (CD-ROM) disks.

Batson, R. M.↗
NASA NTRS1988

Bolometric albedos and diurnal temperatures of the brightest regions on Io

Cylindrical maps of the locations and estimated Bond albedos of the brightest regions on the Io surface have been constructed on the basis of Voyager data; the albedos are then rescaled to correct for radiometric calibration uncertainties. The highest surface albedos are found to be only moderately higher than the Bond albedo of Io as a whole. The brightest regions include two bright patches southeast of the Maui and Amirani active vents, as well as a large equatorial field of high-albedo material and a lone bright patch at high northern latitudes. These maps indicate that Io's albedos are strongly latitude-dependent.

Simonelli, Damon P.↗
NASA NTRS1988

Cloud absorption radiometer

The Cloud Absorption Radiometer (CAR) was developed to measure spectrally how light is scattered by clouds and to determine the single scattering albedo, important to meteorology and climate studies, with unprecedented accuracy. This measurement is based on ratios of downwelling to upwelling radiation within clouds, and so is not strongly dependent upon absolute radiometric calibration of the instrument. The CAR has a 5-inch aperture and 1 degree IFOV, and spatially scans in a plane orthogonal to the flight vector from the zenith to nadir at 1.7 revolutions per second. Incoming light is measured in 13 spectral bands, using silicon, germanium, and indium-antimonide detectors. Data from each channel is digitally recorded in flight with 10-bit (0.1 percent) resolution. The instrument incorporates several novel features. These features are briefly detailed.

Strange, M. G.↗
NASA NTRS1988

Radiance standards

Two radiometric calibration sources that are utilized by various groups are maintained and operated. One source is a 6-ft diameter sphere and the other a 4-ft diameter hemisphere. Both are internally coated with multiple layers of barium sulfate and house an array of 12 tungsten filament-quartz iodine lamps that provide a uniform diffuse target of radiance traceable to NBS. The lamps are baffled and arranged so that they are not part of the scene during calibrations. Both systems have a 10-inch viewing aperture. The hemisphere is somewhat more versatile in that the aperture can be changed and the system is movable so calibrations can be done at other sites. Together, these systems have supported numerous GSFC projects and missions during this review period. They are listed.

Lester, D. L.↗
NASA NTRS1989

Surface reflectance factor retrieval from Thematic Mapper data

Based on the absolute radiometric calibration of the TM and the use of a radiative transfer program for atmospheric correction, ground reflectances were retrieved for several fields of crops and bare soil in TM bands 1-4 for six TM scenes acquired over a 12-month period. These reflectances were compared to those measured using ground-based and low-altitude, aircraft-mounted radiometers. When, for four TM acquisitions, the comparison was made between areas that had been carefully selected for their high uniformity, the reflectance factors agreed to + or - 0.01 over the reflectance range 0.02-0.55. When the comparison was made for two of the above acquisitions and two others on different dates, for larger areas not carefully selected to be of uniform reflectance, the reflectance factors agreed to + or - 0.02 (1 sigma RMS), over same reflectance range.

Holm, Ronald G.↗
NASA NTRS1990

Airborne MSS for land cover classification II

A basic methodology for land cover classification using airborne multispectral scanner (MSS) imagery is outlined. This includes waveband selection and radiometric calibration; correction for scan angle and atmosphere; training and classification and accuracy assessment. Refinements to this basic methodology include per-field sampling and the addition of low-pass filtering, image texture, prior probabilities and two dates of imagery. For a study area in upland England, eight land covers were classified with a mean accuracy of 52.6 percent using the basic methodology. This was increased to 79.0 percent by using a suitability refined methodology. Per-field sampling accounted for the largest proportion of this increase.

Curran, Paul J.↗
NASA NTRS1989

Code and codeless ionospheric measurements with NASA's Rogue GPS Receiver

The NASA/JPL Rogue Receiver is an 8-satellite, non-multiplexed, highly digital global positioning system (GPS) receiver that can obtain dual frequency data either with or without knowledge of the P-code. In addition to its applications for high accuracy geodesy and orbit determination, the Rogue uses GPS satellite signals to measure the total electron content (TEC) of the ionosphere along the lines of sight from the receiver to the satellites. These measurements are used by JPL's Deep Space Network (DSN) for calibrating radiometric data. This paper will discuss Rogue TEC measurements, emphasizing the advantages of a receiver that can use the P-code, when available, but can also obtain reliable dual frequency data when the code is encrypted.

Srinivasan, Jeff M.↗
NASA NTRS1991

Estimating SAR Doppler Shifts From Homogeneous Targets

Algorithm that processes some of information in synthetic-aperture-radar (SAR) echoes from homogeneous targets yields optimal estimates of Doppler frequency shifts. Helps in further processing to extract as much information as possible about targets. Used to improve radiometric calibrations, to estimate direction of radar antenna, and to determine speeds of moving targets more accurately. Also helpful in measurements of speeds of ocean currents and of wind shears at airports.

Jin, Michael Y.↗
NASA NTRS1990

MODIS-N - Moderate Resolution Imaging Spectrometer-Nadir

The Moderate Resolution Imaging Spectrometer-Nadir (MODIS-N) for the Earth Observing System (EOS) is intended to provide daily global surveys for the atmosphere, the oceans, and the land. To achieve this capability, MODIS-N requires an at-least 2300-km swath width, and provides geometric-instantaneous-fields-of-view (GIFOVs) that are either 856 m, 428 m, or 214 m in size with reference to a 705 km satellite altitude. The 214 m GIFOV may or may not be used depending on total data rate impact assessments traded with science needs. To achieve the data for the multiplicity of science investigations MODIS-N provides nominally 36 spectral bands that are selected for specific locations and bandpasses in the spectral range from the visible to the long wave infrared. Another driver of this instrument combination is the need for long term spectral and radiometric calibration stability. Specific calibration capabilities are to be built into MODIS-N to achieve calibration knowledge over a 5 year operational life.

Weber, Richard R.↗
NASA NTRS1991

Particle size distributions in polar mesospheric clouds derived from solar mesosphere explorer measurements

Data from the visible and UV spectrometers on the Solar Mesosphere Explorer are used to derive the color ratios of the reflectance at 265, 296, and 393 nm of light scattered from polar mesospheric cloud particles. This analysis extends the spectral coverage into the visible region of the spectrum. The data reduction technique compared the cloud brightness to the brightness scattered from the background atmosphere at the same wavelength. The ratios determined in this way are independent of systematic errors in instrument radiometric calibration. The data are analyzed using theoretical determinations of the color ratios from the Mie theory of small particle scattering, assuming a lognormal distribution for the particle size dispersion. Here 'size' means the average radius of the sphere having the same ice volume. The present results confirm earlier findings that the effective sizes of polar mesospheric cloud particles are less than 70 nm. Still, there exists a small number of measurements which result in particle sizes of the order of 80 nm. Even for these large particle sizes the required vertical column content of water vapor does not exceed limits imposed by the available atmospheric water vapor concentrations.

Rusch, D. W.↗
NASA NTRS1992

Classification Of Land Cover From Airborne MSS Data

Method for processing images of rural uplands produced by airborne multispectral scanner (MSS), semiautomatically classifies types of land cover, and involves selection of wavelength bands, radiometric calibration, correction for effects of scan angle and atmosphere, training, and assessment of accuracy. Basic version involves classification of each picture element according to spectrum. Augmented with five refinements to increase accuracy: per-field sampling; low-pass filtering; image texture; prior probabilities; and imagery from two dates.

Curran, Paul J.↗
NASA NTRS1992

Temporal variability of the surface and atmosphere of Mars: Viking Orbiter color observations

We are near the final stages in the processing of a large Viking Orbiter global color dataset. Mosaics from 57 spacecraft revolutions (or 'revs' hereafter) were produced, most in both red and violet or red, green, and violet filters. Phase angles range from 13 deg to 85 deg. A total of approximately 2000 frames were processed through radiometric calibration, cosmetic cleanup, geometric control, reprojection, and mosaicking into single-rev mosaics at a scale of 1 km/pixel. All of the mosaics are geometrically tied to the 1/256 deg/pixel Mars Digital Image Mosaic (MDIM). Photometric normalization is in progress, to be followed by production of a 'best coverage' global mosaic at a scale of 1/64 deg/pixel (0.923 km/pixel). Global coverage is near 100 percent in red-filter mosaics and 98 percent and 60 percent in corresponding violet- and green-filter mosaics, respectively. Soon after completion, all final datasets (including single-rev mosaics) will be distributed to the planetary community on compact disks.

Mcewen, A. S.↗
NASA NTRS1991

Intercomparisons of the solar irradiance measurements from the Nimbus-7 SBUV, the NOAA-9 and NOAA-11 SBUV/2, and the STS-34 SSBUV instruments - A preliminary study

Results are presented of solar irradiance measurements in the spectral range 160-400 nm at approximately 0.15-0.20-nm intervals and at 1-nm resolution performed continually since November 1978. Solar irradiance data from the Nimbus-7 SBUV satellite instrument, the SBUV/2 instruments on the NOAA-9 and NOAA-11 satellites, and the October 1989 flight of the Shuttle SBUV instrument are presented and compared. Uncertainties in the instruments' absolute and long-term radiometric calibrations, which vary among the four instruments, are discussed. Comparisons of the initial solar spectra from the four instruments show agreement to within approximately 10 percent, with spectral biases on the order of +/-4 percent. Irradiances measured by the two NOAA instruments and SSBUV agree to within about 5 percent overall from 270 to 360 nm, with spectral biases on the order of about +/-2 percent. The Nimbus-7 SBUV irradiances are an additional 5-10 percent lower in this region than those measured by the other three instruments.

Cebula, R. P.↗
NASA NTRS1991

Global environmental monitoring with the EOS multi-angle imaging spectroradiometer (MISR)

The MISR provides a unique opportunity for studying the ecology and climate of the earth through the acquisition of systematic, global multiangle imagery in reflected sunlight. MISR uses nine cameras: a nadir camera and two banks of four cameras each pointed forward and aftward along the spacecraft ground track to image the earth at +/-30.7, +/-45.6, +/-60.0, and +/-72.5 deg. Radiometrically calibrated images at each angle will be obtained in four spectral bands centered at 440, 550, 670, and 860 nm. MISR will take image data in two different spatial resolution modes: local mode, in which selected targets are observed with 240-m spatial sampling, and global mode, where the entire sunlit eEarth is observed continuously with 1.92-km sampling. The instrument is capable of acquiring global coverage every nine days.

Diner, D. J.↗
NASA NTRS1993

The influence of the hydrologic cycle on the extent of sea ice with climatic implications

Multi-temporal satellite images, field observations, and field measurements were used to investigate the mechanisms by which sea ice melts offshore from the Mackenzie River delta. Advanced Very High Resolution Radiometer (AVHRR) satellite data recorded in 1986 were analyzed. The satellite data were geometrically corrected and radiometrically calibrated so that albedo and temperature values could be extracted. The investigation revealed that sea ice melted approximately 2 weeks earlier offshore from the Mackenzie River delta than along coasts where river discharge is minimal or non-existent. There is significant intra-delta variability in the timing and patterns of ice melt. An estimation of energy flux indicates that 30 percent more of the visible wavelength energy and 25 percent more of the near-infrared wavelength energy is absorbed by water offshore of the delta compared to coastal areas with minimal river discharge. The analysis also revealed that the removal of sea ice involves the following: over-ice-flooding along the coast offshore from river delta channels; under-ice flow of 'warm' river water; melting and calving of the fast ice; and, the formation of a bight in the pack ice edge. Two stages in the melting of sea ice were identified: (1) an early stage where heat is supplied to overflows largely by solar radiation, and (2) a later stage where heat is supplied by river discharge in addition to solar radiation. A simple thermodynamic model of the thaw process in the fast ice zone was developed and parameterized based on events recorded by the satellite images. The model treats river discharge as the source of sensible heat at the base of the ice cover. The results of a series of sensitivity tests to assess the influence of river discharge on the near shore ice are presented.

Dean, Kenneson G.↗
NASA NTRS1993

Commercial Applications Multispectral Sensor System

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. The ATLAS system 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 infrared wavelengths, variable spatial resolution from 2-25 meters; high geometric and geo-location accuracy; on-board radiometric calibration; digital recording; and optimized performance for minimized cost, size, and weight. ATLAS is scheduled to be available in 3rd quarter 1992 for acquisition of data for applications such as environmental monitoring, facilities management, geographic information systems data base development, and mineral exploration.

Birk, Ronald J.↗
NASA NTRS1993

The Ultraviolet Plume Instrument (UVPI)

The Ultraviolet Plume Instrument (UVPI) was launched aboard the Low-power Atmospheric Compensation Experiment (LACE) satellite on 14 Feb. 1990. Both the spacecraft and the UVPI were sponsored by the Directed Energy Office of the Strategic Defense Initiative Organization. The mission of the UVPI was to obtain radiometrically calibrated images of rocket plumes at high altitude and background image data of the Earth, Earth's limb, and celestial objects in the near- and middle-UV wave bands. The UVPI was designed for nighttime observations, i.e., to acquire and track relatively bright objects against a dark background.

Horan, D. M.↗