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  • EARTH RESOURCES AND REMOTE SENSING  (170)
  • SPACECRAFT DESIGN, TESTING AND PERFORMANCE  (166)
  • 1985-1989  (336)
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  • 1
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    Microwave backscatter and emission observed from Shuttle Imaging Radar B and an airborne 1.4 GHz radiometer (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A soil moisture experiment conducted with the Shuttle Imaging Radar B (SIR-B) is reported. SIR-B operated at 1.28 GHz provided the active microwave measurements, while a 4-beam pushbroom 1.4 GHz radiometer gave the complementary passive microwave measurements. The aircraft measurements were made at an altitude of 330 m, resulting in a ground resolution cell of about 100 m diameter. SIR-B ground resolution from 225 km was about 35 m. More than 150 agricultural fields in the San Joaquin Valley of California were examined in the experiment. The effect of surface roughness height on radar backscatter and radiometric measurements was studied.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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    NASA TECHNICAL REPORTS
  • 2
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    SIRTF Telescope Instrument Changeout and Cryogen Replenishment (STICCR) Study (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Space Infrared Telescope Facility (SIRTF) is a long-life cryogenically cooled space-based telescope for infrared astronomy from 2 to 700 micrometers. SIRTF is currently under study by NASA-ARC (Reference AP) and planned for launch in approximately the mid 1990s. SIRTF will operate as a multiuser facility, initially carrying three instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and baseline is currently to be 2 years. The telescope changes required to allow in-space replenishment of the 4,000-L superfluid helium tank was investigated. A preliminary design for the space services equipment was also developed. The impacts of basing the equipment and servicing on the space station were investigated. Space replenishment and changeout of instruments required changes to the telescope design. Preliminary concepts are presented.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-177380 , NAS 1.26:177380 , T-4277
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    NASA TECHNICAL REPORTS
  • 3
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    Identification of large space structures on orbit : A survey (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Task Committee on Methods for Identification of Large Structures in Space was founded in Jul. 1984. The charter of the committee was to prepare a state-of-the-art report on methods of system identification applicable to large space structures (LSS). Funding to support preparation of the report was received in Aug. 1985 from the Air Force Rocket Propulsion Laboratory (now the Air Force Astronautics Laboratory), in the form of a contract to the ASCE. The report was completed, and published by AFRPL in Sep. 1986. The Task Committee consisted of ten members, including ASCE and AFRPL representatives. The membership represented Government, Industry, and Universities, and consisted of electrical, mechanical, and civil engineers, with backgrounds in Structural Dynamics, Optimization, and Controls. An effort was made to use consistent terminology and notation throughout the report which would be compatible with the terminology used in both the structures and controls communities.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: JPL, Model Determination for Large Space Systems Workshop, Volume 1; p 36-53
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  • 4
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    The effect of vegetation type, microrelief, and incidence angle on radar backscatter (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The NASA/JPL Synthetic Aperture Radar (SAR) was flown over a 20 x 110 km test site in the Texas High Plains regions north of Lubbock during February/March 1984. The effect of incidence angle was investigated by comparing the pixel values of the calibrated and uncalibrated images. Ten-pixel-wide transects along the entire azimuth were averaged in each of the two scenes, and plotted against the calculated incidence angle of the center of each range increment. It is evident from the graphs that both the magnitudes and patterns exhibited by the corresponding transect means of the two images are highly dissimilar. For each of the cross-poles, the uncalibrated image displayed very distinct and systematic positive trends through the entire range of incidence angles. The two like-poles, however, exhibited relatively constant returns. In the calibrated image, the cross-poles exhibited a constant return, while the like-poles demonstrated a strong negative trend across the range of look-angles, as might be expected.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL NASA(JPL Aircraft SAR Workshop Proc.; p 25-29
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  • 5
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    Boom potential of a rotating satellite in sunlight (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An interpretation is provided for the behavior of long boom potential measurements taken on the spinning P78-2 (SCATHA) satellite at near geosynchronous altitudes. This study uses data taken during a quiet day, with the satellite in sunlight. The data show periodic variations with a maximum amplitude of 6 V. The theory explains why the variations correlate well with sun direction but not with the geomagnetic field. A current balance model, assuming a Maxwellian distribution of photoelectrons, is studied. The photoelectron temperature, the degrees of positive charging of the boom and of the satellite, and the ambient electron flux are calculated. Deviations from the model are discussed.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 12137-12
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  • 6
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    Neutralization of beam-emitting spacecraft by plasma injection (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An impulsive plasma injection has been used to study charge neutralization of the Space Shuttle Orbiter while it was emitting an electron beam into space. This investigation was performed by Space Experiments with Particle Accelerators on Spacelab-1. A plasma consisting of 10 to the 19th argon ion-electron pairs was injected into space for 1 ms while an electron beam was also being emitted into space. The electron beam energy and current were as high as 5 keV and 300 mA. While the orbiter potential was positive before the plasma injection and began to decrease during the plasma injection, it was near zero for 6 to 20 ms after the plasma injection. The recovery time to the initial level of charging varied from 10 to 100 ms. In a laboratory test in a large space chamber using the same flight hardware, the neutralization time was 8-17 ms and the recovery time was 11-20 ms. The long duration of the neutralization effect in space can be explained by a model of diffusion of the cold plasma which is produced near the Orbiter by charge exchange between the neutral argon atoms and the energetic argon ions during plasma injection.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 227-231
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  • 7
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    Tropical forest biomass and successional age class relationships to a vegetation index derived from Landsat TM data (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Forest stand structure and biomass data were collected using conventional forest inventory techniques in tropical, subtropical, and warm temperate forest biomes. The feasibility of detecting tropical forest successional age class and total biomass differences using Landsat-Thematic mapper (TM) data, was evaluated. The Normalized Difference Vegetation Index (NDVI) calculated from Landsat-TM data were not significantly correlated with forest regeneration age classes in the mountain terrain of the Luquillo Experimental Forest, Puerto Rico. The low sun angle and shadows cast on steep north and west facing slopes reduced spectral reflectance values recorded by TM orbital altitude. The NDVI, calculated from low altitude aircraft scanner data, was significatly correlated with forest age classes. However, analysis of variance suggested that NDVI differences were not detectable for successional forests older than approximately 15-20 years. Also, biomass differences in young successional tropical forest were not detectable using the NDVI. The vegetation index does not appear to be a good predictor of stand structure variables (e.g., height, diameter of main stem) or total biomass in uneven age, mixed broadleaf forest. Good correlation between the vegetation index and low biomass in even age pine plantations were achieved for a warm temperate study site. The implications of the study for the use of NDVI for forest structure and biomass estimation are discussed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Remote Sensing of Environment (ISSN 0034-4257); 28; 143-156
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    NASA TECHNICAL REPORTS
  • 8
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    Optimal integral controller with sensor failure accommodation (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An Optimal Integral Controller that readily accommodates Sensor Failure - without resorting to (Kalman) filter or observer generation - has been designed. The system is based on Navy-sponsored research for the control of high performance aircraft. In conjunction with a NASA developed Numerical Optimization Code, the Integral Feedback Controller will provide optimal system response even in the case of incomplete state feedback. Hence, the need for costly replication of plant sensors is avoided since failure accommodation is effected by system software reconfiguration. The control design has been applied to a particularly ill-behaved, third-order system. Dominant-root design in the classical sense produced an almost 100 percent overshoot for the third-order system response. An application of the newly-developed Optimal Integral Controller - assuming all state information available - produces a response with no overshoot. A further application of the controller design - assuming a one-third sensor failure scenario - produced a slight overshoot response that still preserved the steady state time-point of the full-state feedback response. The control design should have wide application in space systems.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Langley Research Center, Proceedings of the Workshop on Computational Aspects in the Control of Flexible Systems, Part 2; p 1003-1023
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  • 9
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    Retrieval of water vapor profiles from microwave radiometric measurements at 183 and 92 GHz (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Microwave radiometric measurements made from an aircraft altitude of 20 km at 183.3 + or - 2, 183.3 + or - 5, and 183.3 + or - GHz, and at 92 GHz were used to retrieve the atmospheric water vapor profiles. Retrieval techniques shown to function properly in cloudfree conditions, were improved and extended to profile water vapor under moderate cloud cover conditions. The retrieved water vapor profiles compare favorably with those of rawinsonde observations at times nearly concurrent with the radiometric measurements.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: ESA, Proceedings of the 1988 International Geoscience and Remote Sensing Symposium (IGARSS) '88 on Remote Sensing: Moving Towards the 21st Century, Volume 2; p 945-948
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  • 10
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    Field spectroscopy of agricultural crops (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The development of the full potential of multispectral data acquired from satellites, requires quantitative knowledge, and physical models of the spectral properties of specific earth surface features. Knowledge of the relationships between spectral-radiometric characteristics and important biophysical parameters of agricultural crops and soils can best be obtained by carefully controlled studies of fields or plots. It is important to select plots where data describing the agronomic-biophysical properties of the crop canopies and soil background are attainable, taking into account also the feasibility of frequent timely calibrated spectral measurements. The term 'field spectroscopy' is employed for this research. The present paper is concerned with field research which was sponsored by NASA as part of the AgRISTARS Supporting Research Project. Attention is given to field research objectives, field research instrumentation, measurement procedures, spectral-temporal profile modeling, and the effects of cultural and environmental factors on crop reflectance.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); GE-24; 65-75
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