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  • 1
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    SAS 2 observations of the earth albedo gamma radiation above 35 MeV (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The earth albedo gamma radiation above 35 MeV in the equatorial region is investigated using observations from the second Small Astronomy Satellite. The zenith angle distribution of the gamma radiation has a peak toward the horizon which is about an order of magnitude more intense than the radiation coming from the nadir, and nearly two orders of magnitude more intense than the gamma radiation from most parts of the sky. The gamma radiation originating from the western horizon is a factor of four more intense than the radiation from the eastern horizon and a factor of three more intense than that from the northern and southern directions. This reflects the geomagnetic effects on the incident cosmic rays whose interactions produce the albedo gamma rays. The variation of the upcoming gamma ray intensity with vertical cutoff rigidity is consistent with the empirical relationship found by Gur'yan et al. (1979).
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 86; Mar. 1
    Format: text
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  • 2
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    Parameterization of solar cells (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The aggregation (sorting) of the individual solar cells into an array is commonly based on a single operating point on the current-voltage (I-V) characteristic curve. An alternative approach for cell performance prediction and cell screening is provided by modeling the cell using an equivalent electrical circuit, in which the parameters involved are related to the physical phenomena in the device. These analytical models may be represented by a double exponential I-V characteristic with seven parameters, by a double exponential model with five parameters, or by a single exponential equation with four or five parameters. In this article we address issues concerning methodologies for the determination of solar cell parameters based on measured data points of the I-V characteristic, and introduce a procedure for screening of solar cells for arrays. We show that common curve fitting techniques, e.g., least squares, may produce many combinations of parameter values while maintaining a good fit between the fitted and measured I-V characteristics of the cell. Therefore, techniques relying on curve fitting criteria alone cannot be directly used for cell parameterization. We propose a consistent procedure which takes into account the entire set of parameter values for a batch of cells. This procedure is based on a definition of a mean cell representing the batch, and takes into account the relative contribution of each parameter to the overall goodness of fit. The procedure is demonstrated on a batch of 50 silicon cells for Space Station Freedom.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-TM-105885 , E-7188 , NAS 1.15:105885
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  • 3
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    Screening of solar cells (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Because solar cells in a production batch are not identical, screening is performed to obtain similar cells for aggregation into arrays. A common technique for screening is based on a single operating point of the I-V characteristic of the cell, usually the maximum power point. As a result, inferior cell matching may occur at the actual operating points. Screening solar cells based on the entire I-V characteristic will inherently result in more similar cells in the array. An array consisting of more similar cells is likely to have better overall characteristics and more predictable performance. Solar cell screening methods and cell ranking are discussed. The concept of a mean cell is defined as a cell 'best' representing all the cells in the production batch. The screening and ranking of all cells are performed with respect to the mean cell. The comparative results of different screening methods are illustrated on a batch of 50 silicon cells of the Space Station Freedom.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-TM-106298 , E-7987 , NAS 1.15:106298
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  • 4
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    Identification and mapping of coal refuse banks and other targets in the anthracite region (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: ERTS-1 MSS data covering parts of Pennsylvania's southern and eastern middle anthracite coal fields were studied to determine how well accumulations of coal refuse could be identified and mapped by computer analysis and processing. Spectral signatures of coal refuse targets were similar to water, but had higher reflectances in all channels. Relative reflectances were in the order 4 5 or = 6 7. Although no underflight photography was at hand to judge mapping success, correlation was made, with 1:24,000 scale U.S.G.S. maps dated 1947 and 1948. Coal refuse targets correlated well with existing maps.
    Keywords: GEOPHYSICS
    Type: PAPER-L24 , NASA. Goddard Space Flight Center Symp. on Significant Results obtained from the ERTS-1, Vol. 1, Sect. A and B; p 1067-1074
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  • 5
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    IR excitation of contaminant water by oxygen for the space shuttle at low Earth orbit altitude (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: As the water outgas of a space shuttle passes through the rarefied atmosphere at orbital altitude, collisions occur between the gases with sufficient energy to excite infrared-active water molecules to various vibrational and rotational states. An infrared contaminant model (IR model) has been developed to study the shuttle-induced excitation and emission of water molecules outgassed from the space shuttle. The focus of the first application of the model is translation-to-vibration (T-V) energy transfer since estimates suggest that this process should dominate the production of vibrationally excited H2O under typical low Earth orbit conditions. Using the velocity and position distribution functions of interacting neutral gases obtained from a neutral gases interaction model, the spatial distributions of excitation and IR radiation from contaminant water are computed, and typical results are presented. Infrared spectral data (450 - 2500/cm), measured by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) sensor on STS-39 (April 28 to May 6, 1991) at an altitude near 265 km, are used to test model predictions. The dependence of the radiant emission structure and brightness on outgassing rates and altitudes is discussed. The time history of the contaminant water outgassing rate is inferred for STS-39, and it is compared with the mass-spectrometer-based results for STS-4 (June 26 to July 4, 1982). Also, estimates of H2O column density at mission elapsed time (MET) 50 hours are compared for missions STS-2, STS-3, STS-4, and STS-39.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A10; p. 19,585-19,596
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  • 6
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    Identification and Mapping of Coal Refuse Banks and Other Targets in the Anthracite Region (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Identification and mapping of coal refuse banks and other targets in anthracite region of Pennsylvania
    Keywords: GEOPHYSICS
    Type: E73-10222 , PAPER-L24 , NASA. Goddard Space Flight Center Land Use and Mapping; p 117
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  • 7
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    Mapping of anthracite refuse (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: There are no author-identified significant results in this report.
    Keywords: GEOPHYSICS
    Type: E73-11107 , NASA-CR-135575 , ORSER-SSEL-TR-20-73
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  • 8
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    Overview of the effects of neutral gas releases on high-voltage sounding rocket platforms (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: Four recent sounding rocket experiments demonstrate that the release of neutral gas from both positively and negatively charged vechicles returns the vehicle potential to near the plasma potential. Early active experiment payloads, CHARGE-2 and Space Power Experiments Aboard Rockets 1 (SPEAR-1) observed enhanced currents from/to the vehicles during unplanned attitude thruster firings. The follow-on CHARGE-2B ad SPEAR-3 payloads directly measured the changes to the vehicle potential caused by both planned argon and unplanned nitrogen releases. The gas releases from positively charged CHARGE-2B consistently reduced the potential to 20-50 V, wheras the gas releases from negatively charged SPEAR-3 brought the potential to between -200 and -500 V. The difference in grounding levels for positively and negatively charged payloads suggests that the gas responsible for grounding is near the vehicle, within a small fraction of the sheath size.
    Keywords: GEOPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 15; 12; p. (12)83-(12)86
    Format: text
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