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  • Other Sources  (8)
  • NASA Technical Reports  (8)
  • 1
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    A detailed study of the photo-injection annealing of thermally diffused InP solar cells (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A detailed analysis of the annealing of thermally diffused InP solar cells fabricated by the Nippon Mining Co. is presented. The cells were irradiated with 1 MeV electrons, and the induced degradation is measured using deep level transient spectroscopy and low temperature (86 K) IV measurements. Clear recovery of the photovoltaic parameters is observed during low temperature (T is less than 300 K) solar illuminations (1 sun, AMO) with further recovery at higher temperatures (300 less than T less than 500 K). For example, the output of a cell which was irradiated up to a fluence of 1 x 10(exp 16) cm(sup -2) was observed to recover to within 5 percent of the pre-irradiation output. An apparent correlation between the recovery of I(sub sc) and the annealing of the H4 defect and of the minority carrier trapping centers is observed. An apparent correlation between the recovery of VO, and the annealing of the H5 defect is also observed. These apparent correlations are used to develop a possible model for the mechanism of the recovery of the solar cells.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Lewis Research Center, Proceedings of the 12th Space Photovoltaic Research and Technology Conference (SPRAT 12); p 1-7
    Format: application/pdf
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  • 2
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    Low Earth orbit communications satellite (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A current thrust in satellite communication systems considers a low-Earth orbiting constellations of satellites for continuous global coverage. Conceptual design studies have been done at the time of this design project by LORAL Aerospace Corporation under the program name GLOBALSTAR and by Motorola under their IRIDIUM program. This design project concentrates on the spacecraft design of the GLOBALSTAR low-Earth orbiting communication system. Overview information on the program was gained through the Federal Communications Commission licensing request. The GLOBALSTAR system consists of 48 operational satellites positioned in a Walker Delta pattern providing global coverage and redundancy. The operational orbit is 1389 km (750 nmi) altitude with eight planes of six satellites each. The orbital planes are spaced 45 deg., and the spacecraft are separated by 60 deg. within the plane. A Delta 2 launch vehicle is used to carry six spacecraft for orbit establishment. Once in orbit, the spacecraft will utilize code-division multiple access (spread spectrum modulation) for digital relay, voice, and radio determination satellite services (RDSS) yielding position determination with accuracy up to 200 meters.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: USRA, Proceedings of the 8th Annual Summer Conference: NASA(USRA Advanced Design Program; p 287-297
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  • 3
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    Spacecraft design project: Low Earth orbit communications satellite (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This is the final product of the spacecraft design project completed to fulfill the academic requirements of the Spacecraft Design and Integration 2 course (AE-4871) taught at the U.S. Naval Postgraduate School. The Spacecraft Design and Integration 2 course is intended to provide students detailed design experience in selection and design of both satellite system and subsystem components, and their location and integration into a final spacecraft configuration. The design team pursued a design to support a Low Earth Orbiting (LEO) communications system (GLOBALSTAR) currently under development by the Loral Cellular Systems Corporation. Each of the 14 team members was assigned both primary and secondary duties in program management or system design. Hardware selection, spacecraft component design, analysis, and integration were accomplished within the constraints imposed by the 11 week academic schedule and the available design facilities.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-192038 , NAS 1.26:192038
    Format: application/pdf
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  • 4
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    Development of a satellite SAR image spectra and altimeter wave height data assimilation system for ERS-1 (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The applicability of ERS-1 wind and wave data for wave models was studied using the WAM third generation wave model and SEASAT altimeter, scatterometer and SAR data. A series of global wave hindcasts is made for the surface stress and surface wind fields by assimilation of scatterometer data for the full 96-day SEASAT and also for two wind field analyses for shorter periods by assimilation with the higher resolution ECMWF T63 model and by subjective analysis methods. It is found that wave models respond very sensitively to inconsistencies in wind field analyses and therefore provide a valuable data validation tool. Comparisons between SEASAT SAR image spectra and theoretical SAR spectra derived from the hindcast wave spectra by Monte Carlo simulations yield good overall agreement for 32 cases representing a wide variety of wave conditions. It is concluded that SAR wave imaging is sufficiently well understood to apply SAR image spectra with confidence for wave studies if supported by realistic wave models and theoretical computations of the strongly nonlinear mapping of the wave spectrum into the SAR image spectrum. A closed nonlinear integral expression for this spectral mapping relation is derived which avoids the inherent statistical errors of Monte Carlo computations and may prove to be more efficient numerically.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA-CR-182685 , NAS 1.26:182685 , ESA-CR(P)-2710 , REPT-19
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  • 5
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    Why does the perpendicular electric field increase at the edge of auroral arcs? (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Radar, rocket and satellite measurements often indicate that there is a strong increase and subsequent decrease in the perpendicular electric field when traversing one edge of an auroral arc. The analysis of rocket measurements, presented here, shows that above an auroral arc there is a small gradient in the electric field due to polarization effects in the ionosphere, but that the strong increase at the edge of the arc can only be explained if the field-aligned currents associated with the arc are taken into account.
    Keywords: GEOPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 5; 4 19; 79-82
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  • 6
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    Field-aligned currents observed in the vicinity of a moving auroral arc (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The sounding rocket Porcupine F4 was launched into an auroral arc and the field aligned currents were independently deduced from magnetic field measurements; the horizontal current deduced from the electric field measurements and height integrated conductivity calculations; and measurements of electron fluxes. Above the arc the different methods agree. The magnetosphere acts as generator and the ionosphere as load. North of the arc, the first two methods disagree, possibly due to an Alfven wave carrying the observed magnetic field perturbation. The energy flow is out of the ionosphere. Here the ionosphere acts as generator and the magnetosphere as load.
    Keywords: GEOPHYSICS
    Type: ESA Achievements of the Intern. Magnetospheric Study (IMS); p 383-385
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  • 7
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    Influence of the electron source distribution on field-aligned currents (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The field-aligned current density above a discrete auroral arc has been deduced from the downward electron flux and magnetic field measurements onboard the rocket Porcupine flight 4. Both measurements show that the field-aligned current density is, in spite of decreasing peak energies towards the edge of the arc, about 4 times higher there than in the center of the arc. This can be explained by using the single particle description for an anisotropic electron source distribution.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 12; 53-56
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  • 8
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    Dynamics of a discrete auroral arc (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Porcupine Flight 4 data were used to determine the field-aligned currents associated with a southward moving discrete auroral arc in the postmidnight sector. Three different methods were used for determining the field-aligned current which should give identical results if the arcs are quasi-stationary and no parallel electric field exists between the payload and the dynamo region of the ionosphere. As long as the rocket is above the arc, the three methods agree. The integral of precipitating electron flux, the local magnetic field perturbations, and the divergence of the horizontal Pedersen current all indicate an upward current of 5 + or - 3 microamperes/sq m. Immediately north of the arc a strong downward current of about 10-20 microamperes/sq m is detected. The magnitude, however, is not well known because the rocket's velocity relative to the arc cannot be clearly established. Further north of the southward moving arc, the two methods that can be applied (magnetic field perturbations and divergence of the horizontal Pedersen current) yield contradictory results not only about the magnitude of the current but also about the direction of the current. It is suggested that this discrepancy is due to time-dependent electric field.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 7057-706
    Format: text
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