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  • 1
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    Faraday rotation fluctutation spectra observed during solar occultation of the Helios spacecraft (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Faraday rotation (FR) measurements using linearly polarized radio signals from the two Helios spacecraft were carried out during the period from 1975 to 1984. This paper presents the results of a spectral analysis of the Helios S-band FR fluctuations observed at heliocentric distances from 2.6 to 15 solar radii during the superior conjunctions 1975-1983. The mean intensity of the FR fluctuations does not exceed the noise level for solar offsets greater than ca. 15 solar radii. The rms FR fluctuation amplitude increases rapidly as the radio ray path approaches the Sun, varying according to a power law (exponent: 2.85 +/- 0.15) at solar distances 4-12 solar radii. At distances inside 4 solar radii the increase is even steeper (exponent: 5.6 +/- 0.2). The equivalent two-dimensional FR fluctuation spectrum is well modeled by a single power-law over the frequency range from 5 to 50 mHz. For heliocentric distances larger than 4 solar radii the spectral index varies between 1.1 and 1.6 with a mean value of 1.4 +/- 0.2, corresponding to a 3-D spectral index p = 2.4. FR fluctuations thus display a somwhat lower spectral index compared with phase and amplitude fluctuations. Surprisingly high values of the spectral index were found for measurements inside 4 solar radii (p = 2.9 +/- 0.2). This may arise from the increasingly dominant effect of the magnetic field on radio wave propagation at small solar offsets. Finally, a quasiperiodic component, believed to be associated with Alfven waves, was discovered in some (but not all!) fluctuation spectra observed simultaneously at two ground stations. Characteristic periods and bulk velocities of this component were 240 +/- 30 sec and 300 +/- 60 km/s, respectively.
    Keywords: Solar Physics
    Type: International Solar Wind 8 Conference; 29; NASA-CR-199940
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  • 2
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    Space photovoltaic modules based on reflective optics (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The conceptual design and experimental results for two types of space application concentrator photovoltaic modules, employing reflective optical elements, are presented. The first type is based on the use of compound parabolic concentrators, the second type is based on the use of line-focus parabolic troughs. Lightweight concentrators are formed with nickel foil coated silver with a diamond-like carbon layer protection. Secondary optical elements, including lenses and cones, are introduced for a better matching of concentrators and solar cells. Both types of modules are characterized by concentration ratios in the range 20x to 30x, depending on the chosen range of misorientation angles. The estimated specific parameters of these modules operating with single junction AlGaAs/GaAs solar cells are 240 W/sq m and 3 kg/sq m.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 515-518
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  • 3
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    Mechanically stacked concentrator tandem solar cells (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Four-terminal mechanically stacked solar cells were developed for advanced space arrays with line-focus reflective concentrators. The top cells are based on AlGaAs/GaAs multilayer heterostructures prepared by low temperature liquid phase epitaxy. The bottom cells are based on heteroepitaxial InP/InGaAs liquid phase epitaxy or on homo-junction GaSb, Zn-diffused structures. The sum of the highest reached efficiencies of the top and bottom cells is 29.4 percent. The best four-terminal tandems have an efficiency of 27 to 28 percent. Solar cells were irradiated with 1 MeV electrons and their performances were determined as a function of fluence up to 10(exp 16) cm(exp-2). It was shown that the radiation resistance of developed tandem cells is similar to the most radiative stable AlGaAs/GaAs cells with a thin p-GaAs photoactive layer.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 363-366
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  • 4
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    High efficient radiation stable AlGaAs/GaAs solar cells with internal Bragg reflector (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An investigation of solar cells based on AlGaAs/GaAs heterostructures with an internal Bragg reflector as the back-surface reflector is presented. The Bragg reflector is grown by low pressure metalorganic chemical vapor deposition on n-GaAs substrates in a horizontal resistively heated reactor. The Bragg reflector with its maximum reflectance centered at a wavelength of 860 nm consists of 12 pairs of AlAs/GaAs layers. The resulting Bragg reflector has a thickness of 0.072 micrometers for AlAs and 0.059 micrometers for GaAs. The multi-layered quasi-dielectric stack selectively reflects weakly absorbed photons with energies near to the GaAs band gap for a second pass through the photoactive region, thus increasing the photocurrent. The use of the Bragg reflector allows the external quantum efficiency to be increased in the long wavelength of the spectrum. The use of the Bragg reflector and an antireflective coating and prismatic cover allowed an efficiency of 23.4 percent to be obtained.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 367-370
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  • 5
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    About distribution and origin of the peculiar group of sporadic meteors (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A particular group of sporadic meteors are picked out from analysis of meteor catalogs derived from results of radar observations in Mogadisho and Kharkov. The semi-major axes are equal or more than 1.73 AU and inclinations of orbits are equal or more than 90 degrees for these meteors. The distributions of radiants, velocities, and elements of orbits were derived. The probable source of meteor bodies of this peculiar group is the long-period comets, in particular, the comets of the Kreutz's group.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Asteroids, Comets, Meteors 1991; p 5-8
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  • 6
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    Determination of meteor flux distribution over the celestial sphere (1992)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: A new method of determination of meteor flux density distribution over the celestial sphere is discussed. The flux density was derived from observations by radar together with measurements of angles of arrival of radio waves reflected from meteor trails. The role of small meteor showers over the sporadic background is shown.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Asteroids, Comets, Meteors 1991; p 17-22
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  • 7
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    Models of sporadic meteor body distributions (1987)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The distribution of orbital elements and flux density over the celestial sphere are the most common forms of representation of the meteor body distribution in the vicinity of the Earth's orbit. The determination of flux density distribution of sporadic meteor bodies was worked out. The method and its results are discussed.
    Keywords: ASTROPHYSICS
    Type: International Council of Scientific Unions, Middle Atmosphere Program. Handbook for MAP, Volume 25; p 298-304
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  • 8
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    Phobos and Deimos are sources of meteoroids (1992)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Data of Pioneer 10 meteoroid penetration detectors were revised taking into account the orientation of detectors and the spacecraft velocity relative to the sporadic meteor flux. The meteor flux density increases as an exponent to the orbit of Mars for two times for the particles with masses greater than 10(exp -6) g and six times for the particles with masses greater than 10(exp -12) - 10(exp -9) g then decreases after the orbit. Ejections of secondary meteoroid particles from surfaces of Phobos and Deimos are a possible explanation for the increase in meteoroid flux.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Asteroids, Comets, Meteors 1991; p 9-15
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  • 9
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    Berry phase in Heisenberg representation (1994)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: We define the Berry phase for the Heisenberg operators. This definition is motivated by the calculation of the phase shifts by different techniques. These techniques are: the solution of the Heisenberg equations of motion, the solution of the Schrodinger equation in coherent-state representation, and the direct computation of the evolution operator. Our definition of the Berry phase in the Heisenberg representation is consistent with the underlying supersymmetry of the model in the following sense. The structural blocks of the Hamiltonians of supersymmetrical quantum mechanics ('superpairs') are connected by transformations which conserve the similarity in structure of the energy levels of superpairs. These transformations include transformation of phase of the creation-annihilation operators, which are generated by adiabatic cyclic evolution of the parameters of the system.
    Keywords: THERMODYNAMICS AND STATISTICAL PHYSICS
    Type: NASA. Goddard Space Flight Center, Third International Workshop on Squeezed States and Uncertainty Relations; p 437-448
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  • 10
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    Reconstruction of 10(exp 20)ev Showers in EUSO and JEM EUSO (2007)
    In:  Other Sources
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    Publication Date: 2019-07-19
    Description: We describe the procedure to reconstruct 10(exp 20) ev showers in Extreme Universe Space Observatory (EUSO). We show the angular and energy resolution is excellent. We now apply this to the newly proposed Japanese JEM-EUSO and will present results at the meeting.
    Keywords: Astronomy
    Type: MSFC-377 , International Cosmic Ray Conference 2007; Jul 03, 2007 - Jul 11, 2007; Merida, Yucatan; Mexico
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