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  • 1
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    The INTEGRAL scatterometer SPI (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL) mission's onboard spectrometer, the INTEGRAL spectrometer (SPI), is described. The SPI constitutes one of the four main mission instruments. It is optimized for detailed measurements of gamma ray lines and for the mapping of diffuse sources. It combines a coded aperture mask with an array of large volume, high purity germanium detectors. The detectors make precise measurements of the gamma ray energies over the 20 keV to 8 MeV range. The instrument's characteristics are described and the Monte Carlo simulation of its performance is outlined. It will be possible to study gamma ray emission from compact objects or line profiles with a high energy resolution and a high angular resolution.
    Keywords: Spacecraft Instrumentation
    Type: ; 591-598
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Performance of an INTEGRAL spectrometer model (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Model calculations for the INTEGRAL spectrometer (SPI) onboard the future INTErnational Gamma Ray Astrophysics Laboratory (INTEGAL) are presented, where the sensitivity for narrow lines is based on estimates of the background level and the detection efficiency. The instrumental background rates are explained as the sum of various components that depend on the cosmic ray intensity and the spectrometer characteristics, such as the mass distribution around the Ge detectors, the passive material, the characteristics of the detector system and the background reduction techniques. Extended background calculations were performed with Monte Carlo simulations and using semi-empirical and calculated neutron and proton cross sections. In order to improve the INTEGRAL spectrometer sensitivity, several designs and background reduction techniques were compared for an instrument with a fixed detector volume.
    Keywords: Spacecraft Instrumentation
    Type: ; 635-638
    Format: text
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  • 3
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    Monte Carlo Simulations and Generation of the SPI Response (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: In this paper we discuss the methods developed for the production of the INTEGRAL/SPI instrument response. The response files were produced using a suite of Monte Carlo simulation software developed at NASA/GSFC based on the GEANT-3 package available from CERN. The production of the INTEGRAL/SPI instrument response also required the development of a detailed computer mass model for SPI. We discuss ow extensive investigations into methods to reduce both the computation time and storage requirements for the SPI response. We also discuss corrections to the simulated response based on our comparison of ground and infiight Calibration data with MGEANT simulations.
    Keywords: Computer Programming and Software
    Format: text
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  • 4
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    INTEGRAL/SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane (2005)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The center of our Galaxy is a known strong source of electron-positron 511- keV annihilation radiation. Thus far, however, there have been no reliable detections of annihilation radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (INTErnational Gamma-RAy Astrophysics Laboratory) mission, launched in Oct. 2002, is the detailed study of this radiation. The Spectrometer on INTEGRAL (SPI) is a high resolution coded-aperture gamma-ray telescope with an unprecedented combination of sensitivity, angular resolution and energy resolution. We report results from the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic Plane. No positive annihilation flux was detected outside of the central region (|l| greater than 40 degrees) of our Galaxy. In this paper we describe the observations and data analysis methods and give limits on the 511-keV flux.
    Keywords: Astronomy
    Format: application/pdf
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  • 5
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    Monte Carlo Simulations and Generation of the SPI Response (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: In this paper we discuss the methods developed for the production of the INTEGRAL/SPI instrument response. The response files were produced using a suite of Monte Carlo simulation software developed at NASA/GSFC based on the GEANT-3 package available from CERN. The production of the INTEGRAL/SPI instrument response also required the development of a detailed computer mass model for SPI. We discuss our extensive investigations into methods to reduce both the computation time and storage requirements for the SPI response. We also discuss corrections to the simulated response based on our comparison of ground and inflight calibration data with MGEANT simulation.
    Keywords: Numerical Analysis
    Format: text
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  • 6
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    Hydrodynamic Impact Loads on 30 Degree and 60 Degree V-step Plan-form Models with and Without Dead Rise (1958)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Type: NACA-TN-4401
    Format: application/pdf
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  • 7
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    Raychaudhuri equation in the self-consistent Einstein-Cartan theory with spin-density (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The physical implications of the Raychaudhuri equation for a spinning fluid in a Riemann-Cartan spacetime is developed and discussed using the self-consistent Lagrangian based formulation for the Einstein-Cartan theory. It was found that the spin-squared terms contribute to expansion (inflation) at early times and may lead to a bounce in the final collapse. The relationship between the fluid's vorticity and spin angular velocity is clarified and the effect of the interaction terms between the spin angular velocity and the spin in the Raychaudhuri equation investigated. These results should prove useful for studies of systems with an intrinsic spin angular momentum in extreme astrophysical or cosmological problems.
    Keywords: THERMODYNAMICS AND STATISTICAL PHYSICS
    Type: NASA-TM-101145 , NAS 1.15:101145
    Format: application/pdf
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  • 8
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    On-board processing for future satellite communications systems: Satellite-Routed FDMA (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A frequency division multiple access (FDMA) 30/20 GHz satellite communications architecture without on-board baseband processing is investigated. Conceptual system designs are suggested for domestic traffic models totaling 4 Gb/s of customer premises service (CPS) traffic and 6 Gb/s of trunking traffic. Emphasis is given to the CPS portion of the system which includes thousands of earth terminals with digital traffic ranging from a single 64 kb/s voice channel to hundreds of channels of voice, data, and video with an aggregate data rate of 33 Mb/s. A unique regional design concept that effectively smooths the non-uniform traffic distribution and greatly simplifies the satellite design is employed. The satellite antenna system forms thirty-two 0.33 deg beam on both the uplinks and the downlinks in one design. In another design matched to a traffic model with more dispersed users, there are twenty-four 0.33 deg beams and twenty-one 0.7 deg beams. Detailed system design techniques show that a single satellite producing approximately 5 kW of dc power is capable of handling at least 75% of the postulated traffic. A detailed cost model of the ground segment and estimated system costs based on current information from manufacturers are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165419 , NASA/LERC-C-49029-D , MTR-8311
    Format: application/pdf
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  • 9
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    Second year technical report on-board processing for future satellite communications systems (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Advanced baseband and microwave switching techniques for large domestic communications satellites operating in the 30/20 GHz frequency bands are discussed. The nominal baseband processor throughput is one million packets per second (1.6 Gb/s) from one thousand T1 carrier rate customer premises terminals. A frequency reuse factor of sixteen is assumed by using 16 spot antenna beams with the same 100 MHz bandwidth per beam and a modulation with a one b/s per Hz bandwidth efficiency. Eight of the beams are fixed on major metropolitan areas and eight are scanning beams which periodically cover the remainder of the U.S. under dynamic control. User signals are regenerated (demodulated/remodulated) and message packages are reformatted on board. Frequency division multiple access and time division multiplex are employed on the uplinks and downlinks, respectively, for terminals within the coverage area and dwell interval of a scanning beam. Link establishment and packet routing protocols are defined. Also described is a detailed design of a separate 100 x 100 microwave switch capable of handling nonregenerated signals occupying the remaining 2.4 GHz bandwidth with 60 dB of isolation, at an estimated weight and power consumption of approximately 400 kg and 100 W, respectively.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165155 , MTR-8164 , TR-2
    Format: application/pdf
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  • 10
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    A frequency-division multiple-access system concept for 30/20 GHz high-capacity domestic satellite service (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Previously cited in issue 09, p. 1357, Accession no. A82-23484
    Keywords: COMMUNICATIONS AND RADAR
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 20; 619-625
    Format: text
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