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  • Other Sources  (27)
  • Spacecraft Design, Testing and Performance  (14)
  • SPACE RADIATION  (13)
  • 1
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    Mars Reconnaissance Orbiter Interplanetary Cruise Navigation (2007)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Carrying six science instruments and three engineering payloads, the Mars Reconnaissance Orbiter (MRO) is the first mission in a low Mars orbit to characterize the surface, subsurface, and atmospheric properties with unprecedented detail. After a seven-month interplanetary cruise, MRO arrived at Mars executing a 1.0 km/s Mars Orbit Insertion (MOI) maneuver. MRO achieved a 430 km periapsis altitude with the final orbit solution indicating that only 10 km was attributable to navigation prediction error. With the last interplanetary maneuver performed four months before MOI, this was a significant accomplishment. This paper describes the navigation analyses and results during the 210-day interplanetary cruise. As of August 2007 MRO has returned more than 18 Terabits of scientific data in support of the objectives set by the Mars Exploration Program (MEP). The robust and exceptional interplanetary navigation performance paved the way for a successful MRO mission.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of the 20th International Symposium on Space Flight Dynamics; NASA/CP-2007-214158
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  • 2
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    Mars Reconnaissance Orbiter Aerobraking Daily Operations and Collision Avoidance (2007)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The Mars Reconnaissance Orbiter reached Mars on March 10, 2006 and performed a Mars orbit insertion maneuver of 1 km/s to enter into a large elliptical orbit. Three weeks later, aerobraking operations began and lasted about five months. Aerobraking utilized the atmospheric drag to reduce the large elliptical orbit into a smaller, near circular orbit. At the time of MRO aerobraking, there were three other operational spacecraft orbiting Mars and the navigation team had to minimize the possibility of a collision. This paper describes the daily operations of the MRO navigation team during this time as well as the collision avoidance strategy development and implementation.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of the 20th International Symposium on Space Flight Dynamics; NASA/CP-2007-214158
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  • 3
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    Maneuver Recovery Analysis for the Magnetospheric Multiscale Mission (2007)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The use of spacecraft formations creates new and more demanding requirements for orbit determination accuracy. In addition to absolute navigation requirements, there are typically relative navigation requirements that are based on the size or shape of the formation. The difficulty in meeting these requirements is related to the relative dynamics of the spacecraft orbits and the frequency of the formation maintenance maneuvers. This paper examines the effects of bi-weekly formation maintenance maneuvers on the absolute and relative orbit determination accuracy for the four-spacecraft Magnetospheric Multiscale (MMS) formation. Results are presented from high fidelity simulations that include the effects of realistic orbit determination errors in the maneuver planning process. Solutions are determined using a high accuracy extended Kalman filter designed for onboard navigation. Three different solutions are examined, considering the effects of process noise and measurement rate on the solutions.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Proceedings of the 20th International Symposium on Space Flight Dynamics; NASA/CP-2007-214158
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  • 4
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    Columbia/Einstein observations of galactic X-ray sources (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The imaging observations of galactic clusters are presented. These fall into three categories: pre-main-sequence stars in the Orion nebulae, isolated-main-and-post main-sequence stars, and supernova remnants SNR. In addition to SNR, approximately 30 sources were detected.
    Keywords: SPACE RADIATION
    Type: CONTRIB-179 , NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 422-438
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  • 5
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    A search for X-ray polarization in cosmic X-ray sources (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Fifteen strong X-ray sources were observed by the X-ray polarimeters on board the OSO-8 satellite from 1975 to 1978. The final results of this search for X-ray polarization in cosmic sources are presented in the form of upper limits for the ten sources which are discussed elsewhere. These limits in all cases are consistent with a thermal origin for the X-ray emission.
    Keywords: SPACE RADIATION
    Type: NASA-CR-173635 , NAS 1.26:173635
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  • 6
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    Neutron-induced 2.2 MeV background in gamma ray telescopes (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Neutron-induced gamma ray production is an important source of background in Compton scatter gamma ray telescopes where organic scintillator material is used. Most important is deuteron formation when atmospheric albedo and locally produced neutrons are thermalized and subsequently absorbed in the hydrogenous material. The resulting 2.2 MeV gamma ray line radiation essentially represents a continuous isotropic source within the scintillator itself. Interestingly, using a scintillator material with a high hydrogen-to-carbon ratio to minimize the scintillator material with a high hydrogen-to-carbon ratio to minimize the neutron-induced 4.4 MeV carbon line favors the np reaction. The full problem of neutron-induced background in Compton scatter telescopes has been previously discussed. Results are presented of observations with the University of California balloon-borne Compton scatter telescope where the 2.2 MeV induced line emission is prominently seen.
    Keywords: SPACE RADIATION
    Type: OG-9.3-6 , 19th Intern. Cosmic Ray Conf - Vol. 3; p 375-378; NASA-CP-2376-VOL-3
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  • 7
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    Gamma ray polarimetry (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Spectroscopic instruments currently being proposed may possess polarimetric capabilities which sould be nurtured and enhanced to permit characterization of basic emission mechanisms which are impossible using other techniques. Compton scattering and pair production detected the polarization of high energy (E is greater than 50 keV) protons in laboratory experiments. The polarization properties of a detection system consisting of 19 germanium crystals in a closed packed array are examined and the advantages of such a detector over Thompson scattering are discussed. The possiblity of using pair production to detect polarization of high energy gamma rays, and the associated modulation factors are discussed. The central difficulty involved in using pair production polarimeters in astrophysical applications is that the typical opening of the electron or positron direction with respect to the incident photon aircitron is small, of order E/sq mc. Multiple scattering in the material used to convert the photons to an electron positron pair causes deviations in the direction of the electron and positron.
    Keywords: SPACE RADIATION
    Type: CONTRIB-156 , NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 484-491
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  • 8
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    Observations of 1-30 MeV gamma rays from the galactic center (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Preliminary results are reported for gamma ray observations of the galactic center region made during a 15-hour balloon flight from Alice Springs, Australia on April 18, 1979. The observations were carried out with the UGR double-scatter gamma-ray telescope at energies of 1 to 30 MeV. The observations are compatible with a galactic source of approximately equal brightness along the region of system II galactic longitudes between 300 and 60 deg. The energy distribution joins smoothly to previous spark chamber results at energies above 30 MeV and to scintillator results below 1 MeV. It appears to be a combination of nuclear gamma ray lines superimposed on a power-law bremsstrahlung spectrum. The metastable C-12 line at 4.4 MeV appears to be present with a significance of about 16 standard deviations. The flux in the line is 0.0006 + or - 0.0003 photons/sq cm per sec per rad. The oxygen line at 6.1 MeV does not seem to appear significantly above background.
    Keywords: SPACE RADIATION
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  • 9
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    A study of four soft X-ray enhancements (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Four enhanced regions of diffuse X-ray emission are studied in the 0.15-2 KeV band. Two regions are consistent with clouds of plasma with a temperature of 1 million K about 50 pc in diameter at a distance of 150 pc. These clouds require a particle density of only a factor of 3 above an ambient hot component which may fill a substantial portion of the galactic disk in the vicinity of the sun. Another region near Eridanus is consistent with a low integrated amount of atomic hydrogen along the direction of observation, thereby permitting a greater path length of plasma to contribute to the observed flux. Finally, an extended region in Centaurus shows a temperature of about 20 million K and may be an old supernova remnant expanding into a low-density region of the galactic disk.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 212
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  • 10
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    Computational Analysis of a Prototype Martian Rotorcraft Experiment (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: This paper presents Reynolds-averaged Navier-Stokes calculations for a prototype Martian rotorcraft. The computations are intended for comparison with an ongoing Mars rotor hover test at NASA Ames Research Center. These computational simulations present a new and challenging problem, since rotors that operate on Mars will experience a unique low Reynolds number and high Mach number environment. Computed results for the 3-D rotor differ substantially from 2-D sectional computations in that the 3-D results exhibit a stall delay phenomenon caused by rotational forces along the blade span. Computational results have yet to be compared to experimental data, but computed performance predictions match the experimental design goals fairly well. In addition, the computed results provide a high level of detail in the rotor wake and blade surface aerodynamics. These details provide an important supplement to the expected experimental performance data.
    Keywords: Spacecraft Design, Testing and Performance
    Type: AIAA Paper 2002-2815 , 20th AIAA Applied Aerodynamics Conference; Jun 24, 2002 - Jun 26, 2002; Saint Louis, MO; United States
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