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  • ASTRODYNAMICS  (6)
  • LUNAR AND PLANETARY EXPLORATION  (2)
  • SOLAR PHYSICS  (1)
  • 1
    Publication Date: 2013-08-31
    Description: COMPTEL as part of a solar target of opportunity campaign observed the sun during the period of high solar activity from 7-15 Jun. 1991. Major flares were observed on 9 and 11 Jun. Although both flares were large GOES events (greater than or = X10), they were not extraordinary in terms of gamma-ray emission. Only the decay phase of the 15 Jun. flare was observed by COMPTEL. We report the preliminary analysis of data from these flares, including the first spectroscopic measurement of solar flare neutrons. The deuterium formation line at 2.223 MeV was present in both events and for at least the 9 Jun. event, was comparable to the flux in the nuclear line region of 4-8 MeV, consistent with Solar-Maximum Mission (SSM) Observations. A clear neutron signal was present in the flare of 9 Jun. with the spectrum extending up to 80 MeV and consistent in time with the emission of gamma-rays, confirming the utility of COMPTEL in measuring the solar neutron flux at low energies. The neutron flux below 100 MeV appears to be lower than that of the 3 Jun. 1982 flare by more than an order of magnitude. The neutron signal of the 11 Jun. event is under study. Severe dead time effects resulting from the intense thermal x-rays require significant corrections to the measured flux which increase the magnitude of the associated systematic uncertainties.
    Keywords: SOLAR PHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 470-479
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  • 2
    Publication Date: 2011-08-17
    Description: Viking Orbiter-1 (VO-1) made a series of close flybys of the Martian satellite Phobos in February and May 1977. A description is presented of the results obtained during the flybys in February. The flyby geometries for the encounter period in February are shown in a graph. The trajectory design gave flybys on the illuminated side of Phobos within 80 to 300 km during the entire encounter period. The primary encounter observations of Phobos included visual and infrared imaging as well as radio tracking of VO-1 while it was under the gravitational influence of Phobos. Visual imaging was obtained from two narrow-angle television cameras. Infrared observations were obtained from an infrared thermal mapper. Radio data included S- and X-band Doppler and ranging data to VO-1 with a 10-second Doppler count. Assuming for Phobos a volume of 500 + or - 900 cu km, a mean density of 1.9 + or - 0.6 g/cu cm is obtained for it on the basis of the processed data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 199; Jan. 6
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  • 3
    Publication Date: 2011-08-18
    Description: A first-order, semi-analytical method for the long-term motion of resonant satellites is introduced. The method provides long-term solutions, valid for nearly all eccentricities and inclinations, and for all commensurability ratios. The method allows the inclusion of all zonal and tesseral harmonics of a nonspherical planet. We present here an application of the method to a synchronous satellite including J2 and J22 harmonics. Global, long-term solutions for this problem are given for arbitrary values of eccentricity, argument of perigee and inclination.
    Keywords: ASTRODYNAMICS
    Type: Celestial Mechanics; 27; Aug. 198
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  • 4
    Publication Date: 2016-06-07
    Description: A first order, semianalytical theory for the long term motion of resonant satellites is presented. The theory is valid for all eccentricities and inclinations and for all commensurability ratios. The method allows the inclusion of all the zonal and tesseral harmonics as well as luni solar perturbations and radiation pressure. The method is applied to a synchronous satellite including only the J sub 2 and J sub 22 harmonics. Global, long term solutions for this problem, eccentricity, argument of perigee, and inclination are obtained.
    Keywords: ASTRODYNAMICS
    Type: NASA. Goddard Space Flight Center Flight Mech.(Estimation Theory Symp.; p 175-180
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  • 5
    Publication Date: 2019-07-13
    Description: In February 1977, the Viking 1 Orbiter made repeated flybys of the Martian satellite Phobos at distances near 100 kilometers. These close encounters allowed a detailed scientific investigation of the nature and origin of Phobos. A sequence of three maneuvers was required to achieve the encounters. This paper presents the trajectory analysis performed to accommodate the scientific objectives and the spacecraft propulsive maneuver strategy used to achieve the desired trajectory while satisfying operational constraints. The actual maneuvers executed and the resultant Phobos encounter conditions are presented.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 78-49 , Aerospace Sciences Meeting; Jan 16, 1978 - Jan 18, 1978; Huntsville, AL
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  • 6
    Publication Date: 2019-06-27
    Description: The solution to the motion of a satellite in an eccentric orbit and in resonance with the second-degree sectorial harmonic of the potential field is developed. The method of solution used parallels the well known von Zeipel method of general perturbations. The solution consists of expressions for the variations of the Delaunay variables. These expressions are composed of the perturbations developed by Brouwer in 1959 for the motion of an artificial satellite plus first-order perturbations due to the second-degree sectorial harmonic (in terms of the Legendre normal elliptic integrals of the first and second kind).
    Keywords: ASTRODYNAMICS
    Type: Celestial Mechanics; 16; Sept
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  • 7
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    In:  Other Sources
    Publication Date: 2019-07-13
    Description: A set of possible options is being considered for the next mission to Saturn after the Voyager flybys. Many of these options will include a Saturn orbiter which will provide detailed investigations of the atmosphere, magnetosphere, ring system and satellites of Saturn. The feasibility of designing Saturnian satellite tours which satisfy the science objectives and are consistent with mission requirements and constraints is explored. An orbiter mission is possible through using gravity assist trajectories to target the spacecraft from one satellite encounter to the next. A challenge in designing trajectories to encounter all the satellites is that Titan is the only massive satellite available for gravity assist. Two reference tours are presented illustrating different strategies to achieve the science objectives.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AAS PAPER 81-188 , Astrodynamics Specialist Conference; Aug 03, 1981 - Aug 05, 1981; Lake Tahoe, NV; US
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  • 8
    Publication Date: 2019-07-13
    Description: The design of Galileo's tour of Jupiter's Galilean satellites is discussed. The Galileo mission is reviewed, and the gravity-assist trajectory design is described. Attention is given to mission constraints and science requirements, several tour design strategies, and a strawman satellite tour. The software used to design a satellite tour is examined.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 83-0101 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 10, 1983 - Jan 13, 1983; Reno, NV
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  • 9
    Publication Date: 2019-07-13
    Description: The trajectory design process for the Galilean satellite probe, expected to be launched in January 1982, is examined and its interplanetary path, emphasizing arrival dates and the Mars flyby, is presented. The Galileo spacecraft is of dual spin design, combining features of Pioneer, a spinning craft, and Voyager which was 3-axis stabilized. The design of the initial orbit from Orbiter deflection through Jupiter to the beginning of the satellite tour is discussed as well as the use of an Io gravity assist flyby to achieve Jupiter orbit insertion, and the effects of solar perturbation on the initial orbit. Detail is given to the entire satellite tour trajectory design process, starting from the requirements and constraints placed on the tour through the conic design to the final numerically integrated trajectories.
    Keywords: ASTRODYNAMICS
    Type: AAS PAPER 79-141 , American Astronautical Society and American Institute of Aeronautics and Astronautics, Astrodynamics Specialist Conference; Jun 25, 1979 - Jun 27, 1979; Provincetown, MA
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