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Alan Stern - One of the best experts on this subject based on the ideXlab platform.

  • The Pluto reconnaissance Flyby Mission
    Eos Transactions American Geophysical Union, 1993
    Co-Authors: Alan Stern
    Abstract:

    Although Pluto was discovered in 1930, our modern view of this distant world only began taking shape in 1976. Prior to that time, the technology for studying this faint, 14th magnitude object was simply too immature. Virtually all that was known before 1976 was that Pluto circles the Sun in an unusually eccentric 248-year orbit (ranging from 29.5 to 49.4 AU) that is tilted far (17°) from the ecliptic—the plane in which the other planets orbit, that Pluto's rotation period is 6.39 days, that its intrinsic surface color is reddish, and that its rotational lightcurve is the strangest and most variegated of the planets. Since 1976, however, the pace and diversity of discoveries have increased dramatically. First, methane ice was discovered on Pluto's surface, which gave a clear indication that Pluto was formed in the outer solar system rather than simply ejected to it from another region. Next came the discovery of Pluto's large satellite Charon (usually pronounced “Sharon”) in 1978. Lying just 19,400 km from Pluto (

  • the pluto reconnaissance Flyby Mission
    Eos Transactions American Geophysical Union, 1993
    Co-Authors: Alan Stern
    Abstract:

    Although Pluto was discovered in 1930, our modern view of this distant world only began taking shape in 1976. Prior to that time, the technology for studying this faint, 14th magnitude object was simply too immature. Virtually all that was known before 1976 was that Pluto circles the Sun in an unusually eccentric 248-year orbit (ranging from 29.5 to 49.4 AU) that is tilted far (17°) from the ecliptic—the plane in which the other planets orbit, that Pluto's rotation period is 6.39 days, that its intrinsic surface color is reddish, and that its rotational lightcurve is the strangest and most variegated of the planets. Since 1976, however, the pace and diversity of discoveries have increased dramatically. First, methane ice was discovered on Pluto's surface, which gave a clear indication that Pluto was formed in the outer solar system rather than simply ejected to it from another region. Next came the discovery of Pluto's large satellite Charon (usually pronounced “Sharon”) in 1978. Lying just 19,400 km from Pluto (<1 arcsecond as seen from Earth), Charon orbits Pluto every 6.387 days—Pluto's rotation period. Thus, unlike any other satellite in the solar system, Charon orbits Pluto at its synchronous orbit.

  • Pluto Fast Flyby Mission and Science Overview
    1993
    Co-Authors: Alan Stern
    Abstract:

    Planning for the Pluto Fast Flyby (PFF) Mission centers on the launch of two small (110-160 kg) spacecraft late in the 1990s on fast, 6-8-year trajectories that do not require Jupiter Flybys. The cost target of the two-spaceraft PFF Mission is $400 million. Scientific payload definition by NASA's Outer Planets Science Working Group (OPSWG) and JPL design studies for the Pluto Flyby spacecraft are now being completed, and the program is in Phase A development. Selection of a set of lightweight, low-power instrument demonstrations is planned for May 1993. According to plan, the completion of Phase A and then detailed Phase B spacecraft and payload design work will occur in FY94. The release of an instrument payload AO, followed by the selection of the flight payload, is also scheduled for FY94.

Quartullo Renato - One of the best experts on this subject based on the ideXlab platform.

  • Satellite Relative Motion Modeling and Estimation via Nodal Elements
    2020
    Co-Authors: Leomanni Mirko, Garulli Andrea, Giannitrapani Antonio, Quartullo Renato
    Abstract:

    In this paper, a new parametrization of the relative motion between two satellites orbiting a central body is presented. The parametrization is based on the nodal elements: a set of angles describing the orbit geometry with respect to the relative line of nodes. These are combined with classical orbital elements to yield a nonsingular relative motion description. The exact nonlinear, perturbed dynamic model resulting from the new parametrization is established. The proposed parameter set captures the fundamental Keplerian invariants, while retaining a simple relationship with local orbital coordinates. An angles-only relative navigation filter and a collision avoidance scheme are devised by exploiting these features. The navigation solution is validated on a case study of an asteroid Flyby Mission. It is shown that a collision can be detected early on in the estimation process, which allows one to issue a timely evasive maneuver

  • Satellite Relative Motion Modeling and Estimation via Nodal Elements
    'American Institute of Aeronautics and Astronautics (AIAA)', 2020
    Co-Authors: Leomanni Mirko, Garulli Andrea, Giannitrapani Antonio, Quartullo Renato
    Abstract:

    In this paper, a new parameterization of the relative motion between two satellites orbiting a central body is presented. The parameterization is based on the nodal elements: a set of angles describing the orbit geometry with respect to the relative line of nodes. These are combined with classical orbital elements to yield a nonsingular relative motion description. The exact nonlinear, perturbed dynamic model resulting from the new parameterization is established. The proposed parameter set captures the fundamental Keplerian invariants, while retaining a simple relationship with local orbital coordinates. An angles-only relative navigation filter and a collision avoidance scheme are devised by exploiting these features. The navigation solution is validated on a case study of an asteroid Flyby Mission. It is shown that a collision can be detected early on in the estimation process, which allows one to issue a timely evasive maneuver

Alfred Schock - One of the best experts on this subject based on the ideXlab platform.

  • radioisotope thermophotovoltaic rtpv generator and its application to the pluto fast Flyby Mission
    1994
    Co-Authors: Alfred Schock, Meera Mukunda, V Kumar, G Summers
    Abstract:

    This paper describes the results of a DOE-sponsored design study of a radioisotope thermophotovoltaic generator. Instead of conducting a generic study, it was decided to focus the design by directing it at a specific space Mission, Pluto Fast Flyby (PFF). That Mission, under study by JPL, envisages a direct eight-year flight to Pluto (the only unexplored planet in the solar system), followed by comprehensive mapping, surface composition, and atmospheric structure measurements during a brief Flyby of the planet and its moon Charon, and transMission of the recorded science data to Earth during a one-year post-encounter cruise. Because of Pluto's long distance from the sun (30-50 A.U.) and the Mission's large energy demand, JPL has baselined the use of a radioisotope power system for the PFF spacecraft. The chief advantage of Radioisotope Thermophotovoltaic (RTPV) power systems over current Radioisotope Thermoelectric Generators (RTGs) is their much higher conversion efficiency, which greatly reduces the mass and cost of the required radioisotope heat source. Those attributes are particularly important for the PFF Mission, which - like all NASA Missions under current consideration - is severely mass- and cost-limited. The paper describes the design of the radioisotope heat source, the thermophotovoltaic converter, and the heat rejection system; and presents the results of the thermal, electrical, and structural analysis and the design optimization of the integrated RTPV system. It briefly summarizes the RTPV system's current technology status, and lists a number of factors that my greatly reduce the need for long-term tests to demonstrate generator lifetime. Our analytical results show very substantial performance improvements over an RTG designed for the same Mission, and suggest that the RTPV generator, when developed by DOE and/or NASA, would be quite valuable not only for the PFF Mission but also for other future Missions requiring small, long-lived, low-mass generators. There is a duplicate copy.

  • Radioisotope Stirling Generator Options for Pluto Fast Flyby Mission
    AIP Conference Proceedings, 1994
    Co-Authors: Alfred Schock
    Abstract:

    The preceding paper described conceptual designs and analytical results for five Radioisotope Thermoelectric Generator (RTG) options for the Pluto Fast Flyby (PFF) Mission, and the present paper describes three Radioisotope Stirling Generator (RSG) options for the same Mission. The RSG options are based on essentially the same radioisotope heat source modules used in previously flown RTGs and on designs and analyses of a 75-watt free-piston Stirling engine produced by Mechanical Technology Incorporated (MTI) for NASA's Lewis Research Center. The integrated system design options presented were generated in a Fairchild Space study sponsored by the Department of Energy's Office of Special Applications, in support of ongoing PFF Mission and spacecraft studies that the Jet Propulsion Laboratory (JPL) is conducting for the National Aeronautics and Space Administration (NASA). That study's NASA-directed goal is to reduce the spacecraft mass from its baseline value of 166 kg to ~110 kg, which implies a mass goal of less than 10 kg for a power source able to deliver 69 watts(e) at the end of the 9.2-year Mission. In general, the Stirling options were found to be lighter than the thermoelectric options described in the preceding paper. But they are less mature, requiring more development, andmore » entailing greater programmatic risk. The Stirling power system mass ranged from 7.3 kg (well below the 10-kg goal) for a non-redundant system to 11.3 kg for a redundant system able to maintain full power if one of its engines fails. In fact, the latter system could deliver as much as 115 watts(e) if desired by the Mission planners. There are 2 copies in the file.« less

  • Radioisotope Thermoelectric Generator Options for Pluto Fast Flyby Mission
    AIP Conference Proceedings, 1994
    Co-Authors: Alfred Schock
    Abstract:

    A small spacecraft design for the Pluto Fast Flyby (PFF) Mission is under study by the Jet Propulsion Laboratory (PL) for the National Aeronautics and Space Administration (NASA), for a possible launch as early as 1998. JPL's 1992 baseline design calls for a power source able to furnish an energy output of 3963 kWh and a power output of 69 Watts(e) at the end of the 9.2‐year Mission. Satisfying those demands is made difficult because NASA management has set a goal of reducing the spacecraft mass from a baseline value of 166 kg to ∼110 kg, which implies a mass goal of less than 10 kg for the power source. To support the ongoing NASA/JPL studies, the Department of Energy's Office of Special Applications (DOE/OSA) comMissioned Fairchild Space to prepare and analyze conceptual designs of radioisotope power systems for the PFF Mission. Thus far, a total of eight options employing essentially the same radioisotope heat source modules were designed and subjected to thermal, electrical, structural, and mass analy...

  • RTGs Options for Pluto Fast Flyby Mission
    1993
    Co-Authors: Alfred Schock
    Abstract:

    A small spacecraft design for the Pluto Fast Flyby (PFF) Mission is under study by the Jet Propulsion Laboratory (JPL) for the National Aeronautics and Space Administration (NASA), for a possible launch as early as 1998. JPL's 1992 baseline design calls for a power source able to furnish an energy output of 3963 kWh and a power output of 69 watts(e) at the end of the 9.2-year Mission. Satisfying those demands is made difficult because NASA management has set a goal of reducing the spacecraft mass from a baseline value of 166 kg to ~110 kg, which implies a mass goal of less than 10 kg for the power source. To support the ongoing NASA/JPL studies, the Department of Energy's Office of Special Applications (DOE/OSA) comMissioned Fairchild Space to prepare and analyze conceptual designs of radioisotope power systems for the PFF Mission. Thus far, a total of eight options employing essentially the same radioisotope heat source modules were designed and subjected to thermal, electrical, structural, and mass analyses by Fairchild. Five of these - employing thermoelectric converters - are described in the present paper, and three - employing free-piston Stirling converters - are described in the companion paper presented next.more » The system masses of the thermoelectric options ranged from 19.3 kg to 10.2 kg. In general, the options requiring least development are the heaviest, and the lighter options require more development with greater programmatic risk. There are four duplicate copies« less

  • Radioisotope Stirling Generator Options for Pluto Fast Flyby Mission
    1993
    Co-Authors: Alfred Schock
    Abstract:

    The preceding paper described conceptual designs and analytical results for five Radioisotope Thermoelectric Generator (RTG) options for the Pluto Fast Flyby (PFF) Mission, and the present paper describes three Radioisotope Stirling Generator (RSG) options for the same Mission. The RSG options are based on essentially the same radioisotope heat source modules used in previously flown RTGs and on designs and analyses of a 75-watt free-piston Stirling engine produced by Mechanical Technology Incorporated (MTI) for NASA's Lewis Research Center. The integrated system design options presented were generated in a Fairchild Space study sponsored by the Department of Energy's Office of Special Applications, in support of ongoing PFF Mission and spacecraft studies that the Jet Propulsion Laboratory (JPL) is conducting for the National Aeronautics and Space Administration (NASA). That study's NASA-directed goal is to reduce the spacecraft mass from its baseline value of 166 kg to ~110 kg, which implies a mass goal of less than 10 kg for a power source able to deliver 69 watts(e) at the end of the 9.2-year Mission. In general, the Stirling options were found to be lighter than the thermoelectric options described in the preceding paper. But they are less mature, requiring more development, and entailing greater programmatic risk. The Stirling power system mass ranged from 7.3 kg (well below the 10-kg goal) for a non-redundant system to 11.3 kg for a redundant system able to maintain full power if one of its engines fails. In fact, the latter system could deliver as much as 115 watts(e) if desired by the Mission planners. There are 5 copies in the file

P Tsou - One of the best experts on this subject based on the ideXlab platform.

  • follow the plume the habitability of enceladus
    Astrobiology, 2014
    Co-Authors: Christopher P Mckay, Ariel D Anbar, Carolyn C Porco, P Tsou
    Abstract:

    Abstract The astrobiological exploration of other worlds in our Solar System is moving from initial exploration to more focused astrobiology Missions. In this context, we present the case that the plume of Enceladus currently represents the best astrobiology target in the Solar System. Analysis of the plume by the Cassini Mission indicates that the steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. Furthermore, samples from the plume jetting out into space are accessible to a low-cost Flyby Mission. No other world has such well-studied indications of habitable conditions. Thus, the science goals that would motivate an Enceladus Mission are more advanced than for any other Solar System body. The goals of such a Mission must go beyond further geophysical characterization, extending to the search for biomolecular evidence of life in the organic-rich plume. This will require improved in situ in...

Paul R. Weissman - One of the best experts on this subject based on the ideXlab platform.

  • Short-period comets
    1991
    Co-Authors: Paul R. Weissman, Humberto Campins
    Abstract:

    The spacecraft Flybys of Comet Halley in 1986 confirmed Whipple's icy conglomerate hypothesis for cometary nuclei and showed that comets are far richer in volatiles than any other class of solar system bodies. Water is the most abundant volatile, comprising roughly 80 percent of the gas flowing out from the nucleus. Carbon monoxide is next with a content of 15 percent relative to water, though with approximately half of that coming from an extended source in the cometary coma, i.e., hydrocarbon dust grains. The detection of large numbers of hydrocarbon CHON grains was one of the more significant discoveries of the Halley Flybys, as was the ground-based observation that CN occurs in jets, again indicating an extended source. Evidence was also found for more complex hydrocarbons. Estimates of the total dust-to-gas ratio for Halley range as high as 2:1, indicating that a substantial fraction of the volatile material may be tied up in solid hydrocarbons rather than ices. The role of clathrates in trapping more volatile ices is not yet understood. If Halley can be taken to be representative of all short-period comets, then the short-period comets may provide a significant source of volatiles in near-earth space. This resource is more difficult to reach dynamically than the near-earth asteriods, but the high volatile content may justify the additional effort necessary. In addition, there is considerable evidence that at least some fraction of the near-earth asteriods are extinct cometary nuclei which have evolved into asteroid orbits, and which may contain significant volatiles buried beneath an insulating lag-deposit crust of nonvolatiles. Knowledge of comets will be greatly enhanced in the near future by the Comet Rendezvous Flyby Mission now under development by NASA, and by the proposed Rosetta Mission.

  • The comet rendezvous asteroid Flyby Mission: A status report
    1991
    Co-Authors: Paul R. Weissman, Marcia Neugebauer
    Abstract:

    The Comet Rendezvous Asteroid Flyby (CRAF) Mission received a new start in fiscal year 1990. CRAF will match orbits with an active short-period comet and follow it around the Sun, making scientific measurements of the nucleus, coma, and tail. The Imaging system will map the nucleus surface at a resolution of 1 meter/line-pair or better, while Visible and Infrared Mapping Spectrometer (VIMS) and Thermal Infrared Radiometer Experiment (TIREX) will produce spectral and thermal maps of the surface. Onboard instruments will collect cometary dust, ice, and gases and perform elemental and molecular analysis. A suite of fields and particles instruments will observe the solar wind interaction with the cometary atmosphere and tail. Radio tracking of the spacecraft will provide an accurate measure of the nucleus mass and higher harmonics in the comet's gravity field. En route to the comet, the spacecraft will make a close Flyby of a large asteroid, preferably a primitive type from the outer main belt. Observations at the asteroid include remote sensing mapping of the surface, detection of any solar wind interaction observable at the Flyby distance, and measurement of the asteroid mass to better than 10 percent accuracy. Detailed design of the CRAF spacecraft is currently underway at the Jet Propulsion Laboratory (JPL). Recent mass growth has necessitated a switch to Venus-Earth gravity assist type trajectories, similar to that used by the Galileo spacecraft. These trajectories require longer flight times from launch to rendezvous with the target comet. The details of the current baseline Mission, spacecraft design, and instrument payload will be reviewed.