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Representation of the Geosynchronous Plasma Environment for Spacecraft Charging CalculationsHistorically, our ability to predict and postdict surface charging has suffered from both a lack of reliable secondary emission and backscattered electron yields and poor characterization of the plasma environment. One difficulty lies in the common practice of fitting the plasma data to a Maxwellian or Double Maxwellian distribution function, which may not represent the data well for charging purposes. For 13 years Los Alamos National Laboratory (LANL) has been accumulating measurements of electron and proton spectra from Magnetospheric Plasma Analyzer (MPA) instruments aboard a series of geosynchronous satellites. These data provide both a plasma characterization and the potential of the instrument ground. We use electron and ion flux spectra measured by the LANL MPA to examine how the use of different spectral representations of the charged particle environment in computations of spacecraft potentials during magnetospheric substorms affects the accuracy of the results. We calculate the spacecraft potential using both the measured fluxes and several different fits to these fluxes. These flux measurements and fits have been corrected for the difference between the measured and calculated potential. The potentials computed using the measured fluxes, the best available material properties of graphite carbon, and a secondary electron escape fraction of 81%, are within a factor of three of the measured potential for nearly all the data. Using a Kappa fit to the electron distribution function and a Maxwellian fit to the ion distribution function gives agreement similar to the calculations using the actual data. Alternative spectral representations, including Maxwellian and double Maxwellian for both species, lead to less satisfactory agreement between predicted and measured potentials.
Document ID
20040111098
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Davis, V. A. (Science Applications International Corp. San Diego, CA, United States)
Mandell, M. J. (Science Applications International Corp. San Diego, CA, United States)
Thomsen, M. F. (Los Alamos National Lab. NM, United States)
Date Acquired
September 7, 2013
Publication Date
March 1, 2004
Publication Information
Publication: 8th Spacecraft Charging Technology Conference
Subject Category
Spacecraft Design, Testing And Performance
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle20040111031Collected Works8th Spacecraft Charging Technology Conference
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