Accession Number : ADP005698

Title :   High Spacecraft Potentials on ISEE-1 in Sunlight,

Corporate Author : CALIFORNIA UNIV SAN DIEGO LA JOLLA CENTER FOR ASTROPHYSICS AND SPACE SCIENCES

Personal Author(s) : Whipple, E. C., Jr. ; Olsen, R. C.

Report Date : MAY 1987

Pagination or Media Count : 10

Abstract : Data from the two electric field experiments and from the plasma composition experiment on ISEE-1 show that the spacecraft charged to close to -70 V in sunlight at about 0700 UT on March 17, 1978. Data from the electron spectrometer experiment show that there was a potential barrier of some -10 to -20 V about the spacecraft during this event. The potential barrier was effective in turning back emitted photoelectrons to the spacecraft. Potential barriers can be formed by differential charging on the spacecraft or by the presence of space charge. The stringent electrostatic cleanliness specifications imposed on ISEE made by the presence of differential charging seem unlikely, if these precautions were effective. Modeling of this event to determine if the barrier was produced by the presence of space charge, suggested that this could not explain the observed barrier. The angular shape of the distribution could be successfully modeled as a product of differential charging on the solar arrays. This implies that the conductive coating was not completely effective in preventing differential charging, and that differential charging did occur.

Descriptors :   *SCIENTIFIC SATELLITES, ELECTRIC CHARGE, BARRIERS, PLASMAS(PHYSICS), SUNLIGHT, ELECTRONS, PROTECTIVE COATINGS, SPACECRAFT, SOLAR CELLS, PHOTOELECTRONS, SPACE CHARGE.

Subject Categories : Unmanned Spacecraft
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE