Accession Number : ADP005712

Title :   Automatic Charge Control System for Geosynchronous Satellites,

Corporate Author : AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA

Personal Author(s) : Shuman, B. M. ; Cohen, H. A. ; Hyman, J. ; Robson, R. R. ; Santoru, J.

Report Date : MAY 1987

Pagination or Media Count : 17

Abstract : An autonomous system to detect both absolute and differential spacecraft charging, and to reduce those potentials before hazardous arcing levels are reached, is being developed. Operation of the system is based on empirical results of the Space Test Program SCATHA and NASA ATS-6 satellites, both of which successfully demonstrated the principle of safely reducing spacecraft charging levels by emission of a low energy neutral plasma--effectively shorting the spacecraft and charged dielectric surfaces t the ambient space plasma. The charge control system now being designed and built will use a xenon-based plasma source capable of igniting within one second, adn capable of emitting a quasi-neutral plasma containing more than 1 mA of ions. The spacecraft charging level will be detected by sensors similar to those aboard SCATHA. Satellite frame potential (relative to ambient space plasma) will be determined by an electrostatic analyzer capable of detecting both ions and electrons in the energy range 50eV-20 keV. Differential charging (relative to spacecraft from ground) will be determined by a surface potential monitor using two different dielectric surfaces, and covering a range of + or - 20 kV with a response time of one second. A transient pulse monitor will detect the presence of exterior spacecraft arcing by measuring its near-field electromagnetic radiation.

Descriptors :   *ELECTRIC CHARGE, *CONTROL SYSTEMS, MICROPROCESSORS, AUTOMATIC, PLASMA GENERATORS, XENON, SHORT CIRCUITS, DIELECTRICS, ELECTRIC DISCHARGES, SPACE ENVIRONMENTS, DETECTORS, ELECTROSTATIC ANALYZERS, ACTIVATION, THRESHOLD EFFECTS, SYNCHRONOUS SATELLITES, PROTECTION.

Subject Categories : Electricity and Magnetism
      Unmanned Spacecraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE