Spacecraft Charging by Magnetospheric Plasmas

A potentially catastrophic environmental phenomenon was recently discovered; large discharges and arcs on spacecraft. This phenomenon, induced by magnetospheric substorm events, was probably responsible for numerous spacecraft malfunctions and at least one spacecraft failure. More often, however, the electromagnetic interference resulting from the arc is induced into various spacecraft circuits which leads to triggering of integrated circuit switches, multivibrators and one-shots. In addition, the arcing phenomenon has given rise to degradation of thermal blankets (by vaporizing the vacuum deposited aluminum [VDA] present on the blanket), contamination of surfaces by vaporization products, triggering of light sensitive devices, and anomalous functioning of scientific sensors. The general program, undertaken by the engineering and scientific community, in response to this phenomenon, includes the following major elements: 1) the development of a standard environmental specification to cover the geomagnetic substorm environment; 2) the development of general design requirements and criteria-guidelines for design of spacecraft to be resistant to the effects of geomagnetic substorms; 3) the development of analytic tools to determine and predict stress levels induced by the substorm charging environment; 4) the development of test programs to verify the immunity of spacecraft to environmental substorm charging and arcing; and 5) the requirement for housekeeping data, environmental data, and laboratory test data. The purpose of this paper is to review the charging phenomenon, its hazards and the response of the scientific and engineering community during the past few years. The similarities and differences between spacecraft charging and SGEMP will also be discussed.