NASCAP Modelling of Environmental-Charging-Induced Discharges in Satellites

Abstract

SUMMARYA study of the charging and discharging characteristics of a typical geosynchronous satellite experiencing time-varying geomagnetic substorms, in sunlight, is conducted. The NASA Charging Analyzer Program (NASCAP) is used. An electric field criteria of 1.5xl0 5 volts/cm to initiate discharges and transfer of 67% of the stored charge is used in this study, based on ground test results. The substorm characteristics are arbitrarily chosen to evaluate effects of electron temperature and particle density (which is equivalent to current density). It has been found that while there is a minimum electron temperature for discharges co occur, the rate of discharges is dependent on particle density and duration times of the encounter. Hence, it is important to define the temporal variations in the substorm environments.

Modelling of Environmentally Induced Discharges in Geosynchronous Satellites

“…22 The present study extends the earlier work, concentrating on an improved simulation of discharges and parametrically evaluating spacecraft response when specified fractions of the surface charge are lost to space.…”

Computed Voltage Distributions Around Solar Electric Propulsion Spacecraft

“…This study and others (e.g., ref. 27) indicates that this threshold is at an electron temperature of about 5 keV. When the spacecraft moves into a quiescent environment, it rapidly, but not drastically, looses its charge.…”

“…Since it has been shown that the charging rate is a strong function of the number density (ref. 27), then use of the values in this model should promote rapid charging of the surfaces and minimize computer time to expose the areas of concern.…”

“…These irregularities could be an effect due to the large size of the spacecraft since it did not appear in models of smaller satellites studied (ref. 27). It should be investigated further.…”