Studies of spacecraft charging on a geosynchronous telecommunications satellite

Reported here are the results of some initial analysis of space plasma charging of two charge plate sensors that are flying on the AT&T Telstar 402R geosynchronous communications satellite (89 degrees W longitude). Charging occurs on the nightside of Earth during conditions when the plasma sheet in the magnetotail moves earthward under an enhanced cross-tail electric field. The March-June 1996 interval examined occurs during solar minimum conditions and is geomagnetically quiet. Some statistical distributions of the magnitudes of the observed charging show that the normal potential of the charge plate on the anti-Earth panel of the satellite is about -150 V. The charge plate on the north transponder panel is found to have a normal potential of about -150 V during the March equinox period and about -80 V during the June solstice when it is under continual solar illumination. The largest natural charging events measured during this geomagnetically quiet interval should not be of serious design concern. (C) 1998 COSPAR. Published by Elsevier Science Ltd. All rights reserved.