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The Shuttle version of the NAVSTAR Block II Global Positioning System (GPS) Space Vehicle (SV) will be injected into the transfer orbit with a Perigee Kick Motor (PKM) contained in an attached PAM-DII stage. Mission “drift” orbit injection will occur near the 4th apogee of the transfer orbit with an Apogee Kick Motor (AKM) burn. Final mission orbit will be attained following any necessary corrections by the Reaction Control System (RCS) which will also be used throughout the SV lifetime for orbit maintenance. A primary concern in the transfer procedure is GPS/PAM-DII separation following PKM burnout because of the possibility of SV and PAM-DII recontact if large coning angles have developed during the burn. Hence, initial flights will need substantial instrumentation to monitor PKM burn and separation data. The most desirable method of instrumentation readout is by telemetry transmission to an Air Force Remote Tracking station (RTS).

The development of high power, high voltage solar arrays for spacecraft has increased the risk of damage by electrostatic discharge mechanisms, and examples already exist of recently launched 10 kW+ spacecraft which have experienced solar array damage in their first year of operation. While recent analysis coupled with space and ground-based experiments has produced further insight into the problem, unresolved issues continue to exist. In the present experiments, simulation of the GEO space environment has been improved compared to past studies. An electron gun charges the solar cell circuit and its substrate using variable current and energy settings, at 1×10-7 Torr background pressure. A solar simulator lamp provides photons over the 200 nm to near infrared spectral range. The temperature of the substrate is controlled, and a floating power supply simulates the remainder of the solar cell string.