Summary of environmentally induced electrical discharges on the P78-2 (SCATHA) satellite

The mission of the P78-2 (SCATHA) satellite, launched in January 1979, is to measure parameters related to the spacecraft charging process near synchronous orbit. The pulse analyzer experiment onboard measures the shape of pulses on four sensors. A variety of pulse shapes are observed with dominant frequencies between 5 and 32 MHz and peak amplitudes from 0.08 to 30.1 V into a 50- Omega load. The amplitude of four of the pulses exceeded by a factor of five those measured during systems level factory test. This indicates that the present test specification is inadequate to simulate the EMI levels experienced by a payload from worst-case on-orbit discharges.