An investigation during the system test phase of the GOES spacecraft

Spurious RF oscillations were noted during the system test phase of the Geostationary Operational Environmental Satellite (GOES). A space qualified data collection platform report (DCPR) transmitter was subsequently found to have a cracked load resistor in its output isolator. The failure mechanism was caused by heat from the output power of a 20 watt transmitter being reflected into the DCPR transmitter through a sneak path. The reflection from a high VSWR at the rotary joint was not part of the normal operation but was due to unusual circumstances. The reliability of the load resistor under normal operation (low VSWR) over the life of the satellite was determined to be high.