The Command System Malfunction of the Telstar Satellite

After more than four months of successful performance, difficulties were experienced with the Telstar satellite command system. Early in the week of November 18, 1062, the command system became sluggish -- the satellite responded only after a long string of continuous commands had been sent. Normally, a command is carried out as soon as it is received. On November 24, after five days of increasingly sluggish performance, the command system failed to respond. There had been signs of deterioration earlier, which, however, did not affect command system performance. On August 7, about one month after launch, there was an indication that one of the redundant command decoders may have been operating intermittently. By August 21, failure of one decoder appeared to be complete. However, intermittent 1631 1G32 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1963 operation of that decoder was again possible for a three-day period during October. A program was initiated to determine the cause of failure and the action to be taken to recover the command function. Several steps were taken as a result of this study and, 011 December 20, through the use of modified command pulses, certain commands were executed by the satellite. With the command function recovered (in a limited sense), operations were performed on the satellite, and evidence suggests that these operations aided in gradual rejuvenation of both command decoders. On January 3, 1963, with both decoders responding to normal commands, the communications-experiment equipment in the satellite was turned on and tests indicated normal performance.