Relay program
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The Relay program consisting of Relay 1 and Relay 2 were early American satellites.
Relay 1 was launched December 13 1962, and was principally a communications satellite. Included in its payload were radiation experiments designed to map Earth's radiation belts. Shortly after launch, two basic problems evolved. One was the satellite's response to spurious commands, and the other was the leakage of a high-power regulator that caused the first two weeks of operation to be useless. After this period, satellite operation returned to normal. The satellite carried one transmitter for tracking and one for telemetry. The telemetry system was PCM at 1152 bit/s. Each 128 words per telemetry frame (of 1s duration) used 113 words for the particle experiment. The leakage problem caused the spacecraft to revert to a low voltage state early in 1965. Sporadic transmission occurred until February 10, 1965, after which no usable scientific data were obtained.
Relay 2 (launched January 21 1964), was physically similar to Relay 1. Design changes in this satellite improved its performance to the point where response to spurious commands was essentially eliminated. One of the two onboard transponders operated normally until November 20, 1966. From that time until its failure on January 20, 1967, it required a longer time than normal to come on. The other transponder continued to operate until June 9, 1967, when it too failed to operate normally.