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Two spacecraft, designed and built by RCA, to test intercontinental satellite communications technology. Relay was a communications satellite of the active repeater type, in which signals from one ground station were picked up and rebroadcast to another station by the satellite's internal equipment. Relay 1 remained operational for more than 2 years; Relay 2 was used in thousands of tests and experiments and in some 40 public demonstrations through September 1965. Both were launched by a Delta rocket from Cape Canaveral and had a mass of 78 kg.

spacecraft launch date orbit
Relay 1 Dec. 13, 1962 1,319 × 7,440 km × 47.5°
Relay 2 Jan. 21, 1964 1,961 × 7,540 km × 46.4°

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