Relay

Relay 1 ¹ was an early 78-kg spin-stabilized satellite communications system launched by NASA on a Thor-Delta B rocket on 13 December 1962 into an elliptical orbit between 1,300 km and 7,500 km with 47.5° inclination and an orbital period of 185 minutes. Relay was designed as a one-way experimental repeater to demonstrate wideband, multi-channel analog FM voice communication using a 14-MHz bandwidth transponder. It carried two redundant repeaters, operating with an uplink at 1.725 GHz and a downlink at 4.170 GHz, delivering approximately 10 W of RF output power from a traveling-wave tube amplifier. Electrical power was provided by 8,740 solar cells charging six Ni-Cd storage batteries. In addition to its communications payload, Relay 1 supported radiation experiments intended to map the Van Allen belts.

Relay 1 became the first satellite to broadcast TV across the Pacific Ocean, from the United States to Japan. Its first planned broadcast, a pre-recorded address from President John F. Kennedy to the Japanese people on 22 November 1963, was overtaken by the breaking news of Kennedy’s assassination. In August 1964, Relay 1 was again used in a landmark demonstration, carrying coverage of the Tokyo Olympic Games from the United States across the Atlantic to Europe, after Syncom 3 relayed the signal from Japan to the United States. This marked the first use of multi-satellite intercontinental television relays.

Despite early difficulties—including susceptibility to spurious commands and regulator leakage attributed to radiation damage from the Starfish Prime nuclear test in July 1962—Relay 1 functioned successfully until 10 February 1965. With no propulsion or de-orbit capability, it remains in orbit.

A follow-on spacecraft, Relay 2, was launched on 21 January 1964 aboard another Thor–Delta B. Although physically similar in overall configuration, Relay 2 had a substantially higher launch mass of 184 kg, reflecting a more capable and robust second-generation design. The additional mass supported improved power generation and storage, enhanced telemetry, command, and tracking subsystems, and a more reliable and longer-lived communications payload, incorporating lessons learned from Relay 1’s radiation-related anomalies. Relay 2 was inserted into an orbit with an apogee of approximately 7,600 km, a perigee of about 1,870 km, and an inclination of ~46.4°.

NASA officially ceased operations with Relay 2 on 26 September 1965, when the Mojave ground station—the only one capable of communicating with it—was repurposed. However, one of its transponders continued operating until 20 November 1966, albeit with delays coming online, and the other persisted until 9 June 1967, when it stopped working properly. Like its predecessor, Relay 2 was never actively de-orbited and remains in orbit today as space debris.