Courier

On 4 October 1960, the US Department of Defense launched Courier 1B ^1,2,3 aboard a Thor–Able rocket (Courier 1A had failed at launch on 18 August 1960). Courier was placed into an elliptical LEO orbit between 396 km and 1,212 km, with a period of 107 minutes and an inclination of 28.3°. Courier had a launch mass of 102 kg, had a 4-W UHF analog FM transmitter and five magnetic tape recorders to provide store-and-forward (delayed-repeater) transmission of voice, data, and facsimile messages. The satellite operated on uplink frequency of 1.8–1.9 GHz and a downlink frequency of 1.7–1.8 GHz, was powered for the first time by solar cells providing ~55 W, which were also used to trickle-charge Ni-Cd batteries to provide power during eclipse periods. Despite its promise, Courier’s mission lasted only 17 days before a malfunction in its command system prevented further operation. Nevertheless, it demonstrated the feasibility of solar-powered, active communications satellites and laid the groundwork for later operational systems. Courier 1B remained in orbit for more than a decade before decaying naturally and re-entering Earth’s atmosphere on 17 August 1967, nearly seven years after launch.