Launched on March 17, 1958, Vanguard 1 was the fourth artificial satellite to successfully reach Earth orbit and the first satellite to be solar powered. Though small, with the satellite sphere measuring just 6 inches in diameter, Vanguard 1 pioneered new technologies that enabled further space exploration.
The 1.47 kg aluminum alloy satellite was designed by the Naval Research Laboratory (NRL) to test the launch capabilities of multi-stage rockets and study the effects of the space environment. Its main payloads included a 10 mW, 108 MHz transmitter powered by a mercury battery to send back telemetry and tracking data, as well as a 5 mW, 108.03 MHz transmitter powered by six solar cells – making Vanguard 1 the first satellite to rely on the sun for power.
Once in orbit, Vanguard 1 transmitted signals for over 6 years as it circled the Earth. Analysis of subtle variations in its orbit over time allowed scientists to study the upper atmosphere and refine models of atmospheric drag. The longevity of its solar-powered transmitter demonstrated the feasibility of using solar cells to enable long duration satellite missions.
Now in its 65th year in space, Vanguard 1 holds the record for being the oldest human-made object still in Earth orbit. Its legacy paved the way for extensive utilization of solar power on satellites and it continues to provide valuable data for studying space weather effects like solar radiation pressure. Though it is expected to eventually burn up upon reentry in approximately 240 years, Vanguard 1 will have circled the Earth over 200,000 times – a testament to the pioneering science and engineering behind this grapefruit-sized satellite.
