Vanguard 1 is the oldest satellite still in orbit. It was launched on March 17, 1958, and after more than 50 years in space has made over 229,000 orbits. It is expected to stay in orbit for almost another 200 years.
Vanguard-1 was designed to be a scientific satellite, transmitting data about its internal temperature; its transmissions were also useful in measuring the shape of the Earth and the state of its atmosphere. It was the first solar-powered satellite, transmitting for more than six years. It is still tracked optically and the tracking data continues to give information about Earth's atmosphere.
Vanguard 1 was a small earth-orbiting satellite designed to test the launch capabilities of a three-stage launch vehicle and the effects of the environment on a satellite and its systems in Earth orbit. It also was used to obtain geodetic measurements through orbit analysis.
Spacecraft and Subsystems
The spacecraft was a 1.47-kg aluminum sphere 16.5 cm in diameter. It contained a 10-mW, 108-MHz mercury-battery powered transmitter and a 5-mW, 108.03-MHz transmitter powered by six square (roughly 5 cm on a side) solar cells mounted on the body of the satellite. Six 30 cm aerials protruded from the sphere. The transmitters were used primarily for engineering and tracking data, but were also used to determine the total electron content between the satellite and ground stations. Vanguard also carried two thermistors which measured the interior temperature over 16 days in order to track the effectiveness of the thermal protection.
Mission Profile
The three stage launch vehicle placed Vanguard into a 654 x 3969 km 134.2 minute orbit inclined at 34.25 degrees. Original estimates had the orbit lasting for 2000 years, but it was discovered that solar radiation pressure and atmospheric drag during high levels of solar activity produced significant perturbations in the perigee height of the satellite, which caused a significant decrease in its expected lifetime to only about 240 years. The battery powered transmitter stopped operating in June 1958 when the batteries ran down. The solar powered transmitter operated until May 1964 (when the last signals were received in Quito, Ecuador) after which the spacecraft was optically tracked from Earth.
Alternate Names
Vanguard TV4
Facts in Brief
Launch Date: 1958-03-17
Launch Vehicle: Vanguard
Launch Site: Cape Canaveral, United States
Mass: 1.47 kg