Launch date: Dec. 12, 1970
Launch vehicle: Scout B
Launch location: Kenya
Time to orbit Earth: 96 minutes
Orbital speed: 27,300 kilometers per hour (17,000 miles per hour)
Altitude: 540 km (335 miles)
Size: 51 centimeters (20 inches) diameter; 107 centimeters (46 inches) height
Mass: 143 kilograms
Alternate names: Small Astronomy Satellite 1 (SAS-1); Explorer 42
Uhuru was the first telescope satellite in space that was completely devoted to X-ray astronomy.
The Uhuru actually contained two telescopes pointing in opposite directions, which gave the satellite the ability to scan the entire sky in search of X-ray sources. X-rays are given off by high-energy events in space. Prior to Uhuru's launch, X-rays had been detected from our sun, and in 1962, an Aerobee rocket that had been launched to measure X-rays from the moon actually found bright X-rays from the stars instead!
Since X-rays can't make it through the Earth's atmosphere, Uhuru gave us the first look at several events in space that couldn't be seen from Earth. For example, Uhuru delivered early hints that black holes exist, and also mapped X-ray sources such as binary star systems, remnants of supernovas, and galaxies. Uhuru also revealed X-ray pulsars and discovered diffuse X-ray emissions coming from galaxy clusters, which suggested that hot gas may be found between galaxies. Uhuru, which means "freedom" in Swahili, was launched from Kenya on December 12, 1970—the 7th anniversary of Kenya's independence—and stayed in service for three years.
The Science Center's Uhuru
The Uhuru on display at the Science Center is a full-scale model on loan from the National Air and Space Museum, Smithsonian Institution.