Day: May 7, 1975

NASA launches Explorer 53, renamed Small Astronomy Satellite C, from an Italian-owned offshore launch platform off the coast of Kenya. SAS-C is a smaller spacecraft than NASA’s larger Orbiting Astronomical Observatory (OAO) series, but can be aimed very precisely at any cosmic X-ray sources that it detects. One of SAS-C’s discoveries is MXB1730-33, a binary star giving off rapid X-ray bursts. SAS-C will remain in orbit and functional until it re-enters Earth’s atmosphere in 1979.