Uhuru, the first X-ray astronomy satellite. Engineers make final adjustments to Uhuru, also known as Small Astronomy Satellite 1 (SAS-1) and Explorer 42. The first X-ray astronomy satellite, it was launched from Italy on 12 December 1970. It catalogued over 200 X-ray sources, including the black hole candidate Cygnus X-1. Uhuru made observations using a proportional counter behind the collimator at top (black rectangle). Above this are the star-sensors and sun-sensors which were used to record the direction in which the satellite was pointing.
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