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English: The Thor-Delta rocket system became known as the TD satellites. TD-1A was successfully launched on 11 March 1972 from Vandenberg Air Force Base (12 March in Europe). It was put in a nearly circular polar sun-synchronous orbit, with apogee 545 km, perogee 533 km, and inclination 97.6 degrees. It was Europe's first 3-axis stabilized satellite, with one axis pointing to the Sun to within +/- 5 degrees. The optical axis was maintained perpendicular to the solar pointing axis and to the orbital plane. It scanned the entire celestial sphere every 6 months, with a great circle being scanned every satellite revolution. After about 2 months of operation, both of the satellite's tape recorders failed. A network of ground stations was put together so that real-time telemetry from the satellite was recorded for about 60% of the time. After 6 months in orbit, the satellite entered a period of regular eclipses as the satellite passed behind the Earth -- cutting off sunlight to the solar panels. The satellite was put into hibernation for 4 months, until the eclipse period passed, after which systems were turned back on and another 6 months of observations were made. TD-1A was primarily a UV mission however it carried both a cosmic X-ray and a gamma-ray detector.