TD -1A ( Thor - Delta System Satellite 1A ) was a research satellite jointly developed within the framework of ESRO program of France, Great Britain, Sweden and the FRG. Its main task was provided by studies in the UV range, next, he conducted research in X-ray and gamma-ray range.


The satellite was launched on 12 March 1972 on a Thor - Delta rocket (Delta -N ) from the Western Test Range of Vandenberg Air Force Base in California to a 531 x 539 km high Sun-synchronous orbit. On construction was also the German group ERNO involved as prime contractor Matra Engines and Saab. In May 1972, both on-board recording devices fell out, so that only real-time telemetry was possible. One of them started work in October 1973 again. The satellite worked, only by two " sleep stages " interrupted, yet up to the exhaustion of fuel supplies in May 1974 on and burned up on January 9, 1980. The initially planned life was only six months.


Once started, the first astronomical satellite ESRO satellite was the investigation of UV, X-ray, gamma and particle radiation in space. He had a rectangular main structure ( at 2.2 m height, 0.9 x 1.0 m edge length ) and fold-out solar panels with 5 m span and associated nickel -cadmium accumulators. He used cold gas jets for attitude control, the argon used from a tank with initially 280 bar pressure. The total mass of the satellite was 473 kg of which 120 kg was attributable to the scientific payload. These consisted of seven instruments for the investigation of high-energy radiation, high-energy X-ray sources, cosmic and solar particle radiation. These included a spectrometer for the investigation of the entire sky in the range 1350-3000 Å from the Institute d' Astrophysique, Liège (B) and Royal Obs Edinburgh ( UK). A spectroscope for Star investigation in the range of 2000-3000 Å ( 1.8 Å resolution) from the Space Research Lab, Utrecht ( NL). Two solid- Cherenkov detectors for spectrometry of charged particles and a proportional counter in the X-ray range of 2-30 keV at the Centre d' Etudes de Saclay nucléaires (F). A tool to study the solar gamma radiation in the range of 50-500 MeV at the University of Milan. A cesium iodide scintillator for solar X-ray radiation in the range of 20-700 keV of the Space Research Lab in Utrecht ( NL), as well as an instrument with a spark chamber, vidicon camera, particle counter and Tscherenkowzähler for cosmic gamma rays in the range of 70-300 MeV the CENS / University of Milan and the MPI Garching (F / I / D).

The recorded data were transmitted in real time s with 1700 bit / with a transmitter with 0.3 watts of power or when playing the tape devices with 30.6 kbit / s with a 3- watt transmitter.