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OTS 1, 2


OTS 1 and 2 (Orbital Test Satellite) were an experimental communications satellites inherited by ESA in 1975 from its predecessor, the European Space Research Organization (ESRO).

These were the first GEO communications satellites to carry six Ku-band (14/11 GHz) transponders and were capable of handling 7,200 telephone circuits. With a mass of approximately 445 kg on station, the OTS bus was hexagonal with overall dimensions of 2.4 m by 2.1 m. Two solar panels with a span of 9.3 m provided 0.6 kW of electrical power. British Aerospace was the prime contractor from the European MESH consortium which developed the OTS vehicle.

The OTS 1 was lost at launch in September 1977. OTS 2 was successfully launched in May 1978. It completed its primary mission in 1984 after which the spacecraft was involved in a 6-year program of experiments, including the testing of a new attitude control technique taking advantage of solar wind forces. OTS 2 was moved out of the geostationary ring and into a graveyard orbit.

Nation: International
Type / Application: Communication
Operator: ESA
Contractors: British Aerospace
Equipment: 6 Ku-band transponders
Configuration: OTS Bus
Propulsion: SVM-7
Power: 2 deployable solar arrays, batteries
Mass: 865 kg (445 kg BOL)
Orbit: GEO
Satellite COSPAR Date LS Launch Vehicle Remarks
OTS 1 1977-F04 13.09.1977 CC LC-17A F Delta-3914
OTS 2 1978-044A 11.05.1978 CC LC-17A Delta-3914


  • NSSDC Master Catalog: OTS
  • NSSDC Master Catalog: OTS 2
Further ESA communications satellite missions:

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