The Orbital Test Satellite (OTS) programme was an experimental satellite system inherited by the European Space Agency (ESA) in 1975 from its predecessor, the European Space Research Organisation (ESRO). OTS was the first three-axis-stabilised Ku-band satellite, and its design has inspired the conception of almost 30 other satellites in Europe. Its successors, the Maritime European Communications Satellite (MARECS) and European Communications Satellite (ECS) series of satellites, consolidated Europe's position in communications satellite technology and manufacturing.

The European Space Research Organisation (ESRO) was an international organisation founded by 10 European nations with the intention of jointly pursuing scientific research in space. It was founded in 1964. As an organisation ESRO was based on a previously existing international scientific institution, CERN. The ESRO convention, the organisations founding document outlines it as an entity exclusively devoted to scientific pursuits. This was the case for most of its lifetime but in the final years before the formation of ESA, the European Space Agency, ESRO began a programme in the field of telecommunications. Consequently, ESA is not a mainly pure science focused entity but concentrates on telecommunications, earth observation and other application motivated activities. ESRO was merged with ELDO in 1975 to form the European Space Agency.