STV (Satellite Test Vehicle) was a series of vehicle evaluation payloads built for the test flights of the Europa-1 rocket.
The Europa rocket was an early expendable launch system of the European Launcher Development Organisation (ELDO), which was the precursor to the European Space Agency (ESA). It was developed with the aim to delivering space access technology, and more specifically to facilitate the deployment of European-wide telecommunication and meteorological satellites into orbit.
The European Launcher Development Organisation (ELDO) is a former European space research organization. It was first developed in order to establish a satellite launch vehicle for Europe. The three-stage rocket developed was named Europa, after the mythical Greek god. Overall, there were 10 launches that occurred under ELDO's funding.WIKI