Uninstrumented spherical satellite meant to enable atmospheric density measurements by observing its orbital decay. It was destroyed in the failure of the first Black Arrow orbital launch failure.
Black Arrow was a British satellite carrier rocket. Developed during the 1960s, it was used for four launches between 1969 and 1971. Its final flight was the first and only successful orbital launch to be conducted by the United Kingdom, and placed the Prospero satellite into low Earth orbit.
The Royal Aircraft Establishment (RAE) was a British research establishment, known by several different names during its history, that eventually came under the aegis of the UK Ministry of Defence (MoD), before finally losing its identity in mergers with other institutions.WIKI