Either of two microsatellites developed by the UK Defence Research Agency at Farnborough, Hampshire, to test various spacecraft systems and technologies. Each satellite weighed 50 kg. They were launched in June 1994 by the Ariane rocket from Kourou, French Guiana. The STRVs carried instruments to measure radiation, particles, and electrostatic charging. Aboard one vehicle was a cold-ion detector (CID) to monitor the activity of ions and their effects on electronic systems, as the spacecraft passed through the Earth's radiation belts.