SSTL Midisatellite Credit - NASA

Original version of the Surrey Microsat bus.

The original microsatellite platform allowed missions of 50 kg total mass. It was superseded by the Microsat-70, which had a modular design allowing satellites of total masses of 50 to 70 kg to be lofted.

Typical orbit: 662 km circular orbit, 98 deg inclination. Mass: 50 kg (110 lb).

• 1981 October 6 - Oscar 9 - Program: Oscar. Launch Site: Vandenberg. Launch Complex: SLC2W. Launch Vehicle: Delta. Mass: 52 kg (114 lb). Perigee: 372 km (231 mi). Apogee: 374 km (232 mi). Inclination: 97.60 deg. Period: 92.00 min.
  University of Surrey research microsatellite. Radio science; also carried amateur radio package. Communication and geophysics research satellite. Launch time 1127 GMT. Also registered by the United States in ST/SG/SER.E/59, with category D and orbital parameters 95.3 min, 531 x 533 km x 97.5 deg. UoSAT-OSCAR 9 was launched piggyback with Solar Mesosphere Explorer satellite. Weight 52 kg. Box shaped 740 x 420 x 420 mm. Deployable gravity gradient boom. Firsts: First on-board computer (IHU - Integrated Housekeeping Unit) for battery and attitude management, remote control, and experiments. Built by the University of Surrey in the United Kingdom, UO-9 was UoSAT's first experimental satellite. It was a scientific and educational low-Earth orbit satellite containing many experiments and beacons but no amateur transponders. UO-9 was fully operational until it re-entered October 13, 1989 from a decaying orbit after nine years of service.

• 1984 March 1 - Oscar 11 - Program: Oscar. Launch Site: Vandenberg. Launch Complex: SLC2W. Launch Vehicle: Delta. Mass: 52 kg (114 lb). Perigee: 651 km (404 mi). Apogee: 670 km (410 mi). Inclination: 97.80 deg. Period: 98.00 min.
  University of Surrey experimental microsatellite. Built in only 6 months, UoSAT-2 carried the first modern digital store and forward (S&F) communications payload and a prototype CCD camera. Also performed magnetospheric studies. Launch time 1759 GMT. Still operational in 2000.

• 1990 January 22 - Oscar 14 - Program: Oscar. Launch Site: Kourou. Launch Complex: ELA2. Launch Vehicle: Ariane. Mass: 46 kg (101 lb). Perigee: 781 km (485 mi). Apogee: 797 km (495 mi). Inclination: 98.60 deg. Period: 100.70 min.
  University of Surrey experimental satellite. The first of Surrey Satellite Technology Ltd's modular microsatellites. Launched on the Ariane ASAP; carried an operational store and forward communications payload with extensive radiation monitoring experiments for SatelLife and Data Trax Inc (USA). Still operational in 2000. Owner/operator University of Surrey, Dept of Electronic and Electrical Engineering, Guildford, Surrey GU2 5XH.