SSTL Minisatellite Credit - NASA

Basic Surrey Minisat bus.

SSTL's MiniSat-400 platform was a high-capability platform for missions up to 400 kg total mass, with payloads up to 200 kg. SSTL developed this larger platform in response to customers requesting a cost-effective solution for payloads with more demanding mass, volume, power, data-handling and attitude/orbit control requirements.

The MiniSat-400 platform structure was based in part on proven mechanical modules from the MicroSat-70, with three module stacks mounted in a triangular configuration at the heart of the structure. These stacks supported a payload platform providing a large volume for internal payloads, with the possibility of apertures through the side or the top facet of the satellite. The top facet provided a mounting area for external payloads, sensors and antennas. Similarly, the bottom facet had space available for external units and the launcher attach fitting.

Customers could draw upon SSTL's full range of avionics units to configure the MniSat-400 platform. SSTL offered several options for three-axis attitude control, using momentum wheels, reaction wheels or cold-gas thrusters. Key attitude sensors could be selected from a range of proven Earth, Sun, star and magnetic sensors.

The on-board data handling system featured triple redundant internal telemetry and command networks (CAN), parallel on-board computers, Ethernet for high-speed internal communications and either S or X-band downlinks.

Propulsion options included Nitrogen or Xenon cold-gas, resisto-jets and hydrazine based systems, which could be configured for station acquisition, formation flying and end-of-life de-orbiting.

In 1999, SSTL demonstrated the MiniSat-400 bus in orbit on the UoSAT-12 R&D mission. The bus was listed in the NASA Rapid Spacecraft Development Office catalogue for extremely fast procurement by U.S. government agencies.

Typical orbit: 645 km circular orbit, 64.5 deg inclination. Mass: 400 kg (880 lb). Payload: 200 kg (440 lb).

• 1999 April 21 - UoSAT-12 - Launch Site: Baikonur. Launch Complex: LC109. Launch Vehicle: R-36M. Mass: 325 kg (716 lb). Perigee: 639 km (397 mi). Apogee: 654 km (406 mi). Inclination: 64.60 deg. Period: 97.70 min.
  First launch of Russia's Dnepr launch vehicle, a converted R-36M2 ICBM. The Dnepr was launched from a silo. The third stage maneuvring bus (used on the ICBM for dispensing multiple warheads) placed UoSAT-12 into a 638 km x 652 km x 64.6 deg orbit. The third stage separated from the payload at 05:13 GMT and then made a burn into a 599 km x 1403 km x 64.6 deg orbit. UoSAT-12 was the first test of the Minibus platform, at 325 kg a larger spacecraft than earlier 50 kg Surrey UoSATs. It carried a mobile radio experiment (MERLION), a GPS receiver, and imaging cameras.

• 2005 December 28 - Giove-A - Launch Site: Baikonur. Launch Complex: LC31. Launch Vehicle: Soyuz. Mass: 600 kg (1,320 lb). Perigee: 23,616 km (14,674 mi). Apogee: 23,616 km (14,674 mi). Inclination: 56.00 deg.
  Delayed from September, October, December 26. Galileo In-Orbit Validation Element, a prototype for the Galileo European navigation satellite network. Giove carried carried two rubidium atomic clocks and a large L-band phased array antenna.