The TET satellite bus - Future mission capabilities

The TET (TechnologieErprobungsTräger - Technology Experiment Carrier) satellite bus was designed as a modular and flexible bus for LEO (Low Earth Orbit) missions. Its first mission was the TET-1 satellite which was part of the OOV (On Orbit Verification) program of the DLR (German Aerospace Center) and was launched on July 22nd 2012. The next mission for the TET bus is the BIROS satellite which is planned to be launched in 2014. The bus was designed for altitudes between 450 and 850 km and an inclination between 53° and SSO (Sun Synchronous Orbit). Typical mission scenarios include earth observation and technology demonstration. Satellites based on the TET bus can be launched as a piggy back payload. The modular design allows the accommodation of different payloads without major changes to the satellite bus. This makes the TET bus suitable for most kinds of LEO missions. Although TET-1 achieved a high reliability (based on a elaborate redundancy concept and orbit experience) and an excellent payload to spacecraft mass ratio, a study was performed to increase the capabilities even further. The TETX platform is a slightly improved version of the existing satellite bus. It shares the satellite envelope of 670×580×880mm³ and 70 kg satellite bus mass with 460×460×428mm³ payload volume and 50 kg payload mass. The three-axis attitude control system provides a pointing knowledge of 10 arcsec and a position accuracy of 10 m. It contains new lithium ion cells, new transmitters and on-board computer. The spacecraft bus now provides up to 80 W steady state power and 160 W peak power to the payload and up to 155 Mbit/s data downlink with a separate payload transmitter (or 6 MBit via satellite TM/TC (Telemetry/Telecommand)) are possible. Additionally, the design life time is increased to be from 3 to 5 years. Also, a slightly bigger platform, the TET-XL platform, was designed which has an increased payload ma- s, payload power and is additionally equipped with an ADN (Ammonium Dinitramide) propulsion system. This results in 80 kg payload mass, 600×620×460 mm payload volume, 110 to 150W payload steady state and 460W payload peak power, 155 Mbit or 400 MBit/s payload data transmitter and a deltaV capacity of 80 m/s. The satellite bus envelope is 800×800×845mm³ and the bus mass is 120 kg. Furthermore, an increase in lifetime resulting in up to seven years was achieved.