3-axis magnetic control with multiple attitude profile capabilities in the PRISMA mission
- Paper ID
5744
- author
- company
Swedish Space Corporation
- country
Sweden
- year
2006
- abstract
PRISMA will implement Guidance, Navigation and Control strategies for advanced formation flying and rendezvous experiments. The project is funded by the Swedish National Space Board and run by the Swedish Space Corporation in close cooperation with DLR, CNES and the Danish Technical University. The PRISMA test bed consists of a fully manoeuvrable MAIN satellite as well as a 3-axis controlled TARGET satellite without any deltaV capability. The launch is planned for the 2nd half of 2008. The TARGET spacecraft will be the reference satellite for the experiments performed by MAIN, either with a “cooperative” or “non-cooperative” behaviour. Small, light and cheap are the keywords for the TARGET design. The active attitude control will use magnetic torque rods only. Onboard sensors are magnetometers, sun sensors, and GPS. The TARGET mission requirements are multiple. A first mode aims at pointing the GPS antenna towards zenith to optimize conditions for relative GPS navigation. In addition, a sun pointing mode is required, especially during eclipse season. The TARGET shall also be able to mimic a non cooperative spacecraft, tumbling with a low angular rate around one axis. This feature excludes the use of a gravity gradient boom on the spacecraft. Finally, a robust safe mode has to be implemented to stabilize the spacecraft towards the sun in typically less than half an orbit, from any initial attitude and from angular rates of up to 2 deg/s. The attitude control design meets two main challenges. On the one hand, TARGET is controlled with magnetic torque rods only, with neither additional reaction wheel nor gravity gradient boom or appendage. On the other hand, normal operations are not limited to follow the local orbital frame but also multiple attitude references. The paper discusses different approaches for magnetic attitude control of the TARGET spacecraft. It analyses the pros and cons of each algorithm, and describes the way it has been implemented in the PRISMA mission. Simulation results are presented to validate the technical choices and evaluate the whole attitude control system performance.