AsteroidFinder: Attitude Control System
Within the Compact Satellite Programm of DLR it was studied if it is possible to adapt the payload AsteroidFinder to the Compact Satellite Bus.
The primary payload AsteroidFinder is an optical telescope that will search for asteroids. The focus is placed on identifying and discovering asteroids with an orbit that is inside the Earth’s orbit around the Sun. Such Asteroids and Inner Earth Objects (IEOs) could be a potential risk for the Earth. Today there are only a few IEOs discovered.
The optical payload is placing challenging requirements towards the Attitude Control System. Especially the stability during the observation time is a driving requirement. These requirements have to be addressed during every design phase. Due to restrictions of the available hardware it is challenging to meet the required performance with a compact satellite.
To be able to control the satellite reaction wheels are used for the precise control. In addition to this magnetic torquers are used to desaturate the reaction wheels. Beside the attitude control the attitude determination is important. This is realized with Sun sensors, magnetometers, star cameras, gyroscopes and a GPS receiver.
The main task of the attitude control system development is to identify and design algorithms that are suitable for the AsteroidFinder mission. These algorithms have to be precise and autonomous to allow a successful mission. Especially the attitude determination algorithm has to be good enough to determine the attitude and the angular rates of the satellite in an accurate way. Therefore the payload (a telescope) itself is included as an additional attitude sensor.
Another point are the internal and external disturbances which have to be addressed. The internal disturbances introduced by the reaction wheels are a relevant disturbance source for the telescope.