Lehrstuhl für Informatik VII - Robotik und Telematik

ADCS detumbles satellite within minutes


Since the ADCS has been turned on for the first time on Dec. 3rd it has been gathering data showing the tumbling rate of the satellite and its natural decay over several days. Apparent from the data was a natural detumbling rate of about 0.5deg/s per day. The data was recorded in several intervals with different time resolutions between 2 and 65 seconds. In the morning of Dec. 17th we turned on the attitude control system in detumbling mode. We were thrilled to see that the satellite was slowed down from about 16.5deg/s to about 1deg/s quickly. The magnetic torquers were activated less than ten times for one minute at several points in orbit during this time span. Within the first activation time of one minute, the satellite’s rotation was slowed down from 16.5deg/s to about 11deg/s resulting in a deceleration of 0.08deg/sec² which indicates and approximated applied torque of 3µNm. In between the times where the actuators were activated there the controller is deactivated in order for the attitude determination system to obtain a new attitude estimation and to save power. After having slowed down the satellite’s rotation, we have changed the control mode to a controller in which the satellite’s antenna axis follows the magnetic field lines in order to further improve the communication link. For the presented analysis more than 300kB of data have been downloaded from the satellite’s ADCS.