ATTITUDE DYNAMICS ANALYSIS OF AALTO-1 SATELLITE DURING DE-ORBITING EXPERIMENT WITH PLASMA BRAKE

rst six months of the mission are dedicated to remote sensing experiments, executed with an on-board spectral imager and a radiation monitor. The second mission phase is de-orbiting device test, conducted with Electrostatic Plasma Brake (EPB) instrument. This payload and de-orbiting concept is developed by the Finnish Meteorological Institute (FMI) and it is based on the principle of the electrostatic interaction with moving plasma. It uses a charged tether which will experience a drag due to Coulomb force whenever there is a relative motion between plasma and tether. The de-orbiting device experiment is divided into four sub-phases, to obtain all the needed measurements, to prove this concept. The EPB experiment phase begins with spinning up of the satellite using magnetorquers to an angular velocity of 200 =s while maintaining the satellite’s rotation axis parallel to inertial Z-axis. This is needed to keep the tether stretched by centrifugal force during the deployment. The EPB tether will then be deployed to a length of 10 m, using a motor in the EPB system. An analysis has been made to determine that the tether-plasma interaction can be observed from the change in the spin rate of the satellite. The tether will be activated close to the poles, with positive and negative voltages, in order to take advantage of the orientation of Earth’s local magnetic eld. The third sub-phase includes further reel-out of the tether up to a 100 m length. In this last phase of the EPB experiment, the satellite’s spin rate is brought down, by tether extension, to around 27 =s. The charged tether will then exert a force against the direction of orbital velocity and will tend to brake the satellite into Earth’s atmosphere. The collected satellite position, attitude, spin rate, EPB tether charge and satellite deceleration rate measurement data will be sent to the ground station during each pass. The dynamics, ADCS’s operation and eects of the force exerted by the deployed tether have been analysed in dierent phases. Also, the preliminary simulations of its behaviour coupled with the satellite’s ADCS have been performed.