Debris Collision Avoidance by Means of Attitude Control – In-Flight Demonstration with TET-1

Abstract

Collision avoidance is more and more of importance due to the growing amount of space debris posing a threat not only on satellites in orbit but also on upcoming missions. To avoid a collision between space debris and functioning satellites or even between two functioning satellites collision avoidance manoeuvres can be induced if one of the satellites has a functioning propulsion system. An alternative method of collision avoidance operations is presented in this study. By changing the satellites attitude, it is possible to obtain an increase or decrease in the semi-major axis in relation to its nominal orbital decay. The change in the semi major axis together with the time until closest approach provokes a change in the relative geometry of the satellite orbit resulting in a decreasing collision risk. This method enables collision avoidance manoeuvres for satellites in Low Earth Orbits in case of functioning attitude control systems and drag susceptible satellite geometries. Additionally the probability of a collision can be reduced by changing the satellite attitude so that the minimum effective area is perpendicular to the relative velocity vector at the time of closest approach. Both methods can be applied to satellites without propulsion, which otherwise would be defenceless. A test run for verification of collision avoidance by means of drag-minimization was performed in June 2018 with the Technology Experiment Carrier (TET-1) satellite of the FireBIRD constellation. The experiment planning and results are presented along with representative examples for collision avoidance scenarios.