ESA GNC Conference Papers Repository

This paper presents coordinated orbit and attitude control of a satellite formation on an air bearing table. The investigated application is the use of the formation as a telescope. The coordination and exact control of the relative position and attitude of the satellites towards each other is a challenging formation flying problem. The satellite relative dynamics are investigated in a hardware-in-the-loop environment. For the validation of the formation control strategy, the Test Environment for Applications of Multiple Spacecraft (TEAMS), a test facility for satellite formations and swarms based on air cushion vehicles, at the Institute of Space Systems of the DLR in Bremen, Germany is used. Two 5-DoF vehicles are floating on a granite table with a total experiment area of 5m x 4m. Each vehicle has a thruster system, a reaction wheel system and its own onboard computer running the control algorithms. A laser, attached at the first vehicle is pointed at a fixed target on the other vehicle to demonstrate the telescope application. The Clohessy-Wiltshire equations are used for the guidance and feed forward control of the satellites position in orbit. A second controller is used to calculate the correct pointing angles for the laser and the target. The control law is based on the relative distance and velocity of the two satellites. To achieve the optimal control of the linear system, LQR controllers are used together with feedforward for optimal tracking and to cover the nonlinearities. The characteristics of the facility and its devices are introduced, the control algorithms for both satellites are explained and simulation and HIL test results are presented.