Attitude and Orbit Control of Small Satellites and Constellations with FEEP Thrusters

Low thrust electric propulsion systems find a promising application field on small-to-medium sized spacecraft, with mass ranging from a few hundred to about 1000 kg and orbital altitudes of 700 km or higher, like those envisaged for most of the proposed LEO telecommunication constellations. To evaluate the performance of FEEP for such missions, a study was carried out on a typical attitude and orbit maintenance case, using current models for perturbation torques and forces. It was assumed that three-axes attitude control and drag compensation be fully performed by means of FEEP thrusters for a mission duration of 5 years, under a maximum thrust constraint of 1 mN per thruster. A reference case (900 kg spacecraft in 800 km LEO) was analyzed in detail, and a parametric performance analysis was carried out for the spacecraft mass range 100-1000 kg and orbital altitude range 400-800 km. As a result, the use of FEEP to replace momentum and reaction wheels and cold gas or hydrazine thrusters was found to be very attractive for satellites of mass in excess of 400 kg in orbits higher than 400 km about. Outside this mass and altitude ranges, the use of FEEP may still lead to significant mass savings, but the AOCS configuration must be carefully studied on a case by case basis. For all the cases studied, the mass of a full, 16-thrusters propulsion system, including thrusters, neutralizers, propellant, and redundant electronics, is less than 45 kilograms