Orbit Maintenance for Small Satellites Using Electric Propulsion

Abstract

Controlling a small satellite position using low thrust electric propulsion requires continues control. Continues control means that the orbit control system will command the thrusters every small period of time so that the error will not accumulate. This is due to the fact that low thrust level thrusters are unable to correct an accumulated -relatively -big error. In this paper a control algorithm is developed for controlling a small satellite with Field Emission Electric Propulsion (FEEP) thruster. This algorithm takes into account the errors induced in the GPS receiver and an available thrust level of 1 mN. in the satellite velocity direction only Controller gains are chosen so as to optimize the system equivalent noise bandwidth. This approach is based on estimating the states based on the measurements and controlling the satellite position using the estimated states.This algorithm uses the modulation capability of the thruster to produce a proportional thrust for disturbances compensation.A state estimation technique is used to estimate satellite position from GPS receiver. Batched least square estimator is used. The estimated states are used with a PO discrete controller to correct the satellite position. The results pointed out the potential of using state estimation and showed that the satellite position could be kept in orbit with an error in altitude less than one meter using a single 1 mN FEEP thruster.