Drag-Free Satellite Control

Abstract

Scientific satellite missions trying to investigate questions regarding geodesy and fundamental physics have become increasingly dependent on ultra low disturbance environments. The precision demanded by the experiments has risen continuously as experimenters strive to deepen their understanding. Standard attitude and orbital control systems are not capable of providing such an ultra low disturbance environment which lead to the introduction of so called drag-free control systems. Drag-free control is an enabling technology with the capability to provide these ultra low disturbance environments. The application of drag-free control systems is of course not limited to geodesy and fundamental physics. It is a useful technology for every mission that requires a low disturbance free-fall environment. Drag-free control has come a long way since the introduction of the original drag-free concept by Benjamin Lange in 1964. The aim of this paper is to give an introduction and overview about the drag-free technology and its implications for scientific satellite missions. In addition to the original drag-free concept and its advancements the paper introduces key technologies in sensors and actuators whose development was fueled by the application of the drag-free concept in scientific satellite missions. Moreover problems and challenges connected to drag-free satellite control and the technologies involved are discussed and current drag-free missions like LISA and its technology demonstrator LISA Pathfinder, MICROSCOPE, STEP or GOCE are presented.