ARTEMIS orbit raising inflight experience with ion propulsion

Abstract

To demonstrate and promote North/South station keeping (inclination control) using ion propulsion, ESA on July 12, 2001 onboard Ariane 510 launched its most advanced telecommunication satellite: ARTEMIS. Due to a launcher failure the satellite was injected into a useless too low elliptic orbit. The ARTEMIS mission was salvaged by an Alenia Spazio / Astrium / ESA team at Telespazio (Fucino) using in novel modes to operate the on-board chemical and ion propulsion systems provided by Astrium. Using the chemical propulsion_ system provided by Astrium GmbH - Lampoldshausen - the inital orbit, having an apogee of half the targeted altitude. was quickly upgraded to a safe circular parking orbit at 31000 km altitude. The Liquid Apogee Engine was fired in total 8 times to achieve apogee as well as perigee raising. The final orbit raising to geostationary altitude is being performed by means of the ion propulsion system (IPP) applied in a newly designed spacecraft attitude control mode. Alenia Spazio and Astrium, in close cooperation, quickly redesigned all control and data handling software modules affected since the original spacecraft configuration was designed for inclination control only and not to generate thrust with the ion engines in a direction tangential to the orbit. The flexibility of the IPP system consisting of 4 thruster assemblies, provided in its totality by Astrium including the 2 alignment mechanisms for precision thrust direction control, had proven invaluable. To demonstrate the technologies available in Europe and to enhanced reliability, Astrium implemented two different technologies: a Kaufmann type system (EITA) provided by Astrium Ltd. - Portsmouth; and a Radiofrequency Ion Thruster Assembly (RITA) provided by Astrium GmbH - Ottobrunn. Two ion engines of different technology were mounted side by side on one ITAM (Ion Thruster Alignment Mechanism) provided by Austrian Aerospace. Artemis, after EURECA launched on 31 July 1992 and retrieved on 1 July 1993, is the second European satellite equipped with electric propulsion. This paper, after a brief description of the ion propulsion system and the results of the qualification life testing will summarize as well the special testing to support the orbit rising. The core part however will address the IPP performance on ARTEMIS in orbit during activation, inclination control and orbit raising operations. In a prominent chapter the 3-axis attitude control used during the orbit raising phase with the ion thrusters is described. In addition a principle maneuver strategy of the ARTEMIS Salvage Mission is shown.