RITA ion propulsion for ARTEMIS results close to the completion of the life test

Abstract

In Mai 2001 the Radiofrequency Thruster System RITA, based on the RIT10 thruster, has achieved 13,000 hours of operation during its life test. This milestone provided the opportunity to inspect the thruster and to determine the grid erosion. Based on the erosion data the expected life time of the RIT10 is substantially larger than the 15,000 hours required for the ARTEMIS Ion Propulsion Package (IPP) qualification. In addition it could be demonstrated that even an excessive accumulation of sputter material does not cause a shot in the grid system. Artemis is a geosynchronous Telecommunication satellite developed by the European Space Agency ESA to demonstrate future technologies. The DPP is used to provide the Av required for North-SouthStation-Keeping (NSSK). Although the test, is dedicated to the thruster only, Astrium, in order to test the thruster as flight like as possible and to investigate potential interactions with the electronics or the feed system, decided to test the complete subsystem. The RITA subsystem, besides the thruster, consists of the Radiofrequency Generator (RFG), the Power Supply and Control Unit (PSCU), and the Flow Control Unit (FCU). During the life test the EQMs to date have demonstrated more than 120% of the life required for the 10 year mission. Purpose of this paper is to give a report on the status of the lifetime test. After a brief introduction, describing the IPP, with special emphasis on the RITA (a more detailed description of RITA on ARTEMIS is given in [1]), this paper will describe the results of the life test to date, give an update of the life time assessment, and describe the effect of sputter debris in the grid system.. * Copyright © 2001 by astrium GmbH. Published by AIAA, Inc. with permission. 1. The ARTEMIS Mission ARTEMIS is a geo-stationary telecommunication satellite developed by Alenia Spazio as prime contractor for the European Space Agency, as part of the Data Relay Technology Mission (DRTM). ARTEMIS is a three axis stabilized satellite and has a mass of 3100 kg. The main purpose of ARTEMIS is to promote advanced telecommunication technology. The launch of ARTEMIS, after a number of delays, now is scheduled for June 12, 2001 on the ARIANE 5 together with the PAS2B satellite. The planned mission duration is 10 years. In addition the ARTEMIS satellite was selected to demonstrate the advantages of ion propulsion for station keeping of geo-synchronous satellites during a real mission. This will be the second use of ion propulsion in Europe, after its first flight demonstration of RITA on-board of EURECA in 1992. 2. The Ion Propulsion Package (IPP) on ARTEMIS The Ion Propulsion Package (IPP) on ARTEMIS, developed under the leadership of Astrium GmbH, will be used to provide the North-South-StationKeeping. For this purpose one thruster on the north panel will be operated for 3 hours when the satellite passes the ascending node and a second one on the south panel when the descending node is passed. According to the baseline mission planning one RITA and one EITA system will be used alternately. The IPP consists of the following assemblies: • 1 Propellant Storage and Distribution Assembly (PSDA) [Astrium Ltd] including the Xenon Storage Tank (XST) [MAN-Dowty] and the Electric Pressure Regulator Mechanism (PSME) • 2 Electron Bombardment Ion Thruster Assemblies (EITA Kaufman type), which include the Electric Pressure Regulator Electronics EPRE of the PSD A [Astrium Ltd.]. The EITA subassemblies are the thruster EIT, the Propulsion (c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. Control and Electronics PCCE, and the Propellant Supply and Monitoring Equipment (PSME) • 2 Radiofrequency Ion Thruster Assemblies (RITA) [Astrium GmbH]. The detailed description of the RITA is given below. • 1 Ion Thruster Alignment Assembly, consisting of 2 Ion Thruster Alignment Mechanisms (ITAM) [Austrian Aerospace] and 1 Ion Thruster Alignment Electronics (ITAE) [Astrium GmbH]