Electric Propulsion for Station Keeping and Electric Orbit Raising on Eutelsat Platforms
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Electric Propulsion for Station Keeping and Electric Orbit Raising on Eutelsat Platforms 2015-b/IEPC-97 Presented at Joint Conference of 30th International Symposium on Space Technology and Science 34th International Electric Propulsion Conference and 6th Nano-satellite Symposium, Hyogo-Kobe, Japan July 4 – 10, 2015 C. Casaregola1 Eutelsat, Paris, 75015, France Abstract: With a fleet of 34 geostationary satellites and more than 30 years of service from space, Eutelsat is today Europe’s most long-standing satellite operator and one of the world’s leading satellite operators. The first two platforms using Electric Propulsion procured are SESAT-1 (EUTELSAT 16C) and KA-SAT, for which Electric Propulsion is limited to on-station operations. The successful demonstration of sustained capability of Electric Propulsion for these two platforms in addition to the extensive flight heritage with no significant anomalies demonstrated in the last decades on both commercial and scientific platforms, prove the high level of maturity reached by Electric Propulsion systems. Based on that and due to new attractive launch options, one full-electric platform - EUTELSAT 115 West B – has been procured and launched in March 2015. The launch of EUTELSAT 115 West B is a key milestone for telecom platforms as it makes Eutelsat the first Operator to use Electric Propulsion for a complete electric orbit raising. Two additional platforms – EUTELSAT 117 West B and EUTELSAT 172 B - are under procurement and will perform complete electric orbit raising as well. An overview of Eutelsat platforms using Electric Propulsion for station keeping and electric orbit raising is given in the paper. Nomenclature ADSL = Asymmetric Digital Subscriber Line CPS = Chemical Propulsion System EP = Electric Propulsion EOR = Electric Orbit Raising ESA = European Space Agency E/W = East West FAA = Federal Aviation Administration FU = Filter Unit GEO = Geostationary Orbit GPS = Global Positioning System GTO = Geostationary Transfer Orbit Isp = Specific Impulse MMH = MonoMethylHydrazine NTO = Nitrogen TetraOxide N/S = North South PPS = Plasma Propulsion System SPT = Stationary Plasma Thruster 1 Spacecraft Propulsion Mechanical and Thermal Systems Engineer, Department of Engineering; Eutelsat, [email protected] 1 Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan July 4 – 10, 2015 SSTO = Supersynchronous Transfer Orbit TOM = Thruster Orientation Mechanism TMA = Thruster Module Assembly XIPS = Xenon Ion Propulsion System XFC = Xenon Flow Control XPC = XIPS Power Controller WAAS = Wide Area Augmentation System I. Introduction ITH more than 30 years of service from space, Eutelsat is the Europe’s longest-standing satellite operator. WCreated as an international organisation in 1977, Eutelsat took shape in order to operate the first generation of communications satellites ordered by the European Space Agency (ESA) and to reflect Europe’s ambition to develop an industry able to build, launch and operate satellites. From its first satellite launched in 1983, today Eutelsat's fleet of 34 satellites covers Europe, Africa, the Middle East and large parts of the Asian and American continents. Additional six satellites are to be launched by 2017. Eutelsat’s in-orbit resources are positioned in geostationary orbit between 116.9° West and 172° East. From these premium orbital positions, the Eutelsat satellite fleet is able to serve two thirds of the globe, users in 150 countries in Europe, Africa, Asia and the Americas, from the East Coast of North and South America through to the Asia-Pacific coast. Eutelsat experience and quality of service have gained the confidence of a broad and growing portfolio of customers that include broadcasters, pay-TV operators, telecom operators, Internet service providers and government agencies. The procurement of the first Eutelsat telecom platforms using Electric Propulsion (EP) dates back on mid-90s with SESAT-1. Then, a second platform - KA-SAT – was procured and launched in 2010. Both these two platforms were put in their orbital slot by using either direct GEO insertion or by on-board chemical propulsion. Then Electric Propulsion has been used on both platforms only for on-station operations. Their records of operational and flight performance data have shown up to date satisfactory results with respect to Eutelsat requirements. Furthermore, in some cases, flight performances have been even better than the expected ones. However, for next years the use of Electric Propulsion on telecom platforms will be increased. Electric Propulsion used for full or partial orbit raising is becoming more and more frequent justified by the high level of maturity reached by EP systems and by the specific economics of the overall mission. With the launch of EUTELSAT 115 West B in March 2015, Eutelsat opened the door to a new era. Eutelsat is in fact the first operator that has launched a full-electric telecom platform performing a complete Electric Orbit Raising (EOR). Moreover, two additional platforms that will perform complete EOR – EUTELSAT 117 West B and EUTELSAT 172 B – are under procurement and will be launched in the fourth quarter of 2015 and in second quarter of 2017 respectively. II. Electric Propulsion for On-Station Operations on Eutelsat Platforms A. The SESAT-1 (EUTELSAT 16C) Spacecraft Procured at the end of 90s from ISS-Reshetnev (former NPO-PM) with payload manufactured by Thales Alenia Space (former Alcatel Alenia Space), SESAT-1 (Siberian-European SATellite) was designed to provide 18 Ku channels to satisfy the telecommunications needs in Central and Eastern Europe for a minimum operational lifetime of 10 years. SESAT-1– whose commercial name is today EUTELSAT 16C - was launched from Baikonour in April 2000 and was placed directly into geostationary orbit by a Proton K-BlockDM launcher. Figure 1 shows SESAT-1 in the stowed configuration. The propulsion subsystem is composed of a Xenon SPT Propulsion system for station keeping and orbit control and of hydrazine thrusters for attitude control. All components of the propulsion subsystem are Russian built. In detail, the Electric Propulsion system is composed of 4 tanks for Xenon storage, a pressure regulation unit able to deliver the Xenon to the thrusters and 8 SPT assemblies. A power supply provides the power to the subsystem, controlling the propellant feed lines as well as the selection of the operating thrusters. Each thruster assembly is composed of a Xenon flow control unit and Figure 1. SESAT-1 satellite a Hall effect thruster SPT 100 manufactured by Fakel. This 1.5 kW thruster is in the stowed configuration (Courtesy of NPO-PM) 2 Joint Conference of 30th ISTS, 34th IEPC and 6th NSAT, Kobe-Hyogo, Japan July 4 – 10, 2015 able to provide a nominal thrust of 83 mN at an Isp of 1520 s (anode voltage of 300 V) for a total impulse of 670 kNs equivalent to more than 2200 hours at nominal thrust. Each thruster is equipped with 2 redundant cathodes that are periodically cycled in accordance with the NPO-PM and Fakel recommendations. The SESAT-1 satellite in its in-orbit configuration with solar panels and communications antennas deployed is shown in Figure 2. After separation from the Proton-BlockDM and direct insertion in GEO, SESAT-1 station acquisition was performed by using the 4 SPTs (2 prime + 2 redundant) mounted on the E/W faces. Regular station keeping maneuvers to keep the satellite within its allocated orbital slot, i. e. ±0.1 degree N/S and E/W, are performed by other 4 inclined SPTs, 2 Figure 2. SESAT-1 satellite in the deployed configuration mounted on the North face and two mounted on the (Courtesy of NPO-PM) South face. Nominal on-station operations are performed by using 1 thruster at a time and no thruster operation during eclipse period ±1 hour for EW thrusters is possible. As regards the station keeping profile, 1 maneuver per day is generally performed 7 days out of 7. During Equinox, 2 maneuvers per day are performed. Typically, maneuvers near equinox are longer than the ones near solstice period. Spacecraft attitude control is performed by using hydrazine thrusters, a pair of thrusters for each axis. However, a low level pulsing is required by these thrusters as main attitude control requirement is during initial acquisition, station keeping burns and wheels unloading. To date, SESAT-1 has accumulated a total firing duration of almost 5600 hours, in which the most used SPT 100 thruster has been firing for almost 2000 hours and the most used cathode for almost 1000 hours. SESAT-1 was designed for 10 years lifetime and after 15 years of service it is still operating properly as expected. B. The KA-SAT Spacecraft KA-SAT was manufactured by Airbus Defence and Space (former EADS Astrium), based on the Eurostar E3000 platform, with a total weight of about 6.1 tons. It was launched from Baikonour by Proton Breeze M in December 2010 and was positioned at 9° East for a design lifetime of 15 years. KA-SAT is a high throughput telecommunications satellite able to provide broadband Internet access services across Europe and some parts of the Middle East and North Africa. KA-SAT’s revolutionary concept is based on a payload with 82 Ka-band spotbeams connected to a network of ten ground stations. This configuration enables frequencies to be reused, taking total throughput to beyond 90 Gbps and making it possible to deliver Internet connectivity for more than one million homes, at speeds comparable to ADSL. In Figure 3 the KA-SAT spacecraft in deployed configuration. KA-SAT propulsion system is composed of both Chemical Propulsion System (CPS) and Plasma Propulsion System (PPS). The CPS is used for all Figure 3. Artistic view of KA-SAT satellite in the transfer orbit maneuvers including the final deorbiting, deployed configuration E/W station keeping maneuvers, attitude control and (Courtesy of Airbus Defence and Space) wheels off-loading as necessary.