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Aviation History
2002
2002 - 1802.PDF
SPACEFLIGHT INTERNATIONAL SPACE STATION TIM FURNISS / LONDON ISS faces delay in gyro replacement Thrusters from Russian segment of space station may be needed for attitude control as bearing assembly fails One of the four 350kg (7701b) con trol moment gyros (CMGs) aboard the International Space Station (ISS) has failed and a replacement cannot be launched until next year. A bearing assembly in the CMG 1, which is mounted on the sta tion's Zl truss, failed on 8 June as the newly arrived ISS crew was unloading equipment from the Space Shuttle Endeavour STS 111 and preparing for a spacewalk the following day. The CMGs provide attitude con trol for the ISS and without them engineers would have to rely on thrusters on the Russian segment of the station to maintain proper attitude control. The three remaining CMGs are working, with their gyro wheels spinning normally at 6,600rpm in different planes as commanded by the ISS onboard computers to main tain the desired attitude, without using precious thruster propellant. However, NASA considers the CMG 1 problem "a serious compli cation for the long-term space sta tion operations". The ISS can work using two GMGs, but that is the worst-case scenario. "Losing a CMG is a big deal as it is a major component," says flight director Paul Hill. If another unit fails, attitude will not be able to be maintained fully by the two remaining CMGs and the Russian thrusters will have to start using high propellant loads. The L-3 Communications-built gyros and associated assemblies, together weighing 450kg, are mounted inside the truss that extends upwards from the Unity The failure of one gyro is a "serious complication", says NASA node's zenit port. After criticising the Russian Mir space station for its operational problems, NASA is dis covering that operating a space sta tion involves problems and part of the success of operations is the troubleshooting that the Russians were so good at. The Space Shuttle Endeavour docked with the ISS on 8 June on its STS 111 mission to deliver a new crew and cargo, including the European Space Agency's Micro- gravity Science Glovebox, and to return the fourth expedition crew after a 190 day-plus stay. Three planned spacewalks began on 9 June, to continue work on the Mobile Base System and repair the Canadarm 2 manipulator system. The work will complete the Canadian Mobile Servicing System, allowing the mechanical arm to move from the US laboratory on the ISS along the truss to work sites. IN BRIE TDRS RESCUE Boeing hopes to move NASA's Tracking and Data Relay Satellite (TDRS-I) into its correct geostationary orbit this month after it was stranded in a transfer orbit in March when one of two hydrazine fuel tanks failed to be pressurised by helium. Boeing plans to use helium from a sec ond tank for the rescue. ASTROSAT LAUNCH India is to launch its Astrosat multi-wavelength research satel lite on the Polar Satellite Launch Vehicle in 2006-07. Astrosat will measure X-ray energy and pro duce multi-coloured maps of different radiation background. Mumbai-based Tata Institute of Fundamental Research is devel oping three X-ray payloads, while Bangalore-based Indian Institute of Astrophysics in association with the Indian Space Research Organisation is developing an ultraviolet imaging telescope to scan the entire sky. RESTRUCTURE Arianespace to streamline operation to counter stronger competition Arianespace will embark on a 50% cost-cutting exercise following its $183 million loss in 2001. The move is an attempt to safeguard the European launcher company's future in a depressed commercial launch market, against stronger competition from the new Boeing Delta IV and Lockheed Martin Atlas V fleet, which are due to make their debuts this summer. Arianespace has not said where the savings will come from, but industry sources suggest that a workforce reduction and cuts at the Kourou launch site in French Guiana are likely. Meanwhile, Arianespace share holders have approved a plan to divide the chairman and chief exec utive roles in the company. Current chairman and chief executive Jean- Marie Luton will become chairman only, while managing director Jean- Yves Le Gall becomes chief execu tive. The change was required under a French law concerning new economic regulations which moves corporate governance structure closer to the UK/US model. • Arianespace delivered the Intelsat 905 communications satel lite into geostationary transfer orbit after the 71st consecutive success ful launch of an Ariane 4 model - a 44L - from Kourou on 5 June. COMMUNICATIONS SATELLITES Russia launches replacement for Express series A Russian Proton DM booster was launched from the Baikonur Cosmodrome in Kazakhstan on 9 June carrying the national Express A1R communications satellite. The satellite is a replacement for Express A1 which was lost in a Proton launch failure in 1999. The NPO-PM-built 2,600kg (5,730lb) satellite is equipped with a communications payload built by Alcatel Space, comprising 12 C-band and five Ku-band transponders. Express A1R will be operated by the Russian Satellite Communications Company and Intersputnik. The spacecraft was part of a federal programme to renew Russia's civil communications and broadcast satellite constellations, which will see the launch of six new satellites in the Express A and Express AM series by 2005. The next Proton launch will be on 22 June on an International Launch Services mission, carrying EchoStar 8. 40 18-24 JUNE 2002 FLIGHT INTERNATIONAL www.flightinternational.com
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