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Aviation History
2002
2002 - 1136.PDF
TECHNOLOGY MAINTENANCE GRAHAM WARWICK / WASHINGTON DC On-orbit robots to service satellites Boeing servicing aimed at improving capabilities of spacecraft after launch, but tasks must be carefully selected The initial benefit of robotic on- orbit servicing will come from the ability to upgrade satellites after they are launched, says the US Defense Advanced Research Pro jects Agency (DARPA). Boeing Phantom Works is to demonstrate autonomous on-orbit servicing in 2006 under DARPA's Orbital Ex press programme Flight Interna tional, 19-25 March). "We are focusing on what new capabilities servicing can provide, rather than the potential for cost reductions over the lifetime of a satellite constellation," says DARPA Orbital Express programme man ager Maj Jim Shoemaker. "The ini tial applications are for capability improvement. Once on-orbit ser vicing is up and running, it can be used for cost reduction." On-orbit refuelling will allow spy satellites to be manoeuvred to change arrival times and improve coverage of regions of interest. On- orbit upgrading will allow new electronics technology to be inserted into in-service satellites. Boeing's demonstration will inv olve fuel transfer and electronic module exchange on orbit. While manned on-orbit servic ing has been successful, it is expen sive and limited in duration and accessible orbits, Shoemaker says. A robotic servicer will stay on orbit longer, operate at any altitude, and be cheaper. "But we have to be careful selecting what to do autonomously," he says. "Some things are too difficult to engineer to be replaceable, so we have to find components that can be pack aged into orbital replaceable mod ules - standard boxes the robot arm can grab on to, pull out and insert." Orbital Express studies showed an analogy with deep-sea servicing, which is performed using manned and unmanned submersibles. "The human works best on short-dura tion missions where there are a lot of unknowns. Robots work well when they know what to do, it's not very complicated, and they have to stay down longer." Two reference missions have been selected for the Orbital Exp ress demonstration: refuelling of a manoeuvrable intelligence, surveil lance and reconnaissance satellite; and upgrading the electronics in an orbiting spacecraft. Both missions require the satellites to be designed from the outset for on-orbit refu elling and upgrading, and the Boeing-led team will develop indus try-standard interfaces for docking, fuel transfer and module exchange that will be made available to all satellite designers, says Shoemaker. Boeing will conduct a subscale on-orbit demonstration, using the Astro robotic servicer to refuel and upgrade the Nextsat satellite auto nomously. The satellites, weighing a combined 1,000kg (2,2001b), will be launched together. Plans call for the six-month demonstration to reach a point where the Astro can accept then autonomously execute a mission plan involving a ren dezvous with the Nextsat, manoeu vring in close proximity, and dock ing to transfer fuel or remove and replace electronics modules. R&D ESA aims for new approach The European Space Agency (ESA) is implementing a new approach to research and devel opment, called Star Tiger, which is designed to reduce the time it takes to develop promising tech nology. The agency is seeking scientists for the pilot Star Tiger project which is aimed at pro ducing a compact colour terahertz imager using micro- machining technology, which will have a range of space applica tions including astronomy, atmospheric physics and Earth and environment monitoring. Star Tiger projects will bring a small group of researchers together, with full access to labo ratory and production facilities, removing all administrative dis tractions, and allow them to work on the project for an intense period of four to six months. The terahertz imager will be designed to operate in two fre quencies - 250GHz and 300GHz - and provide informa tion on naturally emitted waves invisible to the naked eye. SATELLITE NAVIGATION Lufthansa tests terrain awareness system enhanced with GPS card Flight tests over mountainous terrain achieved better than expected results Lufthansa has conducted satellite navigation flight trials with a Boeing 737 equipped with a terrain awareness and warning system (TAWS) upgraded with global posi tioning system (GPS) functionality. The German airline, which has developed the retrofit with Boeing and Honeywell, equipped a single 737-500 with the system which comprises an additional plug-in card in the aircraft's onboard com puter allowing the aircraft to use more precise position information via GPS. "We installed a new vari ant of Honeywell's Enhanced Ground Proximity Warning System computer with a GPS sensor card built into it. This in turn enables a more accurate terrain avoidance function on the TAWS as well as providing a highly accurate sensor for navigation purposes," says Lufthansa. "This is a highly cost-efficient solution with minimum ground time and cost to install." The car rier claims the retrofit costs a quarter of the price of a GPS multi- mode receiver installation. Flight trials were performed in late March and April. The aircraft flew to Munster Osnabriick airport where it conducted four simulated landings and an actual landing using the satellite navigation system. Position accuracy checks were performed on the runway after which the aircraft tested the terrain warning functions over mountains near the city of Kassel, says Lufthansa. "We achieved even better results than expected," says the airline. German LBA and US Federal Avia tion Administration certification is expected by the middle of the year. Lufthansa says the system is suit able for retrofit on "thousands of aircraft" equipped with a basic flight management computer, incl uding 737s and Boeing MD-80s. The German carrier plans to modify its 68 737s when the change is cert ificated. It does not operate MD-80s and is seeking a partner airline to support certification for the type. 28 9-15 APRIL 2002 FLIGHT INTERNATIONAL www.flightinternational.com
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