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Courtesy of New Scientist Magazine
by Duncan Graham-Rowe
A ROBOT that can refuel and service America's spy satellites while they are in
orbit is being developed by Department of Defense researchers. The new system could extend
a satellite's life many times over, as it would no longer drop out of orbit and burn up
once its fuel was all used.
The robot refueller, dubbed the autonomous space transporter and robotic orbiter (ASTRO),
will shuttle back and forth between the spy satellite and fuel dumps stationed in holding
orbits, says David Whelan, director of the tactical technology office at the Defense
Advanced Research Projects Agency (DARPA).
With today's satellites, it is easy for an enemy to predict the craft's position, unless
it changes course. But course changes use up the satellite's limited supply of hydrazine
fuel and shorten its life. With a steady supply of fuel available to their satellites,
controllers will be able to maneuver them at will, making their orbits more difficult to
The development of ASTRO would revolutionize satellite operators' attitudes. "If an
airplane runs out of fuel you don't throw it away," says Charles Miller of
Constellation Services International in Dayton, Ohio. And yet, he says, that is precisely
what happens with satellites costing as much as $1 billion apiece.
Miller believes a refueling infrastructure is inevitable. His company has been set up to
develop a satellite retrieval and repair service along similar lines for commercial
telecoms and broadcasting satellites. The DARPA program will rely on future military
satellites being fitted with docking stations that allow them to be refueled.
DARPA has secured $5 million to begin designing ASTRO, and expects to commission aerospace
contractors to start building prototypes next year. By building satellites with modular
electronics systems, the robot could also be used to replace faulty or outdated on-board
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