DARPA Takes Aim At Space Junk

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The Defense Advanced Research Projects Agency seeks help solving new technical challenges in an existing program aimed at refurbishing satellites that are already in orbit.

DARPA's Phoenix program is exploring the feasibility of harvesting components from retired satellites, sometimes called space junk, and reusing them. The agency will hold a conference on Feb. 8 in conjunction with a formal announcement of the five technical challenge areas.

The program aims to "improve the economics and lower the cost of space systems," said program manager David Barnhart. "If you have the ability to use what is up there, you might be able to do it at lower cost."

There are three scenarios in development, each requiring new technologies, he said. One is the ability to use the hardware already on retired satellites, such as antennas and solar arrays. A robotic "mechanic," or servicer/tender, would be launched that's capable of retrieving components from retired satellites. That requires new tools that can grasp antennas and cut them from their booms; non-mechanical adhesives that can wrap around and attach components; and micro-cameras able to withstand the hostile environment.

A second scenario involves adding technology to active satellites as a way of lowering maintenance costs or improving performance. A third is the prospect of assembling satellites in space using a combination of salvaged components and new parts.

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The Phoenix program is also assessing the development of small "satlets" that piggyback on commercial satellite launches so they can be retrieved by the in-orbit mechanic. The satlets could carry special tools or comprise components that add capability or be combined to create new satellites.

There's a potential cost-benefit tradeoff with satlets. "The smaller the size, the less benefit you might get," Barnhart said. Ultimately, cost will be a determining factor. "The fundamental precept is cost," he said. "That's the absolute bottom line."

Five technical areas will be discussed at the upcoming Phoenix event. One is the need for a "proximity awareness" system to keep the robotic tender from bumping into other objects. Also needed are rendezvous proximity sensors to both track down retired assets to be salvaged and retrieve the payload orbital delivery systems (PODS) that carry satlets on commercial launches. Another area of discussion will be the possibility of increased efficiencies and lower costs during risk-reduction testing by coordinating the work of small companies.

The two other topics on the conference agenda are development of a "virtual ground station" capability and working with satellite providers to host and transport PODS.

There are roughly 1,300 space objects in geosynchronous orbit, some 22,000 miles above the Earth, Barnhart said. Of those, there are about 500 active and 500 retired satellites, and the remaining are debris and rocket bodies. Not all of those satellites are owned and operated by the federal government or U.S.-based companies. "We're making sure that whatever we [build] can go up to any retired satellite, with permission," Barnhart said. "We have to go through the appropriate permissive steps with the owners."

An initial demonstration, slated for 2015, will test to see if an antenna can be repurposed. "The antenna was chosen because that closes the link to the ground for communications," Barnhart said. As part of that demo, DARPA plans to use satlets to carry parts into orbit to make the antenna operable.