There's a sea of thousands of dead or defunct satellites floating around the Earth. Most people would just see this stuff as mere space junk, but not DARPA: it's now looking to recycle these junked satellites into new space systems.
This new programme is called Phoenix, and it will cull the graveyard of broken, old satellites currently in geosynchronous orbit (GEO for short) 22,000 miles above the earth. Although all of these satellites out of fuel or power, they still have working parts such as functional antennas.
So DARPA’s plan is to launch an orbiting space robot, called the “Tender/Servicer” spacecraft to do automated repairs. But first the tender needs to collect “satlets,” a new class of nano-satellites that would hitch rides on other satellite launches. Once the Tender has collected these satlets into its tool belt, it would travel to the GEO graveyard in search of antennas. The tender would then attach the satlets to the antenna and cut it loose from the rest of the dead satellite.
Finally, the tender would taxi the new satlet-antenna to its new orbit forming a new space array from junk parts. If it works out as planed, the programme could reduce the amount of useless space debris whilst saving thousands of dollars spent on launching new satellites.
The process might seem simple on paper but, "Satellites in GEO are not designed to be disassembled or repaired, so it’s not a matter of simply removing some nuts and bolts," said David Barnhart, DARPA programme manager, in a press release. "This requires new remote imaging and robotics technology and special tools to grip, cut, and modify complex systems, since existing joints are usually molded or welded."
The process is also extremely complex, as a robotic operator needs to work three robotic arms: Two to hold the sides of an object and the third to cut it apart. Meanwhile, both the satellite and tender are in zero-gravity, where any force results in momentum, so the operator will have to be careful to not accidentally fling a satellite out into space.