NASA launches its TDRS-K tracking and data-relay satellite successfully on a Atlas V booster on Jan. 30. Then, on Feb. 1, launch of the Intelsat-27 commercial communications satellite on a Sea Launch booster fails.
TDRS-K cost NASA $350 million and its Atlas V launch another $200 million or so. Intelsat-27 and its launch would have cost less, but its failure still illustrates the high costs and risks in launching space hardware.
So DARPA is looking to dramatically reduce the cost, and risk, of launching communications satellites into geosynchronous orbit by instead removing and reusing antennas from retired spacecraft in graveyard orbit.
All graphics: DARPA
Antennas typically only account for around 2% of a satellite's mass, but the bigger the antenna the bigger and more expensive the spacecraft and the bigger and more costly its booster. Take NASA's TDRS-K, which carries two 4.9m parabolic antennas and cost $550 million to build and launch.
And DARPA calculates that, while a satellite's fuel, batteries and solar arrays should last around 15 years in orbit, its antenna could be good for more than 100 years. And reusing an existing operational aperture avoids the risk-frought process of unfurling a tightly-packaged antenna on orbit.
So DARPA's Phoenix program intends to demonstrate the on-orbit repurposing of an aperture on a retired satellite. A robotic "mechanic" will attach attitude-control, momentum-management, communications, power and other modules to the antenna, remove it from the donor spacecraft and move it to GEO to become an operating comsat.
Instead of the single costly, and potentially risky, launch of a large satellite, the modules or "satlets" would be carried into orbit as hosted payloads on commercial GEO satellite launches, which DARPA estimates provide on average one opportunity a month to send up piggyback hardware.
The Phoenix concept works like this:
- first send the servicer/tender spacecraft with its robotic arms into GEO
- then send up hosted "payload orbital delivery systems" (PODS) containing satlets and tools on commercial GEO launches
- the satellite ejects the PODS on command from the robotic mechanic, which captures them and stores the satlets and tools in its "toolbelt"
- the servicer/tender then heads out to graveyard orbit to rendezvous with a retired, cooperative, donor satellite
- the servicer/tender grapples the satellite and, using its robot arms under a combination of tele-operated and autonomous control, attaches to the antenna all the satlets required to reconstitute an operating spacecraft
- the robot mechanic then severs the antenna support structure from the satellite, and creates and attaches gravity-stabilization "stem" booms
- the servicer/tender then moves the repurposed antenna into position in GEO orbit where it begins to function as a communications satellite
- the service/tender then waits in GEO for its next job, while more satlets are sent up on commercial launches of opportunity
The Phoenix on-orbit demonstration is planned for 2016, and DARPA has released a video showing the progress so far in building and testing key parts of the system, including the FREND dexterous robot arm and a multi-jointed "hyperdexterous" arm that would be used to get lights and cameras close to the work areas.