DARPA is still developing own spacecraft able to perform service on satellites remaining on GEO orbit. Project is called Robotic Servicing of Geosynchronous Satellites (RSGS) and just three days ago DARPA chosen one of the key subcontractors for this project. It is second American government project of future space logistic spacecraft along with NASA Restore-L project for refueling LEO satellites.
Space Systems Loral was chosen for designing and manufacturing two robotic arm systems for RSGS spacecraft; company also announced about receiving the first tranche of the contract value - $20.7 million. Contract is worth $40 million and this sum could grow in future if DARPA will decide to extend project. Execution of the contract will be supervised by U.S. Naval Research Laboratory (NRL), which is responsible for project of the robotic arm; budget will be transferred to MDA US Systems, company which is subsidiary of SSL and was cooperating with NRL under FREND project. It was robotic arm created by DARPA and called Spacecraft for the Universal Modification of Orbits and Front-end Robotics Enabling Near-term Demonstration (FREND); project was under development in years 2006-2011 and cost $60 million. FREND will be also base for project of new robotic arm by SSL, so it could be said, that DARPA spent on project of robotic arm around $100 million and it lasts for over a decade. SSL will design robotic arm along with necessary subsystems; arm will be fully usable in following actions: refueling, servicing, changing orbit of satellite and installing upgrades or updating software. Basing on this specification we can assume, that arm will be equipped in various tools like refueling nozzle with valve systems, various tools for servicing satellites (like grippers and multifunction wrenches), docking device and maybe kind of electronic device to interfere in the software on-board computer of the satellite. Arm will be highly resistant for high level of space radiation on GEO (36000 km) orbit and will be able to conduct multiple service actions during long term mission to make whole program economically justified.
Present vision of the RSGS was showed in conceptual video presented on DARPA website. It shows servicing process of satellite with jammed solar array. RSGS spacecraft is showed as rather conventional looking satellite with two dish antennas on the opposite sides of cubic fuselage with single solar array on the top. In front of the spacecraft there are two robotic arms equipped with interchangeable tools and sensors. Mission is presented as supervised by Control Center, but DARPA is probably planning to equip spacecraft in onboard computer, which could provide high level of independence. In this way less complicated procedures like transferring object to another orbit or refueling could be done automatically. Most desired would be of course creating system of real time monitoring condition of satellites and sending RSGS spacecraft automatically to satellite which requires maintenance at the moment.
On picture above: NASA Robotic Refueling Mission during execution with utilization of Dextre robotic arm installed on International Space Station.