NRL's "tow truck" technology for satellites.

The Naval Research Laboratory's Naval Center for Space Technology says it has achieved a key milestone toward the development of autonomous servicing of unaided spacecraft. Working with the Defense Advanced Research Projects Agency (DARPA), NRL has developed, tested and ground-demonstrated guidance and control algorithms to allow a robotic servicing vehicle to autonomously rendezvous and dock with customer satellites not predesigned for docking.

This demonstration coupled three significant accomplishments into one milestone: the necessary robotic control algorithms are proven to be capable of operating reliably within a realistic spaceflight-processing environment and are now flight traceable; a simulation of a realistic geostationary communications satellite with no visual aids or docking aids was grappled reliably in realistic on-orbit lighting conditions; the demonstration was completed under full autonomy with no human-in-the-loop assistance.

NRL and DARPA are developing the key technologies and reducing the technological risk to allow autonomous spacecraft rendezvous and docking to become a reliable reality. As part of the Front-end Robotics Enabling Near-term Demonstration (FREND) effort, the DARPA/NRL team is advancing the state-of-the-art in spacecraft autonomous rendezvous and grappling, offering "tow-truck" service to nearly every satellite currently, or soon to be, in space. This service offers potential for satellites to operate longer, to be salvaged if they are in an inoperable orbit, to be transferred to a new orbital position if they are unable to make that transit on their own, and has a capability for making certain orbital regimes safer by transferring derelict spacecraft or space debris into graveyard orbits.

Full-scale laboratory demonstrations have now been successfully completed, proving that reliable autonomous grapple of spacecraft hardware is feasible. The NRL team has accomplished autonomous grapples using a 1m-long research grade robot arm, custom-developed flight traceable control algorithms, research grade machine vision cameras, prototype grappling mechanisms, and flight traceable processors. These grapples have been of simulated spacecraft hardware, grappling at the launch vehicle interfaces (Marman ring, separation bolt hole) commonly flown to geosynchronous orbit, and with simulated in-space lighting conditions.

By accomplishing these technology demonstrations, the autonomous control algorithms advance from a spaceflight Technology Readiness Level (TRL) of 4 to a TRL of 5, by having been tested in a variety of relevant environments. The DARPA/NRL team will further improve the TRL by integrating flight-ready robotics, electronics and software with evolving algorithms for grapple demonstrations in the laboratory environment.

Laboratory demonstrations with fully flight-ready components will be another major milestone toward the ultimate goal of reaching the highest TRL of 9, which is reserved for systems that have been proven through successful operations in space.

DARPA and NRL have contracted Alliance Spacesystems to design and build the robotics that would allow a servicing spacecraft to dock with satellites not originally designed for servicing. Alliance is best known for designing and building the robot arms on the Mars Exploration Rovers.