I've just read here that:
Also this week, the agency announced that it is moving ahead with plans to create a robotic spacecraft designed to service satellites. Dubbed Restore-L, the mission has two objectives: refuel a communications satellite, possibly the government-owned Landsat 7, and test autonomous docking and navigation capabilities that could be used in future flights to Mars.
NASA also hopes Restore-L will usher in a new era of robotic servicing for commercial and scientific satellites.
"Restore-L effectively breaks the paradigm of one-and-done spacecraft," Frank Cepollina, who led the five-crewed servicing missions to Hubble, said in a statement. Space robots could be valuable to commercial operators like a joint venture between Airbus and the start-up OneWeb, which wants to send more than 900 mass-produced satellites into orbit starting in 2018.
(I'm not sure if the "communications satellite" is a misnomer, or refers to an additional satellite besides Landsat 7.)
On the outreach page there is a YouTube video, and an animation there caught my eye. Here is a GIF reconstructed from frames of the video:
The announcement says:
Restore-L technologies include an autonomous relative navigation system with supporting avionics, and dexterous robotic arms and software. The suite is completed by a tool drive that supports a collection of sophisticated robotic tools for robotic spacecraft refueling, and a propellant transfer system that delivers measured amounts of fuel at the proper temperature, rate, and pressure.
Future candidate applications for individual Restore-L technologies include on-orbit manufacturing and assembly, propellant depots, observatory servicing, and orbital debris management. NASA is also directly applying several Restore-L technologies to the Asteroid Redirect Mission.
To me, the animation suggests that the satellite (is it Landsat-7?) might have a refueling port for easy access, and the robotic maintenance craft would not need to cut open panels, turn valves, bleed and then cut into lines "manually" in order to replenish propellant. (don't forget to reseal and leak-test the lines and close the panel as well!)
But, if the port were for loading the satellite with propellant before launch, I would suspect that it be sealed reliably somehow - I don't think it would be as simple as a quick connect type of fitting.
How accessible are the couplings and valves for replenishing propellants to Landsat-7?