Part of DARPA's Robotic Servicing of Geosynchronous Satellites (RSGS) project, the concept video shows what such a system might look like and how it would operate. At its center is a robotic servicing vehicle (RSV), which sits in standby in geosynchronous orbit until it's needed, such as when a satellite fails to deploy its solar panels or ends up in the wrong orbit.
The RSV looks pretty much like a satellite with robotic arms and sockets for interchangeable manipulators, which are attached to it like a tool belt. When ordered, it can match orbits with the faulty satellite and fly around it as it collects images and 3D data, which it downloads to Earth for assessment.
Once programmed, the RSV tools up, then approaches and docks with the malfunctioning target satellite. After docking, a ground operator makes a detailed assessment of the satellite and compares the new data against the plan. When given the green light, the RSV carries out the repairs or uses its engine to move the satellite into its proper orbit.
DARPA says that it envisions the RSV in orbit within five years. If successful, the DARPA-developed toolkit module will be attached to a commercial space vehicle to create a commercially owned and operated RSV, which could lower the cost of operating geosynchronous satellites.