Space Infrastructure Servicing (SIS) is a spacecraft concept being developed by Canadian aerospace firm MDA to operate as a small-scale in-space refueling depot for communication satellites in geosynchronous orbit.
[5] In February 2012, MDA said it was awaiting "a decision on a contract bid to the U.S. Defense Advanced Research Projects Agency (DARPA) before deciding whether to shelve its work on a vehicle to service satellites and perform other chores in orbit".
[1] By comparison, the DARPA Project Phoenix program has an even more complex mission concept: "cooperatively harvest and re-use valuable components from satellites in orbit that have been retired.
Intelsat entered into a preliminary agreement to purchase one-half of the 2,000 kg (4,400 lb) propellant payload that the MDA spacecraft would carry into geostationary orbit.
Such a purchase was projected to add somewhere between two and four years of additional service life for up to five Intelsat satellites, assuming 200 kg of fuel is delivered to each commsat.
[9] SIS was envisioned to carry a toolkit designed to open most of the approximately 40 types of "fueling systems aboard satellites now in geostationary orbit".
In January 2013, an extensive series of robotically-actuated propellant transfer experiments on the exposed facility platform of the International Space Station (ISS) were completed by the NASA Robotic Refueling Mission (RRM).
The set of experiments included a number of propellant valves, nozzles and seals similar to those used on a wide variety commercial and government satellites, plus a series of four prototype tools that could be attached to the distal end of a Space Station robotic arm.
The ViviSat (Mission Extension Vehicle) illustrates one alternative approach that would connect to the target satellite in a similar way as MDA SIS, via the kick motor, but will not transfer fuel.
[12] ViviSat believes their approach is simpler and can operate at lower cost than MDA, while having the technical ability to dock with a greater number (90%) of the approximately 450 geostationary satellites in orbit.