DARPA Robotic Servicing of Geosynchronous Satellites (RSGS) Program Fact Sheet

DARPA Robotic Servicing of Geosynchronous Satellites Program satellite. (Credit: DARPA)

DARPA Robotic Servicing of Geosynchronous Satellites (RSGS) Program
Fact Sheet


National security increasingly demands a high degree of flexibility on orbit, including an ability to repair and upgrade satellites in geosynchronous orbit (GEO). The technical challenges of performing such functions in GEO are significant, but success could substantially revolutionize military and commercial space operations, lower satellite construction and deployment costs, and improve satellite lifespan, resilience, and reliability—precisely the kind of high risk/high reward opportunity that DARPA was created to pursue. RSGS is a research and demonstration effort that aims to speed the arrival of capabilities such as high-resolution inspection; correction of otherwise mission-ending mechanical anomalies such as solar array and antenna deployment malfunctions; assistance with relocation and other orbital maneuvers; and installation of attachable payloads, enabling upgrades to existing assets.


  • With the exception of the International Space Station, the former Russian Mir Space Station, and a handful of astronaut-led activities during the Space Shuttle era (most notably the Hubble Space Telescope missions)—all of which were in low-Earth orbit and not GEO, a much higher and more challenging orbit—spacecraft have never been repaired or physically upgraded on orbit.
  • RSGS will demonstrate a suite of capabilities critical to national security and not currently available or anticipated to be offered commercially in the near term, including ultra-close inspection, repair of mechanical anomalies, and installation of technical packages on the exterior of US satellites, all of which require highly dexterous robotic arms. DARPA has already designed and created the required robotic arms.
  • Under the RSGS program, a DARPA-developed modular toolkit (the robotic payload), including hardware and software, would be joined to a privately developed spacecraft to create a commercially operated robotic servicing vehicle (RSV) that could make house calls in space.
  • DARPA’s role will be to contribute the robotics technology, expertise, and a Government-provided launch. DARPA’s selected commercial partner, Space Systems Loral (SSL), based in Palo Alto, CA, would contribute the satellite to carry the robotic payload, integration of the payload onto it and the RSV to the launch vehicle, and the mission operations center and staff.
  • DARPA carefully considered the best acquisition approach to ensure the RSGS capability would be made available to high-value Government assets and concluded that a public-private partnership was the best approach to save taxpayer dollars and accelerate technology development of high value to both the U.S. Government and the commercial satellite industry.
  • Since there are roughly four times as many commercial satellites in GEO as Government satellites, DARPA elected to find a commercial partner capable of servicing both in order to lower the cost of servicing to the Government and commercial entities and collect a broader range of research data. This partnership approach will enable the fastest deployment of RSGS capability.
  • After a successful on-orbit demonstration of the robotic servicing vehicle, SSL would own and operate the vehicle and make cooperative servicing available to both military and commercial GEO satellite owners on a fee-for-service basis. In exchange for providing Government property to SSL, the Government will obtain reduced priced servicing of its satellites and access to commercial satellite servicing data throughout the operational life of the RSV.
  • Government-developed RSGS technologies would not become the exclusive property of DARPA’s commercial partner but would be shared with other qualified and interested U.S. space companies. Qualified companies would be able to obtain and license the technology through cooperative research and development agreements.
  • SSL is currently working with the U.S. Naval Research Laboratory (NRL), through MDA US Systems, a division of MDA managed by SSL, to design and build robotic arm flight hardware for the RSGS program.

Contrast with NASA’s RESTORE-L

  • DARPA has conducted extensive dialogues both with the Spacecraft Servicing Capabilities Office at NASA’s Goddard Space Flight Center and at NASA Headquarters regarding NASA’s RESTORE-L program, which aims to provide certain servicing options for satellites in low-Earth orbit.
  • Engineers from RSGS and RESTORE-L attend each other’s requirements reviews and technical interchanges. NASA has benefited extensively from DARPA’s development of the robotic arm and automation software, and DARPA appreciates the testing that NASA has performed on its own system.
  • The hardware configuration of the RESTORE-L robotics is significantly different from the RSGS configuration, and is not being designed for the RSGS national security capabilities.
  • While RSGS and NASA’s Restore-L mission both aim to showcase on-orbit servicing, the two programs exhibit several important differences:
    • Restore-L will rely heavily on operation from the ground for critical servicing tasks while RSGS must perform many of its missions autonomously because of the communications delay inherent with operating at the greater distances of geostationary orbits.
    • RSGS, unlike Restore-L, will be operated by a commercial partner for several years of operations in GEO following an initial demonstration, necessitating a higher-reliability design.
    • Restore-L is aimed principally at satellite life extension; RSGS will demonstrate life extension while also upgrading or replacing faulty hardware and repairing stuck assemblies.


  • To help ensure the long-term sustainability of RSGS and other future space operations—and provide the foundation for a new commercial repertoire of robust space-based capabilities—DARPA recently solicited for the Consortium for Execution of Rendezvous and Servicing Operations (CONFERS) program. CONFERS will establish an industry/government forum composed of experts from throughout the space community. The forum would develop non-binding, consensus-derived technical and safety standards for on-orbit servicing operations, and help create definitions and expectations of responsible behavior in outer space.

  • Kapitalist

    I think that satellite servicing is best done by launching only smart mass, to upgrade the electronics of the satellites. With the Hubble space telescope as the example. The satellite bus with its infrastructure for power, communication, station keeping, thermal control whatever all, could remain as it is for many decades without need for upgrades. Just like many ships at sea. The economic lifetime of the instrumentation is much shorter than the technological lifetime of the spacecraft infrastructure (bus).

    With one heavy GEO satellite being useful for several decades, one can easily afford to simply launch all the fuel it needs for station keeping to begin with. No need for launching $1 per pound worth of fuel and trying to transfer it in microgravity. If a satellite needs a bigger orbital change, a tug could grab it and push it. Again, just like with the HST.

  • Jeff2Space

    Over the years, Hubble got new solar arrays, gyros, batteries, and instruments. But you also have to remember that Hubble was designed from the start to be serviced.

    As to the idea of launching with “all the fuel you need”, geosynchronous communications satellites already do that, in theory. In practice “stuff happens”. Some comsats have had to make up for shortfalls in delta-V that the launch vehicle should have provided. Others have simply run out of fuel at the end of their planned lifetime, despite the fact that the rest of the satellite is functioning quite adequately.

  • Kapitalist

    Satellites in GEO are all close to each other in terms of delta-v. One mission could dock and service several of them. It is their economic lifetime that needs upgrading because of the rapid development of technology competing with the useful service they provide. Refueling a 10 year old communication satellite has marginal value compared to upgrading it with today’s electronics. I think that fuel for station keeping better be considered as a part of the permanent infrastructure of a satellite and most simply is launched together with it.

    A satellite that needs assistant to get into a useful orbit could be towed by a space tug, with its own fuel and engine. Aren’t there different kinds of hypergolic fuels used in satellites? And don’t they need helium and nitrogen for pressurization too? Why don’t we have ambulating gas “stations” on our roads?

  • redneck

    We do have ambulating gas stations, they are for jobsite equipment that can’t just run down the street to the convenience store. I don’t order Caterpillars with all the fuel they will ever use.

  • Jeff2Space

    The devil is in the details. The companies who own those GEO comsats know better than either of us. Time will tell if it will make them money to service a comsat instead of sending it to a (useless) graveyard orbit because it’s out of fuel.

    Besides, DOD is working on this tech for their own reasons. And again, they know the cost numbers for their satellites. The fact that they’re investing in this tech is telling.