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Quick Facts

Satellite Servicing
Robotic Refueling
RRM Refueling

Satellite Servicing

Q: What is "on-orbit satellite servicing"?

A: "On-Orbit Satellite Servicing" brings the practical options of repair, refueling, and assembly to space-based exploration and commercial space ventures. It allows one to fix mistakes, upgrade quickly and extend operational life when needed.

Q: What can satellite servicing do for America's capabilities in space?

A: Like a reliable toolkit, satellite-servicing capabilities help humans build, repair, and maintain critical space assets. They can be used to extend the lifespan of existent satellites, support the assembly of large structures on orbit, and mitigate orbital debris. These advances can make spaceflight more efficient, sustainable, and cost effective.

Q: Why service satellites in geosynchronous Earth orbit, or "GEO"?

A: Located 22,236 miles (35,786 kilometers) above the Earth, GEO is one of the busiest highways in our solar system. More than 100 government-owned spacecraft and 360 commercial communication satellites commute on it each day, making it a prime location to offer repair, refueling, and tow-truck services. Having the capability to refuel and repair satellites at this orbit could make GEO more sustainable and help mitigate orbital debris problems.

Q: Why would NASA use robots instead of humans to refuel and repair satellites?

A: Two factors: distance and time. A robotic mission would put "refueling and repair" in NASA's toolkit within several years. Sending astronauts to destinations more distant than low Earth orbit remains a goal, but the infrastructure that would support human travel beyond low Earth orbit is still in development. GEO's heightened radiation is especially challenging for astronauts, and the lift capacity of existing human-rated spacecraft is insufficient to carry a crew to this orbit yet.

Q: What would it take to "robotically refuel" a satellite in space?

A: A servicer satellite with a couple of essential components. First, the servicer would need an autonomous rendezvous and docking system-the capability that would allow it to locate, meet, and dock with customer satellites. It would also need robotic refueling technology, which would include a fluid transfer system and robotic tools to access the satellite's fill/drain valve.

Q: How long has NASA been servicing satellites in space?

A: For almost 40 years. NASA's first space station, Skylab, was repaired in space in 1973. The 1980's brought the development of NASA's space shuttle, which enabled the successful repair of Solar Maximum in 1984 as well as the on-orbit retrieval of Palapa B2 and Westar 6, which were subsequently repaired on Earth and re-launched. NASA went on to service Syncon IV on orbit in 1985, to repair the Compton Gamma Ray Observatory immediately after launch in 1991, and to service Intelsat 6 in 1992. The 1990's heralded the immensely successful Hubble Space Telescope Servicing Missions, which supplied new instruments to keep Hubble operating above its designed condition throughout its 20-plus year lifespan. Human and robotic servicing capabilities have contributed to the assembly, upkeep and repair of the International Space Station. From 2011, NASA has been using the International Space Station's unique capabilities to demonstrate robotic satellite-servicing technologies for future Notional Robotic Servicing Mission.


Satellite-Servicing Technologies

Q: Why does NASA do technology demonstrations?

A: On-orbit technology demonstrations, or "demos," test and prove flight hardware, on-orbit techniques, software, and systems before they are launched on a full-scale mission. Demos reveal whether a technology is feasible, functional, and ready to endure the rigorous environment of space. Specifically, NASA uses the "Technology Readiness Level," or TRL method to assess the maturity of evolving technologies before they are incorporated. SSCO's Robotic Refueling Mission, an International Space Station demonstration, will elevate robotic refueling technology from a TRL 6 to a TRL 7-from a "representative model or prototype system tested in a relevant environment, such as a high fidelity laboratory environment or a simulated operational environment" (TRL 6) to "the demonstration of an actual system prototype in an operational environment, such as in an aircraft, vehicle or space" (TRL 7).

Q: Why is NASA advancing robotic servicing technologies, tools, and techniques?

A: Satellite servicing allows satellites to work longer in space. Every year, functional satellites providing weather data, communications and other essential services are retired because they reach the end of their fuel supply or encounter an unexpected problem. As old or ailing satellites are moved to the "graveyard orbit," new models are financed, designed, built and launched-a process that can be costly and time consuming for satellite owners and the consumers.

NASA developed the Robotic Refueling Mission (RRM) and an accompanying ground-based technology development campaign to advance robotic servicing capabilities so that satellites can live longer. Through RRM, NASA is proving the reliability of its robotic servicing technologies, eliminating potential issues through on-orbit testing, and bolstering the foundation for future Notional Robotic Servicing Missions.

Q: What are the greatest challenges to satellite servicing?

A: With the exception of the Hubble Space Telescope and the International Space Station, no satellites to date have been built with satellite servicing in mind. They therefore lack key features that would make them readily accessible to servicing. Advances in critical technologies-such as robotic arms, autonomous rendezvous and docking systems, advanced avionics, sensors, algorithms, and robotic refueling systems-are needed to make satellite servicing a routine and reliable practice.

Q: What is NASA doing to overcome these challenges?

A: NASA launched the Robotic Refueling Mission to the International Space Station in 2011 to demonstrate robotic refueling and spacecraft repair technology. On the ground and in the air, SSCO has been conducting a technology development campaign to advance satellite-servicing capabilities. The Argon autonomous rendezvous and docking ground test is part of this campaign.

Q: What is "Autonomous Rendezvous and Docking" (AR&D) and how does NASA use it?

A: An AR&D system is a satellite's "autopilot" as it rendezvouses and docks with another spacecraft. Cameras, sensors, and advanced computer algorithms allow a satellite to detect another spacecraft's relative position, speed, and direction and successfully navigate to a smooth docking.

AR&D is an important control and safety measure. During a satellite servicing mission, human operators would turn over control of a spacecraft's "flight" to advanced autonomous algorithms during situations when humans would not be able to react quickly enough-such as close-proximity operations with another spacecraft. NASA's Argon test is helping to advance autonomous rendezvous and docking technology.


Robotic Refueling Mission: Overview

Q: What is NASA's Robotic Refueling Mission, or RRM?

A: The Robotic Refueling Mission (RRM) is an external International Space Station experiment that demonstrates the tools, technologies and techniques needed to robotically refuel and repair satellites not designed to be serviced in space. RRM is a joint effort with the Canadian Space Agency.

Through RRM, NASA is proving the reliability of its robotic servicing technologies, eliminating potential issues through on-orbit testing, and bolstering the foundation for future Notional Robotic Servicing Missions.

Q: What is NASA learning about robotic refueling and servicing through RRM?

A: Starting with tests and simulations on the ground and continuing with on-orbit demonstrations, RRM is delivering NASA valuable lessons that NASA is applying to develop even more advanced robotic satellite-servicing capabilities. The exercise of developing and operating RRM refined NASA's concepts and designs for innovative tools, robotic procedures, and state-of-the-art servicing technologies for future missions. With RRM operational in space, NASA can now study how the space environment-with all of its challenging factors, including zero gravity, no air pressure, extreme temperature swings, and harsh lighting conditions-affect the capabilities it developed.

Q: Has robotic refueling been demonstrated before in space? What makes RRM unique?

A: While robotic refueling has been performed on orbit, each of these demonstrations was between cooperative objects. That is, the "refueler" and the "recipient" were designed to interact with each other as two halves of one system. RRM is the first demonstration to test the tools, technologies and techniques needed to refuel satellites that are not cooperative (that were not designed with servicing in mind).

Q: Why is NASA using the International Space Station to demonstrate robotic refueling and repair tasks?

A: The International Space Station's accessibility, unique location and well-established capabilities make it an ideal test bed for demonstrating satellite-servicing technologies. RRM will take advantage of Station's power, communications infrastructure, and robotic Dextre arm to demonstrate RRM's functions. Dextre will use RRM tools to perform refueling and repair tasks on the module's components and activity boards.

Q: Is RRM going to refuel satellites from the International Space Station?

A: No. As a technology demonstration on the International Space Station, RRM will never refuel or service a satellite itself. But by using the Canadian Dextre robot, stand-in satellite parts, innovative tools, a fluid transfer system, and about half a gallon of ethanol, RRM will demonstrate that remotely controlled robots could refuel satellites in geosynchronous Earth orbit and other space destinations.

Q: What are the components covering the Robotic Refueling Mission (RRM) box?

A: RRM is covered with the piece-parts of satellites, including a triple-sealed fuel valve identical to the type that many existing satellites have in orbit now. In addition, RRM's exterior includes multilayer insulation that can be cut and pulled back, door latches, and electrical power and signal receptacles. RRM also features wire to be cut and a host of screws, nuts, and caps that can be unfastened, captured, or resealed.

Q: The Robotic Refueling Mission uses the International Space Station's "Dextre" robot. What was Dextre built to do?

A: "Dextre," the International Space Station's twin-armed Canadian robotic "handyman," was developed by the Canadian Space Agency to perform delicate assembly and maintenance tasks on the station's exterior. Dextre serves as an extension of station's 57-foot-long (17.6 meter) robotic arm, Canadarm2.

Q: How did NASA decide on RRM's tasks?

A: RRM is designed to demonstrate the tasks necessary to refuel and repair a satellite that wasn't built with servicing in mind. Think of all the steps you take to refuel your car. It's simple enough on the ground, but much more complex when you're performing the same sort of tasks by remote control in space-using a lengthy robotic arm, peering through small cameras, and dealing with harsh on-orbit lighting on a cap that is triple-wired shut. RRM lets NASA practice servicing activities in space before they would be done "for real" on a potential future Notional Robotic Servicing Mission. It also gives NASA an opportunity to practice other general robotic servicing operations.

Q: What are RRM's dimensions and weight?

A: The RRM module is about the size of a washing machine and weighs approximately 550 pounds, with dimensions of 33" by 43" by 45". RRM includes 0.45 gallon (1.7 liters) of ethanol that will be used to demonstrate fluid transfer on orbit.

Q: Where are RRM operations being controlled?

A: RRM operations are entirely remote controlled by flight controllers at NASA's Goddard Space Flight Center in Greenbelt, Md., Johnson Space Center in Houston, Marshall Space Flight Center in Huntsville, Ala., and the Canadian Space Agency's control center in St. Hubert, Quebec.


Robotic Refueling Mission: Refueling Demonstration

Q: How does RRM demonstrate robotic satellite refueling?

A: During refueling operations, NASA and CSA direct the completely remote-controlled Dextre robot to pick up RRM tools and use them to:

  1. Work their way through a sealed satellite fuel valve-a multi-step process that will have Dextre working on several satellite fuel-valve piece parts-and
  2. Simulate satellite refueling by transferring fluid through the RRM module.

Q: How does RRM's fluid transfer system work?

A: RRM's fluid transfer system, or FTS, is equipped with a series of valves and pumps that precisely move ethanol fluid - representing satellite fuel - from the FTS tanks, through the RRM Nozzle Tool hose, across the seal that the Nozzle Tool creates with the fuel valve, in a closed loop, and eventually out a vent. RRM also contains a tank of nitrogen that is used to maintain the necessary pressure of the system during operations.

Q: Does RRM transfer real fuel?

A: No. It is not necessary to use real fuel, which can be hazardous, to meet RRM's objectives. Instead the team uses ethanol, which is safer and less costly.

Q: What tools does Dextre use during the refueling demonstration?

A: Dextre uses all four RRM tools during the refueling demo: the Wire Cutter Tool, the Multi-Function Tool, the Safety Cap Tool, and the Nozzle Tool. See the "RRM Refueling Play by Play" for a breakdown of how each tool is used during the refueling demonstration.

Q: How does the RRM Nozzle Tool work?

A: The RRM Nozzle Tool is an innovative problem solver equipped with two drives - one to thread itself onto the fuel valve on RRM, the other to open up the valve. A motorized socket in Dextre's "hand" turns the drives in different directions to accomplish these tasks. Once the Nozzle Tool threads on and opens the fuel valve, the RRM fluid transfer system pushes ethanol up a hose connected to the tool; through the newly formed, sealed interface; and then into the satellite valve and back into the FTS. Once complete, Dextre's socket turns the tool drives again and disconnects the tool.

Q: Why does NASA use multiple tools to demonstrate robotic refueling?

A: NASA uses four tools because there are many steps to the refueling process. Each tool was designed for optimum functionality and

Q: Is it safe to robotically refuel a satellite in space?

A: Robotically refueling a satellite is a multi-step process that demands the right tools, technologies and techniques to be performed safely. To develop the most reliable capabilities, NASA is taking deliberate steps on Earth and on orbit to test and advance robotic satellite servicing. RRM is allowing NASA to practice robotic refueling in the space environment, discover potential hurdles and challenges, and develop solutions applicable to real servicing missions.

Q: Why are satellites' fuel valves so hard to access?

A: Satellite fuel is extremely toxic and combustible. If any were to leak during launch or operations, the people in the surrounding area and the entire spacecraft would be at risk. To prevent any leaks, satellites' fuel valves are triple sealed while the satellites are still on the ground. RRM is demonstrating how a remote-controlled robot could safely access these fuel valves during an on-orbit servicing mission.