Satellites are expensive. They are expensive to develop, expensive to launch, and, should they run out of fuel, expensive because they are not designed to be refueled.
 
NASA wants to change that. The aerospace agency has been working for years on robotic technology that could refuel and relocate satellites, extending their services lives, cutting down on space junk and saving money in the process.
 
Eventually it could lead to more capable spacecraft and a new line of business for commercial space companies.
 
“There is a tremendous need,” says Benjamin Reed, deputy division director for the Satellite Servicing Projects Division, based at Goddard Space Flight Center in Maryland. (Click here to see a video interview with Reed.)
 
There are 450 operational satellites in geosynchronous orbit alone, worth several hundred million dollars each as well as some government satellites whose price tag hovers around $1 billion each, Reed says. An average of 15 of those are replaced every year for various reasons.
 
Throughout space history, however, only two spacecraft have been designed to be serviced in orbit — the Hubble Space Telescope and the International Space Station, and only the ISS was designed to be refueled.
 
“Servicing of clients not designed with servicing in mind is a problem rich environment,” Reed says. “… The complexity comes in the details. How do you find that satellite while it’s whizzing around in the gigantic vastness and blackness of space? How do you safely rendezvous with it without the risk of colliding with it? Once you’ve rendezvoused with it, how do you gently capture it?”
 
To accomplish this, NASA plans to rely on technology to grab satellites traveling at up to 16,000 miles per hour, cut through protective layers, unscrew fuel hoses and top up the tanks.
 
It calls into play a variety of technology that NASA has been working on for at least seven years, including for rendezvous and proximity operations, dexterous robotics and tool drive systems, sophisticated avionics, complicated fluid transfer, and more.
 
“It’s really hard to do,” says Ross Henry of NASA’s Goddard Space Flight Center in Maryland, who is for the project manager for Raven, a navigation system that will be part of the refueling mission.

A model of Raven, which is now monitoring spacecraft flying to the space station. Photo: AUVSI
 
Raven
 
Reed and Henry discussed their work at the summer 2017 Awesome Con convention in Washington, D.C., bringing some real-life tech to a science fiction- themed convention, and Reed also talked separately with Unmanned Systems magazine.
 
Raven represents one component of the technology that NASA has developed for in-orbit servicing, namely enabling rendezvous and proximity  operations. Raven is already at work, as it launched to the space station in February, where it tracks and images the various vehicles that come to the station.
 
“What it’s doing is it’s detecting them and it’s tracking them,” Henry said.
 
Reed said Raven’s technology will not only benefit the satellite servicing missions, but also Orion, the manned space capsule now being developed, and which could one day take humans to Mars.
 
“Orion, or Orions, will need to rendezvous with other things. They don’t go to space to just be by themselves, they go to work on things, build things, explore things, so there will be rendezvous in Orion’s future,” Reed says.
 
Over the course of its life, Raven is expected to monitor 50 rendezvous or departure trajectories, including from Russian Progress and Soyuz vehicles, Japan’s H-II Transfer Vehicle and the private Cygnus and Dragon spacecraft from the United States.
 
Restore-L
 
Skill at finding and tracking vehicles is a prerequisite for the larger satellite refueling effort, called Restore-L. Restore-L has many more components, including an autonomous, real-time navigation system (honed by Raven’s experience); two robotic arms; advanced tools for accessing and refueling satellite “clients,” as NASA calls them; and a propellant transfer system capable of delivering fuel at the correct temperature, pressure and rate.
 
Sensors would spot a given satellite and plot a course to intercept it. The robot arm would grab the satellite, cut through thermal blankets and hold them back, unscrew and remove two caps, attach the fuel hose, pump in the fuel, then replace the thermal blanket section with a thermal cover. A NASA animation shows the process occurring in a matter of minutes, but in real life it will take a few weeks.
 
“That is much more challenging than it would be if the satellite were designed with servicing in mind,” Reed said. “There are many, many steps just to expose the fuel valve.”
 
NASA already has a client in mind for Restore-L: Landsat 7, a satellite expected to run out of fuel by the end of this decade. Landsat 7, launched in 1999, is operated by the U.S. Geological Survey and completes more than 14 orbits of the Earth each day, sending back hundreds of images daily. after launch to try to cut down on space junk, so having a successful Restore-L mission “would allow us to have enough fuel to do that,” Lacasse says.
 
In addition, USGS could use the extra time aloft to cross-calibrate instruments on other satellites if needed.
 
One and done
 
Even after the Landsat 7 demonstration, the technology behind Restore-L will be used in future servicing missions. Reed says the work is ushering in a new age of space exploration, beyond the traditional “one and done,” where spacecraft aren’t refueled, serviced or moved once they are in place.
 
“For the first 60 years of spaceflight, we’ve been one and done,” Reed says, meaning that when satellites fail or are no longer needed, “they die.”
 
As far back as 1984, NASA demonstrated an in-space refueling mission with the space shuttle, but nothing happened beyond that; it was a chicken-and-egg situation. Spacecraft weren’t designed to be refueled because there was nothing to refuel them, and there was no investment in a space tanker because satellites weren’t designed to be refueled.
 
“Restore breaks that paradigm,” he says.
 
Current satellites are beginning to be designed to be serviced in space, which can include relatively simple things, such as redesigning fuel valves to make them easier to open in space to making thermal blanket flaps that can be opened and closed.
 
“We are now actively educating the global aerospace community on the easy, low-hanging fruit steps they can take to make their satellites serviceable,” he says, which includes appearing at science fiction conventions.
 
Beyond that, the servicing technology could open a whole new way of doing business in space, where commercial companies take the know-how NASA developed and create businesses around it. NASA is actively transferring the technologies it develops to interested domestic companies to jumpstart a satellite servicing industry.
 
“NASA wants to develop the technology, get it to operational status, a la Restore, and then move on,” Reed says. “There is a burgeoning commercial services field, and refueling is at the heart of it. Relocation, refueling is at the heart of it. As I mentioned earlier, 15 or so satellites per year retiring from geosynchronous orbit alone, that’s a nice customer set.”
 
The technology goes beyond just servicing, and could include assembling ever-more complicated spacecraft whose parts are launched on separate missions, similar to how the International Space Station was built.
 
Such an approach could give rise to larger orbiting telescopes that can see farther than ever before, potentially finding new planets that can support life. Their size wouldn’t be limited by a single payload bay and by the need to batten everything down carefully to withstand launch vibrations.
 
“Assembly is, one would say, perhaps the killer app for servicing capability,” Reed said.
 
It is, Reed says, a far cry from “one and done.
 
“Now, that will be different. You can upgrade it, you can repair it, you can relocate it, you can build something bigger than you can dream of fitting in a rocket,” he says. “So I think it is truly going to usher in space 2.0. The era of one and done will be over. The era of new opportunity will be upon us.”