For more than 20 years, the Landsat 7 satellite circled Earth every 99 minutes or so, capturing images of almost all the planet’s surface each 16 days. One of many craft that observed the changing globe, it revealed melting glaciers in Greenland, the growth of shrimp farms in Mexico, and the extent of deforestation in Papua New Guinea. But after Landsat 7 ran short on fuel, its useful life effectively ended. In space, regular servicing has not been an option.
Now, though, NASA has a potential fix for such enfeebled satellites. In a few years, the agency plans to launch a robot into orbit and maneuver it to within grabbing distance of Landsat 7. The robot will use a mechanical arm to catch hold of it and refuel it, mid-air.
If successful, the mission would mark a milestone—the first time a satellite would be refueled in space. And this mission is just one of a number of planned public and private ventures intended to use robots to repair and improve the billions of dollars’ worth of satellites in orbit.
Eventually, efforts like these could lead to better and cheaper satellites that lower the cost of Internet and cell phone networks, provide better weather forecasts and give unprecedented views of planetary change and of the Universe. They could even enable a new wave of in-orbit construction, with armies of robots building satellites, space stations, and even Mars-bound spaceships.
Giving satellites longer lives
At the moment there are about 4,852 working satellites in orbit, playing crucial roles in communications, remote sensing, and other tasks. Almost all were launched with the knowledge that if anything broke there was no way of fixing it. Most satellites also need fuel to occasionally adjust their orbits. Once that’s gone they may become so much space junk, adding to the already substantial stream of debris encircling the globe.
“Imagine you’re going to go buy a car tomorrow,” says Brian Weeden, head of an industry group called the Consortium for Execution of Rendezvous and Servicing Operations (CONFERS). “And you have to keep in mind that you’re never going to be able to put more gas in it. You can never change the oil. You can never maintain or fix anything. And you have to use it for the next 10 years. Now, how expensive and how complicated do you think that car is going to be? That’s exactly what we have been doing with satellites.”
To keep satellites working as long as possible, engineers build in redundant systems and pack in as much fuel as they can fit. All this over-engineering adds to the costs of building and launching the satellites—a modern communications satellite can cost about $500 million.
Almost all construction and repair that has happened in space so far has relied at least in part on astronauts, including fixes on the Hubble Space Telescope and construction of the International Space Station. But sending humans into space is tremendously expensive, so the effort to develop robots to do the job has grown in recent years.
“What we would really like to do is have some way of having a robotic mechanic in space that can fix satellites when they break,” says Carl Glen Henshaw, head of the robotics and machine learning section at the US Naval Research Laboratory.