There's a graveyard in space littered with the corpses of dozens of dead satellites, a remote spot in the cosmos reserved to entomb spacecraft at the end of their lives.

Even the most robust and expensive satellites eventually break down or run out of fuel, and must be retired to a remote parking orbit more than 22,000 miles away, safely out of the way of other satellites. There, the graveyard holds billions of dollars-worth of some of the most expensive hardware ever to leave the surface of the Earth — including not just commercial communications satellites, but some of the Pentagon's most sensitive assets, used for spying, guiding bombs and warning against missile launches.

Now, the Defense Advanced Projects Agency, NASA and others, are developing technologies that would extend the life of the critical infrastructure in space. If successful, the agencies would have fleets of robots with arms and cameras that could inspect, refuel and repair satellites, keeping them operational well beyond their expected lifetimes. The spacecraft might even upgrade the satellites they service with the latest technology, like an iPhone update.

"Where else do we build something that costs a billion dollars, and then never inspect it, never maintain it, and never repair it?" said Gordon Roesler, the program manager at DARPA. "But that's what we do in space."

That may be changing as a wave of innovation takes root in the space industry, much of it driven by private billionaires and commercial enterprises. There are companies building lunar landers and others developing probes that could lead to the mining of celestial bodies. Still others are working on 3-D printers designed to build things in space.

"Everything that we now do on Earth we will eventually do on-orbit," said Richard White, the president of SSL Government Systems, which is working with DARPA on the program. "The satellite-manufacturing facility of the future could be located in space."

DARPA's program to service satellites comes at a time when the Pentagon is increasingly worried about, and planning for, war in space. Citing the advancements of Russia and China, the White House's recently released National Security Strategy cited space as one of the Pentagon's top priorities, and issued this warning: "Any harmful interference with or an attack upon critical components of our space architecture that directly affects this vital U.S. interest will be met with a deliberate response at a time, place, manner, and domain of our choosing."

DARPA is focused on fixing satellites in what's known as geosynchronous orbit, or GEO, more than 22,000 miles away. At that altitude, the orbit of satellites matches the rotation of the Earth, meaning that the spacecraft can stay over a fixed spot. GEO is where companies like DirectTV keep their satellites. It's also where the Pentagon keeps classified satellites used for tasks such as detecting nuclear missile launches, guiding precision weapons, conducting surveillance and managing communication.

"The U.S. has some extremely important national security satellites in that region, and they are very concerned about those satellites breaking down having problems or being attacked," said Brian Weeden, a director for the Secure World Foundation, an advocacy organization focusing on space security.

In 2007, China fired a missile that blew up a dead satellite in what's known as low Earth orbit. Then, a few years later, it demonstrated that it could hit satellites in GEO by firing a rocket there.

In response, the Pentagon is moving toward putting up constellations of much smaller satellites, so that if one is damaged, another can take its place. But it also wants the ability to be able to repair its large and most-capable satellites, and to check to see if they've been tampered with.

Initially, the kinds DARPA is looking at "are very simple," Roesler said, such as fixing antennas that didn't deploy properly, or solar arrays that didn't fully unfold.

Orbital ATK, based in Dulles, Virginia, is developing a "mission extension vehicle" that would be able to attach itself to a satellite, and then take over propulsion, firing thrusters to keep the satellite in the correct orbit. The company already has a customer, Intelsat, and plans to demonstrate the technology by early 2019, said Tom Wilson, the company's president of Orbital ATK Space Logistics

NASA's program is focused instead on low Earth orbit, where there are all sorts of communications satellites whizzing about at 17,500 mph. At the end of their lives, those satellites eventually deorbit, falling back to Earth and burning up in the atmosphere. NASA, through a program, called "Restore-L," is working with Space Systems Loral, based in Palo Alto, California, to develop a spacecraft that could reach out with a robotic arm, and refuel the satellites so that they could continue maintain their position.

By 2021, NASA plans to attempt to refuel Landsat 7, an Earth observation satellite launched I 1999. Using its robotic arm, the spacecraft would reach out and refuel it.

Eventually, the agency would like the robots to even update the spacecraft's software. The idea is to "switch out the payload and update the communications technology," said Stephen Jurczyk, the associate administrator of NASA's Space Technology Mission Directorate. "That also could be a game changer in that you could evolve the technology without having to develop and then launch a whole new program."

