NASA to bump telescope back into space to avoid it falling to Earth

US space agency NASA is racing to save an aging telescope from falling back to Earth with a daring rescue mission.

The $US30 million ($43.5m) salvage operation is expected to get underway as soon as this week with the planned launch of a robotic lifesaver.

NASA hired start-up Katalyst Space Technologies to boost the Swift Observatory to a higher orbit where it can continue hunting for some of the universe's biggest explosions.

A three-armed spacecraft built by Katalyst will chase Swift once it takes off from an atoll in the Pacific's Marshall Islands aboard an aeroplane-launched Pegasus rocket.

The rocket's lift-off is expected to occur as early as Tuesday, local time.

New playbook to push Swift and Hubble back into orbit

Scanning the cosmos since its launch in 2004, Swift has been sinking faster and faster because of recent intense solar activity.

It needs to get to a higher, more stable orbit as soon as possible to survive.

NASA's Hubble Space Telescope, also at risk, could be next.

Like Swift, Hubble is losing altitude as the Sun erupts with one flare after another.

Katalyst Space CEO Ghonhee Lee said his company's next-generation robot, which is still in development, could save the day for the much bigger Hubble in a couple of years.

Only China has attempted a mission like the upcoming one, successfully boosting a satellite into a higher graveyard orbit four years ago.

"This is the first American space robot to go up and do anything like this," Mr Lee told The Associated Press.

"NASA has all these big senior observatories … all of them can benefit from a service like this. So, what we're proving with this mission is this is a new play in the playbook that's available."

It will take Katalyst's autonomous spacecraft, named Link, about a month to rendezvous with Swift and catch it, and another couple of months to raise its orbit from the current 360 kilometres to the desired 600km.

The 1.4-tonne gamma ray observatory must be above 300km for the rescue to work. It's expected to reach that point of no return in October, according to the latest estimates.

Roughly the size of a small kitchen refrigerator with a 12-metre solar wingspan, Link sports three arms with a reach of just over 1 metre. Each arm has two finger-like pinching grippers that resemble the hands of a Lego mini figure.

If all goes well, Swift could be back in business by September, according to Mr Lee.

Why NASA can't afford to let Swift fall back to Earth

Worth hundreds of millions of dollars, Swift was never designed to be repaired, let alone retrieved by hands, human or otherwise. That's what makes this so challenging, according to company officials, who stress there is no guarantee it will work.

NASA signed a contract with Katalyst last September with only two requests: it has to be a rush job, but please don't make things worse. Nine months later, the company is ready to rumble.

"I have to be honest. No-one thought it was going to be possible," said Shawn Domagal-Goldman, NASA's astrophysics director.

NASA has bought a little more time for Swift, turning off all scientific instruments to slow its descent. Observations ceased in February.

NASA's science mission chief Nicky Fox said it was worth the effort.

"If we let Swift re-enter, we would lose that telescope. We would lose a lot of capability," she said.

"We don't currently have the budget to build another one to replace that."

While not everything could be saved in space, Swift was special, Mr Domagal-Goldman said.

True to its name, Swift is designed to pivot quickly to capture late-breaking astronomical events such as gamma ray bursts and exploding stars.

With more discoveries expected by the Webb Space Telescope and soon-to-launch Roman Space Telescope, Swift, if saved, would be busier than ever as "NASA's first responder".

Katalyst sees Swift as the jumping-off point for a new repair business in space.

The company's next-generation robotic rescuer, scheduled to fly next year, will tackle satellites as high as 35,800km up.

Mr Lee envisions hundreds of robots in orbit one day, not only fixing and hoisting satellites but also refuelling them and building solar farms, data centres and other platforms.

Thirty-six-year-old Hubble, which received repeat servicing by spacewalking astronauts during the shuttle era, could follow in 2028 with a life-extending Katalyst boost.

"It's a national treasure," Dr Fox said.

"People love Hubble."

AP