Space agency extends mission of comet-orbiting spacecraft Rosetta

(CNN) More than a decade after it first launched, the comet-orbiting spacecraft Rosetta -- already seen as one of the great successes of space exploration -- will be given an extra lease on life.

Rather than coming to a close in December as planned, its mission will be extended until the end of September 2016, the European Space Agency said in a statementTuesday.

At that point, the spacecraft will most likely be landed on the surface of Comet 67P/Churyumov-Gerasimenko, which it reached in August -- 10 years after it launched from Earth.

Earlier this month, the solar-powered spacecraft delighted project scientists when it re-established contact with the Philae comet lander for the first time since it went into hibernation after running out of power seven months ago.

This means Philae, on Comet 67P's surface, can continue with experiments up to and beyond the comet's closest approach to the sun in mid-August -- called perihelion.

Philae is expected to run out of power for good in October, but the extension of Rosetta's mission means scientists can continue to observe the comet's progress as it loops away again from the sun.

"This is fantastic news for science," Matt Taylor, the European Space Agency's Rosetta project scientist, is quoted as saying in a news release.

"We'll be able to monitor the decline in the comet's activity as we move away from the sun again, and we'll have the opportunity to fly closer to the comet to continue collecting more unique data. By comparing detailed 'before and after' data, we'll have a much better understanding of how comets evolve during their lifetimes."

Rosetta and its mission

Slow spiral to comet's surface

By September next year, as the comet recedes ever farther from the sun, there will no longer be enough solar power to run Rosetta's set of scientific instrumentation efficiently, the space agency said.

In June 2011, the spacecraft was put into hibernation for 31 months for the most distant leg of its journey out toward the orbit of Jupiter. But now, with too little fuel remaining to repeat that exercise, scientists instead propose sending it on a slow spiral down to the comet's surface.

Before the potential touchdown, scientists will try to bring the spacecraft nearer to the comet -- a safer prospect as its activity wanes after perihelion -- for detailed observations that may make it possible definitively to spot Philae on the surface.

Rosetta should be able to gather data all the way down to the comet's surface -- a journey that could take three months. But the orbiter's touchdown is likely to mark the end of its groundbreaking mission, the European Space Agency said.

'Quite amazing'

Lander system engineer Laurence O'Rourke told CNN that the spacecraft's dwindling supply of propellant meant there was little alternative to ending Rosetta's mission in this way -- and that it would bring the spacecraft closer and closer to the regions where dust has been raised by perihelion.

"What we are trying to do is achieve science, " he said. "The science to be achieved at 100 kilometers is entirely different to what can be achieved at 10 kilometers or 5 kilometers."

That's not to say there won't be some regrets at Rosetta's demise among the scientists who've directed the spacecraft for so long.

"It's a sad day but also to have achieved what we have achieved up to now already is quite amazing," said O'Rourke. "To know that we are going to be getting closer to a comet than we've ever got is also quite amazing.

"The fact that we are doing another landing on a comet, not only from Philae but from another spacecraft, is amazing."

Philae's bumpy landing

Now it's back in touch, Philae can carry out a whole host of experiments intended to shed light on how comets behave as they approach the sun.

It was originally hoped that after it landed in November, Philae would operate until March when the fierce heat of the sun would likely burn out its components.

But in what now appears to be a happy accident, the probe, which is about the size of a washing machine, bounced across the comet's surface in the weak gravity after anchor devices failed, and it landed in a sheltered spot -- protecting it from the worst of the solar scorching.

O'Rourke said there had been five connections with Philae since its first contact but that each had been too brief for much data to be downloaded.

Project scientists are now working to adjust the orbiter's trajectory to enable connections ideally lasting an hour or more, he said.

Meanwhile, the lander is working "very well," he said, adding that its internal temperature has increased and its secondary battery may be charging.

The team hopes that by the time of perihelion Philae will be fully operational -- giving scientists a ringside seat as the comet reaches its closest point to the sun, with gas and dust explosions at their maximum.

"It's going to be an adventure -- and a very nice one at that," said O'Rourke.

The European Space Agency, which is leading a consortium that includes NASA to find out more about the composition of comets and how they interact with the sun, has already notched up some notable firsts with the project.

It is the first time a mission has successfully orbited a comet, following it on its journey around the sun, and the first time a controlled landing has been made on a comet -- even though Philae encountered a bumpy ride.