Thursday, 7 August 2014 | MYT 10:40 PM

Rosetta catches up to comet after 10-year chase

Rosetta is the first spacecraft ever to tailgate a comet – in a decade-long mission that scientists hope will unlock the secrets of the solar system.

Launched by the European Space Agency (ESA) in 2004, Rosetta finally caught up with its quarry, the comet named "67P/Churyumov-Gerasimenko", rendezvousing with it on Aug 6. It will now accompany the hunk of ice and rock on its trip around the sun and land a probe on it in November this year in an unprecedented manoeuvre.

Because it's never been done before, ESA scientists are on a tight schedule to learn as much as they can about the comet using data from Rosetta to safely land the spacecraft’s probe, called Philae, on it. “We know what the comet’s shape is. But we haven’t really measured its gravity, we don’t know yet where the centre of mass is,” Rosetta flight director Andrea Accomazzo said, ahead of the rendezvous.

Hunter and prey: Above, an artist's impression, not to scale, of the Rosetta orbiter deploying the Philae probe to comet 67P/Churyumov-Gerasimenko. Below, the comet photographed by Rosetta’s OSIRIS narrow-angle camera in August 2014 from a distance of 285km. – Reuters

As it neared 67P/Churyumov-Gerasimenko this year, Rosetta took pictures revealing that it’s not shaped, as had been assumed, like a rugby or American football, but rather comprises two segments connected by a neck, giving it an asymmetrical shape that has been likened to a duck.

Scientists hope data the probe gathers on the surface of the comet will allow them to peek into a kind of astronomical time capsule that has preserved for millions of years clues about what the world may have looked like when our solar system was born.

It has taken Rosetta 10 years, five months and four days to reach the comet, a roughly 3km by 5km rock discovered in 1969. On its way, the spacecraft circled the sun on a widening spiral course, swinging past Earth and Mars to pick up speed and adjust its trajectory.

Aside from being the first craft to catch up to a comet, Rosetta has managed to clinch another historical firsts, including becoming the first spacecraft to orbit a comet rather than just whizzing past to snap some fly-by pictures. And if everything works out in November, Rosetta may just be the first to land a probe on a comet.

Because the trip is so long and took Rosetta so far from the sun’s solar rays, the spacecraft was put in a deep sleep for 31 months and woken up earlier this year. But now there's no time to lose. As the comet nears the sun at almost 55,000km per hour, it will get more active and begin emitting gases that can make it difficult to predict the trajectory of Rosetta and its probe.

“We have a lot of time pressure to produce engineering models of a world that we don’t know yet,” said Accomazzo, based at the ESA’s satellite operations in the German town of Darmstadt, south of Frankfurt, who has been working on the Rosetta mission since 1997. – Reuters

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