Scary times for Europe's comet-chaser Rosetta

Scary times for Europe's comet-chaser Rosetta
A handout released by the ESA/ATG medialab on November 12, 2014 shows an artists impression of the European probe Philae separating from its mother ship Rosetta and descending to the surface of comet 67P/Churyumov-Gerasimenko.

Europe's pioneering probe Rosetta battled breakdowns with navigation and communication with Earth after it ran into blasts of dust and gas from the comet it is tracking, mission control said Thursday.

Swooping close to Comet 67P/Churyumov-Gerasimenko, Rosetta "experienced significant difficulties" last weekend and had to go into safe mode, the European Space Agency (ESA) said. "The spacecraft has now been successfully recovered, but it will take a little longer to resume normal scientific operations," it said in a blog.

On its Twitter feed, Rosetta said, "Had some difficulties... thanks for kind messages. I'm feeling much better & hoping to resume normal activities soon!" Rosetta has been circling Comet 67/P since last August, catching up with the wanderer after a 10-year, 6.5-billion-kilometre (four-billion-mile) chase across the heavens.

The 1.3-billion-euro ($1.4-billion) mission seeks to unveil the secrets of comets, believed to be time capsules from the birth of our Solar System. The target comet is getting closer to the Sun with every second, and the solar heat is causing its surface to warm.

This in turn is causing dust to be stripped away and gases to heat and blast out into space. It is this spectacular show that, at times, can be seen from Earth in the fiery "coma" of the comet. For Rosetta, though, the outpouring proved to be a problem on an unexpected scale, as the orbiter raced to within 14 kilometres (8.75 miles) of the surface.

Flying through dense, outflowing gas and dust exposed the spacecraft's solar panels, like outstretched wings, to drag.

Another problem was that Rosetta is designed to navigate by locking on to the stars - and its trackers mistook hundreds of pieces of comet debris for stars. As a result, the spacecraft began to drift and its high-gain antenna, used to send and receive signals from ground stations on Earth, started to point away from home and communications began to drop.

Rosetta placed itself into safe mode on Sunday, and by Monday, ground teams had brought it back to normal status, the blog said (http://blogs.esa.int/rosetta/2015/04/01/rosetta-status-report-close-flyby-navi gation-issues/). The craft is now at a safer distance of 200 km from the comet, and "limited science operations" will be resumed in the coming days and weeks.

Future trajectories are being reviewed to take into account the likelihood that the comet will discharge even greater dust and gas as it heads towards perihelion, its closest point to the Sun, in August.

On November 12, Rosetta sent down a fridge-sized robot lab, Philae, which carried out a 54-hour roster of experiments before its battery ran out of power. The lander is believed to be in the shadow of a cliff, preventing its solar panels from getting enough sunlight to power up.

The mission hopes Philae will revive as 67/P gets closer to the Sun. Rosetta on Thursday was 423 million km from Earth and 293 million km from the Sun, according to the mission's website (http://sci.esa.int/where-is-rosetta/).

Perihelion will be on August 13, when the comet will be 186 million km from the Sun.

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