ESA has announced that its Rosetta comet orbiter mission will be extended by nine months. The unmanned spacecraft that rendezvoused with comet 67P/Churyumov-Gerasimenko last year will carry out further observations until September 2016, by which time it will be too far from the Sun to power itself and will land on the comet.

The mission was originally planned to end in December of this year, but on Tuesday the agency decided to continue the mission until the comet has travelled far enough from the Sun that it won't be possible to run the solar-powered spacecraft.

ESA says that the extended mission will allow Rosetta to make observations of the comet before and after its closest approach to the Sun, giving scientists a better knowledge of the activity of 67P by moving the probe closer to the comet as it as it approaches and recedes. This data will be correlated with Earth ground observations, which are difficult and often impossible as a comet comes close to the Sun.

Another possibility is that as 67p's activity wanes, Rosetta may be able to pinpoint the location of the unmanned Philae lander, which reestablished radio contact on June 14. ESA has identified several areas where the lander may have landed, but these were taken from a distance of 20 km (12.4 mi). The agency believes that by moving within 10 km (6.2 mi), it may be possible to find the spacecraft.

In addition, ESA says that the extended mission will allow for more daring maneuvers, such as passing across the comet's night side and collecting dust close to the comet's surface.

By the end of the extended mission, Rosetta will be too far from the Sun for the solar panels to power the spacecraft, which will already be low on propellants, so ESA plans to spiral the orbiter down to comet for a soft landing. Once down, it won't be capable of further observations, but during the approach it will gather data at extremely close distances.

Rosetta has been studying 67P since it first went into orbit around the comet in August of last year. For much of that time, it was mapping the surface in anticipation of the Philae probe making the first ever soft landing on a comet. Since then, the spacecraft has been making a detailed study of the comet and its coma in the hopes of gaining a better understanding of the mechanisms that shape comets as they approach the Sun.

"This time, as we’re riding along next to the comet, the most logical way to end the mission is to set Rosetta down on the surface," says Patrick Martin, Rosetta Mission Manager. "But there is still a lot to do to confirm that this end-of-mission scenario is possible. We’ll first have to see what the status of the spacecraft is after perihelion and how well it is performing close to the comet, and later we will have to try and determine where on the surface we can have a touchdown."

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