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ESA approves extension for comet mission Rosetta

Paul Sutherland, Feature writer
Jun 23, 2015, 23:00 UTC

Sen—Europe’s comet chasers are celebrating today after the European Space Agency (ESA) agreed to extend the Rosetta mission for a further nine months.

The original mission was funded until Dec. 31 this year, but now the exciting journey of discovery will continue until the end of September 2016. As Sen reported last month, that is when the mission team want to put their spacecraft down onto the surface of Comet 67P/Churyumov-Gerasimenko.

The comet reaches its closest point to the Sun, known as perihelion, on Aug. 13, after which it will begin to head back into the colder depths of the Solar System again on its 6.5-year elliptical orbit. As it recedes from the Sun, activity from the comet’s nucleus will reduce, leading to less jetting of dust and gas from within.

Today’s decision by ESA’s Science Programme Committee to give formal approval for an extended mission means that Rosetta will be able to learn more about how a comet changes as its orbital position changes. The drop in surface activity as the comet cools will also allow Rosetta to swoop closer to the nucleus again to make detailed studies of how surface features have changed.

The mission extension comes just days after the Rosetta team were cheered by the reawakening of Rosetta’s companion probe Philae from its seven months of sleep on the surface of the comet, with sunlight conditions now powering it up enough to resume its own work on the surface.

Rosetta project scientist Matt Taylor was delighted to learn that his team’s request to extend the mission had been granted. He told Sen: “The extension provides us with a fantastic opportunity to do EVEN more science and unique science, we will have great capability to overlap observations made from ground-based telescopes. The ‘summer’ on the comet lasts until March 2016, so we will be watching how we transit from season to season, studying the dark parts of the comet transiting into sunlight to further understand how comets work.”

As Taylor revealed to Sen in May, the plan now will be to bring Rosetta gradually closer to the comet in its final three months in a slowly spiralling orbit that will allow its cameras and instruments to gain ever more detailed views and measurements of the nucleus with its twin-lobed structure. 

He told us in an update: “Finally, we are looking at and end-of-mission scenario where we spiral into the comet. This will provide us with the best-resolution data from the whole mission. It’s great to know the science of the extension was deemed worthy, such that the proposal was accepted.”

By September 2016, Rosetta’s instruments will no longer be able to operate as efficiently, due to the drop in solar power levels as the Sun becomes ever more distant, and the spacecraft will be low in fuel. In addition, the comet will be lining up with the Sun again as viewed from Earth, making communicating with the spacecraft more difficult in any case by October. So the Rosetta mothership will be brought down to join its lander Philae on the surface of the comet itself the previous month. 

Patrick Martin, Rosetta Mission Manager, said in a statement: “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.

“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.”

Though it is early days in planning the landing, Rosetta is expected to end up in a position that does not allow it to contact Earth again. Taylor told Sen: “It will be tricky, but ultimately, unlike the lander Philae, Rosetta contacting the comet will likely be the last we hear from it, so we won’t know anything after that.”