Comet 67P, Rosetta just days away from perihelion

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Comet 67P/C-G on 7 July 2015. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Comet 67P/Churyumov–Gerasimenko and European Space Agency’s Rosetta are just days away from perihelion – their closest approach to the Sun.

With Rosetta Mission completing a year at the comet on August 6, ESA scientists will be at the front row seat when the comet will be at its maximum activity – thanks to perihelion.

Rosetta was launched in 2004 and after flying past the Earth, Mars and two asteroids, and it became the first ever spacecraft to orbit a comet as well as soft-land a probe on the surface.

Over the course of last one year, ESA scientists have managed to obtain wealth of information about the comet, its current environment, the environment in which it may have been born, temperature variations as it approaches the Sun, its structure among other things.

Key moments in Rosetta’s first year at Comet 67P/Churyumov–Gerasimenko. Credit: ESA
Key moments in Rosetta’s first year at Comet 67P/Churyumov–Gerasimenko. Credit: ESA

“This mission is about scientific discovery and every day there is something new to wonder at and try to understand,” says Nicolas Altobelli, acting Rosetta project scientist.

“A year of observations near to the comet has provided us with a wealth of information about it, and we’re looking forward to another year of exploration.”

Now the comet and spacecraft are a week from perihelion, the point on its 6.5-year orbit that takes it closest to the Sun. On 13 August, they will be 186 million kilometres from the Sun, about a third of the distance at rendezvous last August.

ESA scientists note that the period around perihelion is very important as it will provide scientists with a first row view of this key time in the overall life cycle of the comet. Scientists believe that the closest point may reveal fresh material that has yet to be altered by solar radiation or cosmic rays providing a view of the comet’s subsurface layers.

Rosetta has been watching its activity increase over the last months, as its frozen ices warm, turn to gas, and jet into space, dragging the comet’s dust along with it. Together, the gas and dust have created a fuzzy atmosphere, or coma, around the nucleus and a long tail stretching over 120,000 km into space that can only be seen from afar.

Perihelion may be one of the most interesting points for the exploration, but it is also one of the most challenging as the increasing level of cometary dust confuses Rosetta’s startrackers and without them working properly Rosetta can’t position itself in space.

All those involved with the mission including those from flight control, flight dynamics and science operations, have had to learn and adapt to the conditions ‘on the fly’ while also having to rethink on operation of the spacecraft – specifically its science activities on timescales of just a few days or weeks.

One important aspect of Rosetta’s long-term study will be to watch how the activity subsides again in the months following perihelion. The hope is that Rosetta will eventually be able to get closer to the nucleus again and see how the surface changed during its close encounter with the Sun.