First off: watch this!
It’s a visualisation of Rosetta’s trajectory from the delivery of Philae to the surface of Comet 67P/C-G through to the end of 2014.
Following the lander delivery on 12 November, a series of thruster burns on 19, 22 and 29 November brought the spacecraft to a 30 x 30 km orbit (see ‘Rosetta continues into its full science phase‘ in the main ESA website).
On 3 and 6 December, a pair of burns brought it back down into a 20 km x 20 km circular orbit, following the terminator, i.e. orbiting above the day-night line on the comet’s ragged surface. This is where Rosetta will stay until 20 December, when the first of a new pair of burns will kick it back up to 30 km x 30 km circular orbit. The second burn will take place on 24 December.
Rosetta will stay from then on in a 30 km orbit until 3 February 2015.
“After that, Rosetta will begin flying a series of flybys,” says Spacecraft Operations Manager Sylvain Lodiot. “And that will be the pattern for the rest of the nominal mission.”
“Contrary to the pre-landing phase, where the trajectories flown were designed with the lander delivery always in mind, science now drives trajectory design,” says Michael Küppers, Science Operations Coordinator for the Rosetta mission.
Rosetta’s trajectories are designed by the Science Operations team in ESAC, Madrid, on behalf of the instrument teams, and are delivered to ESOC for implementation. Science planning is performed against two different trajectories: a ‘preferred’ and a ‘high activity’ trajectory. While the intention is to always fly the preferred, in the event that comet activity increases beyond that expected for the preferred case, the spacecraft will move to the high-activity trajectory. This will allow the science operations to continue, besides the initial impact on science planning that such a move would entail.
“The desire is to continue to keep the spacecraft as close as feasible to the comet before its activity becomes too high to maintain closed orbits,” says Laurence O’Rourke, also a Rosetta Science Operations Coordinator at ESAC. “Once we leave the closed orbits, we will then carry out science linked to close & far flybys of the comet.”
High-resolution mapping of the comet will therefore continue, along with the collection of gas, dust and plasma as the comet’s activity continues to increase. The science teams also hope to sample rare molecules in the gas that may include complex organics that could have played a role in the origins of life on Earth.
An exciting manoeuvre is planned for Valentine’s Day 2015, when Rosetta will make the closest-ever flyby of Comet 67P/C-G at just 6 km from the surface. To achieve this, the spacecraft will leave its 30-km orbit on 4 February 2015, flying out to a distance of over 140 km from the comet before beginning to swoop down once more.
This close flyby will allow instruments to take images and spectra of the surface with unprecedented resolution and to directly sample the very inner cometary coma where the nucleus material is processed into the coma and tail as we know it from remote observations.
“Landing week marked an epoch where we began the one-hundred-percent science phase,” says Matt Taylor, Rosetta Project Scientist.
“From now on, that’s all we focus on with the mission. The measurements we make now set the tone for the entire mission. The comet’s activity will continue to increase and we’ll be watching.
Science has started with gusto, thanks to the work of the instrument teams and the Rosetta science operations team.”
The spacecraft is in excellent shape; all systems on board are performing as expected and the mission systems on ground are nominal.