As I type this, the Rosetta Flight Control Team are in a training exercise that simulates a trajectory correction manoeuvre (TCM) at 6 hours before Earth closest approach on 13 November.

This slot is crucial as it would be the last time that the team had the chance to make any corrections to the spacecraft’s trajectory before it closes in on Earth for the swingby; it is not likely to be needed.

The simulation runs for most of the day, with pre- and post-briefings held before and after and focuses on the procedures that would be necessary to make use of the TCM.

The Sims Officer can throw any number of 'real' problems at the team; so far today they have had to deal with loss of a star tracker (a navigation device that helps determine where Rosetta is pointing by viewing the star field) and a faulty reaction wheel (a device that spins so as to cause Rosetta to spin or slew).

Sometimes, the Sims Officer even calls in and announces, "OK - the SOM is sick and can no longer take part," meaning that Spacecraft Operations Manager Andrea Accomazzo has to leave the rest of the team to function without his (considerable) know-how!

But it's all part of preparing for any eventuality. -- Daniel