Rosetta update: Scary safe mode, but all's well now

The Rosetta blog has been strangely quiet of late, after they had been quite actively posting updates on the status of Rosetta during a critical series of orbit adjustment burns, which I wrote about two weeks ago. The total velocity change that Rosetta needed to make in a series of 5 burns was 778 meters per second, enough to enter planetary orbit.

Here's why Rosetta's blog was quiet, from an update posted today:

A number of events conspired to enforce a lag in reporting the results of the manoeuvre activities in January. First, an unexpected 'safe mode' occurred - in which the spacecraft experienced a problem and basically reset itself, waiting for fresh commands - on 18 January during one of the planned long-duration burns.

Next, the flight control team were very involved in resetting Rosetta, figuring out what caused the safe mode and implementing a fix - which they did. :-)

This took time, during which we didn't post while we waited for news on the success of the fix. A safing event in the middle of a long-duration, major trajectory adjustment burn can be a very bad thing, as we saw with Akatsuki. However, this one happened during a deep space maneuver, without the need to be close to a planet for a gravity assist, so it seems the situation was fully recoverable once they got the spacecraft back to a normal operating condition. I look forward to hearing more from the Rosetta mission about what happened -- and I am very glad that nothing worse happened!