On Sunday, 25th february 2007, Rosetta flew by Mars performing a gravityt assist manoeuvre. Rosetta passed by the red planet's surface in a distance of some hundred kilometers. This close approach was a good opportunity to switch on the lander experiment ROMAP in order to calibrate its magnetometer. Additionally, the data set taken during the flyby provides an insight into the plasma environment around Mars.
Magnetic Field measured by ROMAP during Mars flyby
All components of ROMAP worked satisfyingly during the flyby. In the magnetogramm plotted above, one can follow Rosettas itinerary around Mars: its approach through the solar wind and the crossing of the bowshock and he tail.
See also ESA article about Rosettas flyby.