ROMAP

ROMAP (Rosetta Lander Magnetometer and Plasma Monitor) was an experiment designed to determine the plasma environment and any residual magnetic field present on comet 67P.

 
The main electronics for the instrument are located within the Philae lander. The sensors themselves are placed on a 60 cm long retractable rod. One of these sensors was designed to measure the magnetic field while the other would have measured the abundance of the ions and electrons which make up the plasma environment of the comet.  

The ROMAP sensor

The ROMAP sensor. Copyright Max Planck Institute.

For sources and further information visit:

http://sci.esa.int/rosetta/31445-instruments/?fbodylongid=901

http://www.igep.tu-bs.de/forschung/weltraumphysik/projekte/rosetta/romap_en.html