COSIMA (Cometary Secondary Ion Mass Spectrometer) onboard Rosetta performs chemical and isotopical analysis of cometary dust in comet 67P/Churyumov-Gerasimenko’s coma. The instrument is based on secondary ion mass spectroscopy (SIMS). A primary energetic ion beam, 10keV 115In+, hits the target and releases molecules of which 0.1 to 10% are ionized. These are the so-called secondary ions. In order to resolve a large mass range, a time-of-flight mass-spectrometer is used. The target can be scanned with a spatial resolution equal to the diameter of the primary ion beam (around 10 μm).
COSIMA consists of a dust collector, a target manipulator, an optical microscope to check the targets, the primary ion source and the mass spectrometer with its ion-optics and ion-detectors.
The development of the instrument was done in an international cooperation under the lead of the Max Planck Institute for Extraterrestrial Physics, in Garching, Germany. IWF delivered the electronics for the primary ion beam system.
Further information about COSIMA can be found at ESA.