The COSIMA (Cometary Secondary Ion Mass Spectrometer) on board the Rosetta spacecraft will chemically and isotopically analyze the dust particles that are captured in the coma of comet Wirtanen. The experiment works with secondary ion mass spectroscopy (SIMS). A high energy primary ion beam, COSIMA uses 115In+ at 10 keV, hits the target and knocks off molecules, of which typically 0.1 to 10% are ionized, the so called secondary ions. A time-of-flight mass spectrometer is connected in order to enable the measurements over a large mass range. The target can spatially be resolved, limited by the cross section of the primary ion beam (ca. 10 µm).
Cosima consists of a dust collector and target manipulator, a light microscope for target inspection, the primary ion source and the mass spectrometer with its ion optics and ion detector.
The development of the instruments resulted from an international collaboration chaired by the Max-Planck-Institute for extraterrestrial Physics in Garching, Germany. More detailed information can be found at FMI. The institute for space research (IWF) of the Austrian Academy of Sciences is involved in the hardware and electronics for the primary ion beam system.