Collection of cometary dust

Rendezvous Missions to Comets lead to low velocities at the nucleus of the comet. The resulting impact velocity of the cometary dust on a target will range between 10 and 400 m/s. The dust particle which impacts on a target can be collected for a subsequent in-situ analysis.

The collection efficiency of a target depends in addition to obvious geometrical conditions upon the surface of the target. The surface characteristics can be divided into two groups:

• “dirty” surfaces, covered with silicate or hydrocarbon compounds (for example vacuum grease),

• “clean” surfaces, like gold (with additional sputtering).

This paper deals with the experimental and theoretical investigation of the collection efficiency of “clean” targets. Laboratory experiments are described which were conducted at the Technische Universität München, Lehrstuhl für Raumfahrttechnik, and the Max-Planck-Institut für Kernphysik, Heidelberg. In both experiments an electromagnetic accelerator is used to accelerate different types of dust in vacuum to velocities between 10 and 400 m/s.

The target is then examined under the microscope and a secondary ion mass spectrometer (which is a model of the laboratory carried on board of the spacecraft for “in situ” analysis). The adhesion of the dust grains at the target is evaluated experimentally in an ultracentrifuge.