Dust impact monitor (DIM) of the ROSETTA lander

ATTILA PÉTER

The European Space Agency's ROSETTA mission is due to be launched in 2003 for studying comet Wirtanen in-situ for at least one year, from the onset of activity beyond 3 AU to the perihelion.

During the comet nucleus orbit phase, a Surface Science Package (the ROSETTA Lander) will be deployed onto the surface of the comet. The Lander science will focus on the in situ study of the composition and structure of the nucleus material. Measurement goals include determination of the elemental, molecular, mineralogical, and isotopic composition of the cometary surface and subsurface material.
The Small Instrument Package SESAME (Surface Electrical Sounding and Acoustic Monitoring Experiment) contains three experiments: CASSE (Comet Acoustic Surface Sounding Experiment), DIM and PP (Permittivity Probe) to study the internal structure of the nucleus and the mechanical and electrical properties of, at least, near surface matter of the comet.

During the year 2001 the FM and FS (Flight Model and Flight Spare model) of the DIM were manufactured by us and successfully tested. The figures below show the DIM-Sensor and the electronic part of the DIM.

The 3-dimensional sensor of DIM     The printed circuit board of DIM

Active regions of the comet P/Wirtanen are thought to emit particles of different sizes. As a result of the gas drag and gravity force, some part of the particles will be ejected to interplanetary space, some part will fall back onto the nucleus. A dust impact monitor (DIM), placed on the ROSETTA Lander will observe those particles on the surface of the comet which temporarily leave the surface but fall back due to insufficient velocity. The DIM senses the falling particles by an arrangement based on the acoustic impact monitoring principle.

The tasks of AEKI will be to manufacture, tune, and test the DIM Ground Reference Model, to participate in the fine-tuning of DIM; to completr the Final Documentation; to develop Mechanical and Electrical Computerized Ground Support Equipment (MEC-GSE) for simulating the impacts of various materials of different size and energy, and to measure and evaluate the response signals of the DIM Sensor-Electronic. A further task of KFKI AEKI will be to follow-up and evaluate the operation of DIM during the Commissioning Phase.