The Dust Impact Monitor (DIM) is an instrument designed to measure the impact of cometary particles. In principle, DIM is intended to monitor particles that have been volatilised and released from the surface of the comet, but do not have sufficient velocity to escape the gravity of the comet.

DIM is mounted on one of the upper surfaces of Philae and was designed to measure the impact of these particles from three directions. The measurements it makes could be used to infer the velocity at which the particles were ejected from the surface.
The DIM sensors
DIM sensors. Copyright DLR
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