Aerosols are collected by direct impaction during the first sampling phase (135-80 km). The pump unit (PU) draws atmospheric gas through the filter during the two aerosols sampling periods at 80 -32,5 and 22 -17 km nominal altitudes. A kinetic wheel design was selected -- a 19000 to 25000 rpm drag fan. The pump, built by Technofan under sub contract to SEP, is a small light weight unit of approximately 850 grams with over all dimensions 100 x 80 x 100 mm.
The system consists in a casing, the first/second stage pump wheels and the electric motor (PM). The internal assembly is mounted on a shaft carried on two bearings. The first and second stage pump wheels are mounted on the motor shaft and locked to the inner race of the front bearing by the shaft lock nut. A titanium sleeve around the stator protects the internal parts of the pump (and sampling tubing) against chemical contamination.
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