Rocket-borne instrument to detect charged smoke and cloud particles in the mesospheric region

Summary form only given. A design of an instrument is described that is capable of detecting charged sub-visible particles in the upper atmosphere. The instrument is placed at the top of a sounding rocket with a /spl sim/20 cm/sup 2/ entrance slit. The sampled air flows between three pairs of graphite patch electrodes placed one above another, and connected to sensitive electrometers. The pairs of electrodes are biased symmetrically and the bias potential increases downward. The static electric field allows the charge- and mass-selective collection. The first pair of electrodes captures the electrons and light ions. Heavier ions within a mass range of 100-1000 amu are collected on the second pair and smoke particles or heavy cluster ions up to 10000 amu are collected on the third pair. The design of the detector has been optimized with a consideration to the possible coning motion of the rocket, collection efficiency, and gas flow dynamics. Numerical Monte Carlo and Direct Simulation codes were used to study the effect of collisions. The results show that above 50 km collisions with neutrals have only a small effect on the detector performance and that vacuum pumping is not required.