Photogrammetric set-up for the analysis of particle motion in aerosol under microgravity conditions

Abstract

An optical set-up to investigate the motion of aerosol particles under microgravity conditions has been designed and manufactured. It provides accurate measurement of 3D coordinates of up to 1000 particles, discrimination between particles of different nature and estimation of the angular velocity of small aerosol crystals. A photogrammetric technique is applied to track independently moving particles, using the acquisition and processing of stereoscopic image sequences. The optical scheme of the set-up is based on a unique objective that collects the light coming from different directions from the back- and front-illuminated aerosol, and transfers it to four different cameras. Driving parameters for the optical head design and image quality are discussed. The set-up performance was verified on optical test objects, aerosol simulators and also real aerosol under microgravity conditions during parabolic flight. The set-up has been designed for use in the JET experiment on board the Maser 8 sounding rocket. The experiment aims at the first direct observation of the chemojet motion of free-flying small growing crystals. Investigation of chemojet motion along with elaboration of the image analysis technique is focused on the development of highly sensitive, real-time, non-perturbative analysis of the reactions on the surface of aerosol particles.