Optical contamination measurements on early Shuttle missions

Two camera/photometers were included as part of the Induced Environment Contamination Monitor on STS-2, -3, -4, and -9 orbital missions to record photographically Shuttle-induced particulate and background contamination. The cameras collected stereoscopic data continuously during the on-orbit phases of these missions making exposures every 150 s. The results recorded throughout a 32 degrees field-of-view indicate high particle concentrations during early mission operations. These decay to a quiescent rate of 500 particles of >10-microm radius observed per orbit. Preliminary size and velocity distributions of measured particles are presented as are measurements of background brightness due to unresolved particles in the visible spectral region.