Surface Scattering Characteristics and the Measurement of Particulate Contamination

Surface scattering measurement techniques can be adopted for use in spacecraft contamination control programs. A witness mirror measurement program was developed and implemented for the NASA Cosmic Background Explorer (COBE) spacecraft. Scattering measurements were obtained before and after a qualification level vibration test for several COBE prototype instruments. The measurements indicate a significant amount of particle redistribution occurred during the vibration test. This paper summarizes the methodology used and the results obtained from this monitoring program. INTRODUCTION Contamination deposited on optical surfaces can greatly reduce instrument performance, therefore impairing the achievement of mission scientific goaXs. Particulates such as fibers, dust or remains of fabrication processes or chemical species, outgassed from a variety of materials or generated during virtually any mission phase and subsequently adsorbed or deposited on critical surfaces, degrade surface characteristics. Among the principal effects of the presence of contaminants are surface obscuration, scattering and absorption of incident radiation, loss of throughput, and increase of surface absorptivity. Particles in the instrument field of view have an obvious negative influence in the process of data collection. 383 https://ntrs.nasa.gov/search.jsp?R=1988000148