Measurement of Surface Reactions in the Space Environment

Serious degradation is experienced by the external surfaces of spacecraft that operate in low earth orbits for extended periods of time, as a result of the ablative effects of atmospheric atomic oxygen, possibly catalyzed by solar ultraviolet radiation. Improved base materials and surface coatings are being developed by government, university and industry teams to combat the effects of this degradation. A small spacecraft and a suite of associated instruments, designed to measure the performance of improved, atomic-oxygen-resistant materials and coatings in orbit and to telemeter the resulting data and video images to earth at intervals during a one-year mission, have been described in a definition study sponsored by the Langley Research Center under NASA's In-Space Technology Experiments Program. Instruments selected for use in this miniature orbiting laboratory include a radio frequency mass spectrometer, a set of quartz crystal microbalances, a set of osmium-based atomic oxygen sensors, a scatterometer, a set of osmium actinometers and a scanning optical microscope. The design of these instruments and their use in the overall experiment are summarized in this paper.