Preliminary micrometeoroid and debris effects on LDEF thermal control surfaces

Thermal control surfaces returned from space exhibited synergistic effects of simultaneous exposure to various natural environments. The thermal control surfaces of the Long Duration Exposure Facility (LDEF) were exposed to 5.75 years of low Earth orbit environments. Since LDEF was gravity-gradient stabilized and directionally stable (i.e., no rotation), the effects of each of the environments (meteoroid and space debris impacts, thermal cycling, atomic oxygen, and ultraviolet light exposure) can be distinguished via changes in material responses to hypervelocity impacts. The extent of these impacts are being visually and microscopically characterized using thermal control surfaces archived at NASA Johnson Space Center (JSC) in order to determine the relationship between environment exposure and resulting ring sizes, delamination areas, and penetration diameters. The characterization of these affected areas will provide spacecraft system designers with the information they require to determine degradation of thermal control systems during satellite lifetimes.