ELECTRON-MICROSCOPE OBSERVATIONS OF IMPACT CRATER DEBRIS AMONGST CONTAMINATING PARTICULATES ON MATERIALS SURFACES EXPOSED IN-SPACE IN LOW-EARTH-ORBIT

Debris particles extracted from a small sampling region on the leading edge of the Long Duration Exposure Facility (LDEF) spacecraft have be en examined by analytical transmission electron microscopy and the ele mental frequency observed by energy-dispersive X-ray spectrometry and compared with upper atmosphere (Earth) particle elemental frequency an d the average elemental compositions of interplanetary dust particles. A much broader elemental distribution was observed for the exposed sp acecraft surface debris milieu. Numerous metal microfragment analyses, particularly aluminium and stainless steel, were compared with scanni ng electron microscope observations of impact crater features, and the corresponding elemental spectra on selected LDEF aluminium tray clamp s and stainless steel bolts. The compositions and melt features for th ese impact craters and ejecta have been shown to be consistent with mi crocrystalline debris fragments in the case of aluminium, and these ob servations suggest an ever changing debris milieu on exposed surfaces for space craft and space system materials.