Space Electrons Dig Pits in Coatings

One may not think that space-borne telescopes would need much protection from outside elements, but electrons and protons caught in the Earth's magnetic field can have damaging effects on the dielectric coatings of the telescopes' lenses. Researchers at the Ivan A. Getting Laboratories of The Aerospace Corp. in Los Angeles used a JEOL USA scanning electron microscope to examine dielectric coating samples exposed to an equivalent of five years of proton and electron bombardment. They observed small pits measuring 10 to 100 µm across, which are probably the result of electrons creating a large static charge on the substance. They described their findings in the June 1 issue of Applied Optics.