Pit formation observed in a multilayer dielectric coating as a result of simulated space environmental exposure.
Certain spaceborne telescope designs require that dielectric-coated lenses be exposed to the energetic electrons and protons associated with the space environment. Test coupons that were exposed to a simulated space environment showed extensive pitting as a result of dielectric breakdown. A typical pit was 50-100 microm at the surface and extended to the substrate material, in which a 10-microm-diameter melt region was found. Pitting was not observed on similar samples that had also been overcoated with a transparent conductive thin film. Measurement of the bidirectional reflectance distribution transfer function showed that pitting caused a fivefold to tenfold increase in the scattering of visible light.
Fuqua
Peter D
PD
The Ivan A. Getting Laboratories, The Aerospace Corporation, Los Angeles, California 90009-2957, USA. fuqua@aero.org
Presser
Nathan
N
Barrie
James D
JD
Meshishnek
Michael J
MJ
Coleman
Dianne J
DJ