With the use of laser systems in space, laser-induced contamination must be taken account of, specially considering several NASA missions such as LITE, MOLA and ICESAT, which have been unsuccessful for this reason or could not be carried out as planned.
The optical components of laser systems operated in space can be damaged by the outgassing of volatile substances required for adhesives, insulating materials or printed circuit boards. Although only materials with a low outgassing rate (total mass loss [TML] less than 1 percent; collected volatile condensable material [CVCM] less than 0.1 percent) are approved and the corresponding components are conditioned by heating prior to use in space, it is not possible to completely prevent further outgassing. Through the interaction of the outgassed materials with the laser radiation, decomposition of the molecules occurs and the residues are deposited on the optics. This occurs particularly when intense levels of short wavelength radiation are involved. Even the smallest layers of deposits, with thicknesses of a few nanometres, reduce optical properties such as reflectivity and transmission that can significantly reduce the life of the entire laser system or even lead to its complete failure.
In particular, laser-induced contamination occurs in a vacuum, but may also affect the service life of encapsulated laser systems. To avoid this risk, or at least minimise it, fundamental research into the formation and growth of such deposits is required. For this purpose, the Active Optical Systems department of the Institute of Technical Physics operates an ultra high vacuum contamination facility. Here, basic studies on laser-induced contamination and screening tests of the materials used are conducted on behalf of the European Space Agency (ESA).