Operation of high fluence pulsed laser systems in space imposes various risks to optical components involved. Volatile
organic components are omnipresent in vacuum vessels housing space-borne laser systems and can be the source for
selective contamination of optics. Laser systems may respond very sensitively to absorption increases of their multiple
optical surfaces leading to inacceptable transmission losses and system degradation. In the recent past, thorough and
long term laser tests, performed at the optics qualification laboratories at DLR and at ESTEC using space relevant and
model substances, have revealed the onset, the built-up, and the later stages of the deposition process. It was found that
these deposits tend to accumulate preferably on the laser footprint area of the optic. Observed thicknesses are on the
order of several tens of nanometers, which can be sufficient to induce noticeable absorption. Sensitive techniques for insitu
and ex-situ monitoring of these molecular contaminative effects under vacuum conditions were developed and are
applied successfully. They are summarized in this paper, along with the phenomena, which are significant for the
appearance of deposits. In addition, adverse conditions, which are favorable for provoking deposits, are communicated.
Finally, mitigative and preventive methods are discussed.