The objective of the Passive Optical Sample Assembly I (POSA I) experiment is to assess the magnitude of molecular contamination on International Space Station (ISS) critical surfaces and quantify the performance and degradation rate of candidate/baseline ISS exterior surface materials. POSA I will provide environmental effects information that can be utilized to avoid cost overruns necessitated by unscheduled replacement of degraded on-orbit hardware. The POSA I experiment consists of various passive sample trays, carousels, and plates, as well as vacuum ultraviolet diodes and atomic-oxygen pinhole cameras. Many of the various materials chosen for exposure are currently planned for use on the ISS. The POSA I experiment is performed by the Marshall Space Flight Center.