scope:

Description of Driving Event:

The Orbiting Carbon Observatory (OCO), an Earth orbiting satellite mission managed by the NASA/Caltech Jet Propulsion Laboratory (JPL), was designed to make precise, time-dependent, global measurements of atmospheric carbon dioxide (CO2). The instrument, intended to detect CO2 from orbit, employed three channel-specific spectrometers.

During assembly of the OCO Optical Bench Assembly (OBA) at JPL (Figure 1), four spectrometer lenses designed to image the strong CO2 channel were bonded into mounting rings. Following a thermal-vacuum bake-out procedure performed to complete outgassing of the silicone-based "RTV" bonding material, visible contamination was observed on the lenses. Probable sources of the contamination included excessive curing agent in the RTV, use of a lens cleaning solvent containing aliphatic hydrocarbons and esters, use of plastic lens cases, use of gloves that had not been precleaned, and parts handling procedures. The impact of the lens contamination was minimal due to the performance characteristics of the instrument, but migration of the contamination to certain focal plane components would have had a major or catastrophic impact on the OCO mission.