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The development of a spectrophotometric analyzer for use on water samples in microgravity environments is discussed. The instrument is constructed around a commercial spectrophotometer, the Hewlett-Packard HP8453, with a separate turbidimetric analyzer, here a modified Hach 2100P ratio turbidimeter. Flow-through sample cells were constructed for each instrument to support microgravity use and sample deaeration. Spectrophotometric analyses on aqueous samples on orbit are sensitive to the presence of undissolved gases in the samples. In a micro-g environment, free gas in samples can and does remain suspended, clouding the mixture and interfering with spectral optical density measurements. This paper discusses the design of a spectrophotometric analyzer, with particular emphasis on the merits of two approaches to eliminating free gas interferences in on-orbit water analyses: hyperbaric gas redissolution and deaeration across a hydrophobic membrane.

In Space Station Freedom, the water supply will be a closed loop system. Humidity condensate from the cabin and waste hygiene water including urine are to be reclaimed for potable and hygiene uses. Close monitoring of the water quality is mandatory to ensure crew health. The 30-year utilization planned for SS Freedom requires careful planning for water processing and monitoring systems. Perkin-Elmer is developing a Water Quality Monitor (WQM) for the Environmental Control and Life Support System (ECLSS) being developed by the Boeing Aerospace & Electronics Company.* The WQM will monitor impurities in both potable and hygiene water samples.