Description: In this STTR effort, Los Gatos Research (LGR) and the University of Wisconsin (UW) propose to develop a highly-accurate sensor for high-purity oxygen determination. The analyzer, which is based on LGR's patented Off-Axis ICOS technique, will be capable of rapidly quantifying high-purity oxygen (95 – 100 %) with very high accuracy (better than ? 0.03 %), minimal calibration, and no zero drift. Moreover, the sensor will require no consumables and be sufficiently compact and robust for deployment aboard the International Space Station (ISS). In Phase I, LGR and UW successfully demonstrated technical feasibility by fabricating a prototype that quantified high-purity oxygen with a precision of ? 0.017 % and a 24-hour drift of less than 0.05 %. The analyzer distinguished a 0.1 % change in highly pure oxygen and provided a linear response (R2 = 0.999997) over a wide dynamic range (0 – 100 % oxygen). The prototype was found to be accurate to 0.07 % by testing it at NASA Johnson Space Center on oxygen purified by the Cabin Air Separator for EVA Oxygen (CASEO) project. Due to the success of this program, LGR released a commercial O2/CO2 analyzer for environmental applications. In Phase II, LGR and UW will refine the measurement strategy, miniaturize the hardware, ruggedize the analyzer, and test the resulting instrument. The measurement strategy will be improved to reduce long-term drift and extended to include other species (H2O, O2 isotopes, N2). The hardware will be modified to meet the technical requirements for deployment aboard the ISS (e.g. power, size, weight, and environmental specifications). The prototype will be manufactured and tested to empirically determine its accuracy, precision, linearity, long-term drift, and time response. Finally, the Phase II instrument will be delivered to researchers in the Life Support and Habitability Systems Branch at NASA Johnson Space Centers for characterization of high-purity oxygen generators.

Benefits: Extravehicular Mobility Units (EMUs) operating from the International Space Station (ISS) utilize high-pressure (> 1200 psi), high-purity (> 99.5 %) oxygen. This oxygen used to be delivered to the ISS by the space shuttle and stored in High Pressure Gas Tanks (HPGTs). With the retirement of the shuttle program, NASA is working to generate high-purity oxygen aboard the ISS for extravehicular activities (EVAs). One promising solution is the Cabin Air Separator for EVA Oxygen (CASEO) project. In CASEO, ambient oxygen aboard the ISS is purified, compressed, and transferred into the HPGTs. During the filling of the HPGTs, it is necessary to continuously monitor the oxygen purity to assure proper operation and optimize the generator conditions. Moreover, once the HPGTs are filled, it is necessary to confirm that the oxygen purity exceeds 99.5 % prior to usage in EVAs. Thus, NASA requires a high-purity oxygen sensor that can quantify minute changes in oxygen purity with high accuracy. The analyzer must utilize minimal consumables, need infrequent calibration, and withstand harsh environmental conditions. In addition to NASA's EVA oxygen measurement needs, several other NASA programs can benefit from the technologies developed in this STTR program, including the Hypersonic Airbreathing Propulsion Branch, Life Gas Monitoring aboard the ISS, and the NASA Astronaut Health Monitoring Program.

Besides its application to NASA, an ultrasensitive, lightweight oxygen analyzer also has significant commercial application for military life gas sensing, industrial process control monitoring, and environmental sciences. LGR is actively collaborating with several commercial partners to develop oxygen sensors for both life gas monitoring aboard Navy submarines and real-time control and optimization of electric arc furnaces. The proposed work is essential in making these instruments smaller, lighter, and more cost effective, thus enabling LGR to penetrate into these lucrative markets.