The objective of this Phase I STTR project is to develop a highly sensitive oxygen (O2) sensor, with high accuracy and precision, to determine purity levels of high concentration (> 99%) O2 gas streams. This sensor will meet NASA applications for on-orbit O2 purity checks in portable life support systems (PLSS) and during in situ O2 production activities. InnoSense LLC (ISL) will utilize its proprietary Chemical Fingerprint (TM) sensor array fabrication technology in this project coupled with the combinatorial analysis and high throughput sensor evaluation capabilities of the STTR partner. In Phase I, ISL will engineer a working model and demonstrate NASA use potential of the technology. Upon fine-tuning various parameters in Phase II, the system performance will be tested with a prototype hardware. For assuring success of this project, ISL has assembled a technical team with a cumulative 90 person-years of experience in developing commercially viable sensor systems.