Advanced space suit technologies demand improved, simplified, long-life regenerative sensing technologies, including humidity sensors, that exceed the performance of current commercial devices. Intelligent Optical Systems proposes to develop luminescence-based optical sensors to monitor relative humidity (RH). The proposed sensors will offer flexible packaging designs and outstanding performance at high RH levels and under water saturation. Miniature flexible humidity-sensitive patches, connected to an optoelectronics reader by an optical fiber, will allow great flexibility in fitting the sensor element into the space suit. The sensor materials will consist of a luminescent indicator, whose emission lifetime depends on humidity, supported in chemically and mechanically passive polymer film. Since measurements that rely on emission lifetime are insensitive to indicator bleaching, and fluctuations in the light source and/or the photodetector, the measurements will be reliable and stable. The advantages of using optical sensors include easy miniaturization, immunity to electric and electromagnetic fields, and amenability to multiplexing. In Phase I, we will develop and analytically characterize humidity-sensitive materials, and prepare flexible sensor patches. In Phase II, we will manufacture prototypes for aeronautic qualification and conduct extensive testing under simulated environmental conditions. Sensitive patches to O2 and CO2 interrogated by the same electronic unit could be incorporated.