High accuracy measurements of atmospheric parameters, particularly water vapor, are required from balloon-borne, disposable, lightweight, low cost, high precision instruments to support atmospheric and climate research. This project will develop a novel fiber sensor for balloon-borne, high accuracy measurements of water vapor concentrations from point of launch to at least 20 km altitude. The concentrations at these elevations are very low, posing a serious challenge. The proposed sensor relies on a thin film containing fluorescent compounds that are sensitive only to the presence of water molecules. By monitoring changes in fluorescence with a fiber optic interface, it is possible to determine the local water vapor in real time. The very low temperatures found at high altitudes are expected to enhance the fluorescence signal and offset the decreased sensitivity typically seen for humidity sensors at very low water vapor concentrations. In Phase I, a single fiber configuration will be employed for both excitation and emission, and a multiwavelength detection method will be used to provide an internal standard for continuous calibration for better measurement accuracy. The effort will culminate with a successfully tested prototype.
Commercial Applications and Other Benefits as described by the awardee: A fiber optic sensor for moisture measurement that combines rapid response, self-calibration, low cost, and remote monitoring should find commercial applications beyond atmospheric measurements. It also should benefit the food, drug, and chemical industries, where the need for rapid determination of humidity levels is very critical to process optimization and product quality.
