Compact Chemical Monitor for Spacecraft Water Recovery Systems

The International Space Station (ISS) requires lightweight, low-power, easy-to-use, accurate, and stable sensor technology for monitoring wastewater content to ensure proper functioning of the ISS Environmental Control and Life Support System (ECLSS). In particular, continuous and unattended pH, Ca2+, and conductivity monitoring in the Urine Processor Assembly (UPA) in use in the ISS Water Recovery System is required. At present, no such sensor technology exists that can satisfy the demanding operational requirements of the ISS and future exploration missions. Intelligent Optical Systems (IOS) proposes to develop a luminescence-based optical sensor probe to monitor calcium, conductivity, and pH levels directly in ISS wastewater in real time. Optical sensors are superior to electrochemical ones in terms of robustness, reliability, and maintenance. These advantages are most notable in corrosive aqueous environments. Our monitor will incorporate robust sensor elements, interrogated via a compact, low-power optoelectronic unit. The proposed sensors will be remotely connected to the electronic circuitry by an electromagnetic interference (EMI)-proof optical fiber cable. For space systems control, miniature fiber optic sensors connected to the electronic circuitry by an optical fiber cable allow greater flexibility in placing the sensor system in the ISS, where space is highly valuable. Our flow-through monitor will include optical sensors for calcium and pH sensing based on previous sensor technologies developed at IOS. IOS will also incorporate a miniature conductivity sensor into the sensor probe system. In Phase II we will produce prototypes for integration in a Urine Processor Assembly and conduct extensive testing under simulated environmental conditions, culminating in delivery to NASA of a monitoring system, bringing the monitor to TRL 7.