We propose to build, test and deliver a two-channel NOx monitor (NOx= NO + NO2) suitable for deployment on on ground or aerial-based platforms. It will provide simultaneous measurement of total NOx and NO2 concentrations (and thus NO by difference) . It will have a physical time constant of 1 second (e-1) and provide one independent sample per second. Its accuracy will be better than 5% and its precision less than 0.2 ppb in one second sampling. It will utilize less than 100 W power and weigh less than 25 kilograms. The monitor is based on Aerodyne Research’s patented CAPS (Cavity Attenuated Phase Shift) technology which is already used to produce commercial instruments for both the research and regulatory measurement communities.
Nitrogen Dioxide is measured as a column density by NASA satellites. Accurate and precise ground truth measurements must be made in order to provide proper interpretation of such data. It is also designated as a "Criteria Pollutant" by the Clean Air Act of 1970. The relationship between NO and NO2 is also an indicator of plumes originating from combustion systems such as aircraft and diesel engines and electric power generators. The monitors currently used by NASA deploy an outdated technology, chemiluminescence detection of NO, which is subject to numerous chemical interferences. Furthermore, these monitors cannot provide the fast-response sub-ppb precision required for the measurement of fast moving plumes.
High resolution spatial and temporal measurements of NO2 will enhance the interpretation of both ground and space-based (satellite) measurements. Inclusion of a total NOx measurement capability (and thus NO measurements) would provide NASA with a more accurate and reliable replacement for its standard chemiluminescence-based monitors. The fast response aspect and high sensitivity of the proposed monitor will make it suitable for deployment on aerial platforms.
Aerodyne Research has already provided almost 100 CAPS-based NO2 monitors to university and government laboratories on 5 continents. The inclusion of the total NOx channel will enhance sales of these instruments as it becomes clear that they offer a viable replacement for the chemiluminescence-based monitors that are currently used to measure NOx and NO.