Miniature Nitrogen Dioxide Trace Gas Sensor for In Situ Atmospheric Measurements

Nitrogen dioxide (NO2) poses a health risk, particularly for children and individuals with respiratory issues like asthma. It is produced by a variety of sources, including vehicles, industrial plants, and appliances in homes. To better regulate this toxic pollutant, it is important to know where the sources are and how it is dispersed in the atmosphere. Current accounting for NO2 sources and dispersal is done by a combination of measurements and modeling, in which remote sensing from satellites provides data that is used to validate models of chemical transport. However, these models are far from certain and a limiting factor is the interpretation of the satellite data, which requires knowledge of the vertical distribution of NO2 in the troposphere since the satellite measurements do not, by themselves, provide this. Thus, there is a need for in situ measurements of NO2 from airborne platforms on a wide scale. Current sensors are costly and often not suitable for use onboard small aircraft, such as unmanned aerial vehicles, which would help enable widespread measurements. A miniaturized low-cost instrument is proposed for sensitive measurements of NO2 based on laser absorption that will help enable extended in situ measurements that will provide accurate high-fidelity data that is needed to properly interpret satellite measurements and validate chemical transport models. Data obtained with this sensor is expected to lead to an improved accounting of NO2 sources and distribution in the atmosphere. In the proposed effort, we will develop the sensor and confirm its accuracy, which is projected to be significantly better than existing sensors at a lower per unit cost, thus enabling widespread deployment. A compact, affordable high precision sensor for NO2 would find immediate customers in the air pollution research community, and future versions of the technology should be within the reach of general consumers, opening up a new market for home NO2 monitoring. Determination of nitrogen dioxide (NO2) sources and dispersal requires knowledge of the vertical distribution of this pollutant in the troposphere to properly interpret satellite data. Thus, there is a need for in situ measurements of NO2 from versatile airborne platforms on a widespread scale. Current sensors are costly and often not suitable for use onboard small aircraft, such as unmanned aerial vehicles and balloons, which would help enable such measurements. A miniaturized low-cost instrument is proposed for sensitive measurements of NO2 based on laser absorption that will help enable extended in situ measurements to provide accurate high-fidelity data, which is needed also to validate chemical transport models. In the proposed effort, we will develop the sensor and confirm its accuracy, which is projected to be significantly better than existing sensors of similar size and at a lower per unit cost, thus enabling more widespread use for customers in the air pollution research community, with future versions expected to be within the affordable range of consumers.

The proposed work directly addresses NASA activities related to assessing the relationship between high-temporal resolution measurements from space and continuous in-situ tropospheric and surface observations of criteria pollutants. NO2 is a primary measurement objective in existing (OMI, TROPOMI, and TEMPO) satellite instruments and there is a need for airborne measurements to validate and complement measurements from these satellites. NASA’s Goddard Space Flight Center conducts work on measuring vertical profiles of NO2 from balloon platforms, which the proposed sensor is designed to do. The sensor would fill a gap in providing in-situ vertical profile measurements of NO2 from airborne platforms as well as allowing expanded coverage from ground stations. Another NASA program that is expected to benefit is the Chemistry and Physics Atmospheric Boundary Layer Experiment (CAPABLE), which was created to monitor and observe NO2 and other pollutants in the troposphere. While NASA's research aircraft, such as the DC-8, WB-57, ER-2, and P-3B, are equipped with instruments to collect in-situ data on trace gases including NO2, most commercial NO2 monitors are too large and pricey to be mounted on UAVs and balloons and thus are not able to measure the vertical profiles needed for satellite data validation. In addition, the proposed instrument would be affordable enough to enable widespread deployment over a greater number of ground stations, which would strengthen the database for satellite measurement and chemical transport model validation. Examples of previous NASA programs that would have benefitted from this capability are the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission, which allowed scientists to identify the sources and movement of tropospheric pollution over the country, and the Atmospheric Tomography (ATom) mission, which studied the impact of chemically reactive gases in the atmosphere, including validation of satellite data. The Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA) are also involved in activities that will help validate the next generation air quality measurements from space from the TEMPO satellite mission and would benefit from the proposed NO2 sensor. EPA is co-leading validation efforts of satellite data through the long-term deployment of in-situ analyzers to detect nitrogen dioxide and other trace gases in support of NASA and NOAA field campaigns and their data serves as primary validation for the TEMPO mission. Ground-level and airborne data could be obtained with the proposed instrument that would help scientists to evaluate TEMPO observations to improve air pollution forecasts. Eventual findings would help inform decisions by state and local environmental officials about the most effective ways to reduce air pollution. NOAA currently uses a chemiluminescence instrument that is flown on NASA aircraft that provides in-situ measurements of NO2 and other pollutants. The proposed instrument could potentially fill this role with a smaller, less costly package that could be more widely deployed using UAVs that would provide more widespread coverage. In past studies, EPA scientists have performed measurements of trace gases from ground and ship platforms to develop a greater understanding of the underlying causes of high ozone, of which NO2 is a precursor, particularly at shoreline monitoring locations. The proposed instrument would be a cost-effective way to fill this need in future studies and would be more versatile than existing instrumentation due to its small size and robustness. Future versions of the proposed instrument could be used for in-home monitoring of nitrogen dioxide and a handheld version would have an immediate market for sensing NO2 concentrations in industrial settings.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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