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EPA scientists Jim Szykman (left) and Russell Long (right) with NASA scientist Jim Crawford (center) on the NASA P-3B Orion aircraft being used in the DISCOVER-AQ study in Denver.

EPA scientists are collaborating with NASA and other federal partners on a multiyear study to help scientists better understand how current and future measurements from satellites can improve understanding of air quality and lead to improvements in exposure and health effects science. The NASA-led mission, DISCOVER-AQ, which stands for Deriving Information on Surface conditions from COlumn and VERtically resolved observations relevant to Air Quality, was initiated in 2011.

The fourth and final DISCOVER-AQ field mission will take place July 14 – August 12 in Denver, Colo. Two NASA aircraft equipped with scientific instruments will make daily flights over Denver and surrounding areas to measure air pollution.

Study results could lead to better air quality forecasts, specifically under the AirNow program — a web-based clearinghouse that offers daily air quality index forecasts for approximately 300 of the largest metropolitan areas in the United States. DISCOVER-AQ study results are also anticipated to help scientists develop more accurate determinations of where pollution is coming from and why emissions vary. Because many countries, including the United States, have large gaps in ground-based networks of air pollution monitors, experts look to satellites to provide a more complete geographic perspective on the distribution of pollutants — similar to how weather satellites image large-scale weather events.

A challenge for space-based instruments monitoring air quality is to distinguish between pollution high in the atmosphere and pollution near the surface where people live. To address this issue, DISCOVER-AQ is employing NASA aircraft equipped with air monitoring devices to make a series of flights to simulate existing satellite instruments. Data collected will be compared to data gathered at ground-based monitoring sites, as well as data from NASA-operated satellites that will pass daily over the DISCOVER-AQ study area.

About the Denver field study

During the Denver mission, scientists will measure a variety of air pollutants including aerosols, ozone, and nitrogen dioxide using aircraft and ground-based monitoring. EPA is providing support to DISCOVER-AQ by providing equipment and expertise for measuring pollutants at seven ground-based monitoring sites to improve satellite and remote sensing measurement capabilities. In addition, EPA is conducting complementary studies concurrently with DISCOVER-AQ as part of ongoing research to advance air pollution monitoring technology.

DISCOVER-AQ provides an opportunity to evaluate newer air quality measurement methods for ozone and nitrogen dioxide (NO2) for potential use in national monitoring networks to support the implementation of the National Ambient Air Quality Standards (NAAQS). EPA will continue to evaluate technology that provides direct and more accurate measurement of NO2 since the existing Federal Reference Method (FRM) used to measure NO2 is an indirect method. Scientists will also continue evaluations to support a new FRM for measuring ozone. The current ozone FRM is no longer available commercially.

EPA scientists will evaluate and compare compact air sensors to more traditional methods currently used to monitor air quality. Study results will provide a better understanding of how compact air sensors perform in real-world applications. This will also allow EPA scientists to investigate different applications for compact sensors.

Previous DISCOVER-AQ research

Two NASA aircraft equipped with scientific instruments will make daily flights over the Denver area in July-August 2014 to measure air pollution.

During the July 2011 field campaign in the Baltimore-Washington D.C. area, EPA provided key ground-based measurements at multiple sites for both ozone and nitrogen dioxide. The NASA airplanes flew over the Baltimore-Washington Interstate-95 corridor collecting data on ozone, nitrogen dioxide, formaldehyde, aerosols, and sulfur dioxide.

During the January/February 2013 field campaign in California's San Joaquin Valley, EPA scientists and collaborators collected ground and air quality data through a series of flights that took place between Bakersfield and Fresno, Calif. The flight path passed over six ground measurement sites. Sampling focused on agricultural and vehicular traffic areas.

During the September 2013 field campaign in Houston, Texas, EPA scientists and collaborators collected ground and air quality data through a series of flights that centered around the Houston area collecting data on ozone, nitrogen dioxide, and ambient water-soluble organic carbon. This was the first mission to employ the help of citizen scientists to collect ground data and test new compact sensor technologies for measuring ozone and nitrogen dioxide at the Earth’s surface.

Read EPA blog about 2013 DISCOVER-AQ field campaign

Future research

EPA scientists expect to use the DISCOVER-AQ data they collect in the four field studies to help plan for their participation in a newly selected NASA satellite mission called TEMPO, or Tropospheric Emissions: Monitoring of POllution, expected to launch in 2019.

The TEMPO project involves building the first space-based instrument to monitor major air pollutants across the North American continent hourly during daytime. The instrument, to be completed by September 2017, will share a ride in 2019 on a commercial satellite that will orbit about 22,000 miles above Earth’s equator. Current methods utilize satellites orbiting much closer to the earth’s surface, allowing for observations of atmospheric pollutants to be made only once a day.

Led by the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., TEMPO will make the first measurements of tropospheric pollution over North America. The space-based instrument will be able to measure trace concentrations of ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, and aerosols with high frequency and resolution.

In addition to EPA, the TEMPO team includes partnerships with Ball Aerospace and Technologies Corp.; NASA's Langley Research Center; NASA's Goddard Space Flight Center; and several U.S. universities and research organizations.

Technical Contacts:

Jim Szykman, Ph.D.
EPA National Exposure Research Laboratory

Russell Long, Ph.D.
EPA National Exposure Research Laboratory

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