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Using Satellites to Pinpoint and Predict Pollution

The European Space Agency is expanding its satellite data network to better track air pollution on a global scale



Courtesy of the European Space Agency

As NASA gets to work on the Constellation Program—the space agency's next not-so-small-step for mankind that hopes to put U.S. astronauts back on the moon by 2020—the European Space Agency (ESA) has set its sights on learning more about our own planet. Toward that end the agency this month, at its Tropospheric Emission Monitoring Internet Service (TEMIS) conference in Italy, touted its ability to provide free atmospheric and environmental data to help nations assess air pollution problems.

ESA's TEMIS delivers data in what the agency calls "near-real time" and also provides long-term forecasts based on tropospheric trace gas concentrations, aerosols and ultraviolet (UV) radiation. TEMIS gathers information from its own satellites and also has agreements with NASA and the Darmstadt, Germany–based European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) to make their data available on its Web site. This data includes info from the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite and the Global Ozone Monitoring Experiment (GOME-2) instrument on the MetOp satellite, which was developed by EUMETSAT and ESA to provide a closer view of the atmosphere from low Earth orbit.

ESA plans to expand TEMIS to monitor the transboundary and hemispheric movement of air pollution. The OMI and GOME-2 instruments are spectrometers, which can pinpoint different trace gases in wavelength ranges, providing a measure of Earth's entire atmosphere in a single day.

"Key users of this data are environmental agencies [that] have to report on things like greenhouse gases," says Claus Zehner, an ESA Earth observation application engineer, noting that the European Union (E.U.) continues to keep tabs on air quality over its member nations. By law, they have to report each year on the status of the air quality in their countries, he adds. The E.U. is now considering changing its European Air Quality monitoring laws to mandate the use of satellite data.

Among the most important info ESA has provided is data on levels of nitrogen dioxide (NO2) in the atmosphere. NO2, a known pollutant, has been linked to respiratory ills and environmental destroyers such climate change and acid rain. Researchers have identified major NO2 hot spots and industrial culprits, thanks to ESA data gathered between 1996 and 2006.

ESA data has traditionally been used by environmental protection agencies in European Community countries, but its use is spreading. Researchers at Harvard University, for example, used Aura's OMI data to analyze changes in air quality achieved by limiting traffic in Beijing during a China–Africa summit held there last year. In an attempt to ease travel congestion, Beijing officials reduced traffic flow by 30 percent during the conference, barring some 800,000 of its 2.82-million strong fleet of private vehicles from traveling within city limits.

TEMIS enabled Harvard researchers to obtain accurate, independent measurements of NO2 in the city air at that time. By comparing the satellite observations with measurements from the ground, along with a global chemical transport model, they learned that the atmospheric models failed to accurately reflect a dramatic 40 percent drop in nitrogen dioxide levels in Beijing's air during the traffic restriction, says Yuxuan Wang, a Harvard lecturer and research assistant specializing in atmospheric chemistry.

"Without the TEMIS data, I would say that it would be impossible to do" the Beijing emissions study, Wang says. Chinese scientists were able to provide some data, she says, but it didn't come close to the details captured by the satellites. Wang and her colleagues continue to use ESA data to study regional NO2 emission distribution as well as gauge the amount of nitric oxide (NO) plus nitrogen dioxide (collectively known as NOX) present in the air.

ESA data has also been used to study patterns of gaseous pollutant emissions throughout India and to assess the prevalence of disease related to air pollution in New Zealand.

Zehner says that the agency plans to build and launch at least five "sentinel" satellites to monitor not only trace gases that indicate pollution in the atmosphere, but also the surface temperature of the oceans, the movement of ice and the shifting of land masses. The first three are expected to launch by 2012; the remaining two are tentatively scheduled to be sent into orbit by 2015, he says.

ESA's goal is to provide reliable information that can be used to advocate and establish policies designed to improve the environment, Zehner says, adding, "We are offering the first steps needed for monitoring greenhouse gases and other environmental areas."

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