Global distributions of CO in the middle troposphere have been determined by the Measurement of Air Pollution from Satellite (MAPS) instrument. MAPS uses a nadir viewing gas filter correlation radiometry with a maximum signal between 400 and 300mbar and has been flown aboard the U.S. space shuttle four times between 1981 and 1994. Results obtained in October 1984 and 1994 show very high levels of CO over the southern tropics,25'34 evidence of the strong effect the transport of emissions from surface biomass burning can have on the middle troposphere.
Future measurements from space promise to provide long-term global coverage of CO distributions in the troposphere. The Measurement of Pollution in the Troposphere (MOPITT) instrument was launched December 1999 aboard the EOS TERRA (previously known as the AM-1) satellite. MOPITT, like MAPS, is a gas filter radiometer that will determine the column abundance of CO. In addition, MOPITT also will retrieve tropospheric profiles of CO (at 4.7 |im) through pressure and length modulation of the correlation cell. Total column abundances of CO and CH4 will also be measured (at 2.3 |am).35 MOPITT is expected to provide nearly continuous monitoring of tropospheric CO for a period of at least 5 years. The EOS Aura satellite (formerly denoted as CHEM-1) is scheduled for launch in June 2003. The Aura payload will include TES (tropospheric emission spectrometer), an infrared imaging Fourier transform spectrometer with high spectral resolution that will determine global distributions of CO (and other radiatively trace gases) in the troposphere and lower stratosphere (http://aura.nasa.gov/tes).
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