MAPS Overview The MAPS experiment measures the global distribution of carbon monoxide (CO) mixing ratios in the free troposphere. Because of MAPS' previous flights on board the Space Shuttle, Earth system scientists now know that carbon monoxide concentrations in the troposphere are highly variable around the planet, and that widespread burning in the South American Amazon Basin and southern cerrados, the African savannahs,and the Australian grasslands and ranches are major sources of carbon monoxide in the southern hemisphere and tropical troposphere.The 1994 flights of the MAPS experiment provided CO measurements that show seasonal changes in CO emissions, sources, transports, and chemistry.InstrumentThe MAPS instrument is based on a technique called gas filter radiometry. Thermal energy from the Earth passes through the atmosphere and enters the viewport of the downlooking MAPS instrument. Carbon monoxide and nitrous oxide (N2O) in the atmosphere produce unique absorption lines in the transmitted energy. The energy which enters the MAPS instrument is split into three beams. One beam passes through a cell containing CO and falls onto a detector. This CO gas cell acts as a filter for the effects of CO present in the middle troposphere. A second beam falls directly onto a detector without passing through any gas filter. The difference in the voltage of the signals from these two detectors can be used to determine the amount of CO present in the atmosphere at an altitude of 7-8 km. During the dedicated Earth-Observing Space Shuttle mission in 1994, MAPS measured the distribution of carbon monoxide in the middle troposphere to evaluate CO sources and chemistry, and to evaluate the seasonal and interannual variation of this key atmospheric trace gas. Interpretation of these measurements will help us to better understand the atmosphere and the consequences that human activities initiate in global climate change. A third beam of the incident energy passes through a cell containing N2O and falls onto a detector. This N2O gas cell acts as a filter for the effects of N2O present in the atmosphere. The global distribution of N2O is well known, so the N2O signal can be used to detect the presence of clouds in the field of view and to correct the simultaneous CO measurement for systematic errors in the data. SRL2 GoalsThe MAPS SRL-2 mission took place during the Northern Hemisphere summer when global biomass burning is nearing its maximum. The southern hemispheric burning of savanna and agricultural grasslands can be extensive in central and southern South America and in nearly all of Africa, south of the equator. The tundra regions of the northern boreal zone also are approaching the peak burning season. Other regions may experience scattered fire events as a result of lightning strikes during severe thunderstorms. The primary goal of the MAPS experiment on SRL-2 is to provide a near global survey of the distribution of tropospheric carbon monoxide during northern hemisphere summer. The secondary goal is to determine how the global distribution of carbon monoxide changes over the course of the mission.SL2 SummaryThe high values of carbon monoxide are associated with extensive areas of smoke and haze that have been observed by the Endeavour (STS-68) flight crew. The smoke results from fires that are burning in the continental regions. The carbon monoxide is carried by tropical thunderstorms to the altitudes (2 to 10 miles above the surface) at which it is measured by the MAPS instrument.The data that are available from MAPS SRL2 include a 5 by 5 degree gridded box (MAPS_SRL2_5X5_HDF) and a second by second data product (MAPS_SRL2_COSEC_HDF). These data sets are available from the Langley DAAC.