Primary payload was the Space Radar Laboratory (SRL-1), located in payload bay; activated by crew and operated by teams on ground. SRL-1 included the Spaceborne Imaging Radar-C and the X-band Synthetic Aperture Radar (SIR-C/X-SAR) and an atmospheric instrument called Measurement of Air Pollution from Satellites (MAPS). The German Space Agency (DARA) and the Italian Space Agency (ASI) provided the X-SAR instrument. SIR-C/X-SAR covered approximately 38.5 million miles of the Earth, the equivalent of 20 percent of the planet. More than 400 sites were imaged, including 19 primary observation sites (supersites) in Brazil, Michigan, North Carolina and Central Europe. Thirteen countries were represented in the project with 49 principal investigators and more than 100 scientists, coordinated by the Jet Propulsion Laboratory (JPL). Some 133 hours of data were collected. The MAPS experiment measured the global distribution of carbon monoxide in the troposphere, or lower atmosphere.