The ozone monitoring instrument (OMI) is a nadir-viewing visual and ultraviolet spectrometer aboard the NASA Aura spacecraft. Aura flies in formation about 15 minutes behind Aqua, both of which orbit the earth in a polar Sun-synchronous pattern. Aura was launched on July 15, 2004, and OMI has collected data since August 9, 2004.OMI can distinguish between aerosol types, such as smoke, dust, and sulfates, and can measure cloud pressure and coverage, which provide data to derive tropospheric ozone. OMI follows in the heritage of TOMS, SBUV, GOME, SCIAMACHY, and GOMOS. OMI measurements cover a spectral region of 264–504 nm (nanometers) with a spectral resolution between 0.42 nm and 0.63 nm and a nominal ground footprint of 13 × 24 km2 at nadir. The Aura satellite orbits at an altitude of 705