The Ozone Monitoring Instrument (OMI) uses an imaging spectrometer to distinguish between aerosol types, such as smoke, dust, and sulfates. It measures cloud pressure and coverage, which provides data to derive tropospheric ozone. Launched in 2004 aboard NASA’s Aura satellite, OMI provides a record of total ozone and other atmospheric parameters related to ozone chemistry and climate, continuing the record of NASA’s Total Ozone Mapping Spectrometer (TOMS) instrument. OMI also measures criteria pollutants such as ozone, nitrogen dioxide, sulfur dioxide, and aerosols, which the U.S. Environmental Protection Agency (EPA) has designated as posing serious threats to human health and agricultural productivity. OMI is a key instrument for monitoring the recovery of the ozone layer in response to the phase out of ozone-depleting chemicals, such as chlorofluorocarbons, agreed to in the Montreal protocol.