POAM3 data are Polar Ozone and Aerosol Measurement III Version 3.0. The Polar Ozone and Aerosol Measurement (POAM) III instrument measures the vertical distribution of atmospheric ozone, water vapor, nitrogen dioxide, and aerosol extinction. The instrument was developed by the Naval Research Laboratory (NRL). POAM III was launched aboard the French SPOT-4 satellite in March 1998 into a Sun synchronous polar orbit.The POAM III instrument was developed by the Naval Research Laboratory (NRL) to measure the vertical distribution of atmospheric ozone, water vapor, nitrogen dioxide, aerosol extinction, and temperature. POAM III measures solar extinction in nine narrow band channels, covering the spectral range from 354 to 1018 nm. Solar extinction by the atmosphere is measured using the solar occultation technique; the sun is observed through the Earth's atmosphere as it rises and sets, as viewed from the satellite.POAM III was launched aboard the French SPOT-4 satellite in March 1998 into a Sun synchronous polar orbit. As seen from the satellite, the Sun rises in the north polar region and sets in the south polar region 14.2 times per day. Sunrise measurements are made in a latitude band from 55-71 degrees north while sunsets occur between 63-88 degrees south.Each data granule contains one month of data for a particular hemisphere, taken at approximately 101 minute intervals. The latitudinal extent of data for the northern hemisphere is 54.68 to 71.01 and -62.55 to -88.11 for the southern hemisphere. The longitude ranges from 0 to 360. The data consists of profiles of ozone, nitrogen dioxide (NO2), and water vapor concentration, and aerosol extinction at 442 nm and 1018 nm.