A meteorological imaging system to detect radiation in order to determine the Earth's cloud cover and surface temperatures of its clouds, land, and water. AVHRR-1, with a four-channel radiometer, was launched in October 1988 on Tiros-N. The five-channel AVHRR-2 was launched in June 1981 on NOAA-7, and the six-channel AVHRR-3 in May 1998 on NOAA-15.