The AVHRR is a radiation-detection imager that can be used for remotely determining cloud cover and the surface temperature. Note that the term surface can mean the surface of the Earth, the upper surfaces of clouds, or the surface of a body of water. This scanning radiometer uses 6 detectors that collect different bands of radiation wavelengths as shown below.
The first AVHRR was a 4-channel radiometer, first carried on TIROS-N (launched October 1978). This was subsequently improved to a 5-channel instrument (AVHRR/2) that was initially carried on NOAA-7 (launched June 1981). The latest instrument version is AVHRR/3, with 6 channels, first carried on NOAA-15 launched in May 1998.
The AVHRR/3 instrument weighs approximately 72 pounds, measures 11.5 inches X 14.4 inches X 31.4 inches, and consumes 28.5 watts power.
|AVHRR/3 Channel Characteristics|
|Channel Number||Resolution at Nadir||Wavelength (um)||Typical Use|
|1||1.09 km||0.58 - 0.68||Daytime cloud and surface mapping|
|2||1.09 km||0.725 - 1.00||Land-water boundaries|
|3A||1.09 km||1.58 - 1.64||Snow and ice detection|
|3B||1.09 km||3.55 - 3.93||Night cloud mapping, sea surface temperature|
|4||1.09 km||10.30 - 11.30||Night cloud mapping, sea surface temperature|
|5||1.09 km||11.50 - 12.50||Sea surface temperature|
Measuring the same view, this array of diverse wavelengths, after processing, permits multi spectral analysis for more precisely defining hydrologic, oceanographic, and meteorological parameters. Comparison of data from two channels is often used to observe features or measure various environmental parameters. The three channels operating entirely within the infrared band are used to detect the heat radiation from and hence, the temperature of land, water, sea surfaces, and the clouds above them.