Advanced Very High Resolution Radiometer - AVHRR
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.
| 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.
Questions or Comments: Satellite
Information Team ([email protected])
Revised: 17 December 2001