Advanced Very High Resolution Radiometer/3 (AVHRR/3)
The Advanced Very High Resolution Radiometer (AVHRR) is a multi-purpose imaging instrument used for global measurement of cloud cover, sea surface temperature, ice, snow and vegetation cover and characteristics. This instrument is currently flying on the NOAA series of spacecraft in a five channel version (no channel 3a present). AVHRR has 6 channels in the visible and infra-red between 0.63 and 12.0 micrometers, with an instantaneous footprint of 1.1 km at the sub-satellite point. The internal rotating scan mirror also views deep space and a thermal calibration source on each rotation. Scanning is cross-track with a range of ±55.37 about nadir.
Calibration of the IR channels is performed with 4 internal black bodies every scan line. The calibration coefficients for the visible channels are determined pre launch.
AVHRR scans across track of the satellite path in continuous scan. There are 2048 Earth Views per scan over a swath of ±1447 km. The squared instantaneous field of view has a size of 1.1 km at nadir.
AVHRR/3 channel characteristics
| Channel | Central wavelength (um) | Half Power Points (um) | Channel Noise Specifications |
| 1 | 0.630 | 0.58 – 0.68 | S/N 9:1 @ 0.5 % Albedo |
| 2 | 0.862 | 0.727 – 1.00 | S/N 9:1 @ 0.5 % Albedo |
| 3a | 1.61 | 1.58 – 1.64 | S/N 20:1 @ 0.5 % Albedo |
| 3b | 3.74 | 3.55 – 3.93 | 0.12 K @ 300 K |
| 4 | 10.8 | 10.30 – 11.30 | 0.12 K @ 300 K |
| 5 | 12.00 | 11.50 – 12.50 | 0.12 K @ 300 K |