AVHRR data from Eurimage

The National Oceanographic and Atmospheric Administration (NOAA) has been operating its Advanced Tiros-N (ATN) series of satellites since October 1978. Carrying the Tiros Operational Vertical Sounder (TOVS), a low-data-rate atmospheric sounding package, and the Advanced Very-High Resolution Radiometer (AVHRR), these satellites were designed primarily for meteorological applications, but the AVHRR instrument, in particular, has proved very valuable in a variety of environment linked earth observation applications, such as:

drought early warning
regional and global vegetation monitoring
snow and ice mapping
dynamic oceanography
hydrology
geology
detection of forest fires, gas flares and agricultural burning
fire fuel mapping
volcanology
air and sea pollution monitoring
toxic algal bloom detection
continental scale mapping (less than 1:3,000,000).

Eurimage distributes AVHRR data from NOAA, acquired from the TIROS satellites and received mainly at ESA ground stations. Coverage of Europe, Africa, the Middle East and parts of the Far East is provided, as shown in the sketch map below. With at least two satellites operational at any one time, each with a daily repeat cycle, twice daily and twice nightly coverage is possible for any point on the equator and approximately double this number (8 passes in total) at mid-latitudes.

TIROS / AVHRR Technical Summary

Orbit Launch Altitude Inclination
1979 840 km 98.7=B0- 98.9=B0

Sensors band (=B5m)
1 2 3 4 5
AVHRR/1 .55-.90 .72-1.0 3.55-3.93 10.5-11.5
GSD (m) 1000 1000 1000 1000
AVHRR/2 .58-.68 .72-1.0 3.55-3.93 10.3-11.3 11.5-12.5
GSD (m) 1000 1000 1000 1000 1000

Scene size (km) Revisit interval
3000 x 6000 2/day at equator, 4/day at mid-latitudes
GSD (m) 120

TIROS / AVHRR Orbit

The TIROS satellites have a circular, polar, sun-synchronous orbit, with an altitude of approximately 840 km and an inclination of 98.7=B0 to 98.9=B0. NOAA maintain at least two operational satellites in complementary orbits, with one crossing the equator at local solar times of approximately 0730 and 1930, and the other at 0230 and 1430. By convention, the even-numbered satellites cover the 'morning orbit' (0730) and the odd-numbered satellites the 'afternoon orbit' (1430).

The Advanced Very High Resolution Radiometer is a four (AVHRR/1) or five (AVHRR/2) channel passive scanning radiometer. It has one visible channel, one near-infrared, one middle-infrared, and one/two far-infrared channels. The nominal ground resolution is about 1 km. The extra channel of the AVHRR/2 (Channel 5) affords improved atmospheric correction of sea and land surface temperatures.