Advanced Very High Resolution Radiometer (AVHRR)

Overview

More thorough reference document on AVHRR

Back to Global Climatologies from AVHRR Home Page

Contents

Background
Extent of Coverage
Spatial Resolution
Temporal Coverage
Spectral Range
Data formats
Applications and Related Data Sets
References on the Web

Background

The Advanced Very High Resolution Radiometer (AVHRR) is a broad-band, four or five channel (depending on the model) scanner, sensing in the visible, near-infrared, and thermal infrared portions of the electromagnetic spectrum. This sensor is carried on the National Oceanic and Atmospheric Administration's (NOAA's) Polar Orbiting Environmental Satellites (POES), beginning with TIROS-N in 1978. Important functions of AVHRR include:

• Deriving Sea Surface Temperatures (operational NOAA product)
• Deriving the Normalized Difference Vegetation Index (operational NOAA product),
• Deriving atmospheric aerosols over the oceans (operational NOAA product),
• Monitoring volcanic eruptions and supporting an operational NOAA warning of volcanic ash in the atmosphere during eruption events,
• Monitoring cloud patterns (AVHRR supplements the Geostationary Operational Environmental Satellites (GOES) in this activity, and is often preferred over GOES at high latitudes).
• And other applications requiring the high temporal resolution of global daily coverage, with moderate spectral and spatial resolution, operational sidelap stereoscopic coverage, and calibrated thermal sensors.

The AVHRR sensor provides global (pole to pole) on board collection of data from all spectral channels. Each pass of the satellite provides a 2399 km wide swath. The satellite orbits the Earth 14 times each day from 833 km above its surface.

Spatial Resolution

The average instantaneous field-of-view (IFOV) of 1.4 milliradians yields a LAC/HRPT ground resolution of approximately 1.1 km at the satellite nadir from the nominal orbit altitude of 833 km. The GAC data are derived from an on board sample averaging of the full resolution AVHRR data yielding 1.1-km by 4.4-km resolution at nadir.

Temporal Coverage

Satellite  Launch  Ascending  Descending       Service
 Number     Date     Node        Node           Dates
--------   ------    ----        ----     ------------------
TIROS-N    10/13/78  1500        0300     10/19/78 - 01/30/80
NOAA-6     06/27/79  1930        0730     06/27/79 - 11/16/86
NOAA-7     06/23/81  1430        0230     08/24/81 - 06/07/86
NOAA-8     03/28/83  1930        0730     05/03/83 - 10/31/85
NOAA-9     12/12/84  1420        0220     02/25/85 - Present
NOAA-10    09/17/86  1930        0730     11/17/86 - Present
NOAA-11    09/24/88  1340        0140     11/08/88 - 09/13/94
NOAA-12    05/14/91  1930        0730     05/14/91 - Present
NOAA-14    12/30/94  1340        0140     12/30/94 - Present

An ascending node would imply a northbound Equatorial crossing while a descending node would imply a southbound Equatorial crossing.

NOAA-B launched May 29, 1980, failed to achieve orbit. NOAA-13 launched August 9, 1993, failed due to an electrical short circuit in the solar array.

Spectral Range

Band   Satellites:          Satellites:          IFOV
 #     NOAA-6,8,10        NOAA-7,9,11,12,14

 1     0.58  - 0.68        0.58  -  0.68         1.39
 2     0.725 - 1.10        0.725 -  1.00         1.41
 3     3.55  - 3.93        3.55  -  3.93         1.51
 4    10.50  - 11.50      10.3   - 11.3          1.41
 5    band 4 repeated     11.5   - 12.5          1.30
      (micrometers)       (micrometers)    (milliradians)

AVHRR data are acquired in three formats:

• High Resolution Picture Transmission (HRPT) data are full resolution image data transmitted to a ground station as they are collected. The average instantaneous field-of-view of 1.4 milliradians yields a HRPT ground resolution of approximately 1.1 km at the satellite nadir from the nominal orbit altitude of 833 km.
• Local Area Coverage (LAC) are full resolution data that are recorded on an onboard tape for subsequent transmission during a station overpass. The average instantaneous field-of-view of 1.4 milliradians yields a LAC ground resolution of approximately 1.1 km at the satellite nadir from the nominal orbit altitude of 833 km.
• Global Area Coverage (GAC) data are derived from a sample averaging of the full resolution AVHRR data. Four out of every five samples along the scan line are used to compute one average value and the data from only every third scan line are processed, yielding 1.1 km by 4 km resolution at the subpoint.

Applications and Related Data Sets

AVHRR is used to produce various operational data sets, listed above and in the accompanying more detailed review of AVHRR. AVHRR data also provide opportunities for studying and monitoring vegetation conditions in ecosystems including forests, tundra, and grasslands. Applications include agricultural assessment, land cover mapping, producing image maps of large areas such as countries or continents and tracking regional and continental snow cover. (Again, refer to the accompanying more detailed review of AVHRR for more details and references on some of these applications.

References on the Web.

Kidwell, Katherine B., comp. and ed., 1995, NOAA Polar Orbiter Data (TIROS-N, NOAA-6, NOAA-7, NOAA-8, NOAA-9, NOAA-10, NOAA-11, NOAA-12, and NOAA-14) Users Guide: Washington, D.C., NOAA/NESDIS.

Hastings, David A., and William J. Emery, 1992. The Advanced Very High Resolution Radiometer (AVHRR): A Brief Reference Guide. Photogrammetric Engineering and Remote Sensing, vol. 58, No. 8, August 1992, pp. 1183-1188.

World Wide Web starting page for: NOAA Polar Orbiting Environmental Satellites (which include AVHRR data).