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AVHRR - Advanced Very High Resolution Radiometer

 



First used on TIROS-N in October 1978.

SPECTRAL
REGION:
Bands 1-5: 580-12500 nm (range)
TEMPORAL
COVERAGE
RANGES:
Ascending Node: 1340-1930
  Descending Node: 0140-0730
INSTANTANEOUS
FIELD OF VIEW:
1.4 mrad
GROUND
RESOLUTION
CELL:
1.1 km

The AVHRR Concept

Background

Advanced Very High Resolution Radiometer (AVHRR) is carried on NOAA's Polar Orbiting Environmental Satellites (POES), beginning with TIROS-N in 1978. This series of satellites commenced with TIROS-N (launched in October 1978) and continued with NOAA-A (launched in June 1979 and renamed NOAA-6), NOAA-C (launched in June 1981 and renamed NOAA-7), NOAA-E (launched in March1983 and renamed NOAA-8), NOAA-F (launched in December 1984 and renamed NOAA-9), NOAA-G (launched in September 1986 and renamed NOAA-10), NOAA-H (launched in September 1988 and renamed NOAA-11), NOAA-D (launched in May 1991 and renamed NOAA-12), NOAA-I (launched in August 1993 and renamed NOAA-13) and NOAA-J (launched in December 1994 and renamed NOAA-14). This series of satellites (TIROS-N and NOAA-6 through NOAA-14) will henceforth be referred to in this document as the TIROS-N series (technically, TIROS-N through NOAA-D are called the TIROS-N series and NOAA-E through -N are called the TIROS ATN series or Advanced TIROS-N). The complete TIROS series will eventually include NOAA-A through -N.

 

Sensor

The AVHRR sensor 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.

Sensor Applications

AVHRR is primarily used for vegetation studies-the study and monitoring of drought conditions.:

The 1988 drought on the United States Corn Belt was monitored using AVHRR data by the Foreign Crop Condition Assessment Division. Vegetation index numbers were created from the data and monitored for changes over the period of the drought. The use of the data and technique was successful in detecting the early drought conditions and assessing potential damages and crop yields. In Niger, the grasslands are the most important factor in their economic potential. New Mexico State University's International Studies have been using AVHRR and associated data to monitor the size of the grasslands after each rainy season. By doing this they are able to help the government of Niger plan for the economic year and create resource friendly policy. There is current work to help improve the use of AVHRR data on vegetation studies. One such effort was conducted on the vegetation of Mexico. Here vegetation indexes were created and compared to the known vegetation types collected from ground truth data, in hopes of refining the system.

AVHRR is used for other mapping and ecological projects as well.:

Data obtained from the AVHRR sensor can be used to create land use maps and land cover maps. This is very helpful when trying to create maps of large continents and areas that are remote or inaccessible. AVHRR data is being used in a study to determine the amount of inundation in the Florida everglades. The inundation affects the amount of greenhouse gases being produced in the everglades area. This study will help determine the amounts of gasses that can potentially be produced in the area. The sensor is used to track the continental snow cover amounts over seasons and years. It also helps provide data on ice sheets and related phenomena such as iceberg movements.

AVHRR is currently being used to map out global near surface temperatures. This data is useful in monitoring agriculture and forestry resources and is important in calculating global energy budgets. AVHRR is also used in the monitoring of the sea surface temperatures. These temperatures have bearings on the global climate and marine resources.

Orbital Characteristics

Orbits Circular,sun-synchronous
Altitude approx 833 km
Orbital period 102 minutes
Orbits per day 14
Swath 2399 km

Band Characteristics

Band Wavelength (microns)
NOAA 6,8,10,12
Wavelength (microns)
NOAA 7,9,11
IFOV (millirads) Principal Applications
1 0.58-0.68 0.58-0.68 1.39 Daytime cloud/surface mapping.
2 0.725-1.10 0.725-1.10 1.41 Surface water delineation, ice and snow melt.
3 3.55-3.93 3.55-3.93 1.51 Sea surface temperature, night-time cloud mapping.
4 10.5-11.5 10.3-11.3 1.41 Sea surface temperature, day and night cloud mapping.
5 Band 4 repeated 11.5-12.5 1.30 Sea surface temperature, day and night cloud mapping.

Data Acquisition

Data is sent to acquisition stations by three formats:

High Resolution Picture Transmission (HRPT) - this is full resolution image data that is transmitted to the ground station as it is collected.

Local Area Coverage (LAC) data - This form is also full resolution data, but this is recorded on-board for later transmission while over a station.

Global Area Coverage (GAC) - This data is the averaged data for the globe that is preprocessed by the on-board computer and stored for later transmission to ground stations.