Instruments - AVHRR

AVHRR description


Scanning mechanism

The AVHRR/3, a six channel scanning radiometer, provides three solar channels in the visible-near infrared region and three thermal infrared channels. The instrument utilises an 8-inch diameter-collecting telescope of the reflective Mersenne type. Cross-track scanning is accomplished by a continuously rotating mirror direct driven by a hysteresis synchronous motor. The three thermal infrared detectors are cooled to 105K by a two-stage passive radiant cooler.

The Sun angle is defined as the angle between the satellite-to-Sun line and the normal-to-orbital plane with the spacecraft in its operating orientation. The AVHRR/3 instrument, with the exception of the radiant cooler, operates within specification when exposed to any Sun angle from 0° to 80°. The radiant cooler operates within specification for solar angles between 0° to 68°. The spacecraft provides a Sun shield to protect the radiant cooler.

The AVHRR/3 uses an internal rotational scanning mirror that also views deep space and an internal calibration source. Those facilities (view to space and on-board black body targets) are used for the primary calibration of the IR channels (3B, 4 and 5), that occurs at each scan cycle.
 
  
 
 Central wavelength
(mm)		Half power points
(mm)		Channel noise specificationsTime availability
10.6300.580 / 0.680S/N 9:1 @ 0.5% albedo24 hours
20.8620.725 / 1.000S/N 9:1 @ 0.5% albedo24 hours
3a1.16101.580 / 1.640S/N 20:1 @ 0.5% albedoDay (Selectable)
3b3.7403.550 / 3.930NEDT
0.12K @ 300K		Night (Selectable)
410.80010.300 / 11.300NEDT
0.12K @ 300K		24 hours
512.00011.500 / 12.500NEDT
0.12K @ 300K		24 hours
 
AVHRR/3 Channel Characteristics
  
 
  
Last update: 28 June 2006


In depth

 •  About AVHRR (http://www.esa.int/esaLP/SEM9VEG23IE_LPmetop_0.html)
 •  Components (http://www.esa.int/esaLP/ESAOUSVTYWC_LPmetop_0.html)
 •  Performance (http://www.esa.int/esaLP/ESA39TVTYWC_LPmetop_0.html)
 •  Products (http://www.esa.int/esaLP/ESAICTVTYWC_LPmetop_0.html)

Related links

 •  NOAA AVHRR (http://noaasis.noaa.gov/NOAASIS/ml/avhrr.html)

MetOp's instruments

 •  A/DCS (http://www.esa.int/esaLP/SEM3JGG23IE_LPmetop_0.html)
 •  AMSU-A1 (http://www.esa.int/esaLP/SEMAHGG23IE_LPmetop_0.html)
 •  AMSU-A2 (http://www.esa.int/esaLP/SEMIFGG23IE_LPmetop_0.html)
 •  ASCAT (http://www.esa.int/esaLP/SEMBWEG23IE_LPmetop_0.html)
 •  AVHRR (http://www.esa.int/esaLP/SEM9VEG23IE_LPmetop_0.html)
 •  GOME-2 (http://www.esa.int/esaLP/SEMTTEG23IE_LPmetop_0.html)
 •  GRAS (http://www.esa.int/esaLP/SEMTSEG23IE_LPmetop_0.html)
 •  HIRS (http://www.esa.int/esaLP/SEMUREG23IE_LPmetop_0.html)
 •  IASI (http://www.esa.int/esaLP/SEMNQEG23IE_LPmetop_0.html)
 •  MHS (http://www.esa.int/esaLP/SEM7ADG23IE_LPmetop_0.html)
 •  SARP-3 (http://www.esa.int/esaLP/SEMV4DG23IE_LPmetop_0.html)
 •  SARR (http://www.esa.int/esaLP/SEMU2DG23IE_LPmetop_0.html)
 •  SEM (http://www.esa.int/esaLP/SEMD1DG23IE_LPmetop_0.html)