BackForwardInstrument:  WiFS (IRS-P3) 

Instrument details
Acronym WiFS (IRS-P3)
Full name Wide-Field Sensor
Purpose Land and vegetation observation
Short description Two parallel radiometers, 3 VNIR/SWIR channels [see detailed characteristics below]
Background Consolidated technology
Scanning Technique Pushbroom, 4000 pixel/line, swath 770 km (with two instruments)
Resolution 190 m at s.s.p.
Coverage / Cycle Global coverage in 5 days, in daylight
Mass 23 kg Power 22 W Data Rate 2.1 Mbps

 

Providing Agency ISRO
Instrument Maturity Flown on operational programme
Utilization Period: 1996 to 2004-10-15
Last update: 2020-01-07
Detailed characteristics

Central wavelength

Spectral interval

SNR @ specified input spectral radiance

0.650 µm

0.62-0.68 µm

200 @ 263 W m-2 sr-1 µm-1

0.815 µm

0.77-0.86 µm

200 @ 285 W m-2 sr-1 µm-1

1.650 µm

1.55-1.75 μm

200 @ ….. W m-2 sr-1 µm-1

Satellites this instrument is flying on

Note: a red tag indicates satellites no longer operational, a green tag indicates operational satellites, a blue tag indicates future satellites

Instrument classification
  • Earth observation instrument
  • Passive optical radiometer or spectrometer
  • High resolution optical imager
Mission objectives
Primary mission objectives
  • Biomass
  • Fraction of vegetated land
  • Land cover
  • Leaf Area Index (LAI)
  • Normalised Difference Vegetation Index (NDVI)
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Tentative Evaluation of Measurements

The following list indicates which measurements can typically be retrieved from this category of instrument. To see a full Gap Analysis by Variable, click on the respective variable.

Note: table can be sorted by clicking on the column headers
VariableRelevance for measuring this variableOperational limitationsExplanation
Biomass4 - fairCloud sensitive.. Index only.. Infrequent coverage.. Daylight only.VIS, NIR and SWIR channels. Biomass inferred from NDVI and LAI
Cloud cover5 - marginalInfrequent coverage.. Daylight only.VIS, NIR and SWIR channels
Cloud optical depth3 - highLow-density cloud only.. Infrequent coverage.. Daylight only.VIS, NIR and SWIR channels
Fire fractional cover2 - very highCloud sensitive.. Daylight only.VIS channels with high resolution for boundary detection
Fraction of vegetated land1 - primaryCloud sensitive.. Daylight only.VIS, NIR and SWIR channels
Glacier cover3 - highCloud sensitive.. Long time for mapping.. Daylight only.VIS, NIR and SWIR channels, screening ice from clouds
Glacier topography5 - marginalCloud sensitive.. Long time for mapping.. Daylight only.VIS channel(s) and cross-track steering capability for stereoscopy between images from neighbour orbits
Ice sheet topography5 - marginalCloud sensitive.. Long time for mapping.. Daylight only.VIS channel(s) and cross-track steering capability for stereoscopy between images from neighbour orbits
Land cover1 - primaryCloud sensitive.. Daylight only.VIS, NIR and SWIR channels
Land surface topography5 - marginalCloud sensitive.. Long time for mapping.. Daylight only.VIS channel(s) and cross-track steering capability for stereoscopy between images from neighbouring orbits
Leaf Area Index (LAI)2 - very highCloud sensitive.. Daylight only.. Infrequent coverage.VIS, NIR and SWIR channels
Normalised Difference Vegetation Index (NDVI)2 - very highCloud sensitive.. Infrequent coverage.VIS and NIR channels
Sea-ice cover4 - fairCloud sensitive.. Daylight only.VIS, NIR (for contour enhancement) and SWIR (for discrimination from clouds) channels
Short-wave cloud reflectance4 - fairInfrequent coverage.VIS, NIR and SWIR channels. Unsuitable dynamic range (saturation)
Snow cover1 - primaryCloud sensitive.. Infrequent coverage.. Daylight only.VIS, NIR and SWIR channels, enabling screening snow from clouds
Soil moisture at surface5 - marginalCloud sensitive.. Index only.. Infrequent coverage.. Daylight only.VIS, NIR and SWIR channels. Soil moisture inferred from differential brightness
Soil type1 - primaryCloud sensitive.. Daylight only.VIS, NIR and SWIR channels
Upward short-wave irradiance at TOA5 - marginalSpectral interpolation needed.. Information on BRDF needed.. Infrequent coverage.VIS, NIR and SWIR channels
Vegetation type2 - very highCloud sensitive.. Daylight only.VIS, NIR and SWIR channels
Aerosol volcanic ash5 - marginalCloud sensitive.. Infrequent coverage.. Daylight only.VIS, NIR and SWIR channels
Aerosol volcanic ash Total Column5 - marginalCloud sensitive.. Infrequent coverage.. Daylight only.VIS, NIR and SWIR channels