BackForwardInstrument:  VIRR (Seasat) 

Instrument details
Acronym VIRR (Seasat)
Full name Visible and Infra Red Radiometer
Purpose Cloud imagery
Short description Two-channel VIS (0.49-0.94 µm) and IR (10.5-12.5 µm) radiometer. IR NE?T: 4 K @ 185 K or 1 K @ 300 K
Background Adaptation of SR flown on NOAA 1 to 5
Scanning Technique Cross-track, 48 rpm (8.3 km/line), swath 2280 km
Resolution 2.3 km at s.s.p. (VIS) or 4.4 km at s.s.p. (IR)
Coverage / Cycle Near-global once/day (VIS) or twice/day (IR)
Mass 8.1 kg Power 7.3 W Data Rate


Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 1978 to 1978
Last update: 2013-12-03
Detailed characteristics
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
  • Moderate resolution optical imager
WIGOS Subcomponents
  • Subcomponent 1
  • VIS/IR imagery; realisation of a Day/Night band [in SSO]
  • VIS/IR imager [in SSO]
Mission objectives
Primary mission objectives
  • Cloud cover
  • Cloud top temperature
  • Cloud type
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
Note: * Primary mission objective.
VariableRelevance for measuring this variableOperational limitationsExplanation
Cloud cover*4 - fairNo specific limitation.VIS and TIR channels
Cloud top temperature*5 - marginalNo specific limitation.TIR window channel(s)
Cloud type*4 - fairDaylight only.VIS and TIR channels
Fire fractional cover4 - fairCloud sensitive.. Coarse spatial resolution.VIS and TIR channels
Fire radiative power5 - marginalCloud sensitive.. Coarse spatial resolution.TIR channels
Fire temperature5 - marginalCloud sensitive.. Coarse spatial resolution.TIR channels
Sea surface temperature5 - marginalCloud sensitive.TIR window channel(s) around 11 micrometers .
Snow cover5 - marginalCloud sensitive.. Daylight only.VIS channel(s)
Soil moisture at surface4 - fairCloud sensitive.. Index only.VIS and TIR window channels. Soil moisture inferred from thermal inertia
Wind (horizontal)5 - marginalLimited to high latitudes.. Cloud or water vapour tracers needed.TIR channel(s) around 11 micrometers window
Sea-ice cover5 - marginalCloud sensitive.VIS and TIR channels