BackForwardInstrument:  SSM/I 

Instrument details
Acronym SSM/I
Full name Special Sensor Microwave - Imager
Purpose Multi-purpose imager
Short description 4 frequencies, 7-channels MW radiometer [see detailed characteristics below]
Background New development
Scanning Technique Conical: 53.1° zenith angle, swath 1400 km - Scan rate: 31.9 scan/min = 12.5 km/scan
Resolution Changing with frequency, consistent with an antenna diameter of  61 x 66 cm
Coverage / Cycle Global coverage once/day
Mass 48.5 kg Power 45 W Data Rate 3.3 kbps

 

Providing Agency DoD
Instrument Maturity Flown on operational programme
Utilization Period: 1987 to ≥2017
Last update: 2012-09-14
Detailed characteristics
Central frequency (GHz) Bandwidth (MHz) Polarisations NEΔT IFOV Pixel
19.35 400 V, H 0.43 K 45x68 km 25.0x12.5 km
22.235 400 V 0.73 K 40x60 km 25.0x12.5 km
37.0 1500 V, H 0.38 K 24x36 km 25.0x12.5 km
85.5 3000 V, H 0.71 K 11x16 km 12.5x12.5 km
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 microwave radiometer
  • Conical scanning microwave radiometer
Mission objectives
Primary mission objectives
  • Precipitation intensity at surface (liquid or solid)
Secondary mission objectives
  • Cloud liquid water (CLW) total column
  • Integrated Water Vapour (IWV)
  • Sea-ice cover
  • Snow cover
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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
Accumulated precipitation (over 24 h)5 - marginalPoor time sampling.. Time sampling to be interpolated by GEO.MW channels around 19, 23, 37 and 90 GHz
Cloud liquid water (CLW)4 - fairNo specific limitation.MW channels around 37 and 90 GHz
Cloud liquid water (CLW) total column3 - highNo specific limitation.MW channels around 37 and 90 GHz
Long-wave Earth surface emissivity5 - marginalLong time series needed.MW channels around 19, 37 and 90 GHz. Emissivity across this MW range inferred by statistical analysis
Precipitation intensity at surface (liquid or solid)4 - fairNo specific limitation.MW channels around 19, 23, 37 and 90 GHz; 90 GHz very important over land
Sea-ice cover3 - highNo specific limitation.MW channels around 19, 37 and 90 GHz
Sea-ice type5 - marginalNo specific limitation.MW channels around 19, 37 and 90 GHz. Type interpreted as age/roughness
Snow cover3 - highCoarse spatial resolution.MW channels around 19, 37 and 90 GHz. Higher frequencies less sensitive to emissivity from ground under snow
Snow status (wet/dry)3 - highCoarse spatial resolution.MW channels around 19, 37 and 90 GHz. Higher frequencies less sensitive to emissivity from ground under snow
Snow water equivalent4 - fairCoarse spatial resolution.. Ground stations network needed.MW channels around 19, 37 and 90 GHz. Higher frequencies less sensitive to emissivity from ground under snow
Integrated Water Vapour (IWV)2 - very highOver sea only.MW channel(s) in the water vapour band around 23 GHz
Wind speed over the surface (horizontal)4 - fairOver sea only.MW channels around 19 and 37 GHz