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 2020
Last update: 2022-07-25
Detailed characteristics

No.

Central frequency (GHz)

Bandwidth (MHz)

Polarisation

NEΔT

IFOV

Pixel

1

19.35

400

V

0.45 K

45x68 km

25.0x12.5 km

2

19.35

400

H

0.42 K

45x68 km

25.0x12.5 km

3

22.235

400

V

0.73 K

40x60 km

25.0x12.5 km

4

37.0

1500

V

0.37 K

24x36 km

25.0x12.5 km

5

37.0

1500

H

0.38 K

24x36 km

25.0x12.5 km

6

85.0

3000

V

0.69 K

11x16 km

12.5x12.5 km

7

85.0

3000

H

0.73 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
WIGOS Subcomponents
  • Subcomponent 1
  • MW imagery [in SSO]
  • MW imager [in SSO]
Mission objectives
Primary mission objectives
  • Precipitation intensity at surface (liquid or solid)
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
Accumulated precipitation (over 24 h)4 - fairPoor time sampling.. Time sampling to be interpolated by GEO.MW channels around 19, 23, 37 and 90 GHz
Cloud liquid water (CLW)3 - highNo 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
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)2 - very highCoarse spatial resolution.MW channels around 19, 37 and 90 GHz. Higher frequencies less sensitive to emissivity from ground under snow
Snow water equivalent2 - very highCoarse 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)3 - highOver sea only.MW channel(s) in the water vapour band around 23 GHz
Wind speed (near surface)4 - fairOver sea only.MW channels around 19 and 37 GHz
Sea-ice cover3 - highNo specific limitation.MW channels around 19, 37 and 90 GHz
Sea-ice type4 - fairNo specific limitation.MW channels around 19, 37 and 90 GHz. Type interpreted as age/roughness