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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 1997-10-24
Last update:
2019-11-14
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
No WIGOS subcomponents have been defined.
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 Snow status (wet/dry) Snow water equivalent Wind speed (near surface) Opportunity objectives Accumulated precipitation (over 24 h) Cloud liquid water (CLW) Long-wave Earth surface emissivity Sea-ice type Show all Show fewer
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
Variable Relevance for measuring this variable Operational limitations Explanation
Accumulated precipitation (over 24 h) 4 - fair Poor time sampling.. Time sampling to be interpolated by GEO. MW channels around 19, 23, 37 and 90 GHz
Cloud liquid water (CLW) 3 - high No specific limitation. MW channels around 37 and 90 GHz
Cloud liquid water (CLW) total column 3 - high No specific limitation. MW channels around 37 and 90 GHz
Long-wave Earth surface emissivity 5 - marginal Long 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 - fair No specific limitation. MW channels around 19, 23, 37 and 90 GHz; 90 GHz very important over land
Sea-ice cover 3 - high No specific limitation. MW channels around 19, 37 and 90 GHz
Sea-ice type 4 - fair No specific limitation. MW channels around 19, 37 and 90 GHz. Type interpreted as age/roughness
Snow cover 3 - high Coarse 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 high Coarse spatial resolution. MW channels around 19, 37 and 90 GHz. Higher frequencies less sensitive to emissivity from ground under snow
Snow water equivalent 2 - very high Coarse 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 - high Over sea only. MW channel(s) in the water vapour band around 23 GHz
Wind speed (near surface) 4 - fair Over sea only. MW channels around 19 and 37 GHz
Instrument: SSM/I