TABLE 2.1 Characteristics of Satellite Microwave Instruments for Ocean Studies

Instrument and Its Main Features

Measured Electromagnetic Parameters

Inferred Ocean Parameters

Footprint

Swath Width

Additional Information

Altimeter: sends short pulses at nadir incidence (13-GHz carrier frequency; TOPEX altimeter will also have a 5-GHz channel)

Travel time of a return pulse, radar cross section, shape of a return pulse

Sea level height

Wind speed

Significant wave height

Circular, 5- to 12-km diameter, depending on surface roughness

One-pixel diam. ˜10 km

Along-track pixel spacing: ~7 km. Distance between tracks at equator: ~150 km. 10 to 20 days exact repetition of all orbits

Scatterometer: sends short pulses in a range of incidence angles from 20 to 60 degrees, using both strictly horizontal (HH) and strictly vertical (W) polarizations; 14-GHz carrier frequency

A set of radar cross sections for each surface bin, at several azimuthal angles and polariza-tions

Wind speed

Wind direction

Aspect ratio ~1:4. Major axis: 30 to 90 km depending on position within the swath, etc.

Two swaths 600 to 700 km each

Global coverage every 2 days

Synthetic aperture radar: high-spatial-resolution radar images of sea surface roughness distribution for C, L, and X bands. Other bands have also been employed

Analog and/or digital matrices of radar cross section showing spatial varia-tion of surface roughness

Length and direction, or surface gravity and internal waves, wave number spectra of surface roughness spatial variation, surface signatures of mesoscale eddies, fronts, current boundaries, sea ice, bathymetry

10- to 100-m linear size, depending on the mode frequency electromagnetic band, etc.

Hundreds of kilometers

Usually only regional coverage for selected locations

Special Sensor Microwave/Imager (SSM/I) with channels (GHz):

19.4

22.2

37.0

85.5

Radio brightness temperature

Characteristics of atmosphere (e.g., water content); surface wind speed, sea ice

Length

Width

1300 km

Almost total global coverage obtained every day

(km)

70

45

60

40

38

30

16

14

Scanning Multichannel Microwave Radiometer (SMMR) with channels (GHz):

37.0

21.0

18.0

10.7

6.6

Radio brightness temperature

Characteristics of atmosphere (e.g., water content); surface wind speed, sea surface temperature, sea ice

Length

Width

780 km

Almost total global coverage every 2 days

(km)

22

14

28

25

43

28

74

49

120

79

 

SOURCE: Courtesy of Roman Glazman, Jet Propulsion Laboratory, California Institute of Technology.



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