BackForwardInstrument:  ALT (SeaSat) 

Instrument details
Acronym ALT (SeaSat)
Full name Radar Altimeter
Purpose Ocean topography, significant wave height, wind speed on sea surface
Short description Single frequencies (13.5 GHz)
Background New development
Scanning Technique Nadir-only viewing, continuous sampling along track
Resolution 12 km IFOV
Coverage / Cycle Global coverage in 1 month for 30 km average spacing, or in 10 days for 100 km average spacing
Mass Power Data Rate


Providing Agency NASA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 1978 to 1978
Last update: 2013-02-15
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
  • Active and radio-occultation sensor
  • Radar altimeter
WIGOS Subcomponents
  • Subcomponent 1
  • Wide-swath radar altimeters, and high altitude, inclined, high-precision orbit altimeters
  • High-altitude, inclined, high-precision orbit altimeters
  • Conventional radar altimeter
  • Subcomponent 2
  • Magnetospheric energetic particles and magnetometers
  • Ionospheric total electron content sensor [at LEO and cross magnetosphere]
Mission objectives
Primary mission objectives
  • Geoid
  • Ocean dynamic topography
  • Significant wave height
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
Coastal sea level (tide)3 - highAlong-track only.Single-frequency Ku-band radar altimeter
Geoid*2 - very highLong time series needed.. Along-track only.Geoid derived from multi-temporal analysis of radar altimetry data
Gravity field4 - fairPartial information (geoid).. Along-track only.Gravity field derived from multi-temporal analysis of radar altimetry data
Ocean dynamic topography*3 - highLong time for mapping.. Along-track only.Single-frequency Ku-band radar altimeter
Significant wave height*2 - very highAlong-track only.Ku-band radar altimeter
Wind speed (near surface)5 - marginalOver sea only.. Along-track only.Radar altimeter. Wind speed estimated from the intensity of the backscattered signals