BackForwardInstrument:  RA 

Instrument details
Acronym RA
Full name Radar Altimeter
Purpose Ocean topography, significant wave height, wind speed on sea surface
Short description Single frequency (13.8 GHz)
Background Flown on ERS-1 (1991-2000) and ERS-2 (1995-2011)
Scanning Technique Nadir-only viewing, continuous sampling along track
Resolution 20 km IFOV
Coverage / Cycle Global coverage in 1 month for 30 km average spacing, or in 10 days for 100 km average spacing
Mass 96 kg Power 130 W Data Rate 15 kbps


Providing Agency ESA
Instrument Maturity Flown on operational programme
Utilization Period: 1991 to 2011
Last update: 2012-06-06
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