BackForwardInstrument:  IRIS (CRISTAL) 

Instrument details
Full name Interferometric Radar altimeter for Ice and Snow
Purpose To measure and monitor the variability of ice elevation and thickness in polar regions.
Short description Dual-frequency radar altimeter: Ku-band around 13.5 GHz (bandwidth 500 MHz) and Ka-band around 35.75GHz (bandwidth 500 MHz). Along-track SAR capability for high spatial resolution. Two cross-track aligned antennas implementing interferometry to enlarge the swath and capture elevation changes.
Background Follow-on of the CryoSat SIRAL mission, with improved characteristics (main: dual-band).
Scanning Technique No scanning. Several operating modes possible, depending on the target area.
Resolution 10 km IFOV. When used in SAR mode, the along-track resolution is 80 m.
Coverage / Cycle Global coverage on high latitudes in 1 month
Mass Power Data Rate


Providing Agency ESA
Instrument Maturity Flown on an R&D satellite
Utilization Period: ≥2027-02 to ≥2034
Last update: 2022-03-28
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 altimeter
  • Subcomponent 2
  • Interferometric radar altimeter [for wide-swath]
Mission objectives
Primary mission objectives
  • Ice sheet topography
  • Sea-ice elevation
  • Sea-ice thickness
Secondary mission objectives
  • Coastal sea level (tide)
  • Ocean dynamic topography
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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
VariableRelevance for measuring this variableOperational limitationsExplanation
Coastal sea level (tide)1 - primaryInfrequent coverage.Single-frequency Ka-band radar altimeter with large swath for mapping
Geoid2 - very highInfrequent coverage.. Long time series needed.Geoid derived from multi-temporal analysis of radar altimetry data
Gravity field4 - fairPartial information (geoid).Gravity field derived from multi-temporal analysis of radar altimetry data
Ice sheet topography3 - highAlong-track only.. Infrequent coverage.Ka-band radar altimeter
Ocean dynamic topography1 - primaryInfrequent coverage.. Long time for mapping.Single-frequency Ka-band radar altimeter with large swath for mapping
Sea-ice elevation3 - highInfrequent coverage.The large swath helps measuring the elevation of the ice border over the sea level
Sea-ice thickness3 - highInfrequent coverage.. Change detection only.The large swath helps measuring the elevation of the ice border over the sea level. Thickness inferred
Significant wave height1 - primaryInfrequent coverage.The large swath enables more frequent global coverage
Wind speed (near surface)4 - fairOver sea only.. Infrequent coverage.Improved coverage associated to better resolution, that implies better accuracy