BackForwardInstrument:  GNSS-R (PRETTY) 

Instrument details
Full name GNSS Reflectometer
Purpose To measure the ice and sea ice surface elevation and roughness in the polar regions.
Short description Receiver uses interferometric phase delay GNSS-Reflectometry which receives the direct and reflected signal in parallel. The L5 frequency (1176.45MHz), was used to demonstrate grazing altimetry measurements for the first time in space.
Background A new development.
Scanning Technique Scanning provided by the changing relative position of the LEO and the GNSS satellites.
Resolution 10 x 20 cm on the surface.
Coverage / Cycle Over the polar regions each point on the Earth can be measured once a day.
Mass 6 kg Power 24 W Data Rate


Providing Agency ESA
Instrument Maturity Flown on an R&D satellite
Utilization Period: 2023 to 2024
Last update: 2023-06-12
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
  • Other payload component
  • Positioning system
WIGOS Subcomponents
  • Subcomponent 2
  • GNSS reflectometry (GNSS-R) missions, passive MW, SAR
  • Constellation of GNSS receivers [for reflectometry]
Mission objectives
Primary mission objectives
  • Ice sheet topography
  • Sea-ice cover
  • Sea-ice elevation
  • Sea-ice thickness
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
Geoid4 - fairHighly indirect.Opportunity information from GNSS receiver used for precise orbit determination
Gravity field5 - marginalHighly indirect.Opportunity information from GNSS receiver used for precise orbit determination
Wind speed (near surface)5 - marginalOver sea only.. Infrequent coverage.Wind speed estimated from the intensity of signals from different incidence angles, reflected normally