BackForwardInstrument:  GNOS-2 

Instrument details
Acronym GNOS-2
Full name GNSS Radio Occultation Sounder - 2
Purpose Temperature/humidity sounding with highest vertical resolution; also space weather and sea surface wind speed
Short description Measuring the phase delay due to refraction during occultation between GPS and LEO. Also, reception of signals received after reflection by the sea surface, co-processed with those from the precision-orbit-determination antenna, to infer wind speed
Background Implementation in GNOS of the principle demonstrated by the CYGNSS mission
Scanning Technique Limb scanning from the satellite altitude to close-to-surface by time sampling - Azimuth: 90° sectors fore- and aft-. Also, separate earth-surface viewing antenna for reflectometry.
Resolution About 300 km horizontal, 0.5 km vertical
Coverage / Cycle GPS, Galileo and BeiDou GNSS constellations tracked. About 1000 soundings/day - Average spacing 710 km Global coverage (300 km spacing) in 2 weeks
Mass Power Data Rate

 

Providing Agency CMA
Instrument Maturity Flown on operational programme
Utilization Period: 2021 to 2035
Last update: 2022-08-01
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
  • GNSS radio-occultation
WIGOS Subcomponents
  • Subcomponent 1
  • GNSS radio occultation (basic constellation)
  • GNSS radio occultation sounder (basic constellation)
  • Subcomponent 2
  • GNSS reflectometry (GNSS-R) missions, passive MW, SAR
  • Constellation of GNSS receivers [for reflectometry]
  • Magnetospheric energetic particles and magnetometers
  • Ionospheric total electron content sensor [at LEO and cross magnetosphere]
  • Ionospheric electron density sensor [in LEO and cross magnetosphere]
Mission objectives
Primary mission objectives
  • Atmospheric temperature
  • Height of the top of PBL
  • Height of the tropopause
  • Specific humidity
  • Temperature of the tropopause
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
Atmospheric temperature*2 - very highInaccurate in low troposphere.Two directional antennas, two GNSS system tracked, covering about 1000 soundings/day
Geoid4 - fairHighly indirect.Radio-occultation processing implies precise orbitography. Geoid derived from multi-temporal analysis
Gravity field5 - marginalHighly indirect.Radio-occultation processing implies precise orbitography. Gravity field derived from multi-temporal analysis
Height of the top of PBL*2 - very highNo specific limitation.Two directional antennas, two GNSS system tracked, about 1000 soundings/day. PBL top measured as discontinuity of the refraction index
Height of the tropopause*2 - very highNo specific limitation.Two directional antennas, two GNSS system tracked, about 1000 soundings/day. Tropopause height measured as discontinuity of the refraction index
Specific humidity*3 - highInaccurate in high troposphere.Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Temperature of the tropopause*2 - very highNo specific limitation.Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Wind speed (near surface)4 - fairOver sea only.Wind speed estimated from the intensity of signals from different incidence angles
Atmospheric density1 - primaryNo specific limitation.Measuring atmospheric density
Electron Density1 - primaryNo specific limitation.Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Ionospheric Vertical Total Electron Content (VTEC)3 - highNo specific limitation.Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Ionospheric Scintillation4 - fairNo specific limitation.Two directional antennas, two GNSS system tracked, about 1000 soundings/day