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 GNSS reflection by the sea surface, co-processed with those from the precision-orbit-determination antenna, to infer wind speed
  • Calibration monitoring here
Background

New development
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 0.5 km vertical
Coverage / Cycle GPS, Galileo, GloNASS and BeiDou GNSS constellations tracked. No. of atmospheric and ionospheric occultations >1000/day.
Mass Power Data Rate

 

Providing Agency CMA
Instrument Maturity Flown on operational programme
Utilization Period: 2021 to 2035
Last update: 2024-09-09
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
  • Ionospheric Total Electron Content (TEC)
  • 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)5 - marginalInfrequent coverage.. Over 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 Total Electron Content (TEC)*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