BackForwardInstrument:  Tri-G (GRACE-FO) 

Instrument details
Acronym Tri-G (GRACE-FO)
Full name Triple G (GPS, Galileo, GLONASS)
Purpose Temperature/humidity sounding with highest vertical resolution, space weather
Short description Measuring the phase delay due to refraction during occultation between GPS and LEO
Background New development
Scanning Technique Limb scanning from 40 km altitude to close-to-surface by time sampling - Azimuth: 90° sector only aft-
Resolution About 300 km horizontal, 0.5 km vertical
Coverage / Cycle 1 GNSS constellation tracked. About 300 soundings/day (one satellite) - Average spacing 1300 km - Global coverage (300 km spacing) in 20 days
Mass 6 kg Power 50 W Data Rate 40 kbps

 

Providing Agency NASA
Instrument Maturity Backed by strong heritage
Utilization Period: 2019 to 2026
Last update: 2024-01-15
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)
Mission objectives
Primary mission objectives
  • Atmospheric density
  • 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*3 - highInaccurate in low troposphere.One directional antenna, one GNSS system tracked, covering about 250 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*3 - highNo specific limitation.One directional antenna, one GNSS system tracked, about 250 soundings/day. PBL top measured as discontinuity of the refraction index
Height of the tropopause*3 - highNo specific limitation.One directional antenna, one GNSS system tracked, about 250 soundings/day. Tropopause height measured as discontinuity of the refraction index
Specific humidity*3 - highInaccurate in high troposphere.One directional antenna, one GNSS system tracked, about 250 soundings/day
Temperature of the tropopause*3 - highNo specific limitation.One directional antenna, one GNSS system tracked, about 250 soundings/day
Atmospheric density*1 - primaryNo specific limitation.Measuring atmospheric density