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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
2 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 ≥2026
Last update:
2021-11-22
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 sounder (basic constellation) Subcomponent 2 Constellation of GNSS receivers [for reflectometry] 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
Secondary mission objectives Atmospheric density Electron Density Ionospheric Scintillation Ionospheric Vertical Total Electron Content (VTEC) Opportunity objectives Geoid Gravity field Wind speed (near surface) Show all Show fewer
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
Variable Relevance for measuring this variable Operational limitations Explanation
Atmospheric temperature 2 - very high Inaccurate in low troposphere. Two directional antennas, two GNSS system tracked, covering about 1000 soundings/day
Geoid 4 - fair Highly indirect. Radio-occultation processing implies precise orbitography. Geoid derived from multi-temporal analysis
Gravity field 5 - marginal Highly indirect. Radio-occultation processing implies precise orbitography. Gravity field derived from multi-temporal analysis
Height of the top of PBL 2 - very high No 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 high No 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 - high Inaccurate in high troposphere. Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Temperature of the tropopause 2 - very high No specific limitation. Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Wind speed (near surface) 4 - fair Over sea only. Wind speed estimated from the intensity of signals from different incidence angles
Atmospheric density 1 - primary No specific limitation. Measuring atmospheric density
Electron Density 1 - primary No specific limitation. Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Ionospheric Vertical Total Electron Content (VTEC) 3 - high No specific limitation. Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Ionospheric Scintillation 4 - fair No specific limitation. Two directional antennas, two GNSS system tracked, about 1000 soundings/day
Instrument: GNOS-2