GNSS Radio Occultation Sounder-I (GNOS-I)


GNOS-I (Global Navigation Satellite System Occultation Sounder-I) is one of the remote sensing instruments on FengYun-3 (FY3) 02 series satellites. The goals for FY3 GNOS mission include

  • (1) providing all-weather data for operational numeric weather prediction, atmospheric physics study and climate research,

  • (2) monitoring ionoshperic electron density profile for space weather research and operation.

The principle of GNOS-I sounding is to receive the GNSS signal occulted by the Earth atmosphere and ionosphere, using the GNSS receiver on board a FY3 LEO satellite. Measurements can be converted into excess delay by the atmosphere and ionosphere, and then the atmospheric refractivity, temperature, pressure, water vapor profiles and the electron density profiles will be retrieved.

Measuring the phase delay due to refraction during occultation between GNSS satellites and FY-3. GNOS-I receives signal from GPS and BeiDou-2, obtains measurement from about 1000 occultation events per day with GPS and Beidou satellites (either rise or set).


Satellite FY-3C FY-3D 

Data and Products

Satellite Instrument Datasets
FY-3D GNOS-I L1 dataL2L3 product
FY-3C GNOS-I L1 dataL2L3 product

Calibration and Validation

GNOS-I calibration and validation