GNOS — Radio occultation sounder on board of Chinese FY3 satellites

GNOS is a dual-frequency GPS/Beidou receiver developed for GNSS radio occultation studies. It is developed and manufactured by National Space Science Center(NSSC) under a contract with the China Meteorological Administration(CMA) and is designed to provide vertical profiles of atmospheric temperature, pressure, humidity, as well as ionospheric electron density on a global scale. GNOS first flight mission is on-board the Chinese FY3C meteorological satellite, launched on Sep, 2013. It will also be on-board the follow-up FY3 satellites in the future. This paper focuses on the current GNOS design and characteristics for the FY3C mission. The instrument performance derived from analysis of measurement data in laboratory and mountain-based occultation validation experiments is presented. The comparison between Open Loop and Close Loop are shown. The refractivity profiles of GNOS obtained during the mountain-based experiment are also compared with those from radiosondes.