GPS Radiosonde

NARL launches GPS radiosonde (RD-11G, Meisei make) every day around 1730 LT (12 UTC). It provided profiles of Pressure, Temperature, Relative humidity, Wind Speed and Wind Direction up to the balloon burst altitude typically 30-35 km. These are being launched regularly since April 2006. The RD-11G ground station is designed for the Upper Air Observing System using the D- GPS (Differential Global Positioning System). The GPS receiving device in a Radiosonde tremendously improves observation accuracy, thus allowing the GPS ground station simplified and compact. The RD-11G Upper Air Observing System consists of a radiosonde receiving antenna system, GPS receiving antenna, GPS Sonde Receiver, and the data processor, PC computer which is connected to a networking subsystem via a TCP/IP. The system is also provided with the Base Line Checker (BLC) used for ground check before launching a radiosonde. The GPS receiving device in a radiosonde obtains information on the direction and the velocity of the GPS satellite with the frequency deviation of radio signals from the satellite due to the Doppler shift and transmits the positioning information of the radiosonde to the RD-11G ground station. Upon receiving radio signals from the randiosonde, the RD-11G ground stations processes the data obtained by the radiosonde and GPS satellites to observe wind direction and wind speed in the upper air.