Instrument: Radiosonde Vaisala RS80-GPS

Vaisala RS80-GPS radiosondes carried aloft by helium balloons measure atmospheric temperature, humidity, wind speed and direction. The GPS receiver of the GPS-radiosonde measures a shift in Doppler frequencies using a codeless detection and measurement technique. The measured Doppler shifts are a combination of satellite and radiosonde motion and contain the pertinent information for wind speed and
direction computation. Doppler frequency measurements of up to 8 satellites are sent to the ground equipment using a low bandwidth (1200 baud) digital link. New independent GPS Doppler measurements from the GPS-sonde are provided every 0.5 seconds for up to 8 channels with 24-bit resolution. The ground equipment computes the wind
speed and direction using the differential GPS concept. For more information see www.hobeco.net/pdf/RS80_GPS.pdf.