FAAM CORE AVAPS drop sondes


The Vaisala RD94 dropsondes measure and transmit pressure, temperature, relative humidity and GPS information to the aircraft borne AVAPS (Airborne Vertical Atmospheric Profiling System) receiving system. At any one time, up to four dropsondes can be ejected from the aircraft and their data gathered. Each dropsonde transmits data from its launch to the moment it reaches the Earth's surface. Provision for the storage of up to 60 dropsondes is currently provided onboard the aircraft.

The typical fall speed for a standard dropsonde is 11 m/s when the dropsonde is near mean sea level. When launched from 35000 feet, a standard dropsonde takes approximately 13 minutes to reach the surface.


The Aspen software processes the raw data and produces the following data at 2Hz:

  • atmospheric pressure (hPa)
  • temperature (°C)
  • relative humidity (%)
  • wind speed (m/s)
  • wind direction (deg)
  • dropsonde GPS position (lat, long, alt)


Further Details

Contact Steve Devereau at FAAM.