Development of Dropsonde system for antarctic atmospheric profiling

A Dropsonde system was developed to measure temperature and relative humidity profiles of atmospheric boundary layer. This system consists of Dropsondes, a Receiver and a Dropping Mechanism. The Dropping Mechanism carries four Dropsondes those could be dropped individually from an Aerosonde unmanned aerial vehicle. The Dropsonde measures temperature, relative humidity, pressure, and GPS location as it falls. The measurements are transmitted in real time up to a mile and stored by the Receiver onto a secure digital card. The system was designed for deployment in Terra Nova Bay, Antarctica. All systems were optimized to operate in temperature range of -30 to 15°C. The deployment mission consisted of a long flight form McMurdo, Antarctica to Terra Nova Bay, Antarctica.;Dropsondes consist of two pressure sensors, one humidity sensor, GPS module, a microcontroller and a transceiver. Pressure and humidity sensors measure temperature as well. Performances of different instruments were determined by controlled testing. Temperature and relative humidity sensors were calibrated to improve their accuracies. Calibrations for sensors were done for nominal drop rate of 5m/s. After calibration, Dropsondes were capable of measuring temperature with accuracy of 0.7°C and relative humidity with accuracy of 6 %. GPS module was found accurate to 1.5 m and in lateral direction and 3.4 meters in vertical direction. GPS vertical position was not accurate enough for precise altitude profiling so pressure measurements were used instead. With accurate reference, pressure measurements could provide altitude accurate to 1 m. Absolute accuracies of pressure sensors are not known so a reference pressure is required to get absolute altitude from pressure. A method for pressure calibration is outlined but could not be carried out due to lack of time and resources.;Despite extreme weather conditions, Dropsonde system performed relatively well. Fifty percent of Dropsondes deployed worked; other half failed mainly due to power supply malfunction. The power failure occurred due to operational errors related to harsh weather conditions. Other than power failure, lack of GPS lock was a major problem in Antarctica. Testing GPS modules for different possible variables suggested that poor performance of antenna at very cold temperatures is likely the cause.