Rotosonde: Acquiring Vertical Wind Profile of a Tropical Cyclone with Small Unmanned Helicopters

Spinsonde is a chute-free vertical retardation technique specifically developed for fixed-wing unmanned aircraft to acquire accurate measurement of vertical wind speed profile for meteorological applications. Key advantages of spinsonde over the expendable chute-operated dropsondes are the ability to acquire multi-cycle measurement, efficient use of payload capacity and cost-effectiveness. This work proposes the concept of “rotosonde”, which is the spinsonde equivalent for unmanned helicopters. Computer simulations are carried out to evaluate the performance of the rotosonde and results indicate that the measured speed generally correlates with the wind speed to within ±3 km·h﹣1 even for intensities in excess of 180 km·h﹣1. The profound implication of this work is that unmanned helicopters can now be considered for important field of studies such as cyclogenesis given their reliability to operate in gusty wind conditions in remote oceans, particularly during docking and launching from carriers.