High-Altitude Gas Balloon Trajectory Prediction: A Monte Carlo Model

Abstract

The high-altitude gas balloon is an indispensable tool in atmospheric science, meteorology, and other applications requiring stratospheric observations. A prerequisite of the effectiveness of many types of balloon operations is an accurate trajectory forecasting capability. In particular, targeted flights, sample return missions, or flights of expensive instruments (whose recovery is essential) rely on such models. In this paper, the authors describe a new balloon flight simulation model, which takes into account a range of environmental, physical, and operational uncertainties to generate a predicted trajectory equipped with landing site location error estimates. A key source of error in such models is the incomplete understanding of the drag opposing the rise of balloons in the free atmosphere; here the authors propose a new stochastic drag model based on empirical data derived from thousands of radiosonde flights. Other sources of prediction error are also examined, affecting the accuracy of the flight-path forecast, such as uncertainties in the wind profile and balloon envelope manufacturing variability. The authors show how integrating these elements into a process that generates Monte Carlo ensembles of simulated trajectories has yielded a practically useful flight planning tool, which we have made available to the ballooning community as a free online service.