Ascent trajectory of sounding balloons: dynamical models and mission data reconstruction

Abstract

Abstract. Small sounding balloons are a fast and cost-effective transport system to lift up scientific payloads up to stratospheric burst altitudes below 40 kilometres; during ascent and descent phase dedicated instruments may be operated to monitor atmospheric parameters and optical payloads may be used for remote observation. This work will focus on the reconstruction of the trajectory of the ascent phase, which is the longest and dynamically less perturbed part of the flight; in this section the dynamics of the flight system is determined by the lift of the balloon guiding the vertical motion and the local winds controlling the horizontal motion. The presented reconstruction algorithm is based on a linear quadratic estimation predictor corrector using the standard equations of motions in ECEF system to propagate the simulation and the measurement of the on-board sensors (triaxial accelerometer, GPS, pressure and temperature sensors) to correct the estimation and reduce the uncertainty in the reconstruction, which is mainly related to the value of balloon canopy drag coefficient Cd, the lifting gas volume and local wind perturbations. Two different balloon flights, both launched within a joint effort between teams by University of Padova and University of Pisa, are considered: one conducted during daytime, the other in night time. The different environmental conditions and in particular the different temperature evolution within the lifting balloon in the day flight due to Sun heating provide a good proving ground to investigate sensitivity of algorithm to environmental conditions. The prediction of flight dynamic models implementing horizontal and vertical equations of motion are compared with real mission data acquired by on board systems, highlighting the influence of local perturbations on the foreseen ascent trajectory.