Mixed uncertainty quantification for terminal flight state of Mars atmospheric entry

Abstract

China's Tianwen-1 successfully touched down on the surface of the red planet, even though various mixed uncertainties occurred in flight dynamics during Mars atmospheric entry, especially Gaussian mixed uniform uncertainty in the initial state and dynamics parameters. A hybrid algorithm combining sensitivity collocation with nonintrusive polynomial chaos was proposed in this paper. Mixed uncertainty was quantified to reveal the mechanism causing location deviation during parachute deployment from the preplanned point. First, Mars atmospheric entry dynamics containing uncertainty were modeled as stochastic nonlinear dynamics. Second, stochastic variables were approximated using nonintrusive polynomial chaos, and sensitivity collocation was used to characterize state variables under the influence of uncertainty. Finally, the probabilistic distribution of the parachute deployment state was analytically obtained according to the initial and parametric uncertainties at the entry interface. Comparison simulations verified the effectiveness of the proposed technique. Gaussian-uniform mixed uncertainty features from the entry interface to the beginning of parachute deployment were revealed.