Enhanced-Precision Entry Phase Navigation for Mars Landing Using Surface Radio, IMU, and Environmental Sensors

A multi-sensor fusion approach to high-precision entry phase navigation for Entry, Descent, and Landing (EDL) operation is presented. A single Ultra High Frequency (UHF) band radar, two ranging beacons, an on-board Inertial Measurement Unit (IMU), pressure measuring devices on the heat shield of the entry vehicle, and heat flux measuring devices on the spacecraft’s back shell are combined to give highly accurate estimates of states and parameters. Full kinematic states, lift to drag ratio, and nominal atmospheric density are estimated. The Unscented Kalman Filter (UKF) is used for fusion as it yields good performance for systems with high degrees of non-linearity. Smaller position estimation errors enable the exploration of areas of high scientific value. Accurate lift to drag ratio estimates have important implications for achieving control goals during entry. A good estimate of nominal atmospheric density provides an accurate model of the variation of atmospheric density with altitude. This is critical for the design of soft-landing entry vehicles and for environmental study. The utilization of a wider set of sensing modalities than is reported in any literature so far makes this work unique. Our findings are substantiated with MATLAB® simulations.