Landing area analysis for ballistic landing trajectories on the secondary of a binary asteroid

Fodde, Iosto and Feng, Jinglang and Vasile, Massimiliano (2022) Landing area analysis for ballistic landing trajectories on the secondary of a binary asteroid. In: AAS/AIAA Astrodynamics Specialist Conference 2022, 2022-08-08 - 2022-08-11.

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Abstract

Binary asteroid Didymos is the target of ESA's Hera mission, which plans to land a probe on the secondary body of the system, called Dimorphos. This procedure is planned to be performed using a ballistic landing strategy, which reduces the complexity of the spacecraft as no dedicated guidance, navigation, and control system is needed. However, these types of landings are sensitive to uncertainties in the deployment of the lander and the environment models. In this work, a robust ballistic landing trajectory design algorithm is developed, using a polynomial algebra based uncertainty propagation method. Furthermore, the results of this algorithm for different landing areas is compared to allow for the selection of the most robust landing location. The found minimum touchdown velocity and the dispersion of allowable deployment states are shown in different maps of the surface of Dimorphos. These maps show how the selected landing location affects the landing trajectories in different ways. Furthermore, the change in these maps for different magnitudes of the uncertainties in the gravitational parameter of the system and landing area are also obtained. It is shown that there are large areas on Dimorphos which allow low touchdown velocity landings, but which also have a relatively small dispersion of the deployment state. Other areas, mainly at higher latitudes, retain a low impact velocity landing while increasing the allowable deployment states. The region on Dimorphos facing the direction of motion around the primary gives the highest minimum touchdown velocity and are thus infeasible. The maps presented here allow for the selection of a landing location based on the uncertainties present in the system, and thus reduce the chance of failure of the landing.