Mars InSight Entry, Descent, and Landing Trajectory and Atmosphere Reconstruction

Abstract

The InSight mission landed on the surface of Mars on 26 November 2018. The InSight system performance met all design requirements, although several performance metrics fell near the boundaries of the predictions. The peak deceleration was high, the overall timeline was short, and the landing site was uprange and crossrange from the target. This paper describes the reconstruction of the entry, descent, and landing trajectory and atmosphere. The approach uses a Kalman filter to blend sensor data to obtain the vehicle trajectory. The aerodynamic database is used in combination with the sensed accelerations to obtain estimates of the atmosphere-relative state, which in turn is used to derive the freestream atmospheric conditions during entry. The results indicate that the reconstructed atmospheric density was approximately smaller than the preflight atmosphere model. Analysis of the reconstructed vehicle attitude angles indicates that the aerodynamic lift was oriented downward at entry. The vehicle developed a roll rate during entry, which directed a component of the lift to the north. The low density and aerodynamic lift direction are determined to be the primary causes of the high deceleration, short timeline, and location of the landing site relative to the target.