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

The details of the trajectory and atmospheric reconstruction for the Mars Phoenix entry, descent, and landing are presented. The trajectory reconstruction used a six-degree-of-freedom process that included integrating the 200 Hz onboard inertial measurement unit incremental velocity change ΔVΔV data and incremental angle change Δ[Theta]Δ[Theta] data, the derivatives from the ΔVΔV and the Δ[Theta]Δ[Theta] data, smoothing, and correcting the inertial measurement unit accelerations for physical location on the Lander. Lander orientation angles (angle of attack and sideslip) during descent were reconstructed independently of the aerodynamics and atmosphere models. Before parachute deployment, the angle of attack and sideslip were found to be small (less than 3 deg) leading up to about 5 deg at parachute deploy, where the deployment altitude was determined to be approximately 13 km at a Mach number of about 1.7 and a dynamic pressure of 489N/m2489N/m2. In a separate process, the atmosphere structure (i.e., density, pressure, and temperature) encountered for altitudes up to 80 km was determined. The atmosphere structure determination process involved a detailed aerodynamics model of the Lander and the parachute, as well as accounting for configuration changes during descent. Comparisons made with the preflight atmosphere model used in the mission design show good agreement with the three reconstructed atmosphere structure parameters. [PUBLISHER ABSTRACT]