Entry, Descent, and Landing Performance of the Mars Phoenix Lander

Abstract

On May 25, 2008, the Mars Phoenix Lander successfully landed on the northern arctic plains of Mars. An overview of a preliminary reconstruction analysis performed on each entry, descent, and landing phase to assess the performance of Phoenix as it descended is presented and a comparison to pre-entry predictions is provided. The landing occurred 21 km further downrange than the predicted landing location. Analysis of the flight data revealed that the primary cause of Phoenix's downrange landing was a higher trim total angle of attack during the hypersonic phase of the entry, which resulted in Phoenix flying a slightly lifting trajectory. The cause of this higher trim attitude is not known at this time. Parachute deployment was 6.4 s later than prediction. This later deployment time was within the variations expected and is consistent with a lifting trajectory. The parachute deployment and inflation process occurred as expected with no anomalies identified. The subsequent parachute descent and powered terminal landing also behaved as expected. A preliminary reconstruction of the landing day atmospheric density profile was found to be lower than the best apriori prediction, ranging from a few percent less to a maximum of 8%. A comparison of the flight reconstructed trajectory parameters shows that the actual Phoenix entry, descent, and landing was close to pre-entry predictions. This reconstruction investigation is currently ongoing and the results to date are in the process of being refined.

Multibody Modeling and Simulation for Mars Phoenix Entry, Descent, and Landing

“…The test cases started with a simple vertical drop from rest of the fully deployed parachute and capsule, and then gradually increased the simulation complexity to include parachute opening, lander deployment, retrorocket firing, and other effects. The POST II model had been previously compared and validated to a MATLAB-based simulation and another multi-degree-of-freedom simulation [7,8]. In each case, the agreement between the simulations was excellent.…”

“…These results showed that the multibody parachute system reliably damped out rotational motion of the capsule. This rotational damping was of great interest [8,9].…”

“…In each case, the agreement between the simulations was excellent. The verification work is reported in more detail in [7,8].…”

Reconstruction of Entry, Descent, and Landing Communications for the Phoenix Mars Lander

“…The flight trajectory went from northwest to southeast and the actual landing site has been identified to lie just to the left of center of the circular area (marked by a cross hair). The actual landing site was 21 km downtrack and 5.3 km crosstrack from the final preentry prediction for reasons discussed in [2]. The crater to the right of the landing site is Heimdal Crater.…”

“…1. The ellipse outlines the area where Phoenix was predicted to land before arriving at Mars and has a size of 55.1 by 19.2 km [2]. The flight trajectory went from northwest to southeast and the actual landing site has been identified to lie just to the left of center of the circular area (marked by a cross hair).…”