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 en-try, descent, and landing phase to assess the performance of Phoenix as it descended is pre-sented 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 at-tack during the hypersonic phase of the entry, which resulted in Phoenix flying a slightly lift-ing 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 varia-tions expected and is consistent with a lifting trajectory. The parachute deployment and in-flation process occurred as expected with no anomalies identified. The subsequent parachute descent and powered terminal landing also behaved as expected. A preliminary reconstruc-tion of the landing day atmospheric density profile was found to be lower than the best apri-ori 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 on-going and the results to date are in the process of being refined.