Landing-Site Dispersion Analysis and Statistical Assessment for the Mars Phoenix Lander

The Mars Phoenix Lander launched on 4 August 2007 and successfully landed on Mars 10 months later on 25 May 2008. Landing ellipse predicts and hazard maps were instrumental in selecting safe surface targets for Phoenix. Hazard maps were based on terrain slopes, geomorphology maps, and automated rock counts from the Mars Reconnaissance Obiter's High Resolution Imaging Science Experiment images. The expected landing dispersion was used in conjunction with the hazard maps, which led to the selection of Phoenix's surface target. The same statistical assessment was performed with the actual landing dispersion predictions determined during operations in the weeks, days, and hours before landing and compared with criteria levied by the project in order to determine whether or not to perform entry aim-point targeting maneuvers. The statistical analysis was also used by the Phoenix project to verify the effectiveness of a preplanned maneuver menu and to calculate the probability of future maneuvers. An assessment of the statistical distribution of Phoenix landing points (Monte Carlo results) was performed to justify the Phoenix assumption of a bivariate Gaussian distribution, which showed that this assumption did not play a role in Phoenix landing downrange of the expected landing site.