The Impact of Major Anomalies of Robotic Mars Surface Missions on Mission Timeline

Robots exploring the surface of Mars have a set of objectives that must be accomplished within a constrained mission duration. This timeline constraint often comes from the qualified life of the hardware, available energy due to seasonal effects on available solar power, or, as in the case of Mars Sample Return, the proximity of Earth and Mars for the associated return launch window. No matter what the constraint, a mission timeline must be developed to show that the mission’s objectives can be accomplished within the available mission duration. A key factor that must be considered when developing a mission timeline is the loss of operational sols (Martian days) due to encountering and recovering from major anomalies. This paper examines all modern NASA Mars surface missions, including the Spirit and Opportunity rovers, the Phoenix lander, the Curiosity rover, the InSight lander, and the Perseverance rover, to understand the major anomalies encountered during their surface missions. All anomalies resulting in four or more consecutive sols of lost progress are cataloged in this study, providing a complete data set for statistical analysis. Additionally, fifteen specific anomalies are discussed in detail to illustrate key themes and lessons learned during their discovery, investigation, and recovery. Anomalies are found to be the result of seven categories: mechanical hardware, software, environmental interactions, computer hardware, power systems, electrical hardware, and command errors. Our analysis quantifies the loss in surface productivity from each anomaly, with impacts ranging from 4 to 55 sols lost for any given event. When taken cumulatively over the prime mission, it is shown that on average, missions lose 11% of their surface duration to major anomalies. Each of the missions examined have lasted past their expected prime mission with two of the vehicles (Curiosity and Perseverance) still operational. When looking not only at the prime mission, but also including the extended mission, the time lost to major anomalies drops to 6.7%. The data presented is from robotic Mars surface missions, but the lessons are applicable to any space mission. The amount of lost productivity due to encountering and recovering from major anomalies is not always considered when developing mission timelines and allocating appropriate timeline margin for anomalies is critical to ensuring a mission’s success. Pulling from a range of past Mars missions, this paper provides recommendations on mission timeline margin policies that are grounded in robotic exploration experience.