Planned Activity Complexity Evaluation (PACE): Applied to Mars Exploration Rovers Surface Activities

摘要

An Activity Plan for a spacecraft consists of a time-ordered set of engineering and science activities to be performed by the spacecraft over a specified time period (hours, days, weeks, months, etc). Methodologies for measuring the degree of complexity of spacecraft Planned Activities by Earth-based operators is lacking in the spacecraft operations literature. This paper describes a new methodology for the evaluation of the complexity of planned spacecraft activities by Earth-based operators. The methodology is based on a novel computation of the Combined Activity Sequences Entropy (CASE). A command sequence (or sequence) is an ordered list of commands with associated arguments and control flags that will be executed by the spacecraft onboard sequence engine. Each activity in the Activity Plan is expanded into command sequence, and may comprise multiple command sequences. The goal of this research is to develop a methodology which measures the degree of complexity of a spacecraft Planned Activity. For each activity command sequence, a Sequence Entropy (SE) is computed based on the concept of entropy from information theory. The overall Planned Activity Complexity Evaluation (PACE) is computed using the CASE, activity constraints and the resources expended by the spacecraft planning team to build the command sequences. Finally, results from applying PACE to the Mars Exploration Rover mission robotic arm in-situ activities over a period of 1000 sols are presented.