Simulating the Encounters of NASA's Lucy Spacecraft with its Target Trojan Asteroids

NASA's Lucy mission is the 13th Discovery-class mission, and it will be the first to visit the Jupiter Trojan asteroids. Over the course of 12 years, the mission will encounter 7 Trojan asteroids in a series of 5 flybys. Each of these flyby occurs over a short period of time, such that careful planning of time-critical observations must be performed to ensure that the mission's Science Requirement are achieved. Additionally, various sources of uncertainty in the spacecraft's attitude and pointing accuracy must be thoroughly tested and constrained to determine how they impact instrument operation and the resulting data. In order to develop and test observations sequences, we have developed the Science Encounter Simulation Software (SESS). This powerful software allows one to simulate the spacecraft's encounter with each of Lucy's target, and to perform a series of commands to adjust the spacecraft's attitude and trigger data acquisitions with the various instruments of the Lucy payload. The software outputs a variety of information that allows one to construct resolution maps which can be used to determine whether a given observation sequence produces adequate data that meet the Science Requirements. The code also performs numerous checks to ensure that the spacecraft, its instrument pointing platform, and the L'Ralph scan mirror, are operated within their capabilities.