Ground-In-The-Loop Mission Concept Study for Europa Lander Using Modeling and Simulation

Europa Lander is a mission concept to search for biosignatures on the moon of Jupiter, Europa. Due to its inherent and design constraints, the mission requires a highly autonomous lander that makes system-level and science decisions on its own. It is a short (approximately 20 to 30 Earth days) mission with about half of that duration available for communication. Therefore, this mission requires an entirely different mission operations paradigm as the Mars surface operations paradigm (a.k.a., call-and-response) is not viable. The Europa Lander Mission Systems Team designed a novel operations paradigm, Ground-In-The-Loop (no hold): Lander downlinks the required data when ready and proceed with the next planned activities without waiting for the Ground Team. However, Lander will open an uplink window at a predetermined time so that the Ground Team can uplink commands based on the knowledge the team has based on the prior downlink, recognizing that Lander may have progressed to a different point or branch in the known plan. This still costs the mission time and energy because Lander may have to delay certain activities and wait for the predetermined time to open an uplink window. It has been a common perception that the more Ground-In-The-Loop (GITL) opportunities we insert, the less efficient is the utilization of limited mission resources. This study is focused on understanding the sensitivities in a mission concept given different ground ops paradigms varied by number of different attributes including a number of GITL opportunities. The goal is to characterize the opportunity and cost tradeoffs between different mission concepts. The main opportunity offered by increasing GITL opportunities is to increase the level of influence that the Ground Team can have over the activities of Lander. With GITL with hold, (namely, call-and-response), it is relatively straightforward to understand what level of influence the Ground Team can have - the team influences the immediate next activity, with the full knowledge of the data collected. For the GITL (no hold), it becomes highly complex. To address that complexity, the Ground Influence score is developed. It is calculated by counting the number of uplink opportunities on an activity (e.g., excavate or collect and analyze a sample) weighted by the amount of available knowledge that the Ground Team has. In addition, we captured performance metrics such as the number of Samples Collected given 50kwhr battery, Lander Sleep Time indicating the duration in which Lander does not perform any science or communication activity. One of the most surprising results was that the number of GITL (no hold) opportunities did not impact the mission performance as significantly as commonly perceived. This seemingly unintuitive finding was due to rather complex interactions between thermal constraints, durations of activities, and their impact on the overall mission performance. Most importantly, we identified configurations corresponding to the set of assertions that result in higher Ground Influence score, enabling the better informed and optimized ground operations design.