Post-Launch Verification of Lucy Solar Array Deployment

The Lucy spacecraft launched on October 16, 2021, on a mission to conduct flybys of the Jupiter Trojan asteroids during the planned 12 years of operation. During solar array deployment following launch vehicle separation, the Solar Array - Positive Y-axis (SAPY) wing did not fully deploy. The spacecraft was power-positive and thermally safe, but the unknown state of the solar array was a risk to mission success. An Anomaly Response Team was formed to assess the solar array and recommend a path forward. For one year, the team conducted extensive testing, simulations, fishbone analysis, and risk assessments. There were no sensors to indicate the deployed state of the array, so multiple techniques were used to estimate the state, including mathematical models based on circuit current information and detailed Automated Dynamic Analysis of Mechanical Systems (ADAMS) modeling. A ground test setup identified a mistracked lanyard as the likely proximate cause and built confidence in continuing with attempts to retract the lanyard, pulling the array closer to full deployment. In parallel, a Vse-As-Is (UAI) assessment evaluated various options if the array could not be fully deployed or if the main engine could not be fired to maneuver the spacecraft due to the risk of damaging a partially deployed array. The project assessed the risk of maintaining the solar array as is versus making redeployment attempts (RDAs). As a result of these efforts, incremental RDAs were recommended to further deploy the array safely. Eight such RDAs were conducted between May and December 2022, enabling Lucy to follow the nominal mission plan with the SAPY wing estimated to be 99% deployed.