Material Property Sensitivity of Light Curve Attitude Estimation for the Lunar Trailblazer

Abstract The Lunar Trailblazer (LTB) spacecraft launched on 27 February 2025, toward a planned low‐lunar orbit. Eleven hours into its mission, contact with Trailblazer was lost, and recovery efforts began. Estimating the orientation and angular velocity state of Trailblazer was central for recovery to determine whether and when the vehicle could be contacted again. This work documents a method to estimate Trailblazer's attitude state using only ground‐based optical telescopes. This data is cheap to collect and scales favorably with distance compared to radar data. We rely on photometric light curves, time histories of Trailblazer's observed brightness. The process of estimating Trailblazer's orientation and angular velocity from this data is known as light curve inversion. Light curve attitude inversion, in addition to inherent ambiguities caused by symmetries in the observed object's geometry and the geometry of the observation, is sensitive to the object's assumed surface materials. In this paper, we study the impact of surface material accuracy using two light curves of Trailblazer acquired by the 4.2‐m aperture Lowell Discovery Telescope in Arizona on 10 March 2025 and the 8.1‐m aperture Gemini South observatory in Chile on 9 April 2025. We produce two sets of solutions for each light curve: one using material properties derived from a solar radiation pressure model of the LTB, and a second using materials fit to laboratory reflectometry of Trailblazer's materials. We qualitatively compare solutions for both cases and perform a sensitivity analysis to quantify the dependence between the attitude solutions and material property errors.