Goldstone and Green Bank Radar Detection of the Lunar Trailblazer Spacecraft - a second look at the data

NASA's Lunar Trailblazer small sat mission lost ground contact one day after its launch in late February 2025. We describe radar observations conducted at Goldstone and Green Bank during the spacecraft emergency and the data analysis that was undertaken several months after the critical period ended. Our goal was to revisit the spin-state estimate that was initially reported to the mission team (see Ehlmann et al., this issue, for an overview). We found the new analysis largely consistent with the initial findings, where the most likely rotation period for the spacecraft is ~10–13~min, although we cannot fully exclude a rotation period that is twice as long. The spin-pole direction is contained in two symmetric regions on the plane of sky, one prograde and one retrograde. Our analysis suggests that on March 2 and 3 the radar line of sight was close to the equatorial, resulting in echoes dominated by the spacecraft bus, and close to the pole-on on March 6 and 8, resulting in echoes dominated by the solar panels. We also provide an overview of the radar astrometry reported, five Doppler frequency and four time-delay (range) measurements, and their residuals with respect to the latest orbital solution for the spacecraft.