The lifetime of free neutrons measured in the laboratory has a longstanding disparity of $\approx 9$ s. A space-based technique has recently been proposed to independently measure the neutron lifetime using interactions between the galactic cosmic rays and a low atmosphere planetary body. This technique has not produced competitive results yet due to constraints of nonoptimized data that contain large systematic errors. We use data from the neutron spectrometer on-board NASA's Lunar Prospector, and study two large systematics in the measurement of neutron lifetime: the lunar subsurface temperature and the lunar surface composition. We use the HeCd and HeSn neutron spectrometer data when the spacecraft was in a highly elliptical orbit during the orbit insertion period. We report the neutron lifetime using four different models that each have different choices of surface temperature and composition. The $5^{\circ }$ [Prettyman et al., J. Geophys. Res.: Planets 111, 2005JE002656 (2006)] and $2^{\circ }$ [Wilson et al., Phys. Rev. C 104, 045501 (2021)] rebinned maps result in $777.6\pm 11.7$ s and $739.6\pm 10.8$ s, respectively. For the ${20}^{\circ }$ map (Prettyman et al., 2006), constant equatorial and a latitude-dependent temperature model result in $738.6\pm 10.8$ s and $767.3\pm 11.2$ s, respectively. Increasing the complexities of the models accounting for the systematic effects increase the measured lifetime. However, the reported measurements are not competitive with the laboratory results due to large unaccounted systematics resulting from nonoptimized measurements and modeling assumptions. This work serves as a study of systematic uncertainties for future neutron lifetime measurements using the space-based technique. We estimate the effect on the lifetime from the choice of temperature model to be to be $28.7\pm 15.5$ s, and choice of compositional map (for ${20}^{\circ }$ and $5^{\circ }$ maps) to be $10.3\pm 12.2$ s.

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• Lifetimes & widths
• Neutron decay time
• Neutron physics
• Nuclear data analysis & compilation