  Preplanetary nebulae (PPNe) are formed from mass-ejecting late-stage AGB
stars. Much of the light from the star gets scattered or absorbed by dust
particles, giving rise to the observed reflection nebula seen at visible and
near-IR wavelengths. Precursors to planetary nebulae (PNe), PPNe generally have
not yet undergone any ionization by UV radiation from the still-buried stellar
core. Bipolar PPNe are a common form of observed PPNe. This study lays the
groundwork for future dynamical studies by reconstructing the dust density
distribution of a particularly symmetric bipolar PPN, M1-92 (Minkowski's
Footprint, IRAS 19343$+$2926). For this purpose, we develop an efficient
single-scattering radiative transfer model with corrections for
double-scattering. Using a V-band image from the Hubble Space Telescope (HST),
we infer the dust density profile and orientation of M1-92. These results
indicate that M1-92's slowly expanding equatorial torus exhibits an outer
radial cutoff in its density, which implicates the influence of a binary
companion during the formation of the nebula.
