  The need for more accurate asteroid models is perhaps secondary to the need
to measure their quality. The uncertainties of models' parameters propagate to
quantities like volume or density -- the most important and informative
properties of asteroids -- affecting conclusions about their physical nature.
Our knowledge on shapes and spins of small solar system bodies comes mostly
from visual, disk-integrated photometry. In this work we present a method for
asteroid model uncertainty assessment based on visual photometry (lightcurves
and sparse-in-time absolute measurements) allowing the determination of
realistic volume uncertainty, as well as spin axis orientation, rotational
period and local surface features. The sensitivity analysis is conducted by
creating clones of the nominal model and accepting the ones that fit the
observations within a confidence level. The uncertainties of model parameters
are extracted from the extreme values found in the accepted clone population.
Creation of such population of clones enables the conversion of a deterministic
asteroid model into stochastic one, and can be utilized to create observation
predictions with error bars. The method was used to assess the uncertainties of
fictitious test models and real targets, i.e. (21) Lutetia, (89) Julia, (243)
Ida, (433) Eros and (162173) Ryugu. We conclude that volumes, and subsequently,
densities of asteroids derived from lightcurve-based models likely have vastly
understated uncertainties, the biggest source of which is the inability to
establish the extent of the model along its spin axis.
