Simple formulae are given for the surface area, volume, center of mass
, moments of inertia, and principal axes of any homogeneous polyhedron
. These can easily be combined with algorithms for the gravitational h
eld of such polyhedra. A FORTRAN version of our code (available from t
he author) is used to compare digital models of Phobos at different re
solutions. The results indicate that a surface resolution of about 10
degrees is adequate to characterize the inertial properties of a small
satellite or asteroid within a few percent, comparable to the systema
tic uncertainty for Phobos. This accuracy scales as the square of the
resolution. (C) 1996 Academic Press, Inc.