(voxsiz); double = class(voxsiz)

      voxori     Voxel grid origin.  This is the location of the voxel
                 grid origin in the body-fixed frame associated with
                 the target body.  Units are km.

                 [3,1] = size(voxori); double = class(voxori)

      vgrext     Voxel grid extent.  This extent is an array of three
                 integers indicating the number of voxels in the X, Y, and
                 Z directions in the fine voxel grid.

                 [3,1] = 