Comets and nongravitational forces. V

The problem of the variation of the nongravitational forces with heliocentric distance is considered. Calculations are presented for nine short-period and five long-period comets, the variation of the forces with distance being determined from a law based on the vaporization rate of water snow. Results obtained earlier are modified to conform to the new law, and the relative values of the forces on different comets are interpreted. The effect of emissivity of the cometary nucleus on the vaporization rate is also discussed. Particular attention is paid to the matter of deriving "original" and "future" orbits of long-period comets when nongravitational forces are taken into account.