Long-period comets with non-gravitational effects

The influence of non-gravitational effects on the motion of long-period comets is analyzed. Investigations were performed for about 60 nearly-parabolic comets discovered during the last thirty years. All three non-gravitational parameters A(1), A(2), A(3) were detected in the motion of 19 comets on the basis of positional observations only. For these comets the standard g(r) function as well as some of its modifications were used to model the ice sublimation from the cometary nucleus. For 14 of 19 comets the orientation of spin axes of the nucleus were also determined. Finally, the magnitude of the nongravitational effects derived for the long-period comets have been compared with observed the non-gravitational perturbations on periodic comets.