ON THE PERIHELION ASYMMETRY FOR INVESTIGATIONS OF THE NONGRAVITATIONAL MOTION OF COMETS

The standard Marsden's model for nongravitational effects in the motio n of comets with parameters Al, A2, A3 can be modified taking into acc ount asymmetric activity of comets with respect to perihelion: maximum value of the known function g(r) may be shifted by tau from the perih elion time by using in equations of the comet's motion a value of g(r) where tau = r(t - tau). It is shown that a value of tau, nongravitati onal parameters A1, A2, A3, and corrections to the orbital elements ca n be determined by the least squares method from astrometric observati ons of the comet. Numerical results for a number of periodic comets ar e presented. An attempt to link all the apparitions of Comet P/Kopff d uring 1906-1990 has been undertaken.