Evolution of the orbit of comet 46P/Wirtanen during 1947-2013.

The nucleus' surface of comet P/Wirtanen is to be investigated in 2011 during the ROSETTA space mission. An attempt to link all the observed apparitions of the comet is presented. Nongravitational effects in the comet's motion have been examined using several ways. The best solution has been found for forced precession model of the comet by expressing the Marsden's nongravitational parameters A_1_,A_2_,A_3_ in terms of angular parameters of the rotating and precessing oblate cometary nucleus. This model allowed us to determine five nongravitational parameters: A, η, I, φ, and f_p_, together with six corrections to the orbital elements, solving observational equations by the least squares method. Finally, all the seven recorded apparitions of the comet were linked using 67 positional observations covering the period 1948-1991; the mean RMS residual is equal to 2.33". The past and future comet's orbit evolution is presented.