also shown in Fig. 1, as well as those obtained with other dynamical models. The formal uncertainties in ξ and ζ are ∼ 4 km, while using the Marsden et al. (1973) nongravitational perturbation model can cause differences in ζ as large as ∼ 10 km. Despite the small encounter distance, 140500 km, the Mars flyby caused modest changes to the orbit of C/2013 A1 because of the high encounter velocity of 56 km/s and the relatively small mass of the planet. For instance, the angle between the incoming and outgoing relative velocities of the comet was only 0 . 01 $^{◦}$. Interestingly, solution 102 comes with an estimate of C/2013 A1’s spin pole. While this pole allows us to fit the data and accurately describe the comet’s trajectory, it is important to point out that this estimate is model dependent and strongly relies on the accuracy of the RJM and its assump- tions, e.g., number of jets, simple rotation, etc. Table 5 shows the different estimates of the spin pole with the Marsden et al. (1973) model (spin pole approximated by the direction of the ( A$_{1}$, A$_{2}$, A$_{3}$ ) vector at time Δ T , as done in Chesley and Yeomans, 2005) and the different configurations of the RJM. In particular, setting the diurnal lag angle to 0 ◦ moves the pole by 36 $^{◦}$. Comet C/2013 A1 is still observable in the northern sky. Figure 6 shows the predicted total magnitude and declination until 2020, when C/2013 A1 will be at more than 15 au from the Sun. The next few years are the last chance of observing the comet for quite some time. In fact, the post- perihelion orbit of C/2013 A1 with respect to the Solar System barycenter is elliptic and has an orbital period of more than 500000 years. 29