23 Table 5: Orbital fit statistics, b -plane coordinates, and spin pole for different nongravitational perturbation mo dels. The whole arc contains 370 optical and 67 satellite astrometric observations through the end of April 2015. 〈 ΔRA 〉 and 〈 ΔDEC 〉 are the average residuals in RA cos(DEC) and DEC. The sixth column contains the σ shift between the pre-encounter solution and the whole arc solution, i.e., σ 2 = ( x full − x pre ) T Γ − 1 pre ( x full − x pre ) where x pre is the pre-encounter best fitting solution, Γ pre its covariance matrix, and x full the full arc best fitting solution. The last column shows the angular distance between the considered model’s pole and that of the two jets + θ model (numbers in parentheses are for the diametrical opp osite pole). Model N χ 2 〈 ΔRA 〉 〈 ΔDEC 〉 σ ξ ζ Pole Δ pole par. [ ′′ ] [ ′′ ] shift [km] [km] (RA, DEC) Gravity only 6 16523 -0.75 0.17 84.2 -33853 -136340 NA NA A 1 7 510 0.01 0.18 17.0 -33900 -136356 NA NA A 1 , A 2 8 216 -0.04 0.04 8.9 -33900 -136349 NA NA A 1 , A 2 , A 3 9 191 -0.02 -0.02 10.1 -33899 -136350 (311 ◦ , − 23 ◦ ) 115 ◦ (65 ◦ ) A 1 , A 2 , A 3 , Δ T 10 190 -0.02 -0.02 10.0 -33900 -136350 (311 ◦ , − 23 ◦ ) 115 ◦ (65 ◦ ) 1 jet 10 274 0.06 0.12 12.7 -33899 -136359 (141 ◦ , 62 ◦ ) 72 ◦ (108 ◦ ) 1 jet + A 1 11 89 0.01 -0.02 3.2 -33902 -136360 (80 ◦ , 0 ◦ ) 22 ◦ (158 ◦ ) 1 jet + θ 11 165 0.01 0.04 8.5 -33899 -136354 (350 ◦ , 40 ◦ ) 68 ◦ (112 ◦ ) 1 jet + A 1 + θ 12 89 0.01 -0.02 3.4 -33903 -136360 (77 ◦ , 1 ◦ ) 19 ◦ (161 ◦ ) 2 jets 12 86 0.02 0.02 2.6 -33902 -136362 (280 ◦ , − 23 ◦ ) 144 ◦ (36 ◦ ) 2 jets + A 1 13 86 0.02 0.02 2.6 -33902 -136362 (280 ◦ , − 22 ◦ ) 144 ◦ (36 ◦ ) 2 jets + θ 13 73 0.00 0.03 0.9 -33904 -136359 (63 ◦ , 14 ◦ ) NA