2029-b-plane of Apophis. The dotted 3σ-ellipse was computed using solution S₀. The solid one was obtained with solution S₁ and the blurred one with solution S₃. Solution S₂ is not shown because it is not significantly different from solution S₁. For completeness, the center of primary (★) and secondary keyholes leading to collision at ascending node (■ red) and descending node (■ blue) are also represented. The figure is centered on the dotted ellipse and axes are expressed in sigma units of the S₀ solution with (σ_ξ, σ_ζ) = (15, 350) km.