Model fitting of the kinematics for knot j: trajectory Z_n-X_n, core separation r_n(t), coordinates X_n(t) and Z_n(t), the modeled apparent velocity/viewing angle and Lorentz/Doppler factor. In each of the upper plots, two additional model curves (red and green) are also shown for ejection epochs t₀ + 0.3 yr and t₀−0.3 yr (t₀ = 2011.02), demonstrating that most of the observational data points are within the regions confined by the two curves and that the precessing period is determined with an uncertainty of ~0.3 yr.