Astrometric impact of different effects on the S2 star observations obtained during three periods. First plot: Roemer time delay. Second plot: Shapiro time delay. Third plot: Lense-Thirring effect considering the angular momentum parameters a = 0.99, i′ = 45° and Ω′ = 160°. Fourth plot: gravitational lensing. Open red circles and triangles denote the position of the apocenter and the pericenter, respectively. See Appendix E.2 for the precise definition of the various quantities used in these plots.