Simulated difference between the derived semimajor axis a_derived and its true value a_true. Top: a_derived as function of a_true. Filled circles, open circles, and diamonds designate orbits of 1–2σ, 2–3σ, and >3σ significance, respectively. The solid line has unity slope and the dashed line shows the single-measurement precision of σ_Λ = 7.2 mas. Bottom: the relative deviation calculated as (a_derived − a_true)/a_true as a function of significance. The accuracy and relative precision of the solution improve with significance. At the detection limit of 3-σ, the deviation from the true value is smaller than 0.5 mas.