Einstein radius (θ_E) used in the astrometric microlensing data simulation for GaiaDR3-ULENS-001, which reproduces the Gaia DR3 five-parameter astrometric fit to within their 3σ (grey circles), as a function of mean astrometric per-CCD error bar () for the base magnitude, G₀. Black circles mark values that also reproduce the value of the RUWE to within 1σ_RUWE ≈ 0.12. Pink circles mark values that additionally reproduce parallax and proper motion errors to within 1σ_σ, X ≈ 0.0018. X denotes the parameters of ϖ, μ_α*, and μ_δ as their error values exhibit an almost linear correlation and very similar values for every sample. (a) Positive u₀ solution. (b) Negative u₀ solution.