Density parameter statistics for the cases with data limited to less than one full orbit of data, as indicated in the sketches in the top left corner. For data limited to the pericentre half, the MCMC chain for ρ₀ does not converge, but spreads out in a random walk. This means that these data are not sensitive to a dark mass, while in contrast, data limited to the apocentre half are; (c), (d). Panels a and b: the density is increased by a factor 100 such that 10% of M_• are enclosed by S2. Panels e and f: can be compared to Fig. 11c, showing that a doubled sampling of the respective orbital sections cannot make up for the data gap to one full orbit.