Significance analysis of potential H₂O signals, illustrated for the night of 31 March 2022. Top panel: S/N map as a function of radial velocity in the exoplanet’s rest frame (v_rest, horizontal axis) and the projected orbital velocity semi-amplitude, K_p (vertical axis). Horizontal lines mark the expected K_p, and vertical lines show the zero rest-frame velocity. Bottom panel: 1D cross-correlation function at the expected K_p (97.1 kms⁻¹)of GJ 1214b.