Spectra of the residual OPD (shown in black) and the reconstructed perturbation (Η_φ · L, depicted in red) for two observations. The upper panels present data on HR 8799 for one baseline from the UTs, corresponding to the data shown in Fig. 4. The standard deviation of the OPD is 151 nm. The panel below shows a dataset from the ATs for HR 7672 with an OPD standard deviation of 86 nm. The cumulative spectrum for these two dataset are also shown. The data for all baselines are presented in Appendix B.