The University of Colorado Multi-AXis Differential Optical Absorption Spectroscopy (CU MAX-DOAS) instrument measures ultraviolet-visible scattered-sunlight spectra in a sequence of elevation angles (angle above the horizon) and an azimuth angle of ~100° (clockwise from North). The instrument was operational at Maïdo before, during, and after the April -June 2018 eruption of Piton de la Fournaise . Spectra measured during the volcanic eruption were analyzed with respect to a reference spectrum measured in absence of the volcanic plume using a DOAS spectral retrieval algorithm to retrieve SO2, BrO, and IO differential slant column densities (dSCDs).