On 6 April 2014, a Differential Optical Absorption Spectroscopy (DOAS) instrument was used to measure the radiance of scattered solar radiation passing through the plume emitted from Mount Pagan volcano, Mariana Islands. Spectra were recorded in the ultraviolet (UV: 240 - 390 nm) wavelength range at 0.6 nm resolution. A scanner was used to scan the spectrometer's viewing direction vertically throu