Spectra of HO obtained with MIRO on 24 September 2015. The five spectra are 4 min averages that were obtained during a sequence where the line of sight moved from limb sounding to nadir viewing, and the background changed from 0 to 200 K. The line is saturated between − 1.3 and − 0.4 km s⁻¹ , where its intensity corresponds to the gas temperature near the spacecraft. Top: before applying the side-band gain correction. Bottom: after applying this correction.