Quantitative spectroscopy of the aurora. VI. The auroral spectrum from 275 to 815 nm observed by the OSIRIS spectrograph on board the Odin spacecraft

Abstract

Terrestrial auroral spectra over the 275 to 815 nm wavelength range have been recorded by the OSIRIS imaging spectrograph on board the Odin spacecraft. The spectra are from the dark polar region and are averaged over limb tangent altitudes from 100 to 105 km. All wavelengths are exposed simultaneously, thus avoiding the effect of temporal intensity variations inherently present in spectrally scanning systems. Particular care has been taken to quantify the relative spectral sensitivity over the entire wavelength range, and there is an estimated 5% precision in the measurements. To maintain accurate on-orbit spectral calibrations, an atmospheric radiation model with multiple Rayleigh scatter is employed to regularly update the OSIRIS spectral response throughout the mission. A calibrated auroral spectrum is presented, together with matching synthetic spectra for many of the observed features, for potential use as a reference spectrum in general atmospheric research. The relative intensities of the brighter auroral band systems and atomic lines are reviewed. Finally, the observed spectrum is made freely available in digital format in long term archives.