A comparison of CODEX spectra to Cassini observations. The Cassini observations are as described in Fig. 1. CODEX spectra are shown in three shades of red for three phases, advancing in time as colour darkens. The central of these is the nearest tenth of a cycle to each epoch, with the others being the preceding and trailing tenth of a phase. The vertical width of the CODEX spectra encompasses cycle to cycle variations including both compact and extended cycles as detailed in Ireland et al. (2008).