Observational geometry of Saturn from Herschel, and estimations of the contribution of Saturn’s rings to the disc-averaged spectrum. Panel a) shows the size of the planet in arcseconds and the small ring-opening angle as Saturn’s northern hemisphere passed the spring equinox. The SPIRE FWHM at 50 cm^-1 is shown as the dotted line close to Saturn’s limb. The size of the SPIRE beam width is compared to the width of Saturn and the A, B and C rings in panel b). The fractional area of the SPIRE beam occupied by each of the rings is given in panel c), and was used to calculate the contribution of ring emission and absorption to the spectrum as a fraction of the total signal in d). Contributions smaller than 2% are within the estimated uncertainties on the SPIRE data.