Minimum temperature for 5σ detectability as a function of the observed orbital phase and eccentricity for an Io-like moon with an Io-like semi-major axis (top) and for an Earth-like moon with a Callisto-like semi-major axis (bottom). The green and blue contours indicate the contour corresponding to the nominal (zero-eccentricity) required temperature (as marked on the top plot in Fig. 3), and the 10 K deviations from this temperature, respectively; in both cases, these are also marked on the colourbar. We note that in all non-zero eccentricity cases the temperature required for observability is in fact lower than for the circular case over >50% of the orbit.