Comparison of Euclid and SO sky coverage in Galactic coordinates. The blue, semi-transparent regions covering most of the northern and southern Galactic hemispheres away from the Galactic plane is the currently planned Euclid sky coverage (Scaramella et al., in prep.). In addition to a Galactic cut, Euclid also avoids regions within about 15° of the ecliptic plane, seen here as the band running from the lower, left-hand part of the graphic to the upper, right-hand part. The region covering most of the right of the plot (with a light red hue) indicates the sky available to SO, assuming a minimum observation elevation of 40°. Roughly 70% of the celestial sphere is accessible to SO, though this is reduced to around 40% when one makes reasonable Galactic cuts. The underlying, grey-scale map shows the Planck 545-GHz map, which gives one an indication of what regions are most contaminated by thermal emission from Galactic dust.