How Euclid scans the sky

This is an artist impression of how Euclid scans across the night sky using a 'step-and-stare' method, combining separate measurements to form the largest cosmological survey ever conducted in the visible and near-infrared.

Each time Euclid 'stares', its telescope points to a position in the sky, performing imaging and spectroscopic measurements on an area of approximately 0.5 deg² around this position. After each stare, the telescope shifts (or 'steps') to a new position.

The instruments will scan over a total of around 35% of the sky. This is the largest area that includes a complete detection of the galaxies necessary for Euclid’s cosmological studies. The rest of the sky is dominated by the high density of bright stars in our galaxy, and by the dust in the plane of our Solar System, which both disturb the cosmology observations.

Click here for an animated version of this image.