Characterisation of atmospheric effects for the inter-island experiment over 144 kilometres. A laser beam is transmitted from La Palma (in the horizon) towards the ESA's Optical Ground Station (OGS) in Tenerife (part of the dome is visible on the left). The OGS is equipped with a 1 metre telescope and was used as a quantum communication receiver in the inter-island quantum communication experiments. The OGS is also suitable as a quantum communication receiver from a source on a spacecraft.