During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) 2007 campaign, airborne cloud observations were performed over the Arctic Ocean around Svalbard in the period from March till April 2007. On board of the AWI (Alfred Wegener Institute) Polar-2 aircraft, lidar remote sensing, in-situ cloud and albedometer solar radiation measurements were combined to investigate the properties of tropospheric clouds in the Arctic. On April 8th, a mixed-phase cloud formation was observed in a cold-air outbreak over open water. On April 9th, mixed-phase clouds were probed in two different air masses. First we observed remnants of the northerly cold-air outbreak which was gradually replaced by warmer air originating from the South. In the mixing zone between both air masses, the cloud consisted of pure ice.