Cornelius Schiller, an international leader in high-altitude water vapor measurements and quality assessment who took charge of several research campaigns and mentored many young scientists, passed away on 3 March 2012 in Neuss, Germany, after a battle with cancer. He was 50 years old. Cornelius spent his childhood and most of his life in the Niederrhein region of Germany, close to Düsseldorf. He studied physics at the University of Bonn, and his developing interest in the physics and chemistry of the atmosphere led him to work with Dieter Ehhalt at the Forschungszentrum Jülich (Research Centre Jülich) in Germany. Cornelius' career started shortly after the discovery of the ozone hole, and he had the opportunity to participate in the first large-scale ozone measurement campaign in the Arctic, known as the Airborne Arctic Stratospheric Expedition, during January and February 1989; he contributed airborne observations of ozone-depleting chlorine and bromine substances.