GOME, an ESA sensor launched in April 1995, is a nadir-looking spectrometer on the satellite ERS-2 measuring globally a range of atmospheric constituents both in the stratosphere and troposphere, with the main interest on ozone. The ozone layer, protecting our planet from potentially harmful ultraviolet sunlight, is threatened by human activities, in particular by the steady release of chlorofluorocarbons (CFCs) into the atmosphere. Despite international treaties, monitoring during the last 5 years shows that ozone is still globally declining. A record increase in the extent of the ozone hole over the Antarctic has occurred during October 2000. (Image: KNMI)