Four years on, Envisat hailed for its contribution to Earth science   Climate change     Envisat's Advanced Along Track Scanning Radiometer (AATSR) continuously monitors sea surface temperature to an accuracy of a few tenths of a degree. This is a false-colour representation of AATSR results over the Atlantic, with blue corresponding to coldest waters and red the warmest. Ice monitoring     This ASAR Wide Swath Mode image, acquired on 15 April 2005, shows a broken off section of the Drygalski ice tongue after the side of the B-15A iceberg struck it. Atmospheric monitoring     The image shows the global mean tropospheric nitrogen dioxide (NO2) vertical column density (VCD) between January 2003 and June 2004, as measured by the SCIAMACHY instrument on ESA's Envisat. The scale is in 1015 molecules/cm-2. Image produced by S. Beirle, U. Platt and T. Wagner of the University of Heidelberg's Institute for Environmental Physics. Earthquake monitoring     This interferogram shows ground motion associated with the 26 December 2003 earthquake at Bam in Iran. The interferogram was created by combining an Envisat Advanced Synthetic Aperture Radar (ASAR) Wide Swath Mode (WSM) image with an Image Mode (IM) image. Typically IM is the sole ASAR mode exploited for interferography; making use of WSM in this way has the potential to broaden Envisat's InSAR coverage in future. Processed by Politecnico of Milano. Coastal monitoring     Envisat demonstrates the power of two, with combined optical MERIS and radar ASAR views of the eye of Hurricane Katrina acquired 28 August 2005 over the Gulf of Mexico. The MERIS imagery shows the swirling cloud-tops of the storm, while the ASAR image pierces through the clouds to show the shape of the wind-driven sea surface. Providing almost real-time data     This Envisat ASAR wide-swath image acquired 17 November 2002 shows a double-headed oil spill originating from the stricken Prestige tanker, lying 100 km off the Spanish coast. Future of Envisat     Launched in 2002, Envisat is the largest Earth observation satellite ever built. Release date: 1 March 2012