A cloud-free image of the Earth acquired by Meteosat
This Envisat image features the Galapagos Islands, an archipelago situated some 1000 km to the west of Ecuador in the Pacific Ocean. Galapagos’s largest island is Isabela (visible). The five volcanoes seen on the island are (from north to south): Wolf Volcano, Darwin Volcano, Alcedo Volcano, Sierra Negra Volcano and Cerro Azul Volcano. The bigger island to the right of Isabela is Santiago Island.
The image was obtained by combining three Advanced Synthetic Aperture Radar (ASAR) acquisitions (23 March 2006, 14 August 2008 and 1 January 2009) taken over the same area. The colours in the image result from variations in the surface that occurred between acquisitions. Apart from mapping changes on the land surface, radar data can also be used to determine sea surface parameters like wind speed, wind direction and wave height. Different wave types and wind speeds are visible in the image as ripples on the water surface.