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Production of a satellite image. Four images of the Camargue region, France, are used to demonstrate the method by which a satellite produces a natural colour image. The satellite records light in the wavelengths of each of the primary colours: red (top right), blue (top left) and green (bottom left). These are then combined to produce the image in the bottom right. The Camargue is the delta of the River Rhone. It contains large brine lagoons and is important for birdlife. (KEYSTONE/SCIENCE PHOTO LIBRARY/PLANETOBSERVER)