TerraSAR-X - Bonneville Salt Flats
Clouds, darkness, rain - the radar 'vision' of TerraSAR-X is unaffected by these conditions. Dark and light areas contrast clearly in this image, acquired by the German Aerospace Center's (Deutsches Zentrum für Luft- und Raumfahrt; DLR) TerraSAR-X satellite.
The black areas represent water, where radar signals transmitted by the satellite are not returned, as they are reflected away by the smooth surface of the water. The city of Wendover is conspicuous in the upper half of this space radar image. "These are not lights shining. The radar is detecting a strong increase in the local variance of the return signal," explains DLR researcher Daniel Schulze. The reason for this is that the colouring of the image is based on a statistical assessment of the data set, where the variance in the roughness of the surface is colour-coded. Hence, built-up areas appear rough to the radar and appear orange, as there is a high probability that the radar signal will find its way back to the satellite following direct or multiple reflections off the buildings and streets.
The Bonneville Salt Flats is the largest salt pan lying to the west of the Great Salt Lake, in the northern part of the US state of Utah. The salt pan arose towards the end of the last ice age as a consequence of Lake Bonneville drying up. This was a prehistoric lake that stretched across a large section of the major basin to the west of the Rocky Mountains, and of which only the Great Salt Lake now remains. The former Bonneville Lake is history; today the salt flats stretch out over an area of some 10,360 square kilometres.
TerraSAR-X circles the Earth in a polar orbit at an altitude of 514 kilometres. Its active array antenna enables it to provide radar data with a resolution of down to one metre, regardless of weather conditions, cloud coverage and availability of daylight. It acquired this unique image at 13:40 local time on 23 June 2009. The scene measures 50 by 30 kilometres. TerraSAR-X also cast a penetrating eye on the around 2000-metre-high mountains and the salt lake, which lies at an altitude of some 1270 metres. The image shows rough surfaces in orange and smooth ones in grey/black.
View the full resolution image.
Credit: DLR - German Aerospace Center