Earth from Space: Envisat radar mosaic of Europe

This mosaic of Europe was produced using 143 images acquired by Envisat’s onboard Advanced Synthetic Aperture Radar (ASAR) instrument, working in wide swath medium resolution (WSM) mode, between January and May 2006.

White and greyish spots on the mosaic indicate urban cities, with Paris, London, Dublin, Berlin, Lisbon, Vienna and Madrid being particularly evident. Mountain ranges, including the Alps, Apennines and Pyrénées, are also visible, as is Mount Etna.

The Earth observation Grid team of ESA’s Grid Processing on Demand department produced the mosaic in just 18 hours due to the ability of the Grid-based system to distribute the processing load over many computers.

Of Envisat’s 10 onboard instruments, ASAR is the largest. It was built to provide continuity with the Synthetic Aperture Radar (SAR) sensors, which contributed to major scientific achievements, onboard ESA’s ERS-1 and ERS-2 satellites.

Envisat’s ASAR instrument uses radar beams to map the surface of the planet below, with several different modes that allow broad views or detailed snapshots. It is able to map the shape of the land, profile waves and ice, monitor land use and types of vegetation and measure some of the properties of the surface.

The sensor monitors Earth in two different modes: Global Monitoring Mode (GMM), which provides 400-kilometre swath one-kilometre resolution images, and Wide Swath Mode (WSM), which possesses the same swath but with 150-metre resolution for a detailed view of areas of particular interest. Approximately 10 Gigabytes of ASAR WSM products are acquired daily and processed at ground stations in near-real time.

ASAR GMM images are routinely provided to a variety of users, including the US National Oceanic and Atmospheric Administration (NOAA) National Ice Centre, responsible for tracking icebergs worldwide.

ASAR imagery is also being used operationally to track icebergs in the Arctic by the Northern View and ICEMON consortia, which provide ice-monitoring services as part of the Global Monitoring for Environment and Security (GMES) initiative, jointly backed by ESA and the European Union.

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