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Envisat

Oil from the wrecked tanker off the northwest coast of Spain had already reached the Spanish coast when ESA’s Envisat satellite acquired this radar image of the oil slick, stretching more than 150 km, on Sunday, 17 November, at 10.45 UTC.

The 26-year-old tanker, Prestige, can be seen as a bright white point located about 100 km off the coast. Support vessels are identifiable as smaller white points surrounding the ship. The huge oil slick is clearly visible as a dark plume emanating from the stricken ship and stretching to the northwest coast of Spain.
The image was captured by the Advanced Synthetic Aperture Radar (ASAR) onboard the Envisat spacecraft, launched by ESA last March. The ASAR was operating in its wide-swath mode covering an area approximately 400 km by 400 km. Press reports indicate that oil has already fouled a 200-km stretch of Spanish coastline.

ASAR, like other space-based radar systems, essentially provide its own source of illumination and operates at longer wavelengths than optical sensors. This enables it to observe the earth surface at night and through thick cloud cover. This unique capability allowed Envisat’s ASAR to “see” the oil leaking from the tanker despite heavy rain and cloud cover in the region that hindered the coverage of optical instruments.

The ASAR acquisition was scheduled on an emergency basis for Sunday 17 November. Envisat, along with ESA’s ERS-2 spacecraft, will continue to acquire images for the next few weeks over the Galician coast.