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Volcanic monitoring
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The world's oldest volcano observatory has added satellites to its repertoire of instruments to monitor volcanic features flanking Naples. The result has been the most detailed view ever of ground motion in this vicinity.
When it was founded back in 1841, the Vesuvius Observatory of Italy's National Institute of Geophysics and Volcanology was the world's first scientific institution devoted to volcanoes. Now its remit is more than simply scientific: the Observatory's 24-hour volcanic and geophysical monitoring makes it an official reference point for local and national civil protection authorities.

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The historical site of the Observatory is located on the slopes of the active Vesuvius volcano, which stands east of the city of Naples and its surrounding metropolitan areas – the vulnerable home of three million people. To the west is another, unrelated volcanic feature, the cratered, smoky landscape of the Phlegrean Fields (known in Italian as Campi Flegrei).
"Considering this frequency of field measurements, our need is to retrieve information with a higher temporal sampling. Use of satellite data allows optimal coverage in both space and time – every 35 days in the case of ERS-2 or Envisat, against once or twice a year with GPS and levelling techniques." -Sven Borgström of the Vesuvius Observatory.
Using radar images from ESA's ERS-2 satellite and applying Synthetic Aperture Radar (SAR) Interferometry, or InSAR for short, which involves mathematically combining two or more radar images of the same site. Any change to the total signal distance travelled (to the surface and back again) causes a shift in signal phase, leading in turn to rainbow-coloured interference fringes that run like contour lines across the resulting interferogram.

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