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ERS monitors Mount Etna - July 2001
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ERS Monitors Mount Etna - July 2001

The latest data from ERS-2 give a set of complementary views on the recent activity on mount Etna. ERS continues to monitor Etna in terms of small movements, temperature and gas emissions using its multiple sensors to see many aspects of the ongoing eruptions.

The Global Ozone Monitoring Experiment (GOME), one of the ERS instruments, provides information on trace gas levels in the atmosphere. Recent images show that the levels of sulphur dioxide released from the volcano are up to 10 times the normal concentrations. The area of high concentration covers an area almost the size of Germany, and traces can be found up to 1000km away.

The Along Track Scanning Radiometer (ATSR), another ERS instrument, which measures the temperature of the earth's surface, shows clearly the plume of smoke arising from the volcano; nighttime images show particularly well the extent of the lava.

The Synthetic Aperture Radar (SAR) is the highest resolution sensor onboard ERS; it is able to show the movements of lava from the volcano. Using precise techniques known as interferometry SAR has been able to monitor the movements of Etna for over 10 years including the eruption in 1993.
A digital terrain model of the volcano and measurements of geophysical parameters, such as the volcanic mouth deflation, were already generated in 1995 by making use of complex interferometric techniques applied to ERS SAR images.

Current ERS-2 SAR image data are being collected and processed to analyse the current eruption.

The ATSR and GOME images together demonstrate that the visible plume of the volcano (consisting of water vapour and dust) has a far smaller extent than the chemical pollution in the atmosphere.

In the framework of the International Charter on Space and Major Disasters, ESA has been requested to monitor the ongoing activity of Etna by the Italian Civil Protection authorities. This request means that the sensors on board ERS are commanded to give priority to monitoring the volcano's activity to provide precise and timely information for decision makers.

In the near future, ENVISAT, ESA's next satellite for environment monitoring, will continue with observation of Mount Etna. ENVISAT data will provide scientists with improved tools, complementary to the ones used on the ground for volcano monitoring.

(Click on the thumbnail images to see them at a higher resolution)

Etna seen from ATSR

ERS-2's ATSR instrument shows clearly the plumes of smoke from the volcano. The following thumbnail images show the volcano by day and by night using various channels from the ATSR-2 instrument flown onboard the ERS-2 satellite.

The two images to the left show the volcano on the 21st and 24th of July. These daytime images are a false colour combination of the 11 micron e 1.6 micron channels to highlight the extent of the plume of the volcano.

The image to the left shows details using the infrared and 11 micron channel. The plume of smoke is very evident in the image due to the temperature difference between the smoke and the sea. Interestingly, the smoke is cooler than the sea - much like the vapour trails that follow a jet aircraft.

This image was taken at night and is made from two channels, the infrared 3.7 micron and the 11 micron channel. The 3.7-micron channel shows distinctly the extremely high temperature of the lava.

Etna seen from GOME

Scientists of the German Space Agency (DLR) in Oberpfaffenhofen have been monitoring the eruptions of the Etna volcano since Mid of July with the GOME instrument on board ERS-2. The satellite data show a region southeast of Sicily, where the atmosphere is polluted with a concentration of sulphur dioxide (S02 ) up to 10 times higher than normal. To give an idea of the scale, the size of the area of dense concentration is close in size to that of Germany.

GOME Data Processor - SO2 retrieval

    12-14 July 2001             22-24 July 2001    

    0                                                       2 DU    

Area covered by enhanced SO2

Values approx. 1000 km x 300 km

Maximum values up to 3.1 DU ± 0.75 DU

Author: W. Thomas

The toxic sulphur fumes, which are also partially responsible for acid rain, have erupted up to a height of 3 to 5 kms. The biggest extent of the area of smog was on the 25 of July. Due to the constant northwest wind over the days of Etna activity the high S02 concentration can be measured as far as the south of Tobruk in North Lybia about 1000 km away from Etna.

Etna seen from SAR

Digital Elevation Model (above) of Mount Etna, Sicily, derived from ERS-1 and ERS-2 interferometric image pairs.

Interferogram (above) of Mt. Etna derived from ERS-1 and ERS-2 Synthetic Aperture Radar data 1-2 August 1995

Related links:

» The ESA EarthWatching pages show the regular planning of the ERS-2 satellite to monitor special events and natural disasters, including satellite imagery relating to the Etna eruption.

» An extensive study on using ERS SAR interferometry and thermal data to monitor the Etna volcano has been prepared under the Empedocle Project: Monitoring Mount Etna by Space Techniques.

» The EOLI interface to ESA's full catalogue of earth observation images provides a list of ESA's archive of images, the ESASets tab allows you to quickly find the data from 2000 and 2001.

» The ERS homepage provides more information on all aspects of the ESA ERS satellites and their instruments.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry