Astronaut Photography from ISS: Unique Observations of the Earth
Part 1: Unique images of Earth not available from any other source.
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Mount Etna Eruption, Detail:

This image of Mount Etna erupting on Sicily was taken just a few seconds after the previous image. The plume height was approximately 6400 meters above the summit, or roughly 9000 m above sea level.

Why is this image unique?: By using a higher-magnification lens, the astronaut was able to capture a detailed image that shows a three-dimensional profile of the eruption plume, but still provide enough context for interpreting the structure. Lighter colored plumes down slope of the summit are produced by gas emissions from a line of vents on the mountainís north flank.

Even aircraft cannot obtain images with this level of detail. The scale of the eruption is too large for airplane observations. And, because ash can severely damage aircraft engines, pilots avoid active eruptions. Images taken by astronauts of large eruptions have been used in joint studies by the USGS and the FAA to help define the volcanic hazards posed to aircraft and air routes.

ISS crewmembers can use a variety of look angles and lenses to choose the best way to record their observations of the Earth, and make the equipment changes in seconds. Astronauts on the Space Station often document volcanic eruptions before information about them have moved beyond the local area to the international press.

Wide view of Mt. Etna eruption >>

ISS005-E-19024, 30 October 2002, 800 mm lens
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References: USGS Bulletin 2047 Volcanic Ash and Aviation Safety