ESA - Eduspace EN - Global Change - The Islands of Kerguelen

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The Islands of Kerguelen

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Adelie Penguins

Two days after leaving Crozet, Lauren and Didier reached Kerguelen, located at 49-20 South and 70-13 East. The 'Kapitan Khlebnikov' icebreaker arrived on 13 November.

Besides penguins and seabirds, on these remote islands you may also encounter some scientists. There are around 300 islands in total, all of which are of volcanic origin. The highest point is Mont Ross, the glacier dome in the west of the main island, at 1 960 metres.

The plant species of the Kerguelen Islands is thought to have been brought from South America, rather than from comparatively nearer Africa. Can you guess why?


	Seals

The island was discovered in 1772 by the French navigator Yves Joseph de Kerguélen-Trémarec, and was also visited by Captain James Cook.

Let's briefly study the islands by comparing two satellite images provided by Envisat's ASAR radar and Landsat's visible infrared.

Radar image of Kerguelen Islands
The radar image is merely black and white, while the visible infrared one is coloured.
It is coloured because reflecting light in red, green, blue and infrared were captured separately and later combined to produce both a natural and artificial colour picture.

The radar microwave instrument, on the other hand, only has one band. But the oblique viewing of the radar enhances the morphology drastically, and we can appreciate the landforms much better.

Try to map out the different parts of the island. The flat eastern part, the strangely 'curved' rock formations in the centre, and the rugged terrain with the glacier dome in the west. Why does it appear nearly black in the radar image?


	Landsat image of Kerguelen Islands (infrared)

Think about a sea surface on a calm day – it is dark as well, because the surface is smooth. Snow, especially when wet, also represents a smooth surface for radar. But you might also recognise some glacier tongues to the east of the mountain - they are snow-free and crevassed, hence rough. This is revealed by their grey colour.


Radar stereo image of Kerguelen Islands

During the journey, Envisat experienced some technical problems, and missed taking an image of Kerguelen. We therefore asked for the satellite to be reprogrammed. The people in charge agreed and provided us with two images, both taken in late December 2003. They were acquired on two different orbits, but since the imaged strip was 400 km large, the Island of Kerguelen was visible on both.

We combined both images to produce the ASAR-Kerguelen_stereo – image. Use red-green glasses to see the island in 3-D. If you invert the colours using the LEOWorks image processing software, the stereo effect is even stronger.

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