TerraSAR-X image shows spread of lava at Bardarbunga

The lava outflow on the Holuhraun field northeast of Iceland's Bardarbunga volcano continues unabated. 

The lava field has grown to cover an area greater than 25 square kilometres. 

In this satellite image, the extent of the lava field is revealed using different colours.

To create this image, three sets of data were acquired at different times, but from the same viewpoint, and then superimposed.

They date from 13 August, 4 September and 15 September 2014 and were acquired by the German radar satellite TerraSAR-X.

Yellow shows the growth of the lava field between 13 August and 4 September; red shows the expansion between 4 and 15 September.

It is obvious that the area has doubled. A second eruption area can also be seen as a small red spot in the lower right corner of the image.

Researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Remote Sensing Technology Institute (Institut für Methodik der Fernerkundung; IMF) are continuing to monitor the area.

Radar images can be used to analyse changes to Earth's surface throughout the entire process.

The DLR Earth Observation Center also measures the emissions of sulphur dioxide on a daily basis.

Bardarbunga sulphur dioxide cloud

TerraSAR-X image: Coastal cliffs of Christmas Island

In the image acquired with the German Aerospace Center TerraSAR-X radar satellite, one thing is clear - even today, tropical rainforest proliferates on the island and the coastal cliffs continue to make life difficult for mariners.

Christmas Island, which belongs to Australia, has principally been of interest in the past for its phosphate deposits - hence, its ownership has shifted from Britain to Japan, then back to Britain and finally to Australia.

The island is surrounded by some 80 kilometres of cliffs. The choppy waters of the surf on the south coast are not easy to image clearly for the radar on TerraSAR-X - the waves reflect the radar signals back to the satellite very irregularly.

It looks different in the bay between the only harbour on the island, Flying Fish Cove in the northeast, and West White Beach in the northwest: "When the image was acquired on 26 November 2012, the water there was apparently calm," explains mission manager Stefan Buckreuss from the DLR Microwaves and Radar Institute.

"The smooth surface reflects the signals away from the satellite, so it appears as a dark surface."

TerraSAR-X satellite: The Santorini volcano expands

Credit: DLR

British researchers have used images acquired by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) TerraSAR-X satellite to create a map showing changes in the Santorini archipelago. 

The cause of the deformation is the Santorini volcano located beneath the archipelago.

In some places, the Kameni Islands inside the flooded caldera have risen by eight to 14 centimetres. 

The breadth of the caldera as a whole has increased by about 14 centimetres since early 2011. 

In the analysis of the radar data, the red and yellow shading shows the areas where the ground has risen the most. The main island of Thira is unaffected by the deformation, thus appearing blue.

Glasses are rattling on the shelves and the ground is rumbling - since January 2011 the earth under the Santorini volcano has been stirring.

Most of the time, it is barely noticeable, but every now and then the inhabitants notice small tremors jolting the volcanic archipelago. Nearly circular, and seemingly carved from stone, the submerged caldera is located in the Aegean Sea.

"It was clear to the local people that something was happening with the volcano - but it wasn't until we saw, among other things, the images from the TerraSAR-X radar satellite that we realised that molten rock was pooling beneath the volcano," says British scientist Juliet Biggs from the University of Bristol.

Images acquired by the German Aerospace Center's (Deutsches Zentrum fur Luft- und Raumfahrt; DLR) satellite show the entire archipelago not just rising, but also expanding.

It has been 3600 years since a powerful explosion formed the large caldera. Since then, a new vent has been gradually forming in the middle of this basin, where today the Kameni islands protrude from the water.

The volcano last erupted in 1950 and then fell dormant again, so the scientists from Oxford and Bristol were all the more surprised when the inhabitants started reporting tremors.

"Tour guides, who often visit the volcano with tourists on a daily basis, told me there was an increase in the quantity of strong smelling gas being released by the summit," explains PhD student Michelle Parks. "The colour of the sea had changed as well."

Flying in formation, TanDEM-X and TerraSAR-X

Flying in formation, TanDEM-X and TerraSAR-X

Flying in formation, TanDEM-X and TerraSAR-X

Germany's second Earth observation satellite, TanDEM-X, was launched successfully on 21 June 2010 at 04:14 Central European Summer Time (CEST, at 08:14 local time) from the Baikonur Cosmodrome in Kazakhstan.

Atop a Russian Dnepr rocket, the satellite, weighing more than 1.3 tons and five metres in length, started its journey into orbit. At 4.45 CEST first signal was received via Troll ground station in the Antarctic.

Launch of Germany's Earth observation satellite TanDEM-X

The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) manages TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) via its ground segment, and is responsible for mission operations and for generating and utilising the scientific data.

"TanDEM-X is a key German project and will provide us with a homogeneous 3D elevation model of the Earth which will be an indispensable aid for a great many scientific and commercial avenues of enquiry," said DLR Chairman Prof. Dr Johann-Dietrich Wörner at the launch event held in the German Space Operations Center (GSOC) at the DLR site in Oberpfaffenhofen.

"This mission demonstrates Germany's expertise in satellite-based radar technology and is, in particular, the outcome of a consistent focus in the national space programme. Also, TanDEM-X demonstrates a successful public-private partnership," stressed Prof. Wörner.

Public-private partnership

TanDEM-X is being run as a public-private partnership (PPP) between the DLR Astrium GmbH, with DLR funding coming from the German Ministry of Economics and Technology. Infoterra GmbH, a subsidiary of Astrium, is responsible for the commercial marketing of the TanDEM-X data.

Astrium GmbH in Friedrichshafen built the satellite and is sharing the costs for its development and operation. The TanDEM-X mission has a total cost of 165 million Euros. DLR is contributing 125 million Euros and the European space company Astrium is contributing 40 million Euros.

TanDEM-X and its twin satellite, TerraSAR-X, will fly in formation

TerraSAR-X and TanDEM-X flying in close formation

Together with its twin satellite TerraSAR-X, in space since 2007, TanDEM-X will survey the entire land surface area of the Earth - a total of 150 million square kilometres - several times over.

It will accomplish this from an altitude of 514 kilometres within three years.

"This will be the first time we will ever have had a globally standardised 3D digital elevation model of Earth, and with a measuring point density of 12 metres, it will be incredibly accurate," said Prof. Dr Alberto Moreira, Science Director of the TanDEM-X mission and Director of the DLR Microwaves and Radar Institute.

Today, for large areas of Earth, there are only approximate, non-standardised or incomplete elevation models, and it is these gaps that the TanDEM-X mission is designed to fill.

To accomplish this, TanDEM-X and TerraSAR-X will fly just a few hundred metres apart and will constitute the first configurable synthetic aperture radar (SAR) interferometer in space.

With a conventional SAR, the radar on the satellite transmits microwave pulses that are reflected by the surface of the Earth and received back by the radar.

The distance between the satellite and the Earth's surface is calculated from the time it takes the signals to return.

Since the satellite is moving around the Earth, the radar 'illuminates' a strip along the ground, which gives the radar its synthetic aperture, much larger than its real one.

With SAR interferometry, a geographical area is imaged from two different viewing positions, giving different perspectives. This is similar to the way humans use their two eyes to get an accurate, 3D image.

The two 'radar eyes' are on the satellite duo TanDEM-X and TerraSAR-X, and produce an interferogram from the different distances the signals have to cover; elevation data is derived from this

Within three years, this will create a gigantic data record equivalent to the storage capacity of 200 000 DVDs. TanDEM-X is designed for a service life of at least five years and is scheduled to overlap the scheduled service life of TerraSAR-X for at least three of those years.

Satellite-based Earth measurement creates a globally homogeneous terrain model without interruptions at national borders or other inconsistencies (compared with aircraft-based measurements).

Radar can see through bad weather and operates regardless of lighting conditions. Today, this process is without competitors and enjoys considerable respect, especially in the USA.