Viewed from above, the US 'Burning Man' festival resembles a spider web. The structure laid out on the site for this festival looks very much like a small town. In October and September 2011, the TerraSAR-X radar satellite, operated by the German Aerospace Center (Deutsches Zentrum fur Luft- und Raumfahrt; DLR), acquired some impressive images of the festival and its setup process.

Seen from space, the plots in the campsite, intersected by roads and footpaths, can be discerned particularly well. DLR researchers are observing planet Earth with the radar satellite TerraSAR-X.

"One of the unique capabilities of TerraSAR-X is to reveal changes on the Earth's surface that occur over an extended period of time," explains Mission Manager Stefan Buckreub from the DLR Microwaves and Radar Institute.

From these images it is possible to identify how 'Tent City' arose in a semicircle around its central point. Every 11 days at 06:57 local time, TerraSAR-X was able to observe the festival from exactly the same viewing angle.

To make this possible, the satellite orbits Earth at an altitude of 515 kilometres in a Sun-synchronous dusk/dawn orbit, causing it to cross the Equator at almost a right angle. Earth continues to rotate beneath it, meaning that the satellite is able to scan its entire surface every 11 days.

Small details despite great altitude

Despite the great altitude of its orbit, the satellite is even able to identify individual cars. "Artificial structures such as tents and vehicles present themselves almost at right angles to the radar, which means that they reflect the signal straight back to the satellite," explains Buckreub.

They are easily identifiable in an otherwise natural environment. "We have also coloured them, so that they can be seen well," explains the Mission Manager - referring to the red and yellow dots in the image. The white areas are part of the neighbouring mountains, which reflect a particularly high proportion of the radar signals back to the satellite.

In contrast, flat ground only reflects a very small proportion of the signal, so it appears as dark grey; the majority of the signal is diffusely scattered. Smooth, man-made structures such as roads reflect radar signals away from the satellite and appear black in the image.

'Burning Man' is no ordinary festival. There are no large stages, nor are there any big bands; nevertheless, it is extremely popular. More than 50,000 people gather in the Nevada desert over the course of the six days in early September when it is held. Every year, they establish themselves in a new location to seek freedom and self-reliance.

Nevada's dry Black Rock Desert comes to life some weeks before the actual start of the festival. It ends with the burning of a larger-than-life effigy made of wood and straw, from which the festival gets its name.