Where will the satellite crash

At some point in the next few days, a satellite, heavy as a pickup truck and the size of half a diesel locomotive, will crash to earth. The debris will fall somewhere, maybe in the Pacific, maybe in the Sahara, maybe on Lake Constance.

There will probably be around 30 pieces of rubble, but possibly also a lump weighing several tons. One thing is certain: the fall cannot be steered or even prevented.

Basically, that's not unusual. At least six obsolete satellites have already fallen from the sky this year. They are burned, broken and have reached the ground in more or less large pieces. There was no damage, just as little as the two dozen burned-out rocket stages that fell back into the earth's atmosphere in 2011.

The satellite, which is set to crash back to earth between October 21st and 24th, is a German make - and a particularly massive one.

Rose is the name of the spacecraft. It used to search space for X-rays. It is the heaviest object ever lifted from Germany into space, almost nine meters long, 4.7 meters wide and weighing 2,426 kilograms. Up to 1.7 tons of the total mass could survive the fiery re-entry into the atmosphere.

"It can happen that someone is hit," says Johann-Dietrich W├Ârner, chairman of the German Aerospace Center (DLR). "Compared to the other everyday risks, however, the likelihood is so low that there is nothing to worry about."

The DLR experts calculated the probability that Rose hits German soil on re-entry. The risk of harm to a person in Germany is only 0.0014 per thousand. Worldwide, a person will be hit with a probability of 0.5 per thousand. Computers have calculated which populated and unpopulated regions lie under the orbit of the satellite and finally spit out such numerical values. It is an attempt to give a dimension to the tiny, inevitable risk.

You can control it Rose at least not for a long time. The X-ray observatory, which started in June 1990, was originally intended to hold out for 18 months. It was then almost nine years, a success story in space astronomy: As the first imaging telescope, has Rose scoured the entire sky for X-ray sources and created a map with 80,000 cosmic emitters. He studied the remains of exploded stars in detail and discovered for the first time that comets also emit X-rays.

Gradually, however, the instruments and controls on board quit their service. In 1998, the failure of a star sensor resulted in the observatory facing the sun and being irreparably damaged. Had to be blind and without electricity Rose finally abandoned on February 12, 1999.

Even at an altitude of 585 kilometers, in the Rose was originally on the move, existing air molecules have slowed the satellite slowly but surely over the years. Currently amounts to Rosats Altitude still almost 220 kilometers - tendency falling sharply.

"If the satellite reaches an altitude of 150 kilometers, one can assume that it will not stay up there for more than a day," says Heiner Klinkrad, head of the space debris department at the European Space Agency Esa in Darmstadt. Experience has shown that between 110 and 120 kilometers altitude, the next orbit around the earth goes steeply downhill. So within 90 minutes.