Photos of Possible ROSAT Fragments

The ROSAT system of mirrors, composed by four nesting Wolter mirrors with a focal length of 2.4 meters.Each of the ring-shaped mirrors measures 50 centimeters in length, and the largest has a diameter of 84 centimeters - (Credits: MPE).

According to German space agency DLR, the 2.4-ton Roentgen Satellite (ROSAT) is expected to reenter Eart’s atmosphere by October  22 or 23, about a month after the reentry of NASA’s UARS, which occurred in September 24, 2011. The actual time cannot be predicted until the very last moment, due to variations in the tumbling satellite geometry (also photographed from the ground) and  fluctuation in solar activity.

The satellite will break up into fragments, some of which are expected to survive reentry and crash on the Earth’s surface. A study predicts that up to 1.6 tons of satellite fragments, more than half of the spacecraft’s mass, could reach Earth’s surface. Is has been estimated that as many as 30 individual pieces could make to the ground. The heaviest component that may survive is the satellite’s X-ray optical system, whose mirrors and mechanical support is a massive structure made of carbon-fiber reinforced composite.

According to German space officials, there is 1-in-2,000 chance that debris from the satellite could hit someone on Earth. So far, only a single case have been reported of a person who has been hit by a space debris. The strike zone of the satellite’s re-entry extends to 53 degrees northern and southern latitude: though most of the debris are likely to hit the ocean track of the satellite, isolated fragments could descend to Earth in a 80-kilometer swath along that track. The impact speed can reach about 450 kph. Falling debris can be also extremely dangerous to aircrafts: on September 24, 2011, the Federal Aviation Administration (FAA) issued a NOTAM as NASA UARS satellite was approaching Earth’s atmosphere.

The ROSAT is equipped with two four-wire Position Sensitive Proportional Counters detectors (PSPC) - (Credits: MPERosat).

The ROSAT project was developed jointly by Germany, the United States, and the United Kingdom. The launch was procure by the Deutsches Zentrum für Luft- und Raumfahrt (DLR), the Germany’s space agency. Launched on June 1, 1990 on top of a Delta II rocket, the spacecraft operated successfully for nearly nine years, until February 12, 1999. The spacecraft is completely inert, so it can’t be contacted or directed into a controlled reentry.

The satellite is being tracked by  the U.S. Space Surveillance Network and by the Tracking and Imaging Radar, the large radar facility at the Fraunhofer Institute for High-Frequency Physics and Radar Techniques in Wachtberg near Bonn. You can track the satellite trajectory in real time at website.

Video, below, you can see an artistic impression of the reentry of UARS.

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About the author

Andrea Gini

Andrea Gini

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Andrea Gini is a scientific journalist and a professional of the space industry, working as a contractor on ISS Payload Safety. He is the Editor-in-chief of the Space Safety Magazine. Andrea is also Chairman of the Information and Communication Committee of the International Association for Advancement in Space Safety (IAASS), publisher of the Space Safety Magazine, and he is responsible for the communication strategy of the association, Andrea holds a BSc and an MSc in computer science from the University of Milano, a Master in scientific journalism from the International School for Advanced Studies of Trieste and a MSc in Space Studies from the International Space University.