DLR Portal: FAQ on ROSAT mission

Since its launch on 1 June 1990, friction due to Earth's upper atmosphere has been causing the X-ray satellite ROSAT to lose altitude continuously.

When the spacecraft re-enters the atmosphere, which is expected to occur in October 2011, the satellite will disintegrate and most of the fragments will burn up in the extreme heat caused by atmospheric friction.

This FAQ provides answers to the most common questions about the ROSAT mission and its re-entry.

DLR Portal Images of ESA Soyuz Liftoff: Galileo Satellites

DLR Portal Images of ESA Soyuz Liftoff: Galileo Satellites

ESA DLR: ROSAT re-entry

At the start of its mission, the ROentgen SATellite (ROSAT) performed its observations in an elliptical orbit at distances of between 585 and 565 kilometres above the surface of the Earth. Since then, atmospheric drag has caused the satellite to lose altitude.

In June 2011, it was at a distance of only about 327 kilometres above the ground. Due to the fact that ROSAT does not have a propulsion system on board, it was not possible to manoeuvre the satellite to perform a controlled re-entry at the end of its mission in 1999.

When the spacecraft re-enters the atmosphere at a speed of approximately 28,000 kilometres per hour, the X-ray observatory will break up into fragments, some of which will burn up by the extreme heat.

The latest studies reveal that it is possible that up to 30 individual pieces weighing a total of 1.6 tons may reach the surface of the Earth. The largest single fragment will probably be the telescope's mirror, which is very heat resistant.

The time and location of re-entry cannot be predicted precisely. At present, scientists expect the X-ray satellite, which completes an orbit around Earth in about 90 minutes, to re-enter around the beginning of November, 2011.

Currently, this date can only be calculated to within plus/minus five weeks.This time slot of uncertainty will be reduced as the date of re-entry approaches.

However, even one day before re-entry, the estimate will only be accurate to within plus/minus five hours .All areas under the orbit of ROSAT, which extends to 53 degrees northern and southern latitude could well be affected by its re-entry.

The bulk of the debris will impact near the ground track of the satellite. However, isolated fragments could fall to Earth in a 80 kilometre wide path along the track.

Read More of this story here at DLR Portal

ESA ROSAT Satellite: Fall to Earth in November

Another dead, drifting satellite will fall to Earth in November, following UARS, the U.S. satellite that showered pieces over the Pacific Ocean last month, experts say.

Officials at DLR, the German Aerospace Centre, say ROSAT, a decommissioned X-ray space observatory, should enter the atmosphere sometime in early November, but exactly when and where debris from the satellite will land cannot be determined yet.

The 2.4-ton ROSAT satellite is in an orbit that swings between 53 degree of latitude north and south, so any debris surviving its re-entry could land anywhere in a huge area of the Earth, officials said.

The dead satellite is being tracked, but any prediction about the exact time and place of its fall will remain uncertain until roughly 2 hours before it hits Earth, they said.

"It is not possible to accurately predict ROSAT's re-entry," Heiner Klinkrad, head of the Space Debris Office at the European Space Agency, said. "The uncertainty will decrease as the moment of re-entry approaches."

However, he said, it would be possible to rule out certain geographical regions from the potential impact area about a day in advance.

DLR Portal - Early bird special – watch the TanDEM-X launch live

DLR Portal - Early bird special – watch the TanDEM-X launch live



TanDEM-X, Germany's new Earth observation satellite, is scheduled for launch on Monday, 21 June 2010 at 04:14 CEST. Together with its twin, TerraSAR-X, TanDEM-X will survey all 150 million square kilometres of Earth's land surface several times during its three-year mission. We will stream the TanDEM-X launch live from the Baikonur Cosmodrome in Kazakhstan, as well as an exclusive infotainment programme from the control centre in Oberpfaffenhofen, Germany.