Posted on by Nancy Atkinson

ROSAT’s Crash Site Determined

A few days before re-entering Earth's atmosphere, the German X-ray research satellite ROSAT was targeted by the Tracking and Imaging RAdar (TIRA) at the Fraunhofer Institute for High Frequency Physics and Radar Techniques in Wachtberg, near Bonn, which is unique in Europe. TIRA is part of a global network of monitoring stations that collected data about ROSAT. From this data, the orbit was determined and images were produced. This example, acquired on 20 October 2011, clearly shows the antenna mast of the satellite. Credit: Fraunhofer FHR.

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The German Aerospace Center (DLR) has identified the ROSAT’s satellite final resting place as the Bay of Bengal, off South Asia. The minivan-sized satellite re-entered the atmosphere at 0150 GMT on Sunday, October 23, 2011 (9:50 p.m. EDT on Oct. 22) and any pieces of the 21-year old satellite that survived the fiery trip likely crashed into the water. However, the ROSAT_Re-entry Twitter feed reports there is still some ambiguity, and re-entry likely took place sometime between 01:50 and 01:51, with error bar of plus or minus 7 minutes. That could make a huge difference in where debris landed. (Updated with new map, below.)

No sightings of any debris have been reported. Most of ROSAT’s parts were expected to burn up in the atmosphere, but up to 30 fragments weighing a total of 1.87 tons (1.7 metric tons) may have crashed.

Map posted by ROSAT_Reentry Twitter feed, which indicated locations on re-entry path, +/- 7 mins. Still ambiguity between 01:50 and 01:51 locations

The Bay of Bengal is located between India and Myanmar.

Yesterday, some estimations put the satellite as possibly re-entering over Northern Thailand, but again, no debris was reported. DLR now says the more precise determination of the time and location of re-entry was based on the evaluation of data provided by international partners, including the USA’s Space Command.

“With the re-entry of ROSAT, one of the most successful German scientific space missions has been brought to its ultimate conclusion. The dedication of all those involved at DLR and our national and international partners was exemplary; they are all deserving of my sincere thank you,” said Johann-Dietrich Wörner, Chairman of the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Executive Board.

Source: DLR

Posted on by Nancy Atkinson

ROSAT Satellite has Re-Entered; No Reports of Debris

Initial reports said ROSAT fell sometime during this track. Credit: DLR and ROSAT_Reentry Twitter.

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It’s official: the ROSAT satellite has come down. The Deutsches Zentrum für Luft- und Raumfahrt (DLR), the German Space Agency confirmed the satellite plunged to Earth sometime between 1:45 UTC and 2:15 UTC on Oct. 23, 2011 (between 8:45 and 9:15 EDT Oct. 22) There is currently no confirmation if pieces of debris have reached Earth’s surface.

Update: US Strategic Command estimates an entry time of 1:50 UTC +/- 7 Minutes. This entry time would put the satellite in the Indian Ocean, and not over China as reported below. The DLR said that after further analysis they should be able to provide more information about exactly where the debris hit.

The @ROSAT_Reentry Twitter feed posted the picture above, indicating the satellite’s fall occurred sometime during the groundtrack shown.

Other reports via Twitter from skywatchers around the world had no sightings of any lit debris falling, or any actual sightings of the satellite passing overhead since 23:30 UTC on Oct. 22. Some news reports say it could have re-entered over China, but it likely didn’t make it as far as Korea or Japan.

We’ll provide more information when it becomes available.

ROSAT Satellite. Credit: DLR

Posted on by Nancy Atkinson

Latest Update on ROSAT Satellite: Uncontrolled Re-Entry on Oct. 22 or 23

This latest video rendering from from Analytical Graphics, Inc. (AGI) shows ROSAT’s current orbit, the satellite’s ground track, and the estimated model of the break-up and debris scattering. Deutsches Zentrum für Luft- und Raumfahrt (DLR), the German Space Agency has now refined the re-entry to sometime between October 22 and 23, 2011, plus or minus one day. DLR says this 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.

The orbit extends from 53 degrees northern and southern latitude, and all areas in that region could be affected by its re-entry. The bulk of the debris will impact near the ground track of the satellite, but larger parts of the satellite, including its 32 inch, 400 kg mirror, could fall to Earth in a 80-kilometer-wide path along the track.

Update: A report from the ROSAT_Renetry Twitter feed posted at 18:00 UT on October 20 said they expect re-entry in 64 hours. “ROSAT orbit 88.58 minutes 196.8 x 201.7 km, Position 26.6S,164.0W alt=203.2km Lit ~Re-entry 64 hours”

We’ll provide more updates as they become available. You can check the DLR ROSAT webpage for more updates.

Posted on by Nancy Atkinson

Video: Thierry Legault Captures the ROSAT Satellite Just Before Re-Entry

Compare the view of the ROSAT satellite, as seen from Earth on September 23 and October 16, 2011. Credit: Theirry Legault. Used by permission.

I was waiting for this, and I know our readers have been looking forward to seeing astrophotographer Thierry Legault’s images of the ROSAT satellite as it heads towards its uncontrolled re-entry through Earth’s atmosphere to its ultimate demise. Legault took a series of images on October 16, 2011 from France and combined them into a video. The speed of the sequences is accelerated 3 times with regard to real time (30 frames per second vs 10 fps). The distance to observer is 275 km, with the altitude of the satellite at 235 km. Angular speed at culmination: 1.66°/s.

“It looks very steady, no sign of tumbling or flares like UARS,” Legault told Universe Today via Skype.

You can compare it to earlier images taken by Legault on September 23, 2011, below.

This remarkable video was taken with a 14” Schmidt-Cassegrain telescope using a specially made tracking system developed by Legault and Emmanuel Rietsch. You learn more about the system as Legault’s website.

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Legault said he drove 100s of kilometers in order to capture ROSAT, and had to deal with clouds and fog before successfully imaging the satellite.

The latest prediction put out by the German Space Agency (DLR) has the ROSAT satellite re-entering sometime between October 21 and 24. This is a slightly narrower time window than the last prediction, which lasted until October 25. We’ll keep you posted on when and where the pieces of the satellite might fall. Legault told Universe Today that he is hoping ROSAT will provide some nice fireworks right over his location in France!

The video below, taken by Legault on September 23, 2011 at 04:36 UT shows ROSAT at an altitude of 284 km, with distance to observer at 458 km. Angular speed at culmination: 0.94°/s.

See Legault’s website for more information and images.

Posted on by VirtualAstro

ROSAT – Fiery Debris To Rain From The Sky

ROSAT Credit: NASA

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The recent re-entry of the UARS satellite was not the end of falling satellite debris, as the German ROSAT X-ray observatory satellite will soon crash back to Earth.

Last month NASA’s large UARS satellite re-entered the atmosphere and burned up over the Pacific Ocean, with about 500 kg of debris falling into the water. But the smaller Roentgen Satellite or ROSAT will have approximately 30 pieces equaling 1.5 tons that will resist burn up and make it to the surface.

The largest piece of the satellite expected to reach the surface is the heat-resistant, 32 inch, 400 kg mirror.

Compared to UARS, there is an increased chance of someone being hit by a piece of the falling debris. The odds have been estimated as a 1 in 2,000; UARS was 1 in 3,200.

As with UARS, it is unknown where ROSAT will burn up and where its remaining parts will impact the surface, however the satellite is expected to re-enter between the 21st and 24th of October. The Center for Orbital and Re-Entry Debris studies predicts October 23, 2011 a 06:40 UTC ± 30 hours.

For up to date predictions check the Centre for Orbital and Re-Entry Debris Studies.

Prediction Ground Track Credit: Center for Orbital and Reentry Debris Studies

Until then, you can keep an eye out for the small satellite as it is a naked eye object. It’s nowhere near as bright as the ISS, but it is visible. Check Heavens Above or Spaceweather for predictions of when it will pass over your location.

The 2.4 ton Roentgen Satellite (ROSAT) was launched by NASA in 1990 as a joint venture between Germany, Britain and the USA.

The satellite was designed to catalogue X-ray sources in deep space and mapped around 110,000 stars and supernovae. It also discovered that some comets emit X-rays. It was permanently damaged in 1998, and its mission was officially ended in February of 1999.

ROSAT will soon meet its fiery end; will you see it pass over before then?

Keep an eye out for that falling mirror.

Credit: NASA
Posted on by Nancy Atkinson

German ROSAT Satelite Heading Towards Uncontrolled Re-Entry to Earth

A sample of 3 consecutive ROSAT orbits. Credit: DLR

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Here we go again: A satellite without a propulsion system is set to crash to Earth later this month, and officials can’t predict exactly when or where it will fall. This is not the second coming of NASA’s UARS (Upper Atmosphere Research Satellite) but a German X-Ray observatory named ROSAT (ROentgen SATellite), which will likely plummet through Earth’s atmosphere sometime between October 20 and 25, plus or minus 3 days.

Due to fluctuations in solar activity, “the time and location of re-entry cannot be predicted precisely,” the German Aerospace Center (DLR) said in a statement on their website.

Coming in at about 28,000 kilometers (17,000 miles) per hour, DLR said the satellite will break up into fragments, with possibly up to 30 individual pieces weighing a total of 1.7 tons reaching the surface of the Earth. The largest single fragment will probably be the telescope’s mirror, which is very heat resistant and weighs about 1.7 tons.

German officials said there is a 1-in-2,000 chance that debris from the satellite could hit a person on Earth, and added the chance any a German citizen would be hit about 1 in 700,000. They did not include the odds of any one specific person on Earth getting hit by debris, but for the UARS satellite, it was estimated at about 1 in 21 trillion.

Like the UARS satellite, ROSAT’s orbital track takes it over much of Earth’s oceans.

An artist's impression of ROSAT in orbit. Credit: DLR

ROSAT is about the size of a car, and during its mission was in an elliptical orbit at distances of between 585 and 565 kilometers above the surface of the Earth. It was decommissioned in 1999, and since that time, atmospheric drag has caused the satellite to lose altitude. In June 2011, it was at a distance of only about 327 kilometers above the ground.

Since ROSAT does not have a propulsion system on board, it is not possible to maneuver the satellite to perform a controlled re-entry. ROSAT’s orbit extends to 53 degrees north and south latitudes, and all areas in that region could 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 an 80-kilometer wide path along the track.

DLR will provide updates to predict the moment of re-entry as accurately as possible. During the re-entry phase of the satellite, German scientists will be evaluating data from the US Space Surveillance Network (SSN). In addition, the Tracking and Imaging Radar (TIRA), the large radar facility at the Fraunhofer Institute for High-Frequency Physics and Radar Techniques in Wachtberg near Bonn will be monitoring the descent of the X-ray satellite to further improve calculations of its trajectory.

Last month, the bus-sized 6-ton UARS satellite that hurtled uncontrolled toward Earth and plunged into the Pacific Ocean without causing any problems.

Source: DLR