German ROSAT Satelite Heading Towards Uncontrolled Re-Entry to Earth

A sample of 3 consecutive ROSAT orbits. Credit: DLR


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

UARS: When and Where Did It Go Down?

Credit: NASA

After a night of changing predictions and hopes of many to see a fireball in the sky, the UARS (Upper Atmosphere Research Satellite) finally met it’s fiery demise.

The decommissioned, 6.5 ton satellite is believed to have re-entered the Earths atmosphere over the Pacific Ocean, and in it’s death throes the massive satellite broke up, and the surviving debris likely landed in the ocean, off of the West coast of North America.

In regard to the exact re-entry point and position of the debris field, Nicholas Johnson, chief orbital debris scientist at NASA’s Johnson Space Center, said “We don’t know where the debris field might be… We may never know.”

The US Department of Defense’s Joint Space Operations Center at Vandenberg Air Force Base in California and the U.S. Strategic Command radar tracking assessed that the satellite reentered the atmosphere sometime between 0323 and 0509 GMT on September 24, 2011 (the Strategic Command predicted it would re-enter at 04:16 GMT). During this period, the satellite was heading across the Pacific Ocean on a southwest-to-northeast trajectory approaching Canada’s west coast. The mid-point of that groundtrack and a possible reentry location is 31 N latitude and 219 E longitude (green circle marker on the above map).

“If the re-entry point was at the time of 04:16 GMT, then all that debris wound up in the Pacific Ocean,” Johnson said during a media briefing on Saturday. “If the re-entry point occurred earlier than that, practically the entire pass before 04:16 was over water. So the only way debris could have probably reached land would be if the re-entry occurred after 04:16.”

NASA says there are no reports of damage or injury caused by the surviving components that made it to the surface, and there are so far no credible visual reports of anyone seeing the UARS satellite burning up.

The Earth-observing satellite was in orbit for 20 years and 10 days.

Credit: NASA

UARS Update: Satellite Fell in Pacific Ocean

UARS satellite at 22:56 on Sept. 22, 2011, as seen from Puerto Rico. Credit: Effrain Morales Rivera.

NASA has confirmed that it’s decommissioned Upper Atmosphere Research Satellite fell back to Earth on Sept. 24 between 03:23 GMT and 05:05 GMT (11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24.) The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite entered the atmosphere over the North Pacific Ocean, off the west coast of the United States. The precise re-entry time and location of any debris impacts are still being determined. NASA is not aware of any reports of injury or property damage.

NASA will provide more information during a media telecon at 18:00 GMT (2 p.m. ET) to discuss the re-entry.

Artist concept of the UARS Satellite in orbit. Credit: NASA

Where will the UARS Satellite Crash?

ATV re-entry. Credit: ESA


The bus sized UARS (Upper Atmosphere Research Satellite) is expected to re-enter Earth’s atmosphere early morning GMT on September 24. Right now, the Center for Orbital and Reentry Debris Studies lists the projected re-entry time as 05:10 UT on Sept. 24, plus or minus 2 hours.

NASA UPDATE “As of 7 p.m. EDT on Sept. 23, 2011, the orbit of UARS was 90 miles by 95 miles (145 km by 150 km). Re-entry is expected between 11 p.m. Friday, Sept. 23, and 3 a.m., Sept. 24, Eastern Daylight Time (3 a.m. to 7 a.m. GMT). During that time period, the satellite will be passing over Canada, Africa and Australia, as well as vast areas of the Pacific, Atlantic and Indian oceans. The risk to public safety is very remote.”

Due to the robust nature of some of the parts on the satellite, it is likely that approximately 500kg of material will impact the ground or water.

The FAA (Federal Aviation Administration) has released a Local Air Safety Information special notice advising of the possibility of space debris.

The calculated risk that you’ll be hit by the falling space debris has been put at 1 in 3,200, said Nick Johnson, chief scientist with NASA’s Orbital Debris Program. But the chance that any one person on Earth getting hit by debris has been estimated at about 1 in 21 trillion.

It is highly unlikely that any injury or damage will be caused by this falling debris and NASA says; “The risk to public safety or property is extremely small, and safety is NASA’s top priority. Since the beginning of the Space Age in the late-1950s, there have been no confirmed reports of an injury resulting from re-entering space objects. Nor is there a record of significant property damage resulting from a satellite re-entry.”

It is still unsure where exactly the UARS satellite will pass over and re-enter the Earth’s atmosphere, but it will be an incredibly bright fireball visible even in daylight. But if some debris ends up near you, don’t worry too much — it won’t be flaming hot. NASA says any pieces of UARS landing on Earth will not be very hot. The heating of objects passing through the atmosphere stops at about 32 km (20 miles) up, and cools after that.

Stay posted for more updates and if you are lucky enough to get an image of UARS burning up please let us know and post your images on our flickr group

UARS Update: NASA Refines Crashing Satellite’s Debris Region and Location

This video from Analytical Graphics, Inc. shows an updated animated analysis of the break-up of the the 6-ton, bus-sized UARS satellite. It likely will burn up at an altitude between 80-45 kilometers, with an estimated 26 pieces of debris re-entering the atmosphere for land fall or splash down. The debris zone is predicted to be about 500 miles long.

The latest update put out by NASA on the Upper Atmosphere Research Satellite (UARS) is that as of 1:30 p.m. EDT Sept. 21, 2011, (17:30 GMT) the orbit of UARS was 120 mi by 130 mi (190 km by 205 km). Re-entry is expected sometime during the afternoon of Sept. 23, Eastern Daylight Time. NASA says the satellite will not be passing over North America during that time period, but that it is still too early to predict the time and location of re-entry with any more certainty. They will be able to further refine more details in the next 24 to 48 hours.

AGI has created an app for Android phones where you can track the UARS orbit track. See this link for more info.

Sources: NASA, AGI

Must See Video: Falling NASA UARS Satellite Observed While Still in Orbit

Several views of the UARS satellite in orbit, as seen from the ground with a 14" telescope. Credit: Thierry Legault Emmanual Rietsch

The huge Upper Atmosphere Research Satellite (UARS) will be plummeting to Earth in an uncontrolled re-entry this week, but here’s an incredible video from astrophotographer extraordinaire Thierry Legault who shot footage of UARS with his 14-inch telescope. Legault was in Northern France (Dunkerque) last week to attempt to capture views of the satellite, and had success on September 15, 2011 between 04:42:14 and 04:44:02 UTC, just 8-9 days before its atmospheric reentry, when it was at an altitude of only 250 km. The tumbling, uncontrolled nature of the satellite is obvious in this video, and various components are visible, such as the body itself and the solar arrays.

NASA has now refined its prediction for when this bus-sized satellite will fall to Earth. The 20-year-old defunct satellite now has a predicted re-entry Time of about 20:36 UTC on September 23, 2011, plus or minus 20 hours, according the the UARS Reentry Twitter feed. So, heads up!


This is a day earlier than previously anticipated. Pieces of the 6.5-ton satellite are expected to survive the fiery plunge and hit our planet, but NASA does not know exactly where. There was word today that increased activity from the Sun has hastened the decay of the satellite’s orbit.

Legault said his images show the satellite at a 316 km distance to the observer. The angular speed at culmination: 1.36°/s. The speed of the sequence is accelerated two times with regard to real time (20 fps vs 10 fps). The satellite is tumbling, perhaps because of a collision with satellite debris a few years ago.

Here is the equipment Legault used: Celestron EdgeHD 14” Schmidt-Cassegrain telescope (at a focal length of 8500mm) on automatic tracking system, as described on this page. Camera: Lumenera Skynyx L2-2.

Thanks to Legault for sharing his video and images with Universe Today! See more info at Legault’s website.

Map of the UARS orbital path. Credit: @UARS_Reentry Twitter feed.

NASA says there are about 26 components that are big enough to survive and make it down to Earth, the largest weighing more than 150 kg (330 pounds.)

What are you chances of getting hit by debris? Nick Johnson, chief scientist with NASA’s Orbital Debris Program, said that numerically, it comes out to a chance of 1 in 3,200 that any one person anywhere in the world might be struck by a piece of debris. That might sound high, but if you factor in that there are 7 billion people on Earth and that a large part of Earth is covered by water, the liklihood is actually very small. The chance that any one person on Earth getting hit by debris has been estimated at about 1 in 21 trillion.

We’ll provide more updates on the UARS story. For those who would like to catch a last glimpse of UARS streaking across the night sky for yourself should check Heaven’s Above or SpaceWeather’s Satellite Tracker for flyby times in your area.

For more information about this satellite’s uncontrolled re-entry, see our earlier article detailing UARS.

Look Out Below! Huge Satellite Coming in for Uncontrolled Re-Entry

Artist concept of the UARS satellite. Credit: NASA


There’s a defunct 6.5-ton satellite heading our way. Trouble is, NASA’s not sure exactly where and when it might come down. And they’re not sure how much of it might survive its fiery fall through Earth’s atmosphere, either.

“Numerically, it comes out to a chance of 1-in-3,200 that one person anywhere in the world might be struck by a piece of debris,” said Nick Johnson, chief scientist with NASA’s Orbital Debris Program, during a media teleconference on Friday. “Those are obviously very, very low odds that anybody’s going to be impacted by this debris.”

Johnson reminded everyone that “throughout the entire 54 years of the space age, there have been no reports of anybody in the world being injured or severely impacted by any re-entering debris.”

How do you like your odds?

The huge 10-meter (35-ft) -long Upper Atmosphere Research Satellite (UARS) is in an orbit that crosses over six continents and three oceans. Johnson said it is expected to re-enter Earth’s atmosphere in an uncontrolled fall in late September or early October. While much of the spacecraft is expected to burn up during re-entry, it’s likely some pieces will make it to the ground. Current projections on where debris field might be is a 800-km- (500-mile) wide swath from Northern Canada to Southern South America.


Or it might fall in the ocean.

“We do know with 99.9 percent accuracy that it will re-enter the atmosphere somewhere between 57 degrees north and 57 degrees south, which means it will be anywhere from northern Canada to southern South America,” said Major Michael Duncan, deputy chief of space situational awareness with the Air Force’s U.S. Strategic Command. “That is truly the best estimation we can give you at this point in time.”

There are about 26 components that are big enough to survive and make it down to Earth, the largest weighing more than 150 kg (330 pounds.)

But hey, this happens all the time.

“Satellites re-entering is actually very commonplace,” Johnson said. “Last year, for example, we averaged over one object per day falling back uncontrolled into the atmosphere,” and for those coming back in an uncontrolled fashion – meaning it is a crapshoot when and where they fall — there were 75 metric tons of spacecraft and rocket bodies falling back to Earth.

“In perspective, UARS is less than six metric tons,” Johnson added. “So it’s a very small percentage of the annual re-entry of satellites.”

The majority of these satellites, though, were a lot smaller than UARS and they burn up completely in the atmosphere.

The UARS satellite launched from Space Shuttle Discovery in 1991. To give you an idea of how big the satellite is, it filled the shuttle’s payload bay completely. It had ten science instruments to examine the chemistry of the upper atmosphere and measure water vapor and other elements. It monitored the health of the ozone hole, looking at the amounts of aerosols in the atmosphere. In 2005 NASA determined that UARS was to be decommissioned.

It was never designed to be returned on the Space Shuttle, said Paul Hertz, chief scientist, NASA’s Science Mission Directorate.
Hertz said NASA is trying to keep the public informed about the the possibilities of debris failing and want to be up front about it. They will post all current information on

And Space Command will be tracking the satellite and providing updates as to where and when UARS will come down, and provide impact predictions if it looks like it will be coming down over land.

Although there are no hazardous materials on board – unlike the hydrazine on a National Reconnaissance Office spy satellite that was shot down in 2008 to avoid contaminating Earth – it was stressed that if anyone finds a piece of the satellite, they should not pick it up, but notify the local authorities.

But anyone along the final trajectory should get “a nice show,” Johnson said.

“It is a relatively large vehicle,” he said. “It would be visible in daylight. Odds are, though, it’s going to happen over an ocean, unlikely to be seen unless it’s by an airliner. We’ve had reports like that before. Since we don’t know where it’s going to come in, we can’t raise people’s expectations and tell them to go out and look in their backyard. So it’ll be a serendipitous kind of event.”