ROSAT satellite- latest news

(update)
From bbc/news:

“…Just as for Nasa’s UARS satellite, which plunged into the atmosphere in September, there was high uncertainty about the final moments of Rosat.
But if the timings are correct, any wreckage would probably have dived into the Indian Ocean – although no eyewitness reports have yet come in.
If anything did manage to make landfall, the likely areas to be affected would have been Myanmar and China….”

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ROSAT – latest news
Last update: 23 October 2011, 02:45 UTC (04:45 CEST)
On Sunday, 23 October 2011, between 1:45 UTC (3:45 CEST) and 2:15 UTC (4:15 CEST) the german ROentgen SATellite ROSAT has re-entered Earth’s atmosphere. There is currently no confirmation if pieces of debris have reached Earth’s surface.
www.dlr.de

Read also:
1. Europe Safe From Falling German Satellite Debris
2. If Germany’s Satellite Falls on Your House, Who Pays for Repairs?
3. What Are the Odds You’ll Get Struck by the Falling ROSAT Satellite?

If Germany’s Satellite Falls on Your House, Who Pays for Repairs?

The defunct 2.7-ton German ROSAT satellite is slated to make a fiery, uncontrolled re-entry to our atmosphere sometime Saturday or Sunday (Oct. 22 or 23). Experts say the broken-up bits of ROSAT have a roughly 1-in-2,000 chance of hitting someone somewhere on Earth, though they won’t know where until a few hours before it enters the atmosphere.
Let us be clear: There’s an extremely remote chance that ROSAT will fall on you. But, for good measure, if ROSAT, or some other spacecraft, did fall on your property, could you keep it? And, if the bus-size satellite flattened your house, who would be on the hook for the repair bill?
First off, ROSAT was a joint venture between Germany, the United Kingdom and the United States, and remains the property of those countries even after it comes back to Earth. To keep a piece, or to try to sell it, would be illegal — unless the angencies relinquish ownership of the debris. There isn’t a ton of precedent here, but when people tried to sell pieces of the Space Shuttle Columbia, for example, the government shut them down, pulled their auctions from eBay and reclaimed the debris. But that was a special case because the Columbia accident was under investigation at the time. When parts of the space station Skylab landed in Australia in 1979, NASA did not reclaim them. In the present case, the trio of countries may or may not ask for ROSAT debris back.
The good news is that if the satellite, or even just sizable chunks of it, did in fact slam into your house, you wouldn’t need to sell your new space souvenir to pay for repairs. By international law, the three countries would have to foot the bill.


http://youtu.be/W-73gv09nRk

Liability for damage caused by objects falling from space is regulated by the 1972 Convention on International Liability for Damage Caused by Space Objects. All three countries involved with ROSAT have signed the pact, and in doing so agreed to be “absolutely liable to pay compensation for damage caused by its space object on the surface of the Earth or to aircraft in flight.” That goes if ROSAT crashes down in Kansas, France or Zimbabwe.

The terms cover just about everything. In this case, “damage” is defined as loss of life, personal injury or other impairment of health; or loss of or damage to property of states or of persons, natural or juridical, or property of international intergovernmental organizations.

And the payout is fairly good. Again, quoting the treaty: “The compensation which the launching State shall be liable to pay for damage under this Convention shall be determined in accordance with international law and the principles of justice and equity, in order to provide such reparation in respect of the damage as will restore the person, natural or juridical, State or international organization on whose behalf the claim is presented to the condition which would have existed if the damage had not occurred.”

One slight hitch in the treaty is that you have to present your claim no later than one year following the incident (or discovery of the damage). If you’ve got a truck-size satellite sitting in your living room, however, we suspect that satisfying this condition would not be an issue.
lifeslittlemysteries.com/

What Are the Odds You’ll Get Struck by the Falling ROSAT Satellite?

This exclusive image was made by Ralf Vandebergh, who said: “”It is false-color to increase certain visible contrasts. A very special detail visible is the shadow of the body (the telescope) on the solar panels! You can see the angle with the sun and the observer (me) as ROSAT passed not overhead but [at] 51.4 degrees northern latitude. This is a very difficult observation as the object is very small.

Not long after re-emerging en masse from our underground bunkers and panic rooms, having successfully avoided being squashed by a falling NASA satellite on Sept. 24, humanity has learned that the sky is falling yet again. Another huge piece of space debris, a 2.6-ton, defunct German telescope called the Roentgen Satellite (ROSAT), will crash back to Earth Saturday or Sunday (Oct. 22 or 23), and the chances it will hit someone are even greater this time around.

The odds are 1-in-2,000 that a chunk of ROSAT will strike a person. For the UARS satellite that fell into the southern Pacific Ocean in September, the odds were 1-in-3,200. According to Heiner Klinkrad, head of the European Space Agency’s Orbital Debris Office, ROSAT poses a higher risk than UARS because more of its mass is expected to survive atmospheric re-entry and reach Earth’s surface. [Photos: Germany’s ROSAT Satellite Falling to Earth]

“The fact that the ROSAT re-entry risk estimate is higher than for UARS lies in the surviving mass, which, percentage-wise, is considerably higher for ROSAT than for UARS, and hence, the net mass reaching ground is higher for ROSAT than for UARS,” Klinkrad told Life’s Little Mysteries, a sister site to SPACE.com. “This is due to the ROSAT internal mirror assembly that is very resistant to [heat] during re-entry.”

Typically, when a satellite crashes to Earth, only 20 to 40 percent of its mass survives; the rest burns up from heat generated by friction between the satellite and particles in the atmosphere, Klinkrad said. Because ROSAT’s mirrors ? which collected X-rays and extreme ultraviolet light emitted by celestial objects ? resist heat, they reduce the percentage of the spacecraft that will burn up, and over half of the spacecraft’s mass, about 1.7 tons of it, is expected to reach the surface. [If a Satellite Falls On Your Home, Who Pays for Repairs?]

According to scientists in NASA’s orbital debris office at Johnson Space Center in Houston, calculating the risk of space debris hitting someone requires first working out how much debris makes landfall. Analysts then make a grid of how the human population is distributed around the globe. Oceans, deserts and the North and South poles are largely devoid of people, for example, whereas coastlines are brimming with them. In short, the analysts must figure out which patches of Earth have people standing on them.

Throwing in a few more minor details, such as the latitudes over which satellites spend most of their time orbiting ? ROSAT will most likely fall between 53 degrees north and 53 degrees south latitudes ? the scientists calculate how likely it is that a piece of space junk will strike the ground where a person happens to be. This time around, the odds are 1-in-2,000, and there’s a one-in-several-trillion chance that not only will a person get hit, but that person will be you.

Two dead satellites have crashed to Earth in as many months, after years of gradually getting dragged down to lower and lower orbits. More will re-enter the atmosphere in the future. With this in mind, you may be interested to know the overall risk of getting struck in a given year, or in your lifetime.

“The annual risk of a single person to be severely injured by a re-entering piece of space debris is about 1 in 100 billion,” Klinkrad said. In the course of a 75-year lifetime, then, the odds of getting injured by space junk would be a little less than 1 in 1 billion. If this sounds scary, it probably shouldn’t. By comparison, “the annual risk that a single person gets struck by a lightning is about a factor 60,000 higher, and the risk of a serious injury from a motor vehicle accident is about 27 million times higher than the risk associated with re-entry events.”
http://www.space.com

App tracks ROSAT satellite’s crash to Earth


ROSAT, a defunct X-ray telescope, is crashing to Earth sooner than expected owing to enhanced solar activity, says Johann-Dietrich Wörner, executive director of DLR, the German lab in charge of the mission. It was thought that the 2.4 tonne spacecraft would deorbit in late October or early November, but Wörner says the re-entry date is now going to be between 20 October and 25 October.

“Increased solar radiation activity has enlarged the atmosphere, increasing the friction on the satellite. So it will come down earlier than expected,” he says. But he can’t say where in that date range the satellite is most likely to deorbit – it depends on fast-fluctuating atmospheric conditions. Heatproof optics mean much more of ROSAT’s mass is expected to survive re-entry compared to the NASA UARS satellite that fell into the Pacific Ocean last month….. Continue reading App tracks ROSAT satellite’s crash to Earth

G299.2-2.9, a Middle-Aged Supernova Remnant


G299.2-2.9 is an intriguing supernova remnant found about 16,000 light years away in the Milky Way galaxy. Evidence points to G299.2-2.9 being the remains of a Type Ia supernova, where a white dwarf has grown sufficiently massive to cause a thermonuclear explosion. Because it is older than most supernova remnants caused by these explosions, at an age of about 4,500 years, G299.2-2.9 provides astronomers with an excellent opportunity to study how these objects evolve over time. It also provides a probe of the Type Ia supernova explosion that produced this structure.

This composite image shows G299.2-2.9 in X-ray light from Chandra and the ROSAT satellite, in orange, that has been overlaid on an infrared image from the Two Micron All-Sky Survey, or 2MASS. The faint X-ray emission from the inner region reveals relatively large amounts of iron and silicon, as expected for a remnant of a Type Ia supernova. The outer shell of the remnant is complex, with at least a double shell structure. Typically, such a complex outer shell is associated with a star that has exploded into space where gas and dust are not uniformly distributed.

Since most theories to explain Type Ia supernovas assume they go off in a uniform environment, detailed studies of this complicated outer shell should help astronomers improve their understanding of the environments where these explosions occur. It is very important to understand the details of Type Ia explosions because astronomers use them as cosmic mile markers to measure the accelerated expansion of the universe and study dark energy. The discovery of this accelerated expansion in the late 1990s led to the recent award of the Nobel Prize in Physics. http://www.nasa.gov

Second big satellite set to resist re-entry burn-up

Incoming! (Image: Max Planck Institute for Extraterrestrial Physics)

Even if NASA’s 6-tonne UARS satellite does not cause any injury or damage when it re-enters the Earth’s atmosphere today, there is more space junk headed our way next month. A defunct German space telescope called ROSAT is set to hit the planet at the end of October – and it even is more likely than UARS to cause injury or damage in populated areas.

No one yet knows where UARS (Upper Atmosphere Research Satellite) will fall to earth. Although most of the craft’s mass will be reduced to an incandescent plasma, some 532 kilograms of it in 26 pieces are forecast to survive – including a 150-kilogram instrument mounting.

NASA calculates a 1-in-3200 chance of UARS causing injury or damage. But at the end of October or beginning of November, ROSAT – a 2.4-tonne X-ray telescope built by the German aerospace lab DLR and launched by NASA in 1990 – will re-enter the atmosphere, presenting a 1 in 2000 chance of injury.

The higher risk stems from the requirements of imaging X-rays in space, says DLR spokesperson Andreas Schütz. The spacecraft’s mirrors had to be heavily shielded from heat that could have wrecked its X-ray sensing operations during its eight-year working life. But this means those mirrors will be far more likely to survive a fiery re-entry.

Broken mirror, bad luck

On its ROSAT website, DLR estimates that “up to 30 individual debris items with a total mass of up to 1.6 tonnes might reach the surface of the Earth. The X-ray optical system, with its mirrors and a mechanical support structure made of carbon-fibre reinforced composite – or at least a part of it – could be the heaviest single component to reach the ground.”

At the European Space Agency in Darmstadt, Germany, the head of the space debris office, Heiner Klinkrad, agrees that ROSAT’s design means more of it will hit the surface. “This is indeed because ROSAT has a large mirror structure that survives high re-entry temperatures,” he says.

ROSAT was deactivated in 1999 and its orbit has been decaying since then. “ROSAT does not have a propulsion system on board which can be used to manoeuvre the satellite to allow a controlled re-entry,” says space industry lawyer Joanne Wheeler of London-based legal practice CMS Cameron McKenna. “And the time and position of ROSAT’s re-entry cannot be predicted with any precision due to fluctuations in solar activity, which affect atmospheric drag.”

Solar swelling

US Strategic Command tracks all space objects and the US-government-run Aerospace Corporation lists both upcoming and recent re-entries on its website. But ROSAT is not yet on the upcoming list because its re-entry time is far from certain.

The moment a craft will re-enter is difficult to predict because it is determined by two main factors. First, the geometry of the tumbling satellite as it enters the upper atmosphere, which acts as a brake. Second, the behaviour of the upper atmosphere itself, which grows and shrinks with the amount of solar activity, says Hugh Lewis, a space debris specialist at the University of Southampton, UK.

“Solar activity causes the atmosphere to expand upwards, causing more braking on space objects. The reason UARS is coming back sooner than expected is a sudden increase in solar activity. Indeed, we expect to see a higher rate of re-entries as we approach the solar maximum in 2013,” he says.

But don’t expect it to be raining spaceships – what’s coming down is partly a legacy of 1990s space-flight activity. “Some of the re-entries we see today [with UARS and ROSAT] are a heritage of years with high launch rates, which were a factor of two higher than they are today,” says Klinkrad.

“The trend is towards smaller satellites, with more dedicated payloads,” he says, rather than “all-in-one” satellite missions on giant craft like UARS. That means debris from future missions should be smaller.

http://www.newscientist.com/article/dn20955-second-big-satellite-set-to-resist-reentry-burnup.html