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Germany Acknowledges Mir Debris Could Land on Its Territory

BERLIN, Mar 2, 2001 -- (Agence France Presse) The German interior ministry has acknowledged that debris from the doomed Russian space station Mir could land on Germany, according to a Bild newspaper report Friday based on a confidential interior ministry document.

Although debris is thought more likely to land in the southern hemisphere, Bild said the ministry had set up a crisis cell to follow the trajectory of the space station, which is expected to break up between March 11 and March 16 after entering the earth's atmosphere.

"In the event that the crash takes places in the northern hemisphere, one cannot rule out that individual pieces of debris will land on Germany," the document quoted by Bild and dated February 27 states.

The document indicates there is a perceived risk for "all areas roughly south of Hanover" including the cities of Berlin, Cologne, Frankfurt, Stuttgart and Munich, as well as Alsace in France and parts of Poland and Austria.

In a statement Thursday, the German government confirmed that it was "following with attention" the trajectory of the space station.

According to Bild, if any danger from the controlled destruction of Mir does become apparent, the population will be warned over the radio not to go outdoors. ((c) 2001 Agence France Presse)§ion=default

-- Carl Jenkins (, March 02, 2001


This news story needs a little context. Let me try to offer some, speaking as a clueless amateur astronomer and working from memory (if anyone catches me in a big fat error, please jump in and correct me!). This is a lot faster to explain in person with a globe handy, but I'll try in words anyhow. Warning, this is a long explanation.

OK, first let's discuss satellite orbits in general. If something in orbit is lined up right over the equator (i.e. it is circling the globe such that it passes directly overhead as you stand anywhere on earth at zero degrees latitude), it has orbital inclination zero degrees.

If something is orbiting over the poles (i.e. it passes over the north and south poles as it orbits our planet) it has orbital inclination 90 degrees. Something in such a truly "polar" orbit would eventually pass directly above every single point on earth, since the earth is spinning around once a day while the object moves in orbit overhead every 90 minutes or whatever. That's why 90 degrees (i.e. a polar orbit) is a common orbital inclination for spy satellites.

Now imagine something in orbit at the in-between scenario, 45 degrees inclination. The furthest north you could watch it pass directly overhead would be from 45 degrees north latitude, for example if you were standing near Montreal or northern Italy or Mongolia, depending on how the earth was turned beneath the object on any given orbit. Similarly, the furthest south you could watch it pass directly overhead would be 45 degrees south latitude, perhaps from the south Atlantic or New Zealand or wherever. Over time, the object would pass over every point on earth that lies between 45 N and 45 S latitudes.

With me so far?

Now, when you are standing on a particular spot on the earth and want to put something into orbit, the initial and most energy-efficient orbit from that launch site will have an orbital inclination matching your latitude. If you are standing in Florida at the Kennedy Space Center, the initial cheap orbit will be around 25 degrees inclination (I am working from memory here, it's gotta be close to that). As I recall, the Hubble telescope has an orbital inclination close to that. If you desire to alter the orbital inclination from being a match to your latitude, you need to supply more energy at launch or once you achieve orbit (fire up those thrusters, Spaceman Spiff!)

If you are in the former Soviet Union, you are launching your spacecraft from what is now Kazakhstan, at a cosmodrome located around 51.6 degrees north latitude. Guess what? The Mir space station has an orbital inclination of 51.6 degrees (again, this is from memory, please excuse if I'm a little off). So, over its lifetime in orbit, Mir eventually passes directly overhead everywhere on earth between 51.6 degrees N and 51.6 degrees S latitudes. From now on I'll call this "52 deg" for brevity.

Still with me?

Next and last point: Why isn't there great concern that Mir, if it falls uncontrolled, will hit ANYWHERE on the planet between roughly 52 deg N and 52 deg S, in other words essentially all of the populated regions worldwide? Why did the German interior ministry wonks put out this report? The answer is that the orbit is not quite a perfect circle; it is closest to earth at one place each orbit (at "perigee"), and farthest from earth halfway around from perigee (at "apogee").

When Mir was pushed into orbit, it started out closest to earth at its northmost point, i.e. 52 deg N latitude. It is farthest from earth when it passes overhead at 52 deg S latitude. The difference isn't huge -- I think Mir has a fairly circular orbit -- there's probably only 30 or 50 kilometers difference between Mir's altitude at perigee and at apogee, if memory serves. This could be checked over at if you want the exact numbers.

OK, finally you can see why Germany is saying they are at risk. If Mir falls back to earth *uncontrolled*, it will most likely land around 52 deg N latitude since that's where it comes closest to earth with each orbit. The exact place -- i.e., you include the longitude -- will depend on how the earth happens to have turned beneath it (and will also vary to an extent according to atmospheric drag during re- entry).

Take a look at a world map: 52 deg N latitude roughly includes Kazakhstan where Mir started out, also near London, probably Belgium, Germany as noted in the news item above, Warsaw, just north of the most populated strip of southern Canada, et cetera -- pick your favorite city. (Forgive me if this is a little off, I'm working from memory here). Throw in some variation from atmospheric drag, and you can see that some heavily populated territory is at greatest risk if a big chunk of Mir were to hit land.

So, if Mir falls entirely without direction, uncontrolled, the German interior ministry wonks are right: they (along with a lot of other folks) are at risk. You’ll note they mention "south of Hanover"; I bet that Hanover is located at 51.6 degrees N latitude!

I suppose things could change if Mir fell all by itself: it might begin to alter orbit gradually so it hit somewhere else, but my amateur understanding is that it is very very much likely to land somewhere close to 52 deg N latitude (I don't know how probable a wildly different location would be).

That's the basis for the news item that started me going (you can tell I'm on my lunchbreak, and it's a slow Friday!!!).

The key point is *uncontrolled*. The article notes "debris is thought more likely to land in the southern hemisphere." They mean, assuming the Russians fulfill their final responsibilities for Mir. What really must happen is for Mir to be nudged out of orbit deliberately, while using as little rocket thrust as possible (more thrust = bigger rocket sent up = more expensive).

Conveniently, during each orbit Mir (like essentially all other spacecraft) passes over the south Pacific, albeit at apogee. My understanding is, that's where the Russian controllers propose bringing Mir back down: roughly, somewhere far east of New Zealand, perhaps a bit north from there.

Whew! Orbital mechanics isn't quite what we usually see on this Board, but I thought the article focusing on Germany needed to be explicated a little.

On a personal observer's note, from my home in Pennsylvania, at almost exactly 40 degrees north latitude, I have enjoyed watching Mir for many years and will miss it. The new ISS (international space station) is a nice bright substitute, though. A few weekends ago I dragged some houseguests out to watch both ISS and the visiting space shuttle pass about 30 seconds apart -- we caught the spectacle a day after they separated but before the shuttle finally got good weather to land. My guests (along with my long-suffering wife) probably thought I was nuts until they clearly saw the two objects...then they were amazed and talked about it all the rest of the evening.

You too can spot satellites with the naked eye; some are bright enough to see even from only moderately dark areas in or near big cities. Check out . The trick is to get outside at the right time and look in the right direction. Most people, if they happen to look up, probably think it's just an airplane. In fact, the difference between a plane and a satellite is pretty obvious, most of the time. But that's a different essay.

Cheers, keep your helmet handy, and now back to the doom-and-gloom economy and Y2K (?!) news,

-- Andre Weltman (, March 02, 2001.

Andre, you're such a wealth of knowledge. Feel free to drift, whenever....

Okay, I read every word of it. Two questions: what are the risks of the re-entry becoming uncontrolled? And why did the Russians change the re-entry date from March 6 to March 16?

I lived north of 57 for a number of years and was in that vicinity when the Russian satellite came down in the '70s. So did a lot of other people, and even more wildlife. We, the people at least, were not amused.

-- Rachel Gibson (, March 02, 2001.

Glad my thread drift wasn't a bother.

Rachel asks: << Two questions: what are the risks of the re-entry becoming uncontrolled? And why did the Russians change the re-entry date from March 6 to March 16? >>

Two good questions, but I don't know accurate answers. I can speculate however that the answer to your second question *might* be political: there are old-timers in Russia who see Mir as a symbol of the former power of the USSR, and who are upset it will be brought down deliberately. Their anger is of course misplaced, as the space station has far outlived its design lifespan and is now a danger to the world unless brought down. Nonetheless, there were protests in Russia, and perhaps this is part of why the de-orbit was delayed several times.

Meanwhile, from the New York Times, Sunday 4 March 2001 [excerpt, hand typed]:

"...A Progress cargo ship, commanded by ground controllers, is docked at Mir and is steadily lowering the low end of Mir's orbit. At the same time, the atmosphere is dragging the station down even more. Mir will soon be in a lopsided orbit with the low end only 155 miles above Earth. When it reaches that altitude, the Russians hope to use the Progress to push the 135-ton Mir out of orbit and put it on a final trajectory to oblivion, allowing it to crash over an unpopulated swath of the South Pacific midway between New Zealand and Chile..."

So, it appears Mir really, finally is headed for home. Hasta la vista, baby. Like the song says, "It's better to burn out, than it is to rust."

(For something like $10,000 [yes, ten thousand dollars U.S.] one can buy a ticket on a charter flight out of Tahiti that will allow you a good view of the final re-entry fireworks from above the clouds; I think I'll stay at home and catch it on the TeeVee, myself.)



-- Andre Weltman (, March 06, 2001.

Headline: Russian Space Agency to Take Out Insurance on Disposing Mir

Source: Associated Press, Mar 6, 2001


MOSCOW (AP) - Russia's space agency is taking out insurance against any damage the ailing Mir space station might cause when it is guided down later this month, the Russian Aerospace Agency said Tuesday.

Despite official optimism that the Mir safely plunge into a remote area of the Pacific Ocean, the space agency is negotiating with three Russian companies to insure against possible damage, a premium estimated at $200 million.

"The insurance is just another attempt to assuage fears," Russian Aerospace Agency spokesman Sergei Gorbunov said during an Internet news conference.

He added that the three Russian insurance companies expected to participate in the plan had "nothing to fear," because the orbiter's fall would be safe.

Mir will most likely be brought down into the Pacific Ocean between March 18 and March 20, although no exact date has been set, Gorbunov said.

The space agency will pay the insurance costs from its own pocket, because the state budget doesn't provide for it, he said.

Gorbunov wouldn't give further details, saying the contract was still being finalized.

The long history of Mir's glitches, including a fire, a near- disastrous collision with a cargo ship and a string of computer breakdowns and power outages, has fed fears that it could spin out of control and rain debris on populated areas.

Japan has been especially concerned, because Mir is expected to pass over its territory on its final, low orbit. "We have grown tired of repeating that there was no danger for Japan," Gorbunov said.

One of Mir's designers, Leonid Gorshkov, also sought Tuesday to play down public fears. "Debris from dozens of booster rockets and hundreds of meteorites annually reach Earth and nothing terrible happens," Gorshkov said at a separate news conference.

Gorbunov said Tuesday that space officials are now waiting for the station to naturally drift down to an orbit about 155 miles from Earth instead of using up precious fuel to speed up the descent.

"We don't want to spend extra fuel to lower its orbit," Gorbunov said, adding that it's necessary to save as much fuel as possible to make sure that Mir's de-orbit is properly controlled.

After Mir reaches the 160-mile orbit by the end of this week, space officials will take a series of steps to prepare for the moment when a Progress cargo ship docked with the station will fire its engines and send the 143-ton station hurtling down.

The most tricky part will include bringing Mir, which is now rotating slowly, to a fixed position in orbit. The process would require a lot of power, and Mir's batteries are old and unstable.

Most of Mir will burn up when it enters the atmosphere, but some 1,500 fragments with a total weight of up to 28 tons are expected to survive the fiery re-entry and fall over an ocean area between Australia and Chile.

In 1978, a Soviet satellite crashed in northern Canada, scattering radioactive fragments over the wilderness but causing no injuries. A year later, the unoccupied U.S. Skylab space station fell to Earth, spreading debris over western Australia. No one was hurt.

-- Andre Weltman (, March 06, 2001.

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