Posted by Greg Laden on September 23, 2011 Here’s the latest from NASA. Look for an update fairly soon. Or a loud noise, perhaps!
Update #9
Thu, 22 Sep 2011 09:01:35 PM CDTAs of 9:30 p.m. EDT Sept. 22, 2011, the orbit of UARS was 110 mi by 115 mi (175 km by 185 km). Re-entry is possible sometime during the afternoon or early evening of Sept. 23, Eastern Daylight Time. The satellite will not be passing over North America during that time period. It is still too early to predict the time and location of re-entry with any
“The satellite will not be passing over North America during that time period.”
Why the hell don’t they say where it will be, instead of where it won’t be? That seems to be a crucial bit of information for the majority of the population that does not live in North America.
@1: In case you missed it from an earlier thread: Satellites orbit in a plane in inertial space, and the Earth rotates under that plane. Now that the error bar on the reentry time is less than 12 hours, they can start ruling out areas where the satellite debris might end up. They do know where the nominal ground tracks lie, and they are not in the North American sector. However, the uncertainty on the reentry time is still larger than the orbital period of the satellite, and uncertainties in atmospheric drag mean that the satellite might reach a given part of its orbit earlier or later than expected (with corresponding effects on the ground track). Until they get a reasonably precise fix on the reentry time (which probably won’t be much before the satellite actually does reenter), they cannot say with any precision where the debris field will be.
Maybe that’s in the part of the message that got cut off. (Why did the message get cut off???)
Maybe it is something you are not meant to know.
Equisetum, the orbit takes about an hour and a half. “The afternoon or early evening” is what, six hours long? That’s roughly four orbits, with a really rough one at the end. The satellite doesn’t orbit just along the equator the way the Enterprise always does; it swings north and south with every orbit, about 56°. So every orbit covers a lot of ground. A list of all the places it would be over during that time would be very long.
Greg, I’ve been discussing this with people in other forums, and I am astonished at the amount of tinfoil-hat paranoia that surrounds this event. For example, some claim that NASA is motivated politically to give wishy-washy predictions on something they ought to know with precision. I’ve even read posts wherein people conclude that scientists know nothing at all, therefore Global Warming is all hogwash.
With their way of glossing over the important details,
journalists aren’t helping. They’re muddying the water with nonsense that gets interpreted as the satellite going unusually fast or its tumbling being what causes the uncertainty.
The satellite coming down is of moderate interest. But this uninformed, paranoid speculation is fascinating and a little scary.
No idea how accurate this is, but it reassures me.
UARS – Orbit Data
http://www.heavens-above.com/orbit.aspx?satid=21701
@6: AFAICT, that’s a pretty accurate ground track, only it’s graphing in “real time” – where the satellite is now, rather than where it will be at reentry.
@2,@5: An enumerated LIST of locations would be long indeed, but a chart of orbital ground tracks can be fairly concise.
Planetary Society links to the heavens-above chart, so I’d give the latter some credibility:
http://planetary.org/blog/article/00003192/
In a nominal 12-hour window, the satellite does indeed make multiple passes over North America. Its unlikely to reenter there because NA is only 5% of the Earth’s surface. Current best estimate (±3 hours) gives a small chance (~5%) that people in Seattle, San Diego, Houston, St Louis or Chicago could see a dazzling show. Far more likely, we get ‘nuthin:
http://reentrynews.aero.org/1991063b.html
Disclaimer: a “dazzling show” to an amateur astronomer may not impress anyone else.
For example, some claim that NASA is motivated politically to give wishy-washy predictions on something they ought to know with precision. I’ve even read posts wherein people conclude that scientists know nothing at all, therefore Global Warming is all hogwash.
NASA certainly strikes a cord with certain people.
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