(meteorobs) Why so much uncertainty about re-entry?

[Jim Pettit]

Update:

1550 GMT (11:50 a.m. EDT)
The Joint Space Operations Center at Vandenberg Air Force Base in California
says UARS re-entered 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," the space agency said in a statement.

NASA plans a news briefing today at 2 p.m. EDT.

-----Original Message-----
From: meteorobs-bounces at meteorobs.org
[mailto:meteorobs-bounces at meteorobs.org] On Behalf Of Paul Goelz
Sent: Saturday, September 24, 2011 11:48 AM
To: Ed Cannon; Meteor science and meteor observing
Subject: Re: (meteorobs) Why so much uncertainty about re-entry?

At 11:30 AM 9/24/2011, you wrote:
>For Paul and Dan and others questioning the large uncertainty in the 
>re-entry predictions, here's a relevant paragraph from the Aerospace 
>Corporation:
>
>"It is very difficult to predict where debris from a randomly 
>reentering satellite will hit Earth, primarily because drag on the 
>object is directly proportional to atmospheric density, and atmospheric 
>density varies greatly at high altitudes. In general, we can predict 
>the time that reentry will begin to within 10 percent of the actual 
>time. Unfortunately, reentering objects travel so fast that a minute of 
>error in the time is equivalent to many miles on the ground."

Just to be clear.... I am not questioning the difficulty of PREDICTING the
reentry or impact point.  I fully understand those difficulties.  What I am
questioning is the lack of any specific information in the hours/minutes
leading up to the event and especially many hours afterwards.

Yes, I am sure the event was observed by some entity.  I find it odd that
those observations have not been made available.

Paul


Paul Goelz
Rochester Hills, Michigan USA
pgoelz at comcast.net
www.pgoelz.com 

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