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Fwd from Gary Kronk Re: (meteorobs) A "skipping-stone" meteoroid?!


Thanks for the following reply, Gary, and welcome back!

------- Forwarded Message

To: Lew Gramer <dedalus@latradedot com>
From: 
Gary_Kronk/Medlib/Washington_University.WASHINGTON_UNIVERSITY@msnotes.wustldot edu
Date:  5 Aug 96 17:07:40 
Subject: Re: (meteorobs) A "skipping-stone" meteoroid?!

I totally forgot that my e-mail program responded directly to the user rather 
than the list. It will take me a bit to get back into the swing of things. I 
can not believe the mail accumulation, especially from the list! I will need a 
whole day just to go through it all!

Since I did not save my original message (I thought I did!) I will post this 
response directly to you again. If you want to put both letters onto the list, 
feel free to.

The initial computations for the August 10, 1972 asteroid revealed a rough 
pre-Earth-encounter orbit. The effects of perturbations and ablation were taken 
into account and a rough post-Earth-encounter orbit was determined. 
Unfortunately, at that time, the estimated mass of the object was very 
uncertain and ranged from something like 400 to 4000 tons. Depending on the 
mass accepted, the post-encounter orbit varied quite a bit. 

Ceplecha's reanalysis made a major attempt to estimate the mass. His new orbit 
is believed to more closely match the actual orbit, but it is still uncertain 
just how good this new orbit is. Remember, this was a daylight event. 
Researchers had to look at the photos, ascertain the position of the 
photographers, determine the field of views of the photographic equipment, 
detemine the times the object was seen for each photograph, and determine each 
of the object's positions in azimuth and altitude. If the azimuth or altitude 
was off by a few degrees, or the time was off by mere minutes, the motion of 
the object through the atmosphere could be very poorly represented. 
Fortunately, the 8mm movie provided the best information, as the photographer 
started filming the object when nearly directly over the Tetons (apparent) and 
followed it all the way to the horizon. This enabled a good estimate of the 
apparent velocity. The object skipped back into space somewhere over Alberta, 
Canada. 

If you would like, I could get the reference of Ceplecha's article for you, as 
it is at home.

Gary

------- End of Forwarded Message