(meteorobs) Fwd: Fireball Report 3/13/05 19:46 pst, Tenino, WA, USA

[Ed Cannon]

>We've received several reports from the states of Washington 
>and Oregon in the Northwestern US - all calling this fireball 
>brighter than the moon.
>
>Any known reentries around this time this evening?

This is just a general note to mention two things about 
reentries vis-a-vis natural fireballs.

First, in general, the vast majority of reentries travel
between due west-to-east to polar direction because most
satellites move in such orbits.  Very few satellites are 
launched east-to-west, and most of those are small.  Any 
highly retrograde (east-to-west) fireball is not likely 
(by a lot) to be an artifical object.  

Second, most reentries have an velocity (under 8 km/sec) 
that is slower than the slowest meteors, so an object 
that crosses a significant part of the sky (even only 20 
degrees) in just a few seconds is most likely a natural 
object.  (I think that the fastest orbital reentry, from 
a highly elliptical orbit, is less than about 11 km/sec.)

I also wonder if a reentry could ever be as bright as 
the full Moon, due to the slow reentry speed, but I'm 
not qualified to try to do the math or physics on that.  
(Did they mean brighter than last night's tiny crescent 
Moon, or the full Moon, or somewhere in between?)  

Ed Cannon - Austin, Texas, USA