Re: Possible decay?

From: Tony Beresford (
Date: Mon Jul 17 2000 - 19:59:21 PDT

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    At 23:56 17/07/00 , Mark Harris wrote:
    >Does a decay differ much from a meteor?
    >Time: 00.02 GMT
    >Direction: looking South-West
    >Altitude: about 25 degrees
    Yes it does Mark. Decaying satellites are essentially in circular orbits
    at heights around 100Km. This means there speed is that of such an orbit,
    about 8.3Km/second. Meteors must have at least escape velocity ( 11.2 Km/second)
    and most have speeds above 20Km/second right up to the maximum 73 km/sec.
    The relatively slow speed and horizontal direction of velocity for a satellite
    decay mean that you should see it for quite some time, say 30-40 seconds at
    moderate elevations, and may be over a minute if you can see objects
    low on your horizon. So the object you saw HAD to be a meteor, purely on the
    basis of the duration. Since meteoroids follow  power law distribution
    [ 10 times more massive are 100 times less frequent], Sighting a bright
    meteor is a rare occurence. I have only ever seen one meteor approaching
    the brightest Iridium flares observed. 
    Tony Beresford
    Adelaide, So <aust ( 34.96s,138.63E)
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