(meteorobs) Earth grazer ID from single station

stange stange34 at sbcglobal.net
Thu Sep 25 23:32:47 EDT 2008


I believe I understand Pete & Esko.

It also appears that the meteor would have to be at zenith for a common 
composite camera to be used for frame displacement measure.

If more distant toward the horizon as you say,....it would be more than 
difficult to measure without lens angular compensation as you both have 
said.

A (simple) zenith drawing included reflecting what I believe I've 
understood.

 http://www.geocities.com/stange34@sbcglobal.net/grazer

YCSentinel

----- Original Message ----- 
From: "Gural, Peter S." <PETER.S.GURAL at saic.com>
To: <meteorobs at meteorobs.org>
Sent: 2008/09/25 17:17
Subject: Re: (meteorobs) Earth grazer ID from single station


> YCSentinal;
>
> It may be possible to identify a grazer from a single station video record 
> by examining the change in apparent angular velocity across the entire 
> trajectory. You would need angle rate from each frame and a well 
> calibrated field of view that accounts for wide field distortions (3rd 
> order or barrel for fisheye lenses). There is a closed form expression of 
> the apparent angular velocity as seen from the camera that changes with 
> radiant distance, entry velocity, and range. It likely has an inflexion 
> point at CPA and thus could be used to id a grazer. I will have to work on 
> this to see if there is any characteristic to the changing values that 
> could be used to advantage. One normally only considers meteors dropping 
> from higher to lower heights so this has been largely ignored from the 
> perspective of numerical solution. For long length/duration meteors, it is 
> actually possible to solve for the radiant position from the changing 
> angular velocity observed. One issue however may be that very wide field 
> cameras won't have sufficient angular resolution to discriminate changes 
> in the angular velocity.
>
> Pete Gural
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