Re: TiPS Search again unsuccessful

From: John A. Dormer 2 (jad@texas.net)
Date: Tue Oct 24 2006 - 01:37:33 EDT

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    For the past two nights, I've been using a
    quick-hack-of-a-binocular-support, XEphem 3.7.1, and SatTrack 3.1 to try
    to determine where Ralph and Norton have gone. My clocks are set to the
    US atomic clocks, and my main computer uses NTP to stay within 0.2s of
    the canonical time. It agrees very well (<1s delta) with my wristwatch.
    
    No luck so far, but last night I did see >a< vehicle appear which
    Heavens Above didn't identify. It was at 01:22:19 Monday 23 October 2006
    UTC when it passed across a line between V13369 and Dra 76. This is +- 1
    second in time. It was also descending at between a ten and 20 degree
    angle and moving to the east. This would have been the wrong angle and
    about 1m13s late for anything associated with TiPS. The approximate
    location of the observations is 30d8m42.6sN 97d52m43.8sW, 206m MSL,
    WGS84 datum.
    
    A second item which occurred to me is that with the elements being over
    100 days old, is there any sort of perturbation which could be applied
    to estimate where the vehicle(s) might be?
    
    I've been reading my orbital mechanics book (what can I say? I have
    unusual hobbies), and there is mention of low-orbit vehicles'
    inclination (TiPS is 63.3975 degrees) and altitude (somewhere around
    900km at perigee, by inspection) having an effect. But, TiPS is really
    close to the magic 63.4 degree inclination ("Fundamentals of
    Astrodynamics," Bate, Mueller & White, 1971, page 158) where this effect
    on apsidal rotation vanishes. The nodal regression rate (change in
    location of the ascending node) would be small, my guess is less than a
    degree-and-a-half a day, but more than a half-degree, westward in motion
    (ibid, page 157).
    
    So, bludgeoning McCant's data for TiPS, if the longitude of the
    ascending node has moved by 50 degrees in the last 100 or so days (RAAN
    moving from 72 to 22 degrees), could the object described above be TiPS,
    or does SGP4 compensate for these perturbations automatically? And yes,
    I plan to slug my way through the docs for SGP4 some time this week, but
    some insight would be nice.  :)
    
    Feel free to throw tomatoes. I don't learn much talking to myself.
    
    	John
    
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