Re: PAS 1R Seen

From: Björn Gimle (bg_26934@glocalnet.net)
Date: Thu Feb 02 2006 - 17:05:01 EST

  • Next message: Ed Cannon: "Re: PAS 1R Seen"

    Before a geostationary sat runs out of attitude/orbit control fuel, it 
    is usually moved to an orbit with a slightly lower Mean Motion than 
    1.0027. After that, or if it has a control failure, it usually starts 
    tumbling or rotating along its axis of greatest inertia. So the 
    reflecting surfaces will sweep circles (often 90 degrees from the axis), 
    and depending on where the Sun is, there may be two or more points where 
    the reflections appear to come from a point along the observable track, 
    so flashes can be seen, once or twice per rotation.
    
    But the operational (steady - or actually rotating once/day) ones will 
    only show a flare when they are nearly opposite to the Sun in RA,but at 
    the same declination as the Sun (this assumes the solar panels are 
    pointing to the Sun's RA, but constantly in the equatorial plane)
    
    PAS 1R was at RA 09:12  Decl. -5.5  (?)  at 03:00 UTC
    The Sun was at 21:02   -17.  So the hypothesis is almost proved, but the 
    panels are not pointing quite in the equatorial plane.
    
    ----- Original Message ----- 
    From: "Brad Young" <brad.young@domain-engineering.com>
    To: "SeeSat" <seesat-l@satobs.org>; "Kevin Fetter" <kfetter@yahoo.com>
    Sent: Thursday, February 02, 2006 10:26 PM
    Subject: PAS 1R Seen
    
    
    > Saw PAS 1R (26608) last night from 2:58:52 - 3:05:13 UT, ramping up 
    > evenly
    > from ~+7 mag to +5 and back to inv in my 10x50 binoculars. Magnitude
    > compared to 21 & 23 Hydrae that it was near. Not sure how to report 
    > such a
    > sight...PPAS format?
    >
    > First long term flaring geosat I'd seen and it was quite a different 
    > event
    > than the "flashers" like Telstar 401 from earlier this winter. Hope to 
    > try
    > again tonight. Is there posted in the archives or on Web a short 
    > discourse
    > on why this geosat "flares" and the others "flash"?
    >
    > Brad Young
    > +36.1, -95.9
    > Tulsa, OK USA
    >
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