Re: Iridium 73 status mystery

From: Rod Sladen (
Date: Tue Jan 23 2001 - 12:39:52 PST

  • Next message: Jonathan T Wojack: "Observations - 01/06, 2001"

    Bjoern Gimle wrote (in various postings):
    > Also *as expected*:
    That posting referred to Iridium 14 (25777, 99-032A) on Jan.10 giving an apparently
    normal -7 mag flash, and Iridium 77 ? flaring to around predicted -8 Jan.11,
    and *not* to Iridium 73.
    > > Iridium 14 ("?" 25777, 99-032A; formerly 14A)
    > The obs on Jan.12 by me and my friend, reported under 
    > heading "Ir 14",
    > was from the right MMA, and apparantly pointing about 1.4 to 
    > 1.9 degrees E of expected position.
    Both Iridium 77 and Iridium 14, along with the other controllable spares, seem
    to flare as predicted, though possible to considerable more or considerably
    less than the pedicted magnitude.
    > > I am surprised that Iridium 73 can still be maintaining its 
    > > attitude, as it does not appear to have any periodical 
    > > orbital adjustments.
    > It is in a "spares'" orbit, so its MM is not synchronized 
    > with any other Iridium. So, to conserve fuel, it doesn't need 
    > any periodic orbit adjustments.
    The operational spares - Iridiums 77, 82, 86, 20, 14, 21 ("current" numbering)
    [but not Iridium 51] all receive regular adjustments to their orbit.
    > It has to maintain attitude, or at least control, so that it
    > can be thrusted to the operational orbit when required.
    Iridium 73 is thought to be a failure, so I would not expect orbital adjustments.
     Hence I am surprised that it has managed to maintain its orientation.
    Rod Sladen, Beeston, Nottinghamshire, UK, 52.923N, 1.219W
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