Re: Iridium 5 moved to non-operational orbit

From: Rod Sladen (rodsladen@crosswinds.net)
Date: Sat Aug 18 2001 - 15:32:05 PDT

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    Time for some armchair satellite observing, as it is well and truly clouded over
    tonight!
    
    Thanks to Bjoern Gimle for his analysis of the elsets for Iridium 5 and Iridium
    51, and to Tony Beresford for filling in some of the missing elsets.
    
    elsets 674, 675 (2 versions) and 676 match nicely for Iridium 5 pre the mix-up.
    
    
    elset 524 matches well with earlier elsets for Iridium 51.
    
    all elsets seen since the mix-up - 526, 527, 528 (2 versions), 529, 530 and
    678, 679, 680, 683, 684 seem to relate to the same object, which, as Bjoern
    notes, does not match perfectly with Iridium 51 before the mix-up.
    
    elset 525 seems to be the oddball, especailly with its Bstar term of zero:
    Iridium 51       4.0  1.8  0.0  6.0 d   13       751 x 745 km
    1 25262U 98018A   01221.85670839 -.00002954  00000-0  00000-0 0  5251
    2 25262  86.4512 218.3167 0004190  90.6614 269.5641 14.43136998177717
    
    This *could* just be discounted as a rogue elset, leaving Iridium 51 as having
    had a slight orbital adjustment and Iridium 5 as the "lost" bird.
    
    However, another possibility is that the two satellites have indeed exchanged
    positions, and that elset 525 represented the start of the process of raising
    Iridium 51 in prepration to replace Iridium 5 early on August 11 when Iridium
    51 reached the correct slot in the orbital plane (Iridium 51 was "lapping" Iridium
    5 around every 11 days, if my calculations are correct).  The post mix-up elsets
    being reported for both could then represent Iridium 5 having been lowered to
    the engineering orbit, leaving Iridium 51 as the "lost" object.
    
    When OIG access is restored, maybe all will be clear!
    -- 
    Rod Sladen, Beeston, Nottinghamshire, UK
    52.9230N, 1.2190W
    
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    This archive was generated by hypermail 2b29 : Sat Aug 18 2001 - 15:30:18 PDT