RE: 12044A / 38744: altitude increasing?

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Tue Aug 14 2012 - 07:19:00 UTC

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    1. Position Reductions from Kevin Fetter's Video
    
    The following reductions are in the sequence that the pieces passed between the pair of mag 5 stars on the left-hand
    side of the FOV.
    
    38746 12 044C   1775 G 20120807040830550 36 25 2151703+291259 37 S+037 10
    38745 12 044B   1775 G 20120807040831351 36 25 2151703+291297 37 S+060 10
    38747 12 044D   1775 G 20120807040837190 36 25 2151551+291674 37 S+068 10
    38744 12 044A   1775 G 20120807040838257 36 25 2151575+291682 37 S+032 05
    
    I identified the objects with the aid of USSTRATCOM's TLEs. The designations are the current ones adopted by USSTRATCOM.
    Bob Christy independently found the same sequence of transit.
    
    Propagating the TLEs of the pieces back in time, reveals positional convergence during the ~40 min period after the
    Briz-M aborted its third firing, on 2012 Aug 06 at 23:00:01 UTC.
    
    2. Identity of 12044C and D
    
    I agree with Bob Christy and Jonathan McDowell that 12044C is the intact Briz-M stage, and 12044D is the spacer that sat
    between Express MD2 and Telkom 3.
    
    3. Analysis of Rates of Decay
    
    The following analysis is preliminary, based on short data arcs.
    
    The STOAG propagator accounts for the rate of decay of 12044D during Aug 7-13 UTC, with area-to-mass ratio A/m = 0.0243
    m^2/kg, and Cd = 2.2. Assuming mass of 50 to 100 kg, its cross-sectional area is between 1.2 and 2.4 m^2. That is in
    reasonable agreement with the observed brightness. This is the fastest decaying piece from the launch, but it is likely
    to remain in orbit at least several years. Using STOAG's low intensity solar flux model yields decay in spring 2015, but
    the actual solar flux has been well below that model's values. If that is any indication of what we can expect during
    the remainder of the present solar maximum, then the object could remain in orbit much longer.
    
    12044C appears to have experienced a slight boost in altitude late on Aug 08 or early Aug 09 UTC. Since then, it has
    slowly decayed. The STOAG propagator accounts for its rate of decay during Aug 9-13 UTC, with A/m = 0.000815 m^2/kg, and
    Cd = 2.2. 
    
    Based on its dimensions, 12044C's mean cross-sectional area is about 10.3 m^2. Its dry mass is about 2370 kg. Estimated
    remaining fuel load is 11738 kg. The mass of the attached PAF is about 100 kg. The estimated A/m = 0.000725 m^2/kg,
    which is in reasonable agreement with the STOAG estimate. Even with the medium intensity solar activity model, the
    present A/m would keep it in orbit for more than a century. However, its fuel is likely to be released long before then
    - non-violently, I hope. Based on its dry mass, decay would occur within about 12 years.
    
    I have not analyzed the rates of decay of the payloads, but since they are decaying only 30 to 60 percent as fast as
    12044D, they are likely to remain in orbit 5 to 10 years.
    
    I would be interested in learning of estimates made using other propagators.
    
    Ted Molczan
    
    
    
    
    
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