DSP F18 aperture cover search elements

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Wed Sep 29 2010 - 11:35:17 UTC

  • Next message: Greg Roberts: "Optical 28 Sept 2010"

    One of the two UNIDs that Scott Campbell reported from his observing session last night, correlates
    with the orbit of DSP F18, and appears to be its aperture cover. Scott assigned it the temporary ID
    99007:
    
    http://satobs.org/seesat/Sep-2010/0341.html
    
    For the purpose of the search, I am using IDs based at 78000.
    
    Allowing all elements except rate of decay to vary, yields:
    
    1 78000U          10271.44603163  .00000000  00000-0  00000-0 0    06
    2 78000   8.8200  56.3225 0262381 327.4767  31.2990  0.96599856    07
    
    Note the similarity to the orbits of DSP F18 and its IUS 2nd stage:
    
    DSP F18
    1 24737U 97008A   10268.09652703 0.00000000  00000-0  00000-0 0    09
    2 24737   8.7850  58.5528 0007297 129.3006 230.7808  1.00270000    00
    DSP F18 r3
    1 24740U 97008D   10248.60745376 0.00000000  00000-0  00000-0 0    07
    2 24740   8.8557  59.2296 0025223  26.4686 333.6721  0.99500413    07
    
    Note also that 78000's eccentricity is much greater than that of its suspected parent. The orbits of
    the two DSP aperture covers identified to-date, 90095E / 96143 and 00024E / 28156, also are
    considerably more eccentric than those of their parents, due to their much greater susceptibility to
    the effects of SRP (solar radiation pressure):
    
    DSP F15
    1 20929U 90095A   10259.39897984 0.00000000  00000-0  00000-0 0    02
    2 20929  12.6575  37.4872 0006240 310.3660  49.5916  0.98394463    02
    DSP F15 r3
    1 20932U 90095D   10001.00000000  .00000000  00000-0  00000-0 0    04
    2 20932  12.1967  41.2348 0078045 288.7344 219.5950  0.99914171    08
    DSP F15 Cover
    1 96143U 90095E   10001.00000000 0.00000000  00000-0  00000-0 0    01
    2 96143  12.3619  40.1484 0158753 122.6256  79.1160  0.99293506    08
    
    DSP F20
    1 26356U 00024A   10075.14329939 0.00000000  00000-0  00000-0 0    04
    2 26356   5.8583  63.0099 0007421 243.9297 116.0024  1.00270000    04
    DSP F20 r3
    1 26359U 00024D   10220.66341841 0.00000000  00000-0  00000-0 0    02
    2 26359   6.2927  61.3768 0007338  11.2760 348.7526  0.99704776    06
    DSP F20 Cover
    1 28156U 00024E   10219.54841720 0.00000000  00000-0  00000-0 0    05
    2 28156   6.5337  61.3504 0236099 220.3280 137.8983  0.99704389    01
    
    Note also that the mean motion of the known DSP aperture covers is similar to that of their IUS 2nd
    stage, which may be the best guide for 78000. Accordingly, search elset 78002, below, has the same
    mean motion as 97008D.
    
    The greatest difference in mean motion, is between 90095D and E, about 0.006 rev/d, which I have
    used to bracket the range of mean motions relative the 78002 orbit, per elsets 78001 and 78003:
    
    1 78001U          10271.46504067  .00000000  00000-0  00000-0 0    02
    2 78001   8.7971  56.3646 0277262 352.5124   7.1375  0.98900000    07
    
    1 78002U          10271.47006356  .00000000  00000-0  00000-0 0    02
    2 78002   8.7912  56.3756 0288900 358.2002   1.7527  0.99500000    00
    
    1 78003U          10271.47502044  .00000000  00000-0  00000-0 0    08
    2 78003   8.7852  56.3865 0303087   3.3771 356.8767  1.00100000    09
    
    Scott's UNID is faint, and visible only in flashes, which is consistent with a small, flat object,
    like an aperture cover, which likely is rotating due to SRP.
    
    There is a sporting chance of finding it again, especially if not too much time elapses. If not
    found within the range of 78001 - 78003, then the range of mean motions can be expanded.
    
    Happy hunting!
    Ted Molczan
    
    
    
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