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 _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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