Decay watch: June 24

Alan Pickup (alan@wingar.demon.co.uk)
Thu, 24 Jun 1999 20:58:49 +0100

Something quite bizarre has happened with the decaying Molniya rocket...
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Object: #16686 = 86- 31 D = Molniya 3-28 r2

Decay predictions:
Source   Prediction made    Predicted decay at      Latitude Longitude
               UTC                UTC                  deg      deg

SpaceCom   Jun 17 01:00     Jun 23 16:44 +-4d        46.6 S    44.7 W
SpaceCom   Jun 20 05:29     Jun 24 05:35 +-2d        27.7 S   139.1 E
SpaceCom   Jun 21 01:35     Jun 24 05:27 +-2d        56.8 S   102.6 E
SpaceCom   Jun 21 08:42     Jun 24 05:17 +-2d        60.9 S    53.9 E
SpaceCom   Jun 22 16:51     Jun 24 07:40 +-1d        47.4 S    88.3 E
SpaceCom   Jun 23 05:19     Jun 24 05:39 +-15h       60.2 S    84.8 E
SpaceCom   Jun 23 05:19     Jun 24 05:39 +-15h       60.2 S    84.8 E
SpaceCom   Jun 23 21:52     Jun 24 05:55 +-5h        56.8 S    95.8 E

SatEvo     Jun 17 19:35     Jun 24 00:00 +-2d
SatEvo     Jun 20 17:30     Jun 24 09:52 +-1.3d
SatEvo     Jun 21 20:20     Jun 24 05:27 +-18h
SatEvo     Jun 22 19:55     Jun 24 05:31 +-11h
SatEvo     Jun 23 18:40     Jun 24 07:34 +-5h        61.3 S    22.8 E
SatEvo     Jun 24 19:15   ! Jun 27 20:00 +-? !

Latest elset:
Moln 3-28 r2                                     1609 x 86 km
1 16686U 86031D   99175.70663882  .18814004  00000-0  21842-3 0  5167
2 16686  61.7514 149.4822 1053385 261.5169  86.6248 14.13539830 85181

SatEvo prediction:
Moln 3-28 r2                                     1548 x 86 km
1 16686U 86031D   99175.91817360  .20193621  13408-1  22677-3 0 95163
2 16686  61.7479 148.8184 1015602 261.6012  86.7760 14.22572886 85215
Moln 3-28 r2                                     1470 x 86 km
1 16686U 86031D   99176.19830506  .21408175  15637-1  22743-3 0 95165
2 16686  61.7429 147.9263 0967323 261.7147  87.2176 14.34218121 85256
Moln 3-28 r2                                     1389 x 85 km
1 16686U 86031D   99176.47611700  .22822508  18412-1  22842-3 0 95164
2 16686  61.7381 147.0257 0916571 261.8297  87.6859 14.46494934 85290

Note: Sometime before midnight UTC on June 23/24, the drag experienced 
by this decayer fell sharply so that, in the course of the single orbit
beginning at 23:49 UTC, it went from running 12 seconds early against
yesterday's SatEvo prediction to running 117 seconds late! As another
posting by Daniel Deak mentions, the SpaceCom drag rate then fell 
resolutely over several elsets, though it may now have stabilised. 
SpaceCom's decay notices for this have dried up, too, so perhaps I'm 
not the only one who's puzzled.

One clue is that the recent elsets suggest that the perigee has risen
10 km or more to around the 87 km level (relative to a spherical 
Earth). I can't put this down to normal atmospheric decay or 
luni-solar effects. As to when this rocket will finally decay, your 
guess is probably as good as mine :)
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Alan
-- 
 Alan Pickup | COSPAR 2707:  55d53m48.7s N  3d11m51.2s W   156m asl
 Edinburgh   | Tel: +44 (0)131 477 9144     Fax: +44 (0)870 0520750
 Scotland    | SatEvo page:   http://www.wingar.demon.co.uk/satevo/