#24763 decay & geomagnetic storm

Alan Pickup (alan@wingar.demon.co.uk)
Thu, 15 May 1997 21:12:14 +0100

The latest elset for the decaying Cosmos 2340 SL-6 platform is:
Cosmos 2340 SL-6 plat                            272 x 175 km
1 24763U 97015C   97135.50814863  .02114653  83839-5  68610-3 0  1190
2 24763  62.8455 142.8049 0073165 117.0573 243.8297 16.18644026  5567

This shows it running 28 seconds late with respect to the SatEvo
evolution I posted here two days ago.

Another evolution satisfies nine elsets between 97133.52 and 97135.32
with a mean residual of 0.5 sec (maximum error 1.0 sec), yet is 4
seconds late with respect to the above elset after only another 3
orbits. (ie #24763 was 4 sec early on prediction).

This is circumstantial evidence that #24763 is being affected by the
increased atmospheric drag associated with a strong geomagnetic storm
which began this morning. The storm may be the strongest one this year,
beating even the infamous storm of January 10, and appears to have
followed a CME (solar coronal mass ejection) on May 12. Watch out 
STS-84 :-)

I've attempted to extend my earlier evolution by (slightly more than)
doubling the drag after the 97135.32 equator crossing. This satisfies
the equator crossing of the above elset but I don't know how long the
increased drag will (did?) last, so the following predicted elsets are
necessarily uncertain:
Cosmos 2340 SL-6 plat                            251 x 170 km
1 24763U 97015C   97136.00158062  .05017208  93345-2  12349-2 0 91195
2 24763  62.8441 140.8090 0060936 117.1481 243.4738 16.23377466  5649
Cosmos 2340 SL-6 plat                            220 x 163 km
1 24763U 97015C   97136.55484480  .08188782  35595-1  12737-2 0 91193
2 24763  62.8418 138.5533 0043296 117.2510 243.1898 16.30320185  5731

If the increased drag had not occurred, the object would be about 1 and
4 minutes late respectively at these epochs. Of course, the drag could
be more than my guesstimate, in which case the object would be earlier
still. Decay might occur as early as the 17th if the increased drag
persists.

I'll update in 24 hours, if not before.

Alan 
-- 
 Alan Pickup | COSPAR site 2707:  55d53m48.7s N   3d11m51.2s W  156m asl
 Edinburgh   | Home:    alan@wingar.demon.co.uk      +44 (0)131 477 9144
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