Decay watch: January 29

Alan Pickup (alan@wingar.demon.co.uk)
Fri, 29 Jan 1999 20:20:42 +0000

Recent SpaceCom decay notices for the Orbit Adjust Module are:

Object                            Notice issued    Predicted decay
                                       UTC              UTC

#25617 = ROCSAT-1 Orb Adjust Mod  Jan 29 11:11     Jan 29 23:22 +-7h
#25617 = ROCSAT-1 Orb Adjust Mod  Jan 29 16:58     Jan 29 22:38 +-4h


The latest elset for this is:

ROCSAT-1 OrbAdjMod                               291 x 120 km
1 25617U 99002B   99029.63961071  .23777956 -43074-7  40652-3 0   323
2 25617  34.6582 266.4268 0129409 232.2989 126.5747 16.25146363   419

This shows it 61 seconds late on the prediction I posted yesterday. My
revised estimate is for decay at January 29.99 (23:43 UTC +-2h) which
would place it over the Indian Ocean off S Africa. The final orbit takes
it northbound over the equator at 22:41 UTC near 155 deg E longitude,
then N of Hawaii to California where it passes just N of Los Angeles at
23:03. Crossing the S USA, it is over Dallas, Texas, at 23.08 and Tampa,
Florida, at 23:11. Given the position of perigee, however, I think a re-
entry over the USA is unlikely. The track continues SE-wards to a
southbound equator crossing near 36 deg W at 23:25, then onwards to
overfly S Africa from 23:40 to 23:42. In my opinion, re-entry is most
likely along this arc over the S Hemisphere. The track continues across
the Indian Ocean to another northbound equator crossing near 133 deg E
at 00:08.

If SpaceCom is correct, and re-entry occurs on the previous orbit, there
must be a chance of it occurring near the previous pass over S Africa
from the NW coast of Namibia (22:06) to Johannesburg (22:10).

Predicted elsets:

ROCSAT-1 OrbAdjMod                               257 x 121 km
1 25617U 99002B   99029.76225858  .29603675  27071+0  44632-3 0 90326
2 25617  34.6569 265.5229 0104072 233.6083 125.4272 16.31394299   433
ROCSAT-1 OrbAdjMod                               237 x 120 km
1 25617U 99002B   99029.82339553  .33837266  21263+0  45833-3 0 90322
2 25617  34.6561 265.0689 0088781 234.2659 124.9050 16.35288407   440
ROCSAT-1 OrbAdjMod                               213 x 120 km
1 25617U 99002B   99029.88438200  .42305738  87555+0  50249-3 0 90324
2 25617  34.6552 264.6134 0070642 234.9258 124.4097 16.39779982   453
ROCSAT-1 OrbAdjMod                               178 x 119 km
1 25617U 99002B   99029.94518238  .77889736  43978+1  68538-3 0 90326
2 25617  34.6540 264.1559 0045002 235.5886 123.9850 16.46459179   465


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