Re: Decay watch: Iridium Delta and others

Alan Pickup (alan@wingar.demon.co.uk)
Thu, 27 Aug 1998 21:16:09 +0100

The final elset for the Iridium 50 Delta 2 rocket is
Iridm 50 Delta r 5.9  2.4  0.0  5.6 d            154 x 135 km
1 25174U 98010F   98238.78801312  .21266080 -14636-5  30208-3 0  3088
2 25174  83.6194 249.5165 0014226 302.5501  57.4472 16.48080734 29589

This shows it running 65 seconds late against the last elset in the
prediction I posted here two days ago. I estimate decay at August 26.91
(21:50 UTC with uncertainty of less than one hour). USSPACECOM, on the
other hand, report decay on August 27.

                -----------------------------

The Iridium 69 CZ Smart Dispenser decayed more quickly than I expected.
The final elset is
Iridm 69 CZ S/D  4.0  2.0. 0.0  5.5 d            163 x 118 km
1 25322U 98026D   98239.27268273  .34238854 -12238-5  27344-3 0  2048
2 25322  86.2524 231.7925 0034761  60.2997 302.1179 16.49589994 18383
which is 3.2 minutes early against my prediction. Decay was most likely
near perigee on the orbit after this at August 27.34 (08:15 UTC +-15
minutes).

Almost certainly the S/D decay was brought forward by the increase in
atmospheric density associated with today's geomagnetic storm. Many
other satellites are also showing higher drag and will be running
increasingly early against predictions from older elsets.

Alan
-- 
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