Decay watch: September 25
Alan Pickup (alan@wingar.demon.co.uk)
Sat, 25 Sep 1999 18:21:02 +0100
Once again, I have updated my Decay Watch page at
http://www.wingar.demon.co.uk/satevo/dkwatch/
It contains my final (for now) notice for today's decay of #25903, the
Foton 12 Soyuz rocket, plus the initial decay warning for #25921,
apparently debris from the Ikonos launch. I don't know what the latter
might be, but the fact that SpaceCom is issuing decay warnings suggests
that it might be big enough to observe, at least by N observers. It
enters eclipse in the Earth's shadow near 70 deg S latitude at ~23 local
time while northbound. It leaves eclipse, also while northbound, near 63
deg N at ~21h local time.
As readers of this list probably know by now, the Foton 12 Soyuz
appeared to be in the early stages of re-entry as it passed over the USA
from northern Minnesota at 01:32 UTC to South Carolina at 01:37. It was
sighted by Mike DiMuzio (near Cleveland, Ohio) shining brightly at
magnitude -4 and appearing reddish as it passed low above his SW
horizon. At the time it must have been at least 500 km deep in the
Earth's shadow and visible only because it was incandescent through the
heat of friction with the atmosphere. If Mike's brightness estimate is
correct, an observer more directly under the track might have seen it
closer to magnitude -6.
The final published elset (corresponding to this pass) shows a
miraculous rise in the perigee as the orbit became almost circular very
quickly. There is also an implied drop in drag and little increase at
all in mean motion - all of which are unlikely, to say the least. It
suggests to me that SpaceCom was having difficulty reconciling its
observations as the rocket began to decay. Excluding this elset from my
current post-decay analysis, I compute these SatEvo-predicted elsets for
the last two equator crossings:
Foton12 Soyuz r 7.4 2.4 0.0 5.5 d 10 144 x 129 km
1 25903U 99048B 99268.04439822 .41913837 17720+1 36343-3 0 90484
2 25903 62.7681 147.7982 0011911 109.4643 250.6644 16.51166832 2467
Foton12 Soyuz r 7.4 2.4 0.0 5.5 d 10 115 x 108 km
1 25903U 99048B 99268.10481475 2.07377390 50000+2 54357-3 0 90488
2 25903 62.7659 147.5411 0005418 109.4775 250.5810 16.60650556 2474
Based on these I put decay at 02:46 UTC (-60m+10m) near the Kamchatka
Peninsula of NW Russia. Mike's observation, though, suggests that the
decay was already underway more than one hour before this, so it may
have succumbed much earlier. Indeed, it may not have survived far beyond
the southbound equator crossing over W Brazil at 01:47 UTC, 2-3 minutes
after it passed over Caracas, Venezuela.
SpaceCom place their decay point at 02:55 UTC over the Bering Sea with
an uncertainty of only one minute. Unless further elsets appear to
justify this confidence, and given the nature of SpaceCom's final
elset, I am sceptical about this claim.
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/