Re: IAE re-entry time?

Alan Pickup (alan@wingar.demon.co.uk)
Fri, 24 May 1996 00:20:29 +0100

Now I've had time to analyse the final orbits of the Inflatable
Antenna (IAE), and now that I've seen William Leininger's report
of a possible sighting of the object at May 22.43, I think it _is_
reasonable to question NASA's (reported) claim that it re-entered 
over the Altantic at May 22.396. Yes, I know this is/was in 
remarkable agreement with my prediction (for May 22.38) of the day 
before. However.

As I reported yesterday, the final OIG element for this object:
IAE
1 23872U 96032C   96143.35927604  .33369273  58942-5  57057-2 0   166
2 23872  39.0322 253.9177 0008701 300.5494  59.9587 16.31848780   399
showed it running 65s late on my earlier prediction. What I should have
admitted was that this discrepancy (and, indeed, n and ndot) appeared 
inconsistent with a decay so close to my prediction. Of course, this 
is (was) an odd-ball object...

My new analysis carries a SatEvo evolution through three of the final
four OIG elements, those for 96142.61, 43.11 and 43.35, to within
11 milliseconds. The fourth element (for 96143.23) was not included in
the analysis and shows a residual of 1.1s.

The decay time indicated by this evolution is May 23.437, 10 minutes
later than William's putative observation and (almost exactly) one 
hour later than NASA's time.

My final three evolved elements are:
IAE 
1 23872U 96032C   96143.29789367  .33065028  68671+0  89951-2 0 90118
2 23872  39.0093 254.3002 0004088 311.9048  48.0602 16.27002976   460
IAE 
1 23872U 96032C   96143.35917522  .53028532  20195+1  89488-2 0 90117
2 23872  39.0082 253.8730 0003056 312.4599  47.5142 16.32067952   476
IAE 
1 23872U 96032C   96143.42018932  .99999999  43699+2  91073-2 0 90114
2 23872  39.0059 253.4431 0001402 313.0184  46.9698 16.43165044   487

The contemporary STS element is:
STS-77 
1 23870U 96032A   96143.41665509  .00000384  53664-5  46137-5 0   125
2 23870  39.0131 253.6840 0007237 283.1813 334.9017 15.96871726   472
which shows STS running 5 minutes behind the IAE (if still in orbit) 
at the equator crossing. So William might have seen Endeavour, as
Philip Chien suggests, but I havn't run predictions for either object
for William's location. Note that the IAE had completed one extra orbit
at 96143.42 so it is not the case that the two were observable together
thoughout.

Alan
-- 
 Alan Pickup | COSPAR site 2707:  55d53m48.7s N   3d11m51.2s W  156m asl
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