Post-mortems: Mars 96 Block D-2 and Progress M-33 r

Alan Pickup (alan@wingar.demon.co.uk)
Sat, 23 Nov 1996 00:26:10 +0000

Mars 96 Block D-2
=================

The WWW page
        http://flox.kiam1.rssi.ru/MARS/MARS96_5.HTM
contains an analysis of the re-entry of this object and provides state
vectors for the final orbits based on observations by the Russian Space
Surveillance Center (SSC). It is interesting to compare the latter with
the equivalent US data from OIG and with my own SatEvo predictions which
were posted to SeeSat-L at 21.06 UT on the 17th (based on OIG elsets to
96322.7092). Not for the first time, my posting was delayed en route 
(probably at my ISP, Demon) and it may not have been reflected on
SeeSat-L until after the decay.

The following table lists the equator crossing (eqx) times as provided
by SSC and SatEvo and as derived from the OIG elsets. I also give the
residual between my SatEvo evolution and the two sets of observations.

Rev    SSC eqx      OIG eqx   SatEvo eqx  SSC-SatEvo  OIG-SatEvo
        (day)        (day)      (day)      (seconds)   (seconds)

14 96322.76970729  .76969012  .76969833     +0.77        -0.71

15 96322.83017663  .83016208  .83017188     +0.41        -0.85

16 96322.89060209  .89058982  .89060119     +0.08        -0.98

17 96322.95096675   no elset  .95097233     -0.48

18 96323.01125106  .01123341  .01125265     -0.14        -1.66

The analysis on the Russian WWW page gives atmospheric entry at Nov 18
01.13 UTC (ie 96323.051) and splashdown at 01.20 UTC (96323.056); my
SatEvo prediction put "decay" at 96323.041.

A satisfying, and admittedly lucky, outcome for SatEvo which may 
indicate what is possible when/if we have a complete feed of timely 
elsets. Thanks to OIG for their overtime!

Progress M-33 rocket
====================

The final OIG elset for this is:
Progress M-33 r                                  130 x 108
1 24664U 96066B   96327.41277526  .58399191  12743-4  19260-3 0   190
2 24664  51.6425  45.7297 0017318 127.1554 233.1175 16.57786928   401

Not such a success for SatEvo. This is 61 seconds early with respect 
to the prediction I posted on Thursday based on elsets to 96326.50.
However, I am puzzled and suspicious about the indicated increase in 
eccentricity; objects tend to circularise their orbits as re-entry 
approaches and I wonder whether it was already into its re-entry phase
at the time the fix was taken. in any case, I suspect that decay
occurred near perigee on this orbit, around 96327.434 (10.25 UT); SatEvo
had predicted decay at about 96327.49.

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
 Scotland    | Royal Observatory: A.Pickup@roe.ac.uk +44 (0)131 668 8224