re: Raduga 33 not seen

Jim Varney (jvarney@mail2.quiknet.com)
Mon, 19 Aug 1996 22:25:19 -0700

Walter Nissen wrote:

>With objects deep in the atmosphere 
>like this, the accuracy of elsets can degenerate horribly outside of a 
>narrow window.  You don't say what you mean by a few minutes, but that 
>might not be enough. 

>Using only the elset closest to the desired pass, the one with epoch 
>96231, I see only one "predicted" pass: 
> 
>  38.458 121.398   31.    Varney, CA <--------- 1950 13.5  4 F F F F F 
> 
>***  1996 Aug  18  *** Times are UT ***   345 1231 
> 
> H  M  S  TIM AL AZI C   U  MAG   REVS  HGT SHD  RNG  EW PHS  R A   DEC 
>23797 Raduga 33 SL-1 
>11 19 36  1.6 13 180   162 24.0    6.2 1584  54 3528  .5  48  058 -38.8 
> 
>and none of this "activity" appears to occur around the time you looked.

Thanks for looking into this.   

I use Quicksat to generate an evening's worth of predictions.  For objects
such as this that are in unstable orbits, I usually rely on Trakstar because
it is a "pure" implementation of SGP4.  [Not to imply Quicksat isn't pure.
I don't know what routines are in Quicksat, but I do know what is in Trakstar
because Dr. Kelso provides the source code.] 

Using the elset

Raduga 33 R/B(D)
1 23797U 96010D   96229.05467116 +.26361494 +17384-4 +13165-2 0 02771
2 23797 047.8010 213.6600 2868208 063.1898 323.7229 10.02738645004926

Trakstar gives

1996 Aug 18  03:24:50  SAC  281.5746  31.6074    208.127  -5.337090
1996 Aug 18  03:25:00  SAC  307.3956  39.8688    167.616  -2.526458
1996 Aug 18  03:25:10  SAC  345.7169  40.1518    162.841   1.625028
1996 Aug 18  03:25:20  SAC   14.0625  31.1912    196.461   4.852553

which led me to go out and take a chance on seeing it.

Alan Pickup's TLE

Raduga 33 R/B(D)
1 23797U 96010D   96230.02026870  .34378235  20746-1  10964-2 0 92774
2 23797  47.7595 211.3063 2580813  65.3926 319.2471 10.65791595  5023

with Trakstar gives these not very good choices (near culmination)

1996 Aug 18  02:46:20  SAC  149.7443  20.1500    372.418  -1.050338 
1996 Aug 18  04:57:30  SAC  352.3775   3.0607    882.755   0.951147

So, yes, these rapidly changing elsets do generate disparate results.
But I don't know if both elsets are correct, one or the other are
correct, or neither.  Better to go out for ten minutes on the chance
of seeing it rather than miss it due to a decision to not go out
because of a perception that the prediction is spurious.  That said, 
my report of not seeing Raduga 33 r/b(D) can either be taken as a 
"true negative" or a "false negative" depending on your faith in 
the 229 elset.

Now the question that goes begging is: why did Trakstar generate
a pass for 0325 UT while Quicksat did not?  My hunch is that it has
to do with the fact that Quicksat ignores B* while Trakstar does not.
Would like your thoughts or anyone else's on this.

 -- Jim


"Celestial mechanics is entitled to be regarded as the most 
perfect science"
                                         Forest Ray Moulton