re: Raduga 33 not seen

Walter Nissen (dk058@cleveland.Freenet.Edu)
Wed, 21 Aug 1996 19:41:48 -0400

> Subject: re: Raduga 33 not seen (Jim Varney) writes: 
> 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 włth the fact that Quicksat ignores B* while Trakstar does not. 
> Would like your thoughts or anyone else's on this. 
I'm sure there are people who read SeeSat-L who are far better able to 
answer this question than I.  I would guess that many good programs would 
generate similar output, given the same input.  My understanding of 
re-entries is a fraction of that of Bj"orn Gimle and Alan Pickup, and 
probably Mike McCants, Paul Maley and Ted Molczan, as well.  I think the 
second and third derivatives of the MM are changing very rapidly near 
re-entry and it is important to choose an elset with validity (and thus in 
practice, with epoch) near the time of observation. 
It might seem that if you had good second, third, fourth and higher 
derivatives that you might be able to use an elset over a wider interval, 
but I think this idea is thwarted by 3 problems.  1) There is no value for 
the third and higher derivatives in the TLE format.  2) A minor(?) one is 
that the acceleration is not applied continuously, but only at perigee, 
more or less as a step function; so you end up trying to fit a smooth 
curve to a sawtooth resulting in a greater or lesser degree of error at 
different phase angles (= mean anomalies).  3) The killer is that the 
object isn't a point moving in a continuous medium under smoothly varying 
forces but a highly non-spheroidal object which is tossed around by the 
atmosphere when it impacts at various attitudes.  This action has been 
compared to that of a stone skipping along the surface of a body of water. 
I think of it as being somewhat analogous to the non-gravitational jet 
forces which perturb the orbits of comets.  I believe that there have been 
cases of objects actually skipping off the top of atmosphere and going 
(albeit temporarily) into higher and longer-lived orbits. 
You were trying to observe about 96231.14 (in the YYJJJ.JJ format).  What 
does Trackstar say if you give it the 96231. epoch elset from Alan Pickup? 
Raduga 33 SL-12 r2 
1 23797U 96010D   96231.01682533  .42484856  35644-1  11759-2 0 92770 
2 23797  47.7135 208.5812 2232747  67.9484 314.1969 11.41665883  5133 
> "Celestial mechanics is entitled to be regarded as the most 
> perfect science" 
>                                          Forest Ray Moulton 
More perfect than number theory with its gems such as Euclid's 
finite proof of the infinitude of the primes? 
Walter Nissen         


Astronomy is looking up.