re: STS leading Mir

Walter Nissen (dk058@cleveland.Freenet.Edu)
Wed, 3 Apr 1996 00:08:30 -0500

Various observers at various times have reported observations of STS 
orbiters at widely varying magnitudes (after accounting for range, formal 
phase angle (as in QuickSat), and meteorological conditions) during all of 
the following: 
 
1) on successive passes 
2) at different times during the same pass    -and- 
3) from different locations during the same pass. 
 
If you glance at an orbiter, you immmediately see that this can happen 
because of its: 
 
1) varying albedo presented by the combination of shiny payload doors, 
white tile and black tile    -and- 
2) convoluted, boxy, shadowy, concave/convex shape. 
 
Similar, if somewhat less extreme, considerations apply to Mir for similar 
reasons. 
 
Dan Laszlo writes: 
> However, on the previous STS-Mir mission, within a few hours of 
> separation, Mir was clearly ahead of the Shuttle when it made its pass 
> for us in  Colorado. 
 
and then: 
> I was primed to expect STS to lead, and I'll admit initial disbelief at 
> the sight, with a dimmer, yellow tinged object leading the brighter 
> white object. 
 
If by this you mean that the leading object clearly had to be Mir because 
it was dimmer than the trailing object, then I would have to be very 
skeptical, although I would agree that you have some justification for 
suggesting this.  I've noticed other observers tend to pay more attention 
to color, something I am not particularly sensitive to.  Perhaps they will 
comment. 
 
I would suggest that good elsets from the time you observed might be a 
more reliable source of an ID than magnitude. 
 
I really try to live by the maxim:  Never throw out an elset.  Even so, 
I'm not convinced the elsets I have are determinative.  This is what I 
have which seems usable: 
 
Mir Complex post undocking      jsc, http://sh...nasa.gov via Molczan, ele-rq 
1 16609U 86017A   95322.45642709  .00003885  00000-0  46559-4 0  9179 
2 16609  51.6410 104.9926 0002556 336.7720  23.3319 15.58152580557006 
Mir                             ele-rq (i.e., Gary Morris) 
1 16609U 86017A   95322.77713656  .00003885  00000-0  46559-4 0  9219 
2 16609  51.6438 103.3888 0002558 336.7418  23.3621 15.58084095557058 
Predicted Atlantis post undock  jsc 
1 23714U 95061A   95322.45640993  .00019322  00000-0  20677-3 0  9182 
2 23714  51.6410 104.9925 0004889 328.8076  31.2788 15.58711072   948 
 
If someone has superior elsets, particularly if they are accompanied by 
reasons for their superiority, please provide them.  If not, there are a 
few repositories where we could look. 
 
Here is the corresponding QS output: 
  40.000 105.000    0.    CO  <---------------- 1950  9.5  4 F F F F F 
***  1995 Nov  18  *** Times are UT ***   033 1255 
 H  M  S  TIM AL AZI C   U  MAG   REVS  HGT SHD  RNG  EW PHS  R A   DEC 
23714 STS-74                            .1 
12 43  4   .0 67 142 C  52  -.9    1.2  400 275  431 3.0  95 1028  21.2 
16609 Mir Complex                       .1 
12 43  8   .0 67 142 C  52  -.9    1.2  401 277  432 3.0  95 1028  21.4 
12 43 10   .0 68 142 C  52  -.9   -3.8  401 277  432 3.0  95 1028  21.4 
 
This does not seem exceptional.  It follows the general rule imposed by 
energy considerations, that the shuttle trails while chasing Mir from a 
lower orbit, and leads after departing for a lower orbit. 
 
I would welcome additional insights. 
 
Cheers. 
 
Walter Nissen                   dk058@cleveland.freenet.edu 
 
--- 
 
Darkness has its place -- in the night sky.  Look into it.