STS-74, anticipated appearance

Walter Nissen (dk058@cleveland.Freenet.Edu)
Sat, 11 Nov 1995 08:15:38 -0500

> From: n.clifford1@physics.oxford.ac.uk (Neil Clifford) 
> Subject: Re: STS-74 pre-launch elements anyone ? 
 
Neil, thanks for posting the pre-launch STS-74 elsets. 
 
With the launch now scrubbed until November 12th, the details which follow 
in this message (prepared before the scrub) will change, but all the major 
points and major questions remain the same. 
 
The appendix is an excerpt from QuickSat for the Washington, DC, area 
using these elsets: 
 
Mir   OIG 313 
1 16609U 86017A   95313.86156770  .00003998  00000-0  58925-4 0  3081 
2 16609  51.6451 148.0817 0003574 304.4745  55.5910 15.57982282555662 
STS-74  docked Nov 14 approx 06:00 UTC to sep burn on Nov 17 at 09:19 UTC. 
1 99974U          95318.54261102  .00007207  00000-0  10674-3 0    83 
2 99974  51.6448 124.5700 0005368 296.2023  63.8552 15.58324096   498 
 
You will note that for the November 15 pass, the anticipated times for the 
shuttle and the space station differ by more than 2 minutes.  Experience 
from previous shuttle missions, and from the previous rendezvous missions 
in particular, suggests that the Mir elset has much higher reliability. 
It is true that Mir is reboosted from time to time, but perhaps we can 
expect that the RSA wouldn't want to complicate things for JSC during or 
just prior to a rendezvous mission?  I suppose CAMs (collision avoidance 
maneuvers) are still a remote possibility. 
 
Also, previous experience and energy requirements suggest that the shuttle 
orbiter will chase Mir from a lower and faster orbit.  Thus, prior to the 
docking, Atlantis will appear behind Mir.  After undocking, it will again 
return to a lower and faster orbit, thus appearing ahead of Mir. 
 
Also, when looking just above the Sun, as the low passes in the southeast 
just before dawn require, I tend to be a bit skeptical about the computed 
magnitudes.  The phase relationship is based on spherical shape and a 
rough texture to the surface.  Real satellites, manned and otherwise, seem 
to be boxier, shinier, and more shadowy.  Thus, the variance of brightness 
with phase tends to be more pronounced than for the theoretical model. 
Thus when the phase angle is unfavorable and the object is near the Sun, 
the computed magnitude may be brighter than the actual observed magnitude. 
This has been, roughly, confirmed by previous experience.  However, if you 
get a specular glint off a long, shiny tube or a nice, near-specular glint 
off a white surface, the opposite can occur. 
 
Can anyone confirm these various speculations? 
 
Cheers. 
 
Walter I. Nissen, Jr., CDP      216-243-4980      dk058@cleveland.freenet.edu 
 
--- 
 
They don't all occult Capella. 
 
--- 
 
  39.000  77.000    0.    DC  <---------------- 1950  9.5  4 F F F F F 
 
***  1995 Nov  15  *** Times are UT ***  2244 1058 
 H  M  S  TIM AL AZI C   U  MAG   REVS  HGT SHD  RNG  EW PHS  R A   DEC 
99974 STS-74  docked 
10 44 39   .0 11 131 C  40  4.2   14.3  401 395 1369  .8 143 1244 -21.8 
16609 Mir Complex                       .1 
10 46 55   .1 12 131 C  41  4.1   87.2  401 395 1334  .9 143 1244 -21.5 
 
***  1995 Nov  17  *** Times are UT ***  2243 11 0 
16609 Mir Complex                       .1 
10 31 16   .2 25 135 C  45  1.7  118.2  401 299  850 1.4 128 1150 -13.5 
 
***  1995 Nov  18  *** Times are UT ***  2242 11 1 
16609 Mir Complex                       .1 
 9 35 34   .2 12 131 C  41  3.4  133.2  400  93 1342  .9 127 1145 -21.6 
16609 Mir Complex                       .1 
11 11 33   .2 65 325 C  55 -1.2  134.2  401 312  440 2.9  62  8 1  57.1 
 
***  1995 Nov  19  *** Times are UT ***  2242 11 2 
16609 Mir Complex                       .1 
10 15 40   .2 55 140 C  50  -.6  149.2  401 102  480 2.6  98 1025  10.5