Re: STS DEBRIS AVOIDANCE

Ed Cannon (ecannon@mail.utexas.edu)
Sun, 23 Feb 1997 05:08:30 -0600

Jay Respler asked:

> Has anyone identified the specific piece of Pegasus debris that the 
> shuttle/HST raised its orbit to avoid?

After finding (using DejaNews) a story that mentioned that maneuver:

   "Astronauts inspect telescope's tattered skin", by IRENE BROWN, 
   UPI Science Writer, Copyright 1997 by United Press International, 
   Sun, 16 Feb 1997 3:37:23 PST

I got Bjoern Gimle's program COLA.EXE and, using the following HST elements 
from Ted Molczan's molczan.tle (358.n21)

   HST             13.3  4.3  0.0  4.2 d
   1 20580U 90037  B 97 44.21359034  .00000326  00000-0  32049-4 0  9246
   2 20580  28.4689 109.0959 0006249 173.0551 187.0079 14.91170054174590

and part of Mike McCants' alldat.tle, I found the following close approaches:

   Date    Local Time Norad           Name           Range (km)  EphAge
  2/18/1997  9:57:13.7 24358 94029PK                       4.4     -2.37
  2/20/1997 16:32:19.5 24554 94029XE                       2.8      0.00

I don't fully understand that output, because I'm sure I told COLA.EXE to 
use UT not CST, but this is the first time I've ever used that program.
Below are elements for those two objects from alldat.tle.  (I wish I'd had 
the previous week's alldat.tle, but it's at my office and I'm at home.)

   94029PK
   1 24358U 94029PK  97051.78113561 +.00008300 +00000-0 +33476-2 0 00863
   2 24358 081.4990 331.6372 0620588 328.1625 028.3139 13.55824591524893
   94029XE
   1 24554U 94029XE  97051.69406959 +.00024582 +00000-0 +43199-2 0 00983
   2 24554 081.6409 311.1925 0412332 290.4768 065.2456 14.24432452034661

Now, who uses a program that will tell us *where* those close approaches
would have occurred, had they not maneuvered HST/STS82 complex to avoid
them?  The same goes for the following.  (I haven't gotten that sort of 
program yet.)

It appears that there was an even closer approach (of less than 1 km) to 
HST on Feb. 11:

   Date    Local Time Norad           Name           Range (km)  EphAge
  2/11/1997  9:19:25.6 13153 Cosmos 1356      5.0  1.5     0.7     -1.51

Here are the molczan.tle (358.n21) elements I used for that object:

   Cosmos 1356      5.0  1.5  0.0  5.4 v
   1 13153U 82039  A 97 43.89490546  .00000263  00000-0  27784-4 0  5497
   2 13153  81.1732 196.9862 0017262 241.8210 118.1265 14.89214771798725

Ed Cannon
ecannon@mail.utexas.edu
Austin, Texas, USA
30.308N, 97.728W