Re: STS DEBRIS AVOIDANCE

Bjoern Gimle (b_gimle@algonet.se)
Thu, 27 Feb 1997 08:37:23 +0100

Ed Cannon <ecannon@mail.utexas.edu> wrote:

>I got Bjoern Gimle's program COLA.EXE=20
(Rob Matson's !)

I sent that comment, but didn't answer any of Ed's questions. Here is some:

Phil Clark later reported that it was 94029HU
1 24169U 94029HU  97053.11593097  .00011640  00000-0  10530-2 0  1462
2 24169  81.9345 290.2378 0131193  62.5071 298.9404 14.88879443147615

This was the oldest elset I found at OIG. Using this as the target object,
and the file STS82.TLE from OIG as 'all other' it appears that a near
collision could occur on Feb.15 at 15:03. Since STS made a slow burn
on four occasions to raise HST's orbit, it is essential to study only
the results from the closest epoch elsets, from grapple around 97044.34
to release on 97050.35.

   Date    Local Time Norad           Name           Range (km)  EphAge
 2/15/1997 15:03:41.4 24719 STS82                         9.7     +1.29
...
 2/15/1997 15:03:44.1 24719 STS82                        34.0     +0.16
...
 2/15/1997 15:03:43.9 24719 STS82                        32.1     -0.08
However, it appears that the next orbit became closer :
 2/15/1997 16:40:22.9 24719 STS82                        16.5     +0.23
...
 2/15/1997 16:40:24.0 24719 STS82                         7.0     -0.01
...
 2/15/1997 16:40:23.9 24719 STS82                         7.8     -0.22
This could however be safer, if the vertical separation was larger.
Pertinent elsets:
STS82
1 24719U 97004A   97046.46875000  .00000155  00000-0  44696-6 0   176
2 24719  28.4714  94.5890 0000717 118.5598 131.8376 14.90044116   603
STS82
1 24719U 97004A   97046.70504630  .00000155  00000-0  43608-6 0   184
2 24719  28.4686  93.0730 0003041  40.3628  39.8770 14.89388845   633
STS82
1 24719U 97004A   97046.91666667  .00000155  00000-0  43766-6 0   192
2 24719  28.4719  91.7171 0002810  41.8756  95.2592 14.89399835   667

>
>I don't fully understand that output, because I'm sure I told COLA.EXE to=
=20
>use UT not CST, but this is the first time I've ever used that program.

COLA uses the time derived from its "Observation longitude" prompt,
(CST =3D -90) or possibly corrected by the next prompt to correct the
time (CST=3D-6). 0 is used as 'Local GMT time'.

>Below are elements for those two objects from alldat.tle.  (I wish I'd had=
=20
>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
>
With later STS/HST elsets, these objects are not within 44 km.
HST after release
1 20580U 90037B   97053.19919963 +.00000519 +00000-0 +40998-4 0 09400
2 20580 028.4685 051.5719 0014766 080.2856 279.9386 14.86416374175934

>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=20
>program yet.)

I use TRAKSTAR (TS Kelso) and its Lat/Long/Alt option to find where,
and its ECI Pos/Vel option to produce input for my SAT-DIST program
to compute distances and relative velocity vectors.

#24169:
1997 Feb 15  15:03:41   11=F819'57" N   103=F838'59" E    594.577 ECL
1997 Feb 15  15:03:42   11=F816'15" N   103=F839'16" E    594.676 ECL
1997 Feb 15  15:03:43   11=F812'32" N   103=F839'34" E    594.776 ECL
1997 Feb 15  15:03:44   11=F808'49" N   103=F839'52" E    594.875 ECL
#24719 elset 17:
1997 Feb 15  15:03:41   11=F810'56" N   103=F814'54" E    595.379 ECL
1997 Feb 15  15:03:42   11=F812'36" N   103=F818'03" E    595.378 ECL
1997 Feb 15  15:03:43   11=F814'16" N   103=F821'13" E    595.377 ECL
1997 Feb 15  15:03:44   11=F815'55" N   103=F824'22" E    595.376 ECL
#24169:
1997 Feb 15  16:40:23   11=F839'04" N    79=F817'36" E    594.412 ECL
1997 Feb 15  16:40:24   11=F835'21" N    79=F817'54" E    594.511 ECL
1997 Feb 15  16:40:25   11=F831'39" N    79=F818'11" E    594.610 ECL
1997 Feb 15  16:40:26   11=F827'56" N    79=F818'29" E    594.709 ECL
#24719 elset 18:
1997 Feb 15  16:40:23   11=F831'52" N    79=F817'44" E    595.324 ECL
1997 Feb 15  16:40:24   11=F833'32" N    79=F820'54" E    595.324 ECL
1997 Feb 15  16:40:25   11=F835'12" N    79=F824'03" E    595.323 ECL
1997 Feb 15  16:40:26   11=F836'51" N    79=F827'13" E    595.322 ECL

#24169 XYZ, XdotYdotZdot
1997 Feb 15  16:40:23  -2898.459   6184.188   1399.677
                       -1.664000   0.997817  -7.316012 ECL
1997 Feb 15  16:40:24  -2900.121   6185.182   1392.360
                       -1.660586   0.990535  -7.317660 ECL
1997 Feb 15  16:40:25  -2901.780   6186.169   1385.042
                       -1.657170   0.983251  -7.319300 ECL
1997 Feb 15  16:40:26  -2903.435   6187.149   1377.721
                       -1.653752   0.975966  -7.320931 ECL
#24719 elset 18:
1997 Feb 15  16:40:23  -2900.311   6187.527   1385.645
                       -5.860688  -3.486708   3.278927 ECL
1997 Feb 15  16:40:24  -2906.170   6184.037   1388.923
                       -5.857270  -3.493989   3.277289 ECL
1997 Feb 15  16:40:25  -2912.025   6180.539   1392.199
                       -5.853846  -3.501266   3.275648 ECL
1997 Feb 15  16:40:26  -2917.877   6177.034   1395.474
                       -5.850414  -3.508540   3.274003 ECL

                      Dist.    Along    Cross    Veloc.
15-Feb-1997 16:40:23  14.542   14.410   1.953    11.582  =20
15-Feb-1997 16:40:24  7.051    4.500    5.428    11.520  =20
15-Feb-1997 16:40:25  13.707   -5.409   12.594   11.459  =20
15-Feb-1997 16:40:26  25.021   -15.321  19.782   11.397  =20

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