FW: Satellite Encounters

Jeff Hunt (jhunt@eagle1.eaglenet.com)
Thu, 14 Aug 97 15:28:49

Hello All,

Rob Matson has asked me to forward his following three posts regarding 
satellite close encounters as his posts are not getting through to SeeSat-L.

He plans to unsubscribe and re-subscribe to see if that fixes the problem.

--- On 14 Aug 1997 11:58:10 -0800  ROB MATSON 
<ROBERT.D.MATSON@cpmx.saic.com> wrote:


>Post #1 - 12 Aug 97 5:32pm PDT
>-------------------------------------------
>
>Greetings All,
>
>Based on the latest available elements, it appears that the Hubble Space
>Telescope (NORAD #20580) will have a fairly close encounter with STEP 2
>Pegasus Debris LE (NORAD #24231) early Saturday morning August 16th at
>0:43:22.3 UTC.  Predicted closest approach range is 1.4 km; the Pegasus
>debris will be 1 km higher than Hubble at this time.  Prediction is based
>on the following TLEs from OIG:
>
HST
1 20580U 90037B   97224.08088929 +.00000249 +00000-0 +11086-4 0 00303
2 20580 028.4653 041.0885 0014517 055.1252 305.0699 14.86469949201385
>
STEP 2 Pegasus Deb LE
1 24231U 94029LE  97223.84916601 +.00000368 +00000-0 +49701-4 0 00964
2 24231 082.0930 133.6979 0092869 277.8244 081.2441 14.73683318063577
>
>
>Post #2 - 13 Aug 97 12:03pm PDT
>-------------------------------------------
>
>Here's an update on the upcoming close approach between the Hubble Space
>Telescope (#20580) and STEP 2 Pegasus Debris LE (#24231):
>
>Virtually no change since yesterday's prediction.  Closest approach still
>predicted for 16 Aug 97 at 0:43:22.3 at a range of 1.4 km -- less than one
>mile!  Current prediction based on the following elements from OIG which
>will be a little over 3 days old at the time of the encounter:
>
HST
1 20580U 90037B   97224.88660857 +.00000246 +00000-0 +10782-4 0 00395
2 20580 028.4653 035.9474 0014521 063.4517 296.7554 14.86470092201503
>
STEP 2 Pegasus Deb LE
1 24231U 94029LE  97224.79974050 +.00000366 +00000-0 +49377-4 0 00979
2 24231 082.0930 132.7716 0092796 274.7386 084.3258 14.73684243063712
>
>
>Post #3 - 13 Aug 97 4:073pm PDT
>-------------------------------------------
>
>I've located another upcoming close approach between two satellites, this 
>time Iridium 7 (#24793) and Spot 1 r Deb C (#16615).  The pair actually 
>make a number of close approaches at 100-minute intervals, the closest 
>occurring on 15 Aug 97 at 0:20:26.5 UTC at a range of 1.2 km (3/4 of a 
>mile).  Here are the particulars of that encounter and the two on either 
>side of it:
>
>               Target satellite:  Spot 1 r Deb C (#16615)
>
>  UTC Date  UTC Time  Norad   Name      Range (km) NdAng EphAge (days)
> 8/14/1997 20:59:44.1 24793 Iridium 7      6.7     81.5     +1.76
> 8/14/1997 22:40:05.3 24793 Iridium 7      3.2     70.8     +1.83
> 8/15/1997  0:20:26.5 24793 Iridium 7      1.2     26.1     +1.90
> 8/15/1997  2:00:47.7 24793 Iridium 7      4.0     73.6     +1.97
> 8/15/1997  3:41:08.9 24793 Iridium 7      7.2     80.5     +2.04
>
>TLEs used for this prediction:
>
Spot 1 r Deb C
1 16615U 86019C   97225.11207926 +.00000584 +00000-0 +20912-3 0 02117
2 16615 098.3115 275.6221 0019808 321.6398 038.3389 14.37436297599329
>
Iridium 7
1 24793U 97020B   97225.11850591 +.00000172 +00000-0 +54454-4 0 00951
2 24793 086.4002 107.1963 0002126 248.9586 111.1385 14.34215259014323


>-----------------------
>
>And here's the latest information on these two encounters.  The Hubble
>encounter has tightened up a bit.  Closest approach is now 1.1 km (about 
>3600 feet!) on Aug 16 at 0:43:22.45.  At the
>time of the encounter, the orbital elements are now only a little over 2 
>days old, so this is going to be close.
>
>Likewise, Iridium 7 and Spot 1 r Deb C are still predicted to come quite
>close.  In fact, as I write this (8/14 18:55 UTC), their "dance" has 
>already begun.  Here are the latest predictions:
>
>Close approach to Iridium 7 (#24793)
>
  Date     UTC Time   Norad           Name           Range (km) NdAng EphAge
8/14/1997 17:39:01.82 16615 Spot 1 r Deb     1.5  0.0    14.4    93.4  +0.58
8/14/1997 19:19:23.01 16615 Spot 1 r Deb     1.5  0.0    10.5    95.0  +0.65
8/14/1997 20:59:44.19 16615 Spot 1 r Deb     1.5  0.0     6.7    98.4  +0.72
8/14/1997 22:40:05.38 16615 Spot 1 r Deb     1.5  0.0     3.1   109.1  +0.79
8/15/1997  0:20:26.56 16615 Spot 1 r Deb     1.5  0.0     1.2   152.6  +0.86
8/15/1997  2:00:47.75 16615 Spot 1 r Deb     1.5  0.0     4.1   106.0  +0.93
8/15/1997  3:41:08.94 16615 Spot 1 r Deb     1.5  0.0     7.2    99.3  +1.00
8/15/1997  5:21:30.13 16615 Spot 1 r Deb     1.5  0.0    10.2    96.8  +1.07
8/15/1997  7:01:51.31 16615 Spot 1 r Deb     1.5  0.0    13.1    95.4  +1.14