New HST close approaches

ROB MATSON (ROBERT.D.MATSON@cpmx.saic.com)
24 Mar 1997 16:19:33 -0800

Well, I see that one cannot underestimate the importance of having
VERY fresh orbital elements for purposes of predicting near-
collisions between orbiting bodies.  All but one of my previously
calculated close-approaches to HST changed considerably with newer
elements.  For example, #10493 was previously predicted to come
within 1.2 km of HST on 3/22 at 14:12:43.0 UTC.  However, the age
of the ephemeris for Himawari 1 r Deb ES was 9.6 days at the time
of close approach.  Using newer elements for HST and this object,
the new value for the close approach is 25.2 km (ephemeris age
1.49 days).  Thus for future predictions, I'm going to ignore
anything with an ephemeris age greater than one week at the time
of close approach.

I reran the prediction using the following elements for HST:

HST
1 20580U 90037B   97083.50000000  .00000330  00000-0  20083-4 0  9427
2 20580  28.4672 218.2187 0014577  35.0921  63.2507 14.86428795180432

... and used the latest ALLSAT.DAT file, dated 3/22/97.  The closest
approaches were as follows:

   Date     UTC Time  Norad           Name           Range (km)  EphAge
---------- ---------- ----- ------------------------ ----------  ------
 3/22/1997  8:59:22.8 24400 STEP 2 Pegasus Deb RD        17.8     +1.37
 3/23/1997  0:36:53.5 16611 Cosmos 1733                  13.8     +1.89
 3/23/1997  0:49:32.4 14168 Galaxy 1 PAM-D PKM stage      4.9     +2.36
 3/23/1997  1:25:22.1 16611 Cosmos 1733                  18.5     +1.92
 3/23/1997  3:02:12.1 16611 Cosmos 1733                  16.6     +1.99
 3/23/1997 15:14:36.9 13271 Cosmos 1378                  18.7     +2.45
 3/23/1997 17:39:57.2 13271 Cosmos 1378                  17.5     +2.55
 3/24/1997 12:31:19.7 19435 Ariane V.16 r Deb UY         15.7     +3.12
 3/24/1997 12:41:59.2 15889 Cosmos 1666                   2.5     +3.41
 3/24/1997 13:30:47.8 24043 STEP 2 Pegasus Deb CQ         8.1     +3.87
 3/24/1997 13:36:56.3  3927 Explorer 9 Deb F             18.4     +6.54
 3/24/1997 14:28:58.5 20979 DMSP B5D2-5 Star 37S AKM     19.7     +3.46
 3/25/1997  8:43:50.1  2085 ESSA 1 de-spin weight        19.3     +4.36
 3/25/1997 12:04:22.7 24695 1994-029ABD                  11.0     +6.48
 3/25/1997 12:49:54.7  5137 Cosmos 397 Deb AF            11.3     +4.36
 3/25/1997 14:37:14.5 24165 STEP 2 Pegasus Deb HQ        15.3     +4.84
 3/25/1997 16:46:40.9 14209 Cosmos 1484 Deb C             3.5     +4.25
 3/25/1997 17:33:44.2 17296 Cosmos 1812 R/B              13.9     +4.26
 3/25/1997 23:45:58.8 13121 Cosmos 1346 R/B              17.5     +4.61
 3/26/1997 10:33:48.7 24229 STEP 2 Pegasus Deb LC        19.4     +5.70
 3/26/1997 13:57:49.4  1613 OV 1-2                       10.6     +5.80
 3/26/1997 21:55:40.7 24478 STEP 2 Pegasus Deb UB        17.1     +5.39
 3/27/1997  1:13:21.9 11671 Cosmos 1151 (5-sec flash)    16.0     +5.51
 3/27/1997 10:14:12.1  4621 Cosmos 374 Deb H             14.7     +6.33
 3/28/1997  0:18:21.5 17295 Cosmos 1812 (74.5-sec per    13.6     +6.60

Cosmos 1666 was pretty close earlier today.  Cosmos 1484 Deb C may be
close in about 16 hours. --Rob