Re: Fragmentation ... View from N

From: b_gimle@algonet.se
Date: Mon May 31 2004 - 10:48:40 EDT

  • Next message: b_gimle@algonet.se: "Ang: Re: Fragmentation ... View from N"

    It seems Dan's images are produced relative to Earth-Fixed (rotating) coordinates,
    so the tracks shift about 25 degrees west during an orbit.
    
    I used AllCola, and then SkyMap in Polar (siderial) coordinates.
    
    I ran the "initial" elsets of the DMSP 5D-2 F11 91-082 debris through
    "AllCOLA". I had a large range limit, but sorted them on range, then
    those under 10 km on date and time.
    
    It listed 34 encounters 04/11, 18 on 04/12, 42 on 04/13, 98 on 04/14,
    604(!) on 04/15, 110 on 04/16, 64 on 04/17, 72 on 04/18, 10 on 04/19,
    14 on 04/20, 30 on 04/21, 12 on 04/22.
    
    Obviously, the defragmentation occurred on the 15th April 2004.
    Some spread is due to age and inaccuracy of elsets, some because
    the mean motions were spread between 13.84 (82BJ) and 14.49 (82AD),
    so encounters happened every 37 hours.
    (Inclinations are 98.23 [S] to 99.01 [AD])
    
    On 04/15, the encounters over 1.5 h intervals were
    22 22 16 16 20 24 40 42 48 172(!) 42 50 18 22 22 32
    Close encounters with the satellite itself during peak hours were:
    12:20 12:40 12:48 12:53 12:59 13:38(2) 13:39 14:00 14:24 14:28(2)
    14:36 14:41 14:55 14:56 14:57 14:58 15:04 15:13 16:12 17:08 17:43.
    
    Based on the orbit count of the TLE, fragments F-L were tracked
    late on Apr.15
    
    At 14:54, 32 debris objects where within +-4 degrees of orbital
    longitude from the satellite. Best clustering of the orbits appears
    to have been around 64E (on that orbit), 10N.
    Graphing the orbital height vs. latitude for the ascending and
    descending halves of the orbit at that time confirms this.
    Excluding the six most differing orbits, the remainder are
    815-841 km at latitude 9S (ascending).
    On the other half, I get 798-997 km.
    
    My charts are about 60k in .gif or .jpg, so I can't put them on DSat.
    
    -------------------------------------------------------------------------
    Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive:  
    http://www.satobs.org/seesat/seesatindex.html
    



    This archive was generated by hypermail 2b29 : Mon May 31 2004 - 10:53:14 EDT