KeyHole manoeuvre alert for 2001 May 08

From: Ted Molczan (molczan@home.com)
Date: Fri May 04 2001 - 10:25:46 PDT

  • Next message: Alan Pickup: "Decay watch: 2001 May 4"

    USA 129's (96072A / 24680) mean motion is now high enough to require a major
    re-boost. Moreover, its argument of perigee is nearing the equator, as has been
    the case of many past such manoeuvres.
    
    The first re-boost opportunity will occur within a day or two of 2001 May 08
    UTC, when USA 129's perigee will cross the equator.
    
    If that opportunity passes without a manoeuvre, then the next opportunity
    occurs about 10 days later, when sister KeyHole USA 116's (95066A / 23728)
    argument of perigee crosses the equator.
    
    One of the advantages of making manoeuvres with perigee near the equator, is
    the ability to efficiently change several of the orbital elements using a
    single impulse, including the inclination. The KeyHoles' sun-synchronous orbits
    are perturbed by the sun's gravity, resulting in oscillation of the
    inclination.
    
    I note that 96072A's inclination has decreased from in excess of 97.95 deg in
    1998, to about 97.82 deg, which is about the lowest observed value, suggesting
    that it is due to be adjusted upward.
    
    I also note that in the spring of 1998, 96072A's inclination had declined to
    about 97.82 deg, just before its major re-boost manoeuvre, after which it was
    found to have increased to more than 97.95 deg. I have appended several pre and
    post-manoeuvre elsets that document this change.
    
    The first two post-manoeuvre elsets did not reflect the change in inclination,
    but I suspect that was due to the inclination having been held constant by the
    analyst(s), pending receipt of a sufficient number of post-manoeuvre
    observations to confidently re-compute all of the elements.
    
    Using 1998 as my precedent, I suspect that 96072A's operators will take
    advantage of its perigee crossing of 2001 May 08, to increase its inclination
    to exceed 97.9 deg, as well as re-boost its apogee, within a day or two of that
    date.
    
    Whatever the date of the major re-boost, both KeyHoles can be expected to
    manoeuvre on that same date.
    
    Ted Molczan
    
    
    96072A's pre and post-maneouvre elements - Spring 1998
    
    1 24680U 96072A   98107.88796393  .00024000  00000-0  23788-3 0    02
    2 24680  97.8370 168.6228 0507000  33.0792 326.9207 14.82889041    09
    
    1 24680U 96072A   98107.95605925  .00027220  00000-0  24872-3 0    57
    2 24680  97.8216 168.6511 0513577  33.0321 330.1891 14.82899771  4165
    
    1 24680U 96072A   98108.90064327  .00027449  00000-0  27485-3 0    10
    2 24680  97.8178 169.5787 0505804  29.3849 333.4817 14.82951788    15
    
    1 24680U 96072A   98108.90064540  .00024829  00000-0  26098-3 0    04
    2 24680  97.8321 169.6079 0501810  30.9717 332.0397 14.82942565    05
    
    1 24680U 96072A   98110.85679330  .00027000  00000-0  26831-3 0    09
    2 24680  97.8370 171.5481 0506000  23.3416 336.6582 14.83057259    00
    
    1 24680U 96072A   98117.87270499  .00027700  00000-0  27252-3 0    06
    2 24680  97.8280 178.4465 0505000   0.3193 359.6806 14.83450297    07  last
    pre-manoeuvre elset
    
    1 24680U 96072A   98125.86915017  .00027700  00000-0  26006-3 0    02
    2 24680  97.8280 186.1920 0550004 334.4276  25.5723 14.74583910    02  1st
    post-manoeuvre elset
    
    1 24680U 96072A   98129.86815410  .00027700  00000-0  23394-3 0    09
    2 24680  97.8280 190.0900 0550004 321.4345  38.5654 14.76385319    09
    
    1 24680U 96072A   98131.15591023  .00018000  00000-0  12437-3 0    04
    2 24680  97.9780 191.6605 0565004 317.2494  42.7504 14.76388113    04
    
    1 24680U 96072A   98137.86506743  .00017500  00000-0  11591-3 0    07
    2 24680  97.9630 198.2953 0567004 295.7211  64.2787 14.76615585    04
    
    1 24680U 96072A   98140.10125422  .00014000  00000-0  10755-3 0    02
    2 24680  97.9590 200.5198 0556004 289.6731  70.3267 14.76648161    01
    
    -----------------------------------------------------------------
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org
    http://www2.satellite.eu.org/seesat/seesatindex.html
    



    This archive was generated by hypermail 2b29 : Fri May 04 2001 - 10:27:17 PDT