Updated elements

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Mon Oct 11 2010 - 14:59:59 UTC

  • Next message: Marco Langbroek: "SATOBS ML (4353), 10 Oct 2010 (Pt. II): USA 198 (SDS F3-5)"

    Scott Campbell, Marco Langbroek, Tim Luton, Mike McCants, Peter Wakelin, Brad Young, and I,
    ontributed observations used to determine one or more of the following element sets.
    As the arc grows, AEHF 1's mean motion is settling down near 1.40206 rev/d. HCT (hall current
    thruster) burns appear not to have begun as of Peter's obs of Oct 10 at 21 h UTC.
    AEHF 1                                                4713 X 49977 km
    1 36868U 10039A   10283.87482639  .00000000  00000-0  00000-0 0    08
    2 36868  15.1042 297.2259 6711143 201.7716 250.5525  1.40206170    04
    Arc 20101003.07-1010.87 WRMS resid 0.005 totl 0.003 xtrk
    As I suspected, 10046A made at least one more small manoeuvre. One probably occurred on Oct 10,
    between my 08:30 UTC and 10:17 UTC passes; there may have been others. This solution is based on my
    latter Oct 10 pass, and Marco and my obs of Oct 11 UTC. Pierre Neirinck's obs arrived as I was about
    to send this; I will analyze them later today, and revise the orbit if necessary.
    FIA Radar 1                                            1099 X 1103 km
    1 37162U 10046A   10284.37940731  .00000000  00000-0  00000-0 0    02
    2 37162 122.9962 160.4760 0002571  96.8767 263.2486 13.42221091    00
    Arc 20101010.43-1011.4 WRMS resid 0.023 totl 0.007 xtrk
    The coincidence of these latest small manoeuvres with the argument of perigee having reached ~90
    deg, suggests that a frozen orbit is being set up, which employs perturbations of Earth's
    gravitational field to cause the argument of perigee to oscillate around a value near 90 deg, and
    eccentricity to oscillate around a small value. The manoeuvres also have resulted in a more nearly
    27:2 resonance. The first four Lacrosses had similarly frozen orbits, and 29:2 resonance. Lacrosse 5
    is a bit different: it is not frozen in argument of perigee, and it is in nearly a 43:3 resonance.
    Frozen orbits are a common feature of remote sensing satellites, especially radars. Ground tracks
    that approximately repeat every 2, 3, or 4 days, are a common feature of U.S. IMINT satellite
    Ted Molczan
    Seesat-l mailing list

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