AEHF 1 - post REA manoeuvre #2 elements

From: Ted Molczan (
Date: Wed Sep 01 2010 - 06:13:18 UTC

  • Next message: Russell Eberst: "2010AUG31.OBS"

    Derek Breit has reported observations of AEHF 1, running about 245 s late relative my epoch
    10242.84673563 elements:
    The late arrival is likely due to a second burn of the REA (reaction engine assembly) thrusters,
    probably near the apogee passage of Aug 31, at 13:25:32 UTC. Here are preliminary elements:
    AEHF 1                                                 594 X 49978 km
    1 36868U 10039A   10244.13816125  .00000000  00000-0  00000-0 0    05
    2 36868  21.6235 306.2265 7798000 187.7859 141.3094  1.54112411    04
    Arc 20100831.56-0901.17 WRMS resid 0.008 totl 0.005 xtrk
    I obtained the above by propagating the pre-manoeuvre elements forward, and adjusting them to fit
    the new observations plus a synthetic observation at the assumed time of the manoeuvre (spacecraft's
    position relative the centre of the Earth). Since the arc is short, I allowed only RAAN, mean
    anomaly and mean motion to vary; eccentricity was set manually to maintain apogee. Several
    iterations of this process were required to converge on a solution. I also experimented with
    allowing inclination to vary, but the change was little more than 0.1 deg - much less than the ~0.4
    deg of the REA burn #1, and may not be real, so for now, I assume it did not change.
    Two to three additional manoeuvres can be expected in the coming days, resulting in a perigee of 950
    Ted Molczan
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