AEHF 1 - post manoeuvre elements

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Mon Aug 30 2010 - 14:18:20 UTC

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    Analysis of new observations of AEHF 1 by Derek Breit, Peter Wakelin and Brad Young, on the night of
    Aug 29/30 UTC, revealed that it had made a small manoeuvre during the ~14 hours since it was last
    observed. Their reports are here:
    
    http://satobs.org/seesat/Aug-2010/0394.html
    
    http://satobs.org/seesat/Aug-2010/0400.html
    
    http://satobs.org/seesat/Aug-2010/0408.html
    
    The following preliminary elements are based on the assumption that it manoeuvred near the
    intervening apogee, on Aug 29 at 14:52:08 UTC:
    
    AEHF 1 Post-manoeuvre                                  428 X 49984 km
    1 36868U 10039A   10242.20269607  .00000015  00000-0  96487-4 0    02
    2 36868  21.6728 306.7095 7845000 186.9033 145.0138  1.54699565    05
    Arc 20100829.62-0830.21 WRMS resid 0.008 totl 0.008 xtrk
    
    I obtained the above by propagating the pre-manoeuvre elements (below) 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). Initially, all elements except rate of
    decay were permitted to vary; finally, eccentricity was set manually to maintain apogee. The result
    seems reasonable, but I caution that the arc is less than one revolution, so the results must be
    considered preliminary. Barring further manoeuvres today, observers tonight should allow for at
    least several minutes prediction time uncertainty.
    
    Comparison with the pre-manoeuvre elements (below) reveals the main changes: inclination decreased
    by ~0.4 deg; perigee increased by ~150 km.
    
    AEHF 1 Pre-manoeuvre                                   278 X 49989 km
    1 36868U 10039A   10240.91700349  .00000109  00000-0  96487-4 0    05
    2 36868  22.1043 307.1018 7887796 186.2855 147.6097  1.55238162    09
    Arc 20100826.92-0829.27 WRMS resid 0.006 totl 0.005 xtrk
    
    I estimate 15.3 m/s delta-V. The spacecraft has 16 monopropellant (hydrazine) reaction control
    thrusters. Assuming Isp of 220 s, and initial spacecraft mass of 6169 kg, I estimate 44 kg of
    propellant was burned. Assuming total thrust of 20 pounds for the manoeuvre (a guess), the burn
    would have lasted about 18 minutes. 
    
    Derek and Brad's observations also confirmed my earlier finding, based on observations by Kevin
    Fetter, that the spacecraft produces bright specular reflections at intervals of 301 s, which
    indicate that it is rotating at 0.1 RPM.
    
    http://satobs.org/seesat/Aug-2010/0385.html
    
    Ted Molczan
    
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