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 _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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