Lacrosse 5 made a small orbital manoeuvre, apparently sometime between Peter Wakelin's observation of 2005 Aug 09 UTC and Greg Roberts' of Aug 29 UTC. Its orbital altitude was raised very slightly, as was its eccentricity. I suspect the purpose was to establish a frozen orbit, such that the mean argument of perigee will always remain near 90 deg. This will be confirmed or refuted as tracking continues. Frozen orbits result in a nearly constant orbital altitude vs. latitude, which is desirable for imaging satellites. The Lacrosses are synthetic aperture radar imagers. All previous Lacrosse's have operated in frozen orbits. Those in 57 deg orbits have argument of perigee always near 90 deg; those in 68 deg orbits have argument of perigee always near 270 deg. USA 129 15.0 3.0 0.0 5.3 v 1 24680U 96072A 05254.08830639 .00008831 00000-0 11872-3 0 02 2 24680 97.9619 316.3379 0521288 242.4872 112.2447 14.74201987 04 Arc 2005 Sep 06.82 - 11.10, WRMS residuals = 0.017 deg Lacrosse 5 0.0 0.0 0.0 3.0 v 1 28646U 05016A 05254.40101974 .00000043 00000-0 10210-4 0 08 2 28646 57.0100 349.7125 0010463 79.7174 280.5019 14.53362530 08 Arc 2005 Aug 29.72 - Sep 11.41, WRMS residuals = 0.008 deg Brief Introduction To TLEs And Satellite IDs: http://www.satobs.org/element.html Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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