Russell Eberst has reported that the Lacrosse 2 (91017A / 21147) radar imagery intelligence satellite was missing from its predicted path last night, 2011 Mar 30 near 20:40 UTC, so it is possible that it has changed its orbit, or even been de-orbited: http://satobs.org/seesat/Mar-2011/0380.html The last reported observation was by Pierre Neirinck, on Mar 24, near 21:33 UTC. Brad Young also observed it on the 24th, at about 01:55 UTC. If any one has either seen or not seen it between Pierre's observation and Russell's non-observation, it would be useful to know the date and time. If seen, please state whether it appeared to be on-time. That would help narrow the time of its apparent orbit manoeuvre. The object has a history of small orbit changes that increase or decrease its period by a fraction of one second, more likely the result of momentum wheel unloading manoeuvres than intended orbit manoeuvres. Had it made such a manoeuvre shortly after it was last observed, then last night it could have been early or late by at least 30 s, up to 1 or 2 min. If so, then even if it passed earlier than expected, I suspect Russell would have had time to recover it; however, a larger orbit change cannot be ruled out, and given the object's age, it could well have been de-orbited. It is a reliable magnitude 2 or 3 object on favourable passes, so it will not be difficult to determine whether it remains in orbit. In case its mean motion changed more than usual, I suggest looking for it within +/- 10 min of prediction, with allowance for Earth's rotation. If it is not seen eventually, then we will be able to safely conclude that it has been de-orbited. This is the last known orbit: Lacrosse 2 1 21147U 91017A 11083.88616256 .00000250 00000-0 35917-4 0 07 2 21147 67.9850 102.4518 0005000 214.0069 145.9930 14.76331375 01 Happy hunting! Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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