Lutz Schindler's obs of 2007 Mar 24 and 25 UTC reveal a significant increase in rate of decay, due to moderate to high geomagnetic activity during Mar 23-25: USA 193 5.0 2.5 0.0 4.4 v 1 29651U 06057A 07084.80961172 .00034153 00000-0 23852-3 0 06 2 29651 58.5029 45.5507 0009311 113.4328 246.7739 15.73703151 07 Arc 2007 Mar 22.84 - 25.82, WRMS residuals = 0.024 deg Recently, I was asked to comment on when USA 193 might be expected to make a reboost manoeuvre. Reuters has reported several times that the spacecraft failed almost immediately upon reaching orbit, possibly due to a problem with its on-board computer, and that it was likely to be written-off as a total loss: http://satobs.org/seesat/Mar-2007/0057.html So, I doubt there will be a manoeuvre, and the object will decay about Feb 2008. Had it not been for this news, my rationale for the timing of manoeuvres would have been as follows. At launch, USA 193's ground track repeated almost exactly at 31 rev intervals, which takes about 2 days. I suspect that this 31:2 resonance was by design, with some tolerance. The actual revs per 2 days at launch were 30.948, which suggests a tolerance of about 0.05 rev/2d, in which case, the first reboost might be expected at or before reaching 31.05 rev/2d. That would occur when mean motion reaches 15.75 rev/d, about Apr 28, at typical rates of decay. Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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