Here are updated elements of both objects: XSS-11 1.0 0.6 0.0 8.3 v 755 X 771 km 1 28636U 05011A 06118.66440878 .00000245 00000-0 81408-4 0 00 2 28636 99.1809 120.0867 0011060 203.1264 156.9424 14.37852141 00 Arc 2006 Apr 06.74 - 28.73, WRMS residuals = 0.016 deg XSS-11 r 1.3 1.1 0.0 7.6 v 844 X 862 km 1 28637U 05011B 06118.66911613 .00000045 00000-0 25243-4 0 04 2 28637 98.8689 111.9004 0012674 209.2919 150.7542 14.11064258 00 Arc 2006 Mar 01.19 - 28.73, WRMS residuals = 0.016 deg XSS-11 has now drifted 8.2 east of the plane of the upper stage of its rocket (05011B), which was it first rendezvous target. Based on their present planes and rates of precession, XSS-11's manoeuvres to its present orbit would have occurred about 2006 Jan 17 UTC; however, they could have been carried out over several days around that date. This did not square with the epoch 06022.23397126 elset of XSS-11, which had it in its pre-manoeuvre orbit. That elset was derived from a couple of observations by Bruce MacDonald on January 22nd: http://satobs.org/seesat/Jan-2006/0211.html Further investigation reveals that Bruce must have mistaken 05011B for 05011A. The latter had been manoeuvring in close proximity to the former for months, so there was a considerable risk of confusing the two. The first clue was the brightness, mag 6, which was nearly 3 mag brighter than expected of 05011A, given the circumstances of the pass; in contrast, 05011B routinely reaches mag 6 in maxima. The decisive evidence is that at the times of both observations, 05011B made close appulses of stars suitable for accurate positional observations; the first within about 0.1 deg of a mag 5.2 star; the second nearly coincident with a mag 8.9 star. Both could yield very good position and time residuals relative 05011B, depending upon the accuracy of the observation. So, the epoch 06022.23397126 elset of XSS-11 should be discarded, and Bruce should re-reduce his Jan 22 observations and report them as 05011B. Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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