Greg Roberts completed a successful planar search for X-37B OTV-1 on 2010 Aug 19. The orbit was not optimally placed, but he managed so search for 89 min, which is nearly one full revolution of the last known orbit, to there was a good probability of detecting the object. His subsequent examination of the video revealed that it had indeed been captured, at about 17:53 UTC, and he reduced 8 points, spanning 53 s: http://satobs.org/seesat/Aug-2010/0249.html The following elements are the result of propagating my epoch 10210.093 elements to the revolution of Greg's observation, and adjusting only RAAN, mean anomaly and mean motion. Greg's five points of 0.1 s time resolution were weighted 100 percent; his first and last point have only 1 s time accuracy, but they extend the arc considerably, so were worth including, at a bit lower weight, 70 percent. OTV-1 427 X 444 km 1 36514U 10015A 10231.69817710 .00000000 00000-0 00000-0 0 05 2 36514 39.9851 347.3161 0012533 164.0919 196.0285 15.44559742 02 Arc 20100819.75-0819.75 WRMS resid 0.042 totl 0.012 xtrk Another night or two of observations are required to refine the elements, but based on this preliminary result, it appears that a couple of manoeuvres were made on Aug 08, within a few hours of 06 h UTC, which raised the orbit about 24 km. Their planes nearly coincide at that time, which tends to support this conclusion. Although Greg observed it ~5 min earlier than predicted by the previous orbit, it had in fact gone higher, and been nearly lapped by the previous orbit. The ~0.5 min increase in period, results in more than a 7 min per day divergence in the predicted time of passage, so despite the small size of the manoeuvre, a planar search was required to recover it. This small change of orbit may have been a test of OTV-1's manoeuvring system, or a requirement of whatever payload may be aboard, or both. The new orbit appears to very nearly repeat every 6 days, instead of the 4 days of the previous orbit, but I will wait for a more precise orbital solution before attempting to draw conclusions (repeating ground tracks can occur unintentionally). Nice work, Greg, and thank you to all who volunteered to assist in the hunt. Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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