X-37B OTV-1 post manoeuvre elements

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Fri Aug 20 2010 - 15:07:44 UTC

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    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
    
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