NROL-39 observations and elements

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Sat Dec 07 2013 - 15:18:34 UTC

  • Next message: Scott Tilley: "Fia Radar 3 Obs"

    I observed FIA Radar 3 and its Centaur.
    
    USSTRATCOM has yet to release any data. I assume that FIA Radar is 2013-072A. I propose that we freeze its temporary
    catalogue number at 78817, until the official one is released. Allowing for the 12 secondary payloads, I assume the
    Centaur is 2013-072P. I propose using 78820 as its temporary catalogue number.
    
    78820 13 072P   2701 G 20131207110046460 17 25 2255867+622291 47 S
    78820 13 072P   2701 G 20131207110129020 17 25 0009587+591844 28 S
    78817 13 072A   2701 G 20131207112329600 17 25 2253976+841785 57 S
    78817 13 072A   2701 G 20131207112346960 17 25 0105794+815820 67 S
    78817 13 072A   2701 G 20131207112436330 17 25 0247645+714373 67 S
    78817 13 072A   2701 G 20131207112749370 17 25 0321929+424925 57 S
    
    FIA Radar 3                                            1071 X 1090 km
    1 78817U 13072A   13341.45965117  .00000000  00000-0  00000-0 0    07
    2 78817 123.0033 228.4347 0012548 299.0987  60.8721 13.47758670    01
    Arc 20131206.76-1207.48 WRMS resid 0.025 totl 0.006 xtrk
    
    FIA Radar 3 r                                            493 X 884 km
    1 78820U 13072P   13341.44424121  .00000000  00000-0  00000-0 0    05
    2 78820 120.4883 230.9287 0276875 339.4109  19.5967 14.61190032    02
    Arc 20131206.44-1207.46 WRMS resid 0.016 totl 0.002 xtrk
    
    I derived the orbit of the Centaur from the orbit of IPEX:
    
    http://polysat.calpoly.edu/ipex-tracking/
    
                                                             462 X 888 km
    1 00005U          13340.44037616  .00000000  00000-0  00000-0 0    00
    2 00005 120.4883 227.3812 0301504 340.0132 137.1239 14.65467927    12
    
    The epoch appears to have been that of the time of deployment, when the Centaur and IPEX were at the same position. In
    the differential correction, I generated a synthetic observation from the IPEX TLE, at epoch, relative the centre of the
    Earth. Fifteen revs later, my two observations of the Centaur trailed the IPEX TLE by nearly 5 min, indicating it was in
    a higher orbit. The synthetic observation enabled computing the mean motion with reasonable accuracy. I fixed the
    inclination at the IPEX value. In one solution, I also fixed eccentricity and argument of perigee, with reasonable
    results. But the solution I am reporting, instead fixed RAAN and permitted eccentricity and argument of perigee to vary.
    The deployment of IPEX occurred near apogee. Since its orbit is lower than the Centaur's, its perigee must be lower,
    which is evident comparing the above TLEs.
    
    As I was writing this, Greg Roberts reported three closely spaced positions of a mag ~8 object trailing the above IPEX
    TLE by ~7 s, and within 0.06 deg of its expected track.
    
    http://satobs.org/seesat/Dec-2013/0046.html
    
    The object seems far too bright for a cubesat, but it was also somewhat fainter than expected of the Centaur. My
    ephemeris generator places the observation just past eclipse exit, but it does not always predict eclipse events
    accurately. Including them with my observations of the Centaur yields a reasonable result, differing from the above
    mainly in mean motion, with a value of 14.5932 rev/d. For now, I suggest using the above TLE for the Centaur, with a
    prediction time uncertainty of at least 1 min per 15 revs from epoch. Subsequent observations will reveal the correct
    mean motion, and settle the question whether Greg's faint object was the Centaur or a cubesat.
    
    Ted Molczan
    
    
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