http://www.minorplanetcenter.net/mpec/K12/K12S63.html

Orbital elements:
    C/2012 S1 (ISON)
Epoch 2013 Dec. 14.0 TT = JDT 2456640.5
T 2013 Nov. 28.87041 TT                                 MPC
q   0.0124527            (2000.0)            P               Q
z  +0.0000029      Peri.  345.56137     +0.31509387     +0.51287068
 +/-0.0002325      Node   295.65952     -0.75896421     -0.36901142
e   1.0000000      Incl.   62.36426     -0.56981504     +0.77510918
From 54 observations 2011 Dec. 28-2012 Sept. 23, mean residual 0".3.



http://www.minorplanetcenter.net/mpec/K12/K12T08.html

    C/2012 S1 (ISON)
Epoch 2013 Dec. 14.0 TT = JDT 2456640.5
T 2013 Nov. 28.78555 TT                                 MPC
q   0.0124431            (2000.0)            P               Q
z  -0.0001056      Peri.  345.56521     +0.31513672     +0.51238734
 +/-0.0000482      Node   295.65272     -0.75894398     -0.36932439
e   1.0000013      Incl.   62.39824     -0.56981829     +0.77527976
From 163 observations 2011 Dec. 28-2012 Oct. 2, mean residual 0".4.
  (1/a)_orig = +0.00005808, (1/a)_fut = +0.00000785.



;;IDL:
tperi=anytim('2013/11/28')+86400.*.7615 - 66.184 & q=0.012472 & O=295.6952 & i=62.1101 & w=345.5360 & e=1
;;OR:
;elements={tperi_ET_ccsds:anytim(anytim('2013/11/28')+86400.*.7615,/CCSDS),q:0.012472,e:1.000005,O:295.6952,i:62.1101,w:345.5360}