C/2009 K5 McNaught
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Comet C/2009 K5 was discovered on 27 May 2009 by Robert H. McNaught (Siding Spring); that is about 11 months before its perihelion passage. The comet was observed until 26 October 2011.
Comet had its closest approach to the Earth on 18 April 2010 (1.264 au), 12 days before its perihelion passage.
Some trends in O-C time variations in the pure gravitational model based on entire data set were noticed, unfortunately, the NG effects cannot be reliably determined for this comet.
Preferred solution given here is based on data taken at large perihelion distances and spanning over 2.50 yr in a range of heliocentric distances: 4.35 au – 1.422 au (perihelion) – 6.49 au; however, two separate gravitational osculating orbits based on pre-perihelion (solution pa) and post-perihelion data (ra) are also presented.
This Oort spike comet suffers moderate planetary perturbations during its passage through the planetary system; these perturbations lead to a more tight future orbit (see future barycentric orbits).
See also Królikowska and Dybczyński 2013 and Królikowska 2020.

solution description
number of observations 894
data interval 2009 05 27 – 2011 11 26
data arc selection only data taken in large heliocentric distance (DIS)
range of heliocentric distances 4.35 au – 1.42 au (perihelion) – 6.49 au
detectability of NG effects in the comet's motion NG effects not determinable
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 1727
RMS [arcseconds] 0.36
orbit quality class 1a
orbital elements (heliocentric ecliptic J2000)
Epoch 2010 03 25
perihelion date 2010 04 30.02301780 ± 0.00006174
perihelion distance [au] 1.42239391 ± 0.00000019
eccentricity 1.00084621 ± 0.00000037
argument of perihelion [°] 66.172406 ± 0.000009
ascending node [°] 257.855657 ± 0.000006
inclination [°] 103.879376 ± 0.000012
recip semi-major axis [10-6 au-1] -594.92 ± 0.26
Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line – the moment of perihelion passage