C/2011 R1 McNaught
more info
Comet C/2011 R1 was discovered on 3 September 2011 by Robert H. McNaught (Siding Spring), that is more than a year before its perihelion passage. It was observed until 11 April 2014.
Comet had its closest approach to the Earth on 8 April 2013 (1.960 au), 5.5 months after its perihelion passage; however on 8 August 2012 (2.5 months before perihelion) the comet approached the Earth only a little further (2.035 au, see picture).
Solution given here is based on data spanning over 3.5 yr in a range of heliocentric distances: 7.47 au – 2.08 au (perihelion) – 5.91 au.
This Oort spike comet suffers tiny planetary perturbations during its passage through the planetary system that cause a bit tighter future orbit with original semimajor axis of about 10,000 au (see future barycentric orbits).
See also Królikowska 2020.

solution description
number of observations 1504
data interval 2010 10 11 – 2014 04 11
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 7.47 au – 2.08 au (perihelion) – 5.91 au
type of model of motion NT - non-gravitational orbits for asymmetric, standard g(r)
data weighting YES
number of residuals 2909
RMS [arcseconds] 0.37
orbit quality class 1a+
orbital elements (heliocentric ecliptic J2000)
Epoch 2012 09 30
perihelion date 2012 10 19.62340531 ± 0.00010449
perihelion distance [au] 2.07956724 ± 0.00000097
eccentricity 1.00069412 ± 0.00000203
argument of perihelion [°] 308.861852 ± 0.000044
ascending node [°] 221.408286 ± 0.000012
inclination [°] 116.197082 ± 0.000016
recip semi-major axis [10-6 au-1] -333.78 ± 0.97
Upper panel: 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.
Lower panel (panels): O-C diagram for this(two) solution (solutions) given in this database, where residuals in right ascension are shown using magenta dots and in declination by blue open circles.
non-gravitational parameters
A1 [10-8au/day2] 1.4469 ± 0.2778
A2 [10-8au/day2] 2.594 ± 0.101
A3 [10-8au/day2] 0.048861 ± 0.02403
m -2.15
n 5.093
k -4.6142
r0 [au] 2.808
α 0.1113
ΔT [days] 55.4170 ± 8.061