C/2011 R1 McNaught
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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 427
data interval 2010 10 11 – 2012 03 21
data arc selection data generally limited to pre-perihelion (PRE)
range of heliocentric distances 7.47 au – 3.19au
detectability of NG effects in the comet's motion comet with determinable NG~orbit
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 846
RMS [arcseconds] 0.29
orbit quality class 1a
orbital elements (heliocentric ecliptic J2000)
Epoch 2012 09 30
perihelion date 2012 10 19.62184072 ± 0.00065197
perihelion distance [au] 2.07958826 ± 0.00001036
eccentricity 1.00069866 ± 0.00000353
argument of perihelion [°] 308.861211 ± 0.000231
ascending node [°] 221.408199 ± 0.000065
inclination [°] 116.196937 ± 0.00008
reciprocal semi-major axis [10-6 au-1] -335.96 ± 1.70
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.