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Comet C/2011 L4 was discovered on 6 June 2011 with Pan-STARRS 1 telescope (Haleakala); that is about a year and 9 months before its perihelion passage. Next, pre-discovery images of the comet taken on 21 May (Pan-STARRS 1), 24 May (Mt. Lemmon Survey), and 30 May (iTelescope Observatory, Mayhill), 2011 were found. The comet was observed until 27 August 2014.
Comet had its closest approach to the Earth on 5 March 2013 (1.097 au), 5 days before its perihelion passage.
Preferred solution given here is based on data spanning over 3.27 yr in a range of heliocentric distances: 3.27 au – 0.302 au (perihelion) – 6.97 au. The non-gravitational solution was chosen as preferred orbit; however, uncertainties of NG parameters are relatively large. Additionally, there are two further nongravitational solutions: NG orbit for pre-perihelion arc of data, and NG orbit based on post-perihelion data. All solutions (NG and GR type) give a narrow range of original 1/a values from 29.7 to 32.0 in units of 10-6 au-1.
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 2020.

solution description
number of observations 5501
data interval 2011 05 21 – 2014 08 27
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 8.04 au – 0.30 au (perihelion) – 6.97 au
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 10911
RMS [arcseconds] 0.44
orbit quality class 1a+
orbital elements (heliocentric ecliptic J2000)
Epoch 2012 03 20
perihelion date 2013 03 10.15177529 ± 0.00000856
perihelion distance [au] 0.30161323 ± 0.00000007
eccentricity 1.00008814 ± 0.00000006
argument of perihelion [°] 333.642132 ± 0.000002
ascending node [°] 65.665464 ± 0.000002
inclination [°] 84.199847 ± 0.000003
recip semi-major axis [10-6 au-1] -292.24 ± 0.20
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