C/2015 X5 PANSTARRS
more info
Comet C/2015 X5 was discovered on 6 December 2015 with Pan-STARRS 1 telescope (Haleakala), that is almost 2 years before its perihelion passage.

Comet had its closest approach to the Earth on 4 January 2018 (5.909 au); 4 days after its perihelion passage.

The preferred solution given here is based on data spanning over 4.19 yr in a range of heliocentric distances: 8.38 au – 6.80 au (perihelion) – 8.45 au.

This Oort spike comet suffers tiny planetary perturbations.
solution description
number of observations 227
data interval 2015 12 06 – 2020 02 14
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 8.38 au – 6.80 au (perihelion) – 8.45 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 439
RMS [arcseconds] 0.24
orbit quality class 1a+
orbital elements (barycentric ecliptic J2000)
Epoch 1709 01 22
perihelion date 2017 12 30.04679766 ± 0.00040629
perihelion distance [au] 6.80458119 ± 0.00000278
eccentricity 0.99959688 ± 0.00000313
argument of perihelion [°] 27.662307 ± 0.000028
ascending node [°] 122.248863 ± 0.000005
inclination [°] 124.311546 ± 0.000008
reciprocal semi-major axis [10-6 au-1] 59.24 ± 0.46
file containing 5001 VCs swarm
2015x5b5.bmi
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.
Middle panel(s): O-C diagram for a given solution (sometimes in comparison to another solution available in CODE), where residuals in right ascension are shown using magenta dots and in declination by blue open circles.
Lowest panel: Relative weights for a given data set(s).
Six 2D-projections of the 6D space of original swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.