C/2015 X7 ATLAS
more info
Comet C/2015 X7 was discovered on 12 December 2015 by Asteroid Terrestrial-impact Last Alert System (ATLAS) Team, that is about 7.5 months before its perihelion passage. Some prediscovery images of this comet were found: taken on 28 January 2015 by Pan-STARRS 1, Haleakala. This comet was observed until 16 June 2017.
Comet had its closest approach to the Earth on 8 February 2017 (5.909 au); about 6 months after its perihelion passage.
Solutions given here are based on data spanning over 2.38 yr in a range of heliocentric distances: 5.95 au – 3.685 au (perihelion) – 4.64 au.
This Oort spike comet suffers small planetary perturbations during its passage through the planetary system that lead to a more tight future orbit with a semimajor axis of about 5,000 au (see future barycentric orbits).

solution description
number of observations 628
data interval 2015 01 28 – 2017 06 16
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 5.95 au – 3.69 au (perihelion) – 4.64 au
type of model of motion NC - non-gravitational orbits for symmetric CO-g(r)-like function
data weighting YES
number of residuals 1244
RMS [arcseconds] 0.43
orbit quality class 1a+
orbital elements (heliocentric ecliptic J2000)
Epoch 2016 07 31
perihelion date 2016 07 30.23263295 ± 0.00047201
perihelion distance [au] 3.68453524 ± 0.00000162
eccentricity 1.00176023 ± 0.00000303
argument of perihelion [°] 348.485470 ± 0.000085
ascending node [°] 139.883871 ± 0.000008
inclination [°] 57.580949 ± 0.000007
recip semi-major axis [10-6 au-1] -477.73 ± 0.82
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
non-gravitational parameters
A1 [10-8au\day-2] -0.20423 ± 0.07756
A2 [10-8au\day-2] 0.24064 ± 0.11494
A3 [10-8au\day-2] 0.1608 ± 0.02653
m -2.00
n 3.000
k -2.6000
r0 [au] 10.000
α 0.0100