C/2017 M4 ATLAS
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Comet C/2017 M4 was discovered on 21 June 2017 by Asteroid Terrestrial-impact Last Alert System (ATLAS) Team, that is about  months after its perihelion passage.

Some prediscovery images of this comet were found: taken on 16 June 2017 by Pan-STARRS 1 telescope (Haleakala).

Solutions given here are based on data spanning over 4.46 yr in a range of heliocentric distances: 6.09 au – 3.252 au (perihelion) – 9.19 au.

NG orbits using full data-arc as well as independently using pre-perihelion and post-perihelion data are determinable.

See also Królikowska and Dones 2023.
solution description
number of observations 430
data interval 2019 02 01 – 2021 11 30
data arc selection data generally limited to post-perihelion (POS)
range of heliocentric distances 3.25 au – 9.19au
type of model of motion NC - non-gravitational orbits for symmetric CO-g(r)-like function
data weighting YES
number of residuals 834
RMS [arcseconds] 0.31
orbit quality class 1a
orbital elements (heliocentric ecliptic J2000)
Epoch 2019 02 06
perihelion date 2019 01 18.17848976 ± 0.00167435
perihelion distance [au] 3.25175483 ± 0.00000645
eccentricity 1.00230083 ± 0.00001261
argument of perihelion [°] 167.619006 ± 0.000405
ascending node [°] 65.867721 ± 0.000026
inclination [°] 105.657509 ± 0.000116
reciprocal semi-major axis [10-6 au-1] -707.57 ± 3.88
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).
non-gravitational parameters
A1 [10-8au/day2] 2.0982 ± 0.2322
A2 [10-8au/day2] -0.88176 ± 0.29757
A3 [10-8au/day2] 0.17223 ± 0.14085
m -2.00
n 3.000
k -2.6000
r0 [au] 10.000
α 0.0100