C/1956 R1 Arend-Roland
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Comet C/1956 R1 was discovered on 8 November 1956 by Sylvain Julien Victor Arend and Georges Roland (Royal Observatory, Uccle, Belgium), that is 5 months before its perihelion passage. Later, Sigeru Kaho (Tokyo Observatory, Konko Station, Japan) found an image of this comet on a plate he had exposed on 7 November 1956 during observations of variable stars. C/1956 R1 was observed until 11 April 1958 [Kronk, Cometography: Volume 4].
Comet had its closest approach to the Earth on 20 April 1957 (0.569 au), 12 days after its perihelion passage.
This is a comet with nongravitational effects strongly manifested in positional data fitting. Two NG solutions given here are based on data spanning over 0.602 yr in a range of heliocentric distances: 1.16 au – 0.778 au (perihelion) – 2.86 au; asymmetric NG solution was chosen as preffered orbit.
All solutions given here are based on data spanning over 1.42 yr in a range of heliocentric distances: 2.83 au – 0.316 au (perihelion) – 5.36 au.
This Oort spike comet suffers rather notable planetary perturbations during its passage through the planetary system; these perturbations lead to escape the comet from the planetary zone on a hyperbolic orbit (see future barycentric orbits).
See also Królikowska 2014 and Królikowska 2020.

solution description
number of observations 239
data interval 1956 11 08 – 1958 04 11
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 2.83 au – 0.32 au (perihelion) – 5.36 au
detectability of NG effects in the comet's motion comet with NG effects strongly manifested in positional data fitting
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 461
RMS [arcseconds] 1.68
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 1956 10 14
perihelion date 1957 04 08.03034928 ± 0.00004877
perihelion distance [au] 0.31601661 ± 0.00000097
eccentricity 1.00024993 ± 0.00000170
argument of perihelion [°] 308.778899 ± 0.000045
ascending node [°] 215.855876 ± 0.000066
inclination [°] 119.939323 ± 0.000054
reciprocal semi-major axis [10-6 au-1] -790.89 ± 5.39
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.