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
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 458
RMS [arcseconds] 1.39
orbit quality class 1b
previous orbit statistics, both Galactic and stellar perturbations were taken into account
no. of returning VCs in the swarm 1448
no. of escaping VCs in the swarm 3553 *
no. of hyperbolas among escaping VCs in the swarm 926
previous reciprocal semi-major axis [10-6 au-1] -4.18 – 10.29 – 24.92
previous perihelion distance [au] 730 – 1200 – 1400 R
previous aphelion distance [103 au] 76 – 150 – 640
time interval to previous perihelion [Myr] 5.5 – 9.6 – 13 R
percentage of VCs with qprev > 20100
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.
previous orbit statistics, here only the Galactic tide has been included
no. of returning VCs in the swarm 1462
no. of escaping VCs in the swarm 3539 *
no. of hyperbolas among escaping VCs in the swarm 910
previous reciprocal semi-major axis [10-6 au-1] -4.05 – 10.39 – 24.99
previous perihelion distance [au] 1.6 – 27 – 130 R
previous aphelion distance [103 au] 76 – 150 – 640
time interval to previous perihelion [Myr] 5.5 – 9.5 – 13 R
percentage of VCs with qprev < 1032
percentage of VCs with 10 < qprev < 2012
percentage of VCs with qprev > 2056