C/1973 A1 Heck-Sause
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Comet C/1973 A1 was discovered on 11 January 1973 by André Heck and Gérard Sause (Haute Provence Observatory, France), that is more than 3 months after its perihelion passage.In the next few months prediscovery images were found taken on 4 January (Sendai Municipal Observatory, Japan) and 10 January (Montpellier, France). This comet was observed until 26 February 1974 [Kronk, Cometography: Volume 5].
Comet had its closest approach to the Earth on 11 February 1973 (1.978 au), a month after its discovery.
Solution given here is based on post-perihelion data spanning over 1.13 yr in a range of heliocentric distances from 2.70 au to 5.53 au.
This Oort spike comet suffers rather small planetary perturbations during its passage through the planetary system; these perturbations lead to a more tight future orbit.
See also Królikowska 2020.

solution description
number of observations 201
data interval 1973 01 04 – 1974 02 19
data type observed only after perihelion (POST)
data arc selection entire data set (STD)
range of heliocentric distances 2.7 au – 5.53au
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 400
RMS [arcseconds] 1.24
orbit quality class 1b
orbital elements (barycentric ecliptic J2000)
Epoch 1671 03 02
perihelion date 1972 10 05.33953009 ± 0.00227173
perihelion distance [au] 2.50898352 ± 0.00001464
eccentricity 0.99983430 ± 0.00003043
argument of perihelion [°] 346.199797 ± 0.000833
ascending node [°] 175.803902 ± 0.000144
inclination [°] 138.589327 ± 0.00014
reciprocal semi-major axis [10-6 au-1] 66.04 ± 12.13
file containing 5001 VCs swarm
1973a1a5.bmi
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.
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.