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 (heliocentric ecliptic J2000)
Epoch 1972 10 10
perihelion date 1972 10 05.45988519 ± 0.00244124
perihelion distance [au] 2.51109947 ± 0.00001461
eccentricity 1.00046034 ± 0.00003078
argument of perihelion [°] 346.233721 ± 0.000833
ascending node [°] 175.877044 ± 0.000146
inclination [°] 138.62815 ± 0.000139
recip semi-major axis [10-6 au-1] -183.32 ± 12.26
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