C/1991 C3 McNaught-Russell
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Comet C/1991 C3 was discovered on 12 February 1991 by Robert H. McNaught and Kenneth S. Russell with U> Schmidt at Siding Spring [IAUC 5187, February 13], almost four months after perihelion passage; however, two days later the prediscovery observation taken on 26 January was found [IAUC 5189, 15 Feb].
The comet was observed 1.3 yr in a range of heliocentric distances from 4.84 au to 6.41 au with almost one-year gap between 16 May 1991 and 30 April 1992.
C/1991 C3 made its closest approach to the Earth on 11 March 1991 (3.98 au), that was one month after its discovery.
This comet suffers strong planetary perturbations during its passage through the planetary system that lead to notable more tight future orbit with semimajor axis shorter than 1000 au (see future barycentric orbit).
See also Królikowska and Dybczyński 2017.

solution description
number of observations 42
data interval 1991 01 26 – 1992 04 30
data type observed only after perihelion (POST)
data arc selection entire data set (STD)
range of heliocentric distances 4.84 au – 6.41au
detectability of NG effects in the comet's motion NG effects not determinable
type of model of motion GR - gravitational orbit
data weighting NO
number of residuals 82
RMS [arcseconds] 0.96
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 1990 11 05
perihelion date 1990 10 18.19724910 ± 0.00924786
perihelion distance [au] 4.77707372 ± 0.00005293
eccentricity 1.00174603 ± 0.00010724
argument of perihelion [°] 320.886310 ± 0.001085
ascending node [°] 161.709637 ± 0.000174
inclination [°] 113.430375 ± 0.000389
recip semi-major axis [10-6 au-1] -365.50 ± 22.44
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