C/1999 S2 McNaught-Watson
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C/1999 S2 was discovered on 19 September 1999 by Robert H. McNaught on an R-survey film taken by F.G. Watson using UK Schmidt Telescope, 1.8 yr after perihelion passage.
This comet made its closest approach to the Earth on 20 June 1997 (5.670 au), 5 months before perihelion.
Solution given here is based on data spanning over 2.4 yr in a range of heliocentric distances from 7.84 au to 11.7 au.
This Oort spike comet suffers moderate planetary perturbations during its passage through the planetary system that lead to escape of the comet from the solar system on hiperbolic orbit (see future barycentric orbit).
See also Królikowska 2014 and Królikowska and Dybczyński 2017.

solution description
number of observations 98
data interval 1999 09 19 – 2002 02 16
data type observed only after perihelion (POST)
data arc selection entire data set (STD)
range of heliocentric distances 7.84 au – 11.7au
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 184
RMS [arcseconds] 0.48
orbit quality class 1a
previous orbit statistics, both Galactic and stellar perturbations were taken into account
no. of returning VCs in the swarm 5001 *
no. of escaping VCs in the swarm 0
no. of hyperbolas among escaping VCs in the swarm 0
previous reciprocal semi-major axis [10-6 au-1] 52.12 – 56.42 – 61.27
previous perihelion distance [au] 6.5 – 9.1 – 49
previous aphelion distance [103 au] 32.6 – 35.4 – 38.3
time interval to previous perihelion [Myr] 2.1 – 2.4 – 2.7
percentage of VCs with qprev < 1081
percentage of VCs with 10 < qprev < 203
percentage of VCs with qprev > 2016
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 5001 *
no. of escaping VCs in the swarm 0
no. of hyperbolas among escaping VCs in the swarm 0
previous reciprocal semi-major axis [10-6 au-1] 51.53 – 56.45 – 61.30
previous perihelion distance [au] 8.32 – 9 – 10.1
previous aphelion distance [103 au] 32.6 – 35.4 – 38.8
time interval to previous perihelion [Myr] 2.1 – 2.4 – 2.7
percentage of VCs with qprev < 1089
percentage of VCs with 10 < qprev < 2011