C/1999 U1 Ferris
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C/1999 U1 was discovered on 18 October 1999 by W.D. Ferris of LONEOS team [IAUC 7283, 1999 October 18]. Later, pre-discovery measurements taken by Siding Spring on 22 December 1998 were found.
This comet made its closest approach to the Earth on 11 December 1998 (3.667 au), 3.3 months after perihelion.
Solution given here is based on data spanning over 1.1 yr in a range of heliocentric distances from 4.24 au to 5.89 au.
This Oort spike comet suffers rather strong planetary perturbations during its passage through the planetary system that lead to notable more tight future orbit with semimajor axis shorter than 2000 au (see future barycentric orbit).
See also Królikowska 2014 and Królikowska and Dybczyński 2017.

solution description
number of observations 208
data interval 1998 12 22 – 2000 01 28
data type observed only after perihelion (POST)
data arc selection entire data set (STD)
range of heliocentric distances 4.24 au – 5.89au
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 410
RMS [arcseconds] 0.51
orbit quality class 1a
orbital elements (barycentric ecliptic J2000)
Epoch 2308 10 09
perihelion date 1998 09 03.43011000 ± 0.00344200
perihelion distance [au] 4.12996080 ± 0.00002416
eccentricity 0.99777930 ± 0.00001238
argument of perihelion [°] 290.958233 ± 0.000631
ascending node [°] 58.287371 ± 0.000024
inclination [°] 105.882515 ± 0.000122
reciprocal semi-major axis [10-6 au-1] 537.70 ± 3.00
file containing 5001 VCs swarm
1999u1a2.bpl
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 future swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.