C/1997 A1 NEAT
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Comet C/1997 A1 was discovered by the Near-Earth-Asteroid Tracking Team (cf. IAUC 6341), on images obtained by the on-site USAF/Ground-based Electro-Optical Deep Space Surveillance Team in Hawaii (IAUC 6532). A day later, two preperihelion measurements from 9 January were announced by Kobayashi (IAUC 6534). Then the comet was more than 5 months before its perihelion passage. C/1997 A1 was last seen on 28 December 1997.
The comet made its closest approach to the Earth on 5 February 1997 (2.44 au), that was one month after discovery and 4.5 months before perihelion passage.
Solution given here is based on data spanning over 0.97 yr in a narrow range of heliocentric distances: 3.52 au – 3.16 au (perihelion) – 3.65 au.
This Oort spike comet suffers rather small planetary perturbations during its passage through the planetary system that lead to escape of the comet from the solar system (see future barycentric orbit).
See also Królikowska 2014 and Królikowska and Dybczyński 2017.

solution description
number of observations 204
data interval 1997 01 09 – 1997 12 28
data type perihelion within the observation arc (FULL)
data arc selection entire data set (STD)
range of heliocentric distances 3.52 au – 3.16 au (perihelion) – 3.65 au
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] 0.55
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 1997 06 01
perihelion date 1997 06 19.59248900 ± 0.00050100
perihelion distance [au] 3.15719754 ± 0.00000229
eccentricity 1.00205075 ± 0.00000507
argument of perihelion [°] 40.013168 ± 0.000111
ascending node [°] 135.766750 ± 0.000017
inclination [°] 145.071757 ± 0.000026
reciprocal semi-major axis [10-6 au-1] -649.55 ± 1.60
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.