C/1997 BA6 Spacewatch
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Comet C/1997 BA6 was discovered as an asteroidal object by the Spacewatch program on 31 January 1997 (with also prediscovery images on January 11) (IAUC 6561). In February, two independent groups on the basis of exposures with 2.4-m Hiltner Telescope at Kitt Peak and 2.2-m telescope on Mauna Kea detected coma around C/1997 BA6 (IAUC 6561).

At the moment of discovery the comet was almost three years before its perihelion passage. C/1997 BA6 was last seen on 15 September 2004.

The comet made its closest approach to the Earth on 27 July 2000 (3.21 au), that was eight months after perihelion passage, however in the previous opposition it was within 3.66 au on 20 March 1999 (about seven months before perihelion).

Solutions given here is based on data span over 7.68 yr in the range of heliocentric distances: 9.15 au – 3.44 au (perihelion) – 13.39 au.

NG orbits using full data-arc as well as independently using pre-perihelion and post-perihelion data are determinable.

See also Królikowska and Dones 2023, Królikowska and Dybczyński 2017,and Królikowska 2014.
solution description
number of observations 258
data interval 1997 01 11 – 1999 11 12
data arc selection data generally limited to post-perihelion (POS)
range of heliocentric distances 3.54 au – 13.39au
detectability of NG effects in the comet's motion comet with determinable NG~orbit
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 509
RMS [arcseconds] 0.71
orbit quality class 1a+
orbital elements (heliocentric ecliptic J2000)
Epoch 1999 12 08
perihelion date 1999 11 27.53633602 ± 0.00113443
perihelion distance [au] 3.43606061 ± 0.00001362
eccentricity 0.99876871 ± 0.00000680
argument of perihelion [°] 285.926892 ± 0.000323
ascending node [°] 317.663834 ± 0.000013
inclination [°] 72.714702 ± 0.000038
reciprocal semi-major axis [10-6 au-1] 358.34 ± 1.98
Upper panel: 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.
Middle panel(s): O-C diagram for a given solution (sometimes in comparison to another solution available in CODE), where residuals in right ascension are shown using magenta dots and in declination by blue open circles.
Lowest panel: Relative weights for a given data set(s).