C/1999 S2 McNaught-Watson

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C/1999 S2 McNaught–Watson

General description

C/1999 S2 was discovered on 19 September 1999 by R.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 Earth on 20 June 1997 (5.670 au), 5 months before perihelion.

Solution given below is based on data span over 2.4 yr in a range of heliocentric distances from 7.84 au to 11.7 au.

Figure caption: 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.

SSDP Cometary Note C1999S2A2-001

Comet C/1999 S2 McNaught–Watson

number of observations	98
number of residuals	184
data interval	1999 Sep. 19 — 2002 Feb. 16
rms [arcsec]	0.48
orbit quality class	1a

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT)	19971108.0	= JD 2450760.5
time of perihelion passage (TT)	19971122.532219	± 0.006487
perihelion distance	6.46669745	± 0.00004864
eccentricity	1.00725540	± 0.00002471
argument of perihelion [deg]	223.477051	± 0.000614
longitude of the ascending node [deg]	74.427229	± 0.000142
inclination [deg]	65.813130	± 0.000028
inverse semimajor axis [10^-6 au^-1]	-1121.96	± 3.82

Note: Epoch is given in a format: yyyymmdd.d, time of perihelion passage in a format of yyyymmdd.dddddd.

Figure caption: Six 2D-projections of the 6D space of original swarm (5001 VCs) of C/1999 S2. Each density map is given in logarithmic scale presented on the right in the individual panel.
The same figure in the new window

Original orbital elements (barycentric; at 250 au from the Sun)

Epoch (TT)	16890725
time of perihelion passage (TT)	19971122.443555	± 0.006530
perihelion distance	6.46202592	± 0.00004912
eccentricity	0.99963528	± 0.00002453
argument of perihelion [deg]	223.496648	± 0.000617
longitude of the ascending node [deg]	74.396105	± 0.000142
inclination [deg]	65.872236	± 0.000027
inverse semimajor axis [10^-6 au^-1]	56.44	± 3.80

Note: Values of uncertainties of original/future orbital elements were derived using a swarm of 5001 osculating orbits of VCs (including the nominal osculating orbit given above) for original/future orbital evolution calclulations and then by fitting the distribution of a given orbital element of original/future swarm of VCs to Gaussian distribution.

Original barycentric positions and velocities of 5001 VCs at 250 au from the Sun are given here (data format), i.e. before entering the planetary zone.

Future orbital elements (barycentric; at 250 au from the Sun)

Epoch (TT)	23011006
time of perihelion passage (TT)	19971121.877189	± 0.006539
perihelion distance	6.46116610	± 0.00004892
eccentricity	1.00207639	± 0.00002446
argument of perihelion [deg]	223.382735	± 0.000623
longitude of the ascending node [deg]	74.395135	± 0.000142
inclination [deg]	65.865297	± 0.000028
inverse semimajor axis [10^-6 au^-1]	-321.37	± 3.79