C/1997 A1 NEAT

Solar System
Dynamics &
Planetology
Group

C/1997 A1 NEAT

General description

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). Day later two preperihelion measurements from 9 January were announced by Kobayashi (IAUC 6534). Then the comet was about six 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 5.5 months before perihelion passage.

Solution given below is based on data span over 0.97 yr in the range of heliocentric distances: 3.52 au – 3.16 au (perihelion) – 3.65 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 C1997A1A5-001

Comet C/1997 A1 NEAT

number of observations	204
number of residuals	400
data interval	1997 Jan. 9 — 1997 Dec. 28
rms [arcsec]	0.55
orbit quality class	1b

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT)	19970601.0	= JD 2450600.5
time of perihelion passage (TT)	19970619.592489	± 0.000501
perihelion distance	3.15719754	± 0.00000229
eccentricity	1.00205075	± 0.00000507
argument of perihelion [deg]	40.013168	± 0.000111
longitude of the ascending node [deg]	135.766750	± 0.000017
inclination [deg]	145.071757	± 0.000026
inverse semimajor axis [10^-6 au^-1]	-649.55	± 1.60

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

Epoch (TT)	16950405
time of perihelion passage (TT)	19970620.169495	± 0.000519
perihelion distance	3.16326982	± 0.00000236
eccentricity	0.99993098	± 0.00000519
argument of perihelion [deg]	40.022006	± 0.000115
longitude of the ascending node [deg]	135.720211	± 0.000018
inclination [deg]	145.046895	± 0.000027
inverse semimajor axis [10^-6 au^-1]	21.82	± 1.64

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

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/1997 A1. Each density map is given in logarithmic scale presented on the right in the individual panel.
The same figure in the new window

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)	22961031
time of perihelion passage (TT)	19970621.802449	± 0.000517
perihelion distance	3.15501004	± 0.00000235
eccentricity	1.00071733	± 0.00000517
argument of perihelion [deg]	40.095287	± 0.000114
longitude of the ascending node [deg]	135.813600	± 0.000018
inclination [deg]	144.984535	± 0.000027
inverse semimajor axis [10^-6 au^-1]	-227.36	± 1.64