C/1999 U1 Ferris

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C/1999 U1 Ferris

General description

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 Earth on 11 December 1998 (3.667 au), 3.3 months after perihelion.

Solution given below is based on data span over 1.1 yr in a range of heliocentric distances from 4.24 au to 5.89 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 C1999U1A2-001

Comet C/1999 U1 Ferris

number of observations	208
number of residuals	410
data interval	1998 Dec. 22 — 2000 Jan. 28
rms [arcsec]	0.51
orbit quality class	1a

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT)	19980815.0	= JD 2451040.5
time of perihelion passage (TT)	19980903.028007	± 0.003494
perihelion distance	4.13756580	± 0.00002406
eccentricity	1.00365011	± 0.00001242
argument of perihelion [deg]	291.063317	± 0.000628
longitude of the ascending node [deg]	58.257256	± 0.000024
inclination [deg]	105.734810	± 0.000121
inverse semimajor axis [10^-6 au^-1]	-882.19	± 2.99

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 U1. Each density map is given in logarithmic scale presented on the right in the individual panel.
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Original orbital elements (barycentric; at 250 au from the Sun)

Epoch (TT)	16940808
time of perihelion passage (TT)	19980903.427579	± 0.003547
perihelion distance	4.13652185	± 0.00002415
eccentricity	0.99984302	± 0.00001239
argument of perihelion [deg]	291.151039	± 0.000628
longitude of the ascending node [deg]	58.213827	± 0.000024
inclination [deg]	105.825193	± 0.000122
inverse semimajor axis [10^-6 au^-1]	37.95	± 3.00

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)	23081009
time of perihelion passage (TT)	19980903.430110	± 0.003442
perihelion distance	4.12996080	± 0.00002416
eccentricity	0.99777930	± 0.00001238
argument of perihelion [deg]	290.958233	± 0.000631
longitude of the ascending node [deg]	58.287371	± 0.000024
inclination [deg]	105.882515	± 0.000122
inverse semimajor axis [10^-6 au^-1]	537.70	± 3.00