C/2009 U5

Solar System
Dynamics &
Planetology
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C/2009 U5 Grauer

General description

C/2009 U5 was discovered by A.D. Grauer on 23 October 2009 on images taken with the Mt Lemmon 1.5-m reflector [IAUC 9088, 2009 October 25].

This comet made its closest approach to Earth on 3 February 2010 (5.191 au), 4.7 months before perihelion.

Solution given below is based on data span over 1.4 yr in a narrow range of heliocentric distances: 6.32 au – 6.094 au (perihelion) – 6.41 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 C2009U5A5-001

Comet C/2009 U5 Grauer

number of observations	187
number of residuals	359
data interval	2009 Oct. 23 — 2011 Apr. 2
rms [arcsec]	0.52
orbit quality class	1a

Osculating orbital elements (heliocentric; ecliptic J2000.0)

Epoch (TT)	20100613.0	= JD 2455360.5
time of perihelion passage (TT)	20100622.379910	± 0.009093
perihelion distance	6.09432663	± 0.00001434
eccentricity	0.99967469	± 0.00001116
argument of perihelion [deg]	23.804900	± 0.000786
longitude of the ascending node [deg]	121.172427	± 0.000045
inclination [deg]	25.470398	± 0.000086
inverse semimajor axis [10^-6 au^-1]	53.38	± 1.83

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/2009 U5. 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)	17021205
time of perihelion passage (TT)	20100622.599308	± 0.009099
perihelion distance	6.09719567	± 0.00001441
eccentricity	0.99974726	± 0.00001129
argument of perihelion [deg]	23.807853	± 0.000785
longitude of the ascending node [deg]	121.202798	± 0.000045
inclination [deg]	25.459103	± 0.000086
inverse semimajor axis [10^-6 au^-1]	41.45	± 1.85

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)	23141018
time of perihelion passage (TT)	20100622.526457	± 0.009063
perihelion distance	6.10059323	± 0.00001434
eccentricity	1.00138990	± 0.00001129
argument of perihelion [deg]	24.000202	± 0.000782
longitude of the ascending node [deg]	121.012427	± 0.000047
inclination [deg]	25.467175	± 0.000086
inverse semimajor axis [10^-6 au^-1]	-227.83	± 1.85