2005 YU55 close approaches
From Jon Giorgini, Oct 29, 2011:
The following table lists planetary approaches within 0.1 AU, bounded
in the past and future by the Earth encounters where the uncertainty in
encounter time first exceeds +/- 10 days (3-sigma), or encounter distance
exceeds +/- 0.1 AU, whichever occurs first. Prior to the 2011 radar
experiment, this time-span is 1827 to 2011.
Although there are "possibilities", prior to the radar experiment we
cannot confidently predict when the next such close encounter with Earth
might occur. This is because close encounters with Earth in 2011, and
Venus in 2029 increase prediction uncertainty.
Radar measurements from this experiment will reduce prediction uncertainty
and permit meaningful Earth encounter predictions to be extended further
into the future.
(AU) (AU) (AU) (km/s) (min.)
Date (CT) Body CA Dist MinDist MaxDist Vrel TCA3Sg P_i/p
----------------- ----- ------- ------- ------- ------ ------ -------
1782 Nov 03.90961? Earth .001927 .001826 .613831 13.742 42884. .000000
....
1803 Jan 22.33074 Mars .043688 .030690 .133335 5.472 32538. .000000
1806 Nov 28.83813 Mars .037160 .032034 .042972 4.863 37913. .000000
1810 Oct 05.43562 Mars .047549 .044064 .051502 5.567 5191.9 .000000
1813 Sep 20.03762 Venus .027439 .003028 .072738 12.565 6290.8 .000000
1814 Dec 23.75657 Venus .039899 .006320 .088827 9.613 15698. .000000
1816 Apr 05.66252 Venus .075503 .069533 .082533 9.348 22336. .000000
1817 Jul 19.70019 Venus .062431 .049074 .084977 9.246 15278. .000000
1818 Oct 26.05852 Venus .041058 .038266 .059462 11.834 4926.6 .000000
1827 Apr 16.92106 Earth .018103 .013581 .022599 14.216 309.80 .000000
1858 Apr 21.43025 Earth .073596 .072411 .074784 11.466 81.05 .000000
1864 Nov 04.60067 Earth .015106 .014912 .015301 13.228 13.59 .000000
1868 Dec 19.42163 Mars .035392 .035386 .035398 4.823 38.31 .000000
1872 Nov 06.10338 Mars .095370 .095348 .095392 6.504 4.94 .000000
1890 Nov 03.09813 Earth .061731 .061480 .061981 11.792 18.48 .000000
1891 Nov 03.37622 Venus .068179 .067926 .068432 14.625 24.10 .000000
1893 Jan 28.02975 Venus .038557 .038371 .038744 13.172 22.20 .000000
1894 Apr 23.94700 Venus .021480 .021416 .021544 12.344 9.01 .000000
1895 Jul 16.98278 Venus .024894 .024779 .025009 12.520 15.47 .000000
1896 Oct 06.48044 Venus .047234 .047017 .047451 13.607 23.81 .000000
1897 Dec 27.52431 Venus .080815 .080542 .081089 15.239 23.90 .000000
1933 Jan 02.17018 Mars .056921 .056891 .056951 5.335 18.38 .000000
1949 Apr 14.17919 Earth .090399 .090300 .090498 16.282 6.57 .000000
1957 Jun 12.69401 Mars .051513 .051475 .051551 5.169 30.60 .000000
1984 Dec 05.94302 Venus .048640 .048585 .048695 12.703 11.14 .000000
1986 Feb 21.62180 Venus .043931 .043902 .043961 10.192 16.09 .000000
1987 May 04.38269 Venus .071146 .071124 .071167 9.243 24.19 .000000
1988 Jul 11.93138 Venus .080562 .080560 .080564 9.438 21.19 .000000
1989 Sep 19.89067 Venus .065809 .065795 .065823 9.292 12.23 .000000
1990 Dec 01.43515 Venus .028811 .028800 .028822 10.115 3.15 .000000
1992 Feb 17.98617 Venus .012636 .012628 .012644 11.975 1.25 .000000
1993 May 06.14822 Venus .093596 .093587 .093605 15.903 0.73 .000000
2002 Jul 14.60371 Mars .039709 .039709 .039710 4.684 0.96 .000000
2010 Apr 19.51424 Earth .015194 .015194 .015194 13.124 0.00 .000000
2011 Nov 08.97848 Earth .002173 .002172 .002174 13.716 0.03 .000000
2011 Nov 09.30173 Moon .001602 .001601 .001603 13.509 0.02 .000000
2027 Oct 20.64160 Venus .088563 .087822 .089304 15.414 63.75 .000000
2029 Jan 19.78509 Venus .001965 .001730 .002365 11.158 125.08 .000000
2030 May 27.61576 Venus .064356 .052808 .082007 9.114 15475. .000000
....
2041 Nov 06.06984? Earth .033621 .001798 .314045 12.662 20465. .000000
Column meaning:
Date (CT) =
Nominal close-approach date (Coordinate Time) in the Gregorian calendar
system.
Body =
Name or abbreviation of the planetary body or major asteroid being
closely approached by the selected small-body.
CA Dist =
Nominal geometric close-approach distance at the close-approach time,
uncorrected for light travel time. Units: AU
MinDist =
Minimum close-approach distance possible (formal 3 standard-deviations
with linearized covariance mapping). Units: AU
MaxDist =
Maximum close-approach distance possible (formal 3 standard-deviations
with linearized covariance mapping). Units: AU
Vrel =
Relative velocity of the object and the body it is approaching at the
nominal time of close-approach. Units: KM/S
TCA3Sg =
Close-approach-time 3-standard deviation uncertainty. Units: MINUTES
Nsigs =
The number of standard deviations (sigmas) required for the error ellipse
to intersect the body being closely approached. Units: STANDARD DEVIATIONS
P_i/p =
Linearized probability of the object impacting the body.
+++++++++++++++++++++++++++++
IMPORTANT NOTE:
All tabulated statistical quantities (MinDist, MaxDist, TCA3Sg, Nsigs and
P_i/p) are based on a linearized covariance mapping in which higher-order
(small) terms in the variational partial derivatives of the equations of motion
are dropped.
Due to possible non-linearities in any given object's actual dynamics, this
can result in significant errors at epochs distant in time from the solution
epoch. Consequently, long linearized mappings (thousands, or hundreds, or
sometimes just dozens of years from the present time) should be considered
approximate, pending additional analysis, especially in these cases:
A) objects with numerous close planetary encounters (dozens),
B) objects with very close planetary encounters (< 0.01 AU),
C) objects with very short data arcs (days or weeks).
While linearized projections will tend to indicate such cases with obviously
rapid uncertainty growth, the specific numbers output can tend to understate
orbit uncertainty knowledge.
"Nominal" here effectively means "highest-probability for the given orbit
solution"), although there can be other possible orbits of equal probability.
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