Supplemental (Feb 15): 2012 DA14 may not be visible at the time of close approach since it is likely to be passing through the Earth's shadow during the middle of the night.
Friday, February 15, 2013
2012 DA14 Close Approach Details
I just got through recalculating today's close approach details for 2012 DA14. I used the fitted position and velocity of the asteroid on Feb 9.0 and subtracted the values for the motion of the Earth's center relative to the Earth-Moon barycenter to get the position and velocity relative to the Earth's center at that time. The gravitational attraction of the Sun, Earth and Moon were used to compute 2013 DA14's trajectory. Since the Earth and Moon are also accelerating due to the Sun's attraction the difference between the asteroid's acceleration and the Earth's was used to get the acceleration relative to the Earth. My computed time for close approach is Feb 15, 2013 23:46 UT (15:46 PST) at a distance from the Earth's center of 6.477 Earth radii. The JPL ephemeris gave a time of 19:20 UT and a radial distance of 5.492 Earth radii.