The following is from Dan Adamo, guest astrogator and a former Flight Dynamics Officer at JSC. Dan runs a mail list called the ATIG (Astrodynamics Technical Interchange Group). Last year he graciously allowed me(Mike) to be a part of the group, and since then I get interesting articles from him every month or so. This month, Dan sent the following, which I thought was a great topic for the guild.
The near-Earth object (NEO) designated 2011 AG5 is currently associated with a relatively high linearized Earth impact probability of 0.001557 (odds of 1-in-642.3) during its predicted 5 February 2040 close approach to Earth. This probability appears in Table 1 (reference the P_i/p column), together with data pertaining to other near-term 2011 AG5 planetary approaches closer than 0.1 AU (15 million km). These predictions are obtained from JPL’s Horizons on-line solar system data and ephemeris computation service* using the current JPL#45 orbit solution for 2011 AG5. Note that coordinate time (CT) is a uniform time scale void of leap seconds and used as the fundamental ephemeris argument by Horizons. To a precision of ±0.002 s, CT is related to atomic time (TAI) by CT = TAI + 32.184 s.