Traffic Timeline & Statistics

Refreshed at 1730 UTC on 2 September 2010

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Boundary crossing times and distances at time of observation are interpreted by A/CC from JPL SSD Horizons data. Boundary crossing times should be considered approximate since they can be off by many minutes or even hours, depending on the length of an object's observation time span and other factors. See JPL's Close Approach Tables for nominal vs. minimum passage time and distance estimates. Note that there is no exact boundary for a Hill sphere (about 3.9 lunar distances for Earth's own), and ten lunar distances from Earth is a useful arbitrary "bubble" within which to organize this reporting but has no special astronomical importance.

The chart below seems to suggest a flux in how many objects fly near the Earth-Moon system during different times of year. This illusion comes from not having an even distribution of asteroid discovery programs and follow-up observers to counter observational gaps caused by changes in length of night and regional weather as well as by program down times. As it is today, most observers are in the northern hemisphere, and most discoveries are made from two locations in Arizona and New Mexico. There probably are always more objects in Earth's neighborhood than are known, including some traveling in our daytime and twilight skies (radar works in daytime but not for discovery).

Note that the data and statistics list only objects that make one close passage during a year. Thus not included is 2006 RH120, which was apparently a temporary natural Earth satellite. It made three close passages in 2007 before departing Earth's vicinity: 1.4 LD on January 3rd, 0.9 LD on March 25th, and 0.7 LD on June 14th.

All data on this page derived from orbit solutions comes from the NASA JPL Solar System Dynamics (SSD) Group through its Horizons system. All information about optical observations comes from the IAU Minor Planet Center (MPC) and info about radar observations comes from JPL SSD. NASA, JPL, and the MPC are not affilliated with this page or A/CC, and responsibility for the interpretation of this information and its use here rests entirely with A/CC.

Notes about these pages:

• 2010 April 25: Finally isolated and (hopefully) fixed a problem in correlating uncertainty information from JPL's close approach pages for objects with multiple Earth passages of less than 10 LD since our reporting began (2007).
• 2010 April 23: Just in time for the return arrival within 10 LD of 2009 BD, many scripts were modified to properly handle objects which since 2007 have had multiple Earth passages or periods of observation outside 10 LD. (Only implemented so far for 2009 BD, more to come).
• 2009 Dec. 27: Timeline charts have been reworked to handle more than three years of data, with a truncated current chart and a new separate page with full chart.
• 2009 June 10: The May 17th changes introduced a major bug that was not understood and fixed until today, after ongoing problems were noted in processing updated JPL orbit solutions and with flagging radar targets.
• 2009 May 17: Pages updated for first time since yesterday morning after major revisions in multiple scripts to better handle multi-apparitional asteroids. (There is more work left and it's likely there will be some hiccups in how these pages work.)
• 2008 Sept. 21: Fixed a problem in characterizing an object's direction (in/outbound) at the time of a particular observation.
• 2008 June 17-19: Added data and statistics for January through September 2007.
• 2008 June 16: The EBN Timeline & Statistics page goes to a new multipage format to carry many more details and allow faster page loading.
• 2008 May 10: Object counts here rose with the addition of seven close-passing asteroids, including one briefly observed intruder (2007 VF189), that hadn't been picked up in early EBN reporting during October-November 2007. They were noticed now by a new diagnostic tool that will help avoid missing any more.
• 2008 March 24: The Timeline page was first posted.

Got questions, comments, or corrections? Please contact us.

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