Traffic Timeline & Statistics

Refreshed at 2319 UT on 23 September 2018

[ Jump to the CURRENT timeline ]

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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 nominalvs. minimum passage time and distance estimates. Note that there is no exact boundary for a gravitational sphere of incluence (about 2.41 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 Arizona with some help previously from New Mexico and now from Hawaii. 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 here list only objects that are in solar rather than geocentric orbits. This excludes tiny 2006 RH120 (links), which apparently was captured as a temporary natural Earth satellite in 2006, first coming within a distance of ten LD from our planet on April 16th and remaining closer than that until October 20th of the following year. It wasn't discovered until 14 September 2006 and at first it was believed to be a human artifact. It approached Earth four times during these months in temporary orbit: 2.2 LD on Sepember 16th, 1.4 LD on January 3rd, 0.9 LD on March 25th, and 0.7 LD on June 14th. (The Earth's Hill sphere -- the theoretical region within which our planet can retain natural satellites rather than lose them to solar orbit, extends out to about 3.89 LD, which this object was within from November 25th until July 13th.)

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:

• 2014 July 6: Went public with an improved EBN timeline home page that better handles growing data tables and also implements a separate table tallying the asteroid designation credits that replaced the formal discovery credits that stopped being noted in discovery MPECs in October 2010.
• 2014 June 29: Began noting any previous close passes since 2007 in the Object Details section of A/CC home page ("Earth's Busy Neighborhood").
• 2014 June 20: Finished general updating of timeline pages to report and count Earth SOI boundary crossings.
• 2014 June 2: Noticed and fixed a major error in presenting JPL Earth-passage uncertainties in the monthly timeline pages for a few dozen objects that have made more than one pass at less than ten LD since 2007. Also began uploading recompiled versions of these pages after revising our database and program scripts to more completely and easily count and present objects that have made multiple close passes since this reporting began in 2007.
• 2014 May 28: First opportunity to reference Earth's SOI in A/CC's EBN daily traffic report.
• 2014 May 24: Implemented methods for correctly handling impactors (two so far for Earth, none yet for the Moon) without manual intervention.
• 2014 May 19: Began switch to reporting counts of objects within Earth's gravitational sphere of influence (SOI) instead of the Hill sphere, beginning with counts only valid from May 2014 forward. The changeover was completed three days later and by June 20th SOI transits had been calculated and counts updated back through 2007.
• 2012 Feb. 22: Replaced the old static-image sky chart with a new animated sky chart and discontinued the home page "Traffic Report."
• 2012 Jan. 13: Began running a parallel "Traffic Report" generated from a new narrator script, posted to the daily Tracking News, where it now can remain part of the permanent record.
• 2011 Jan. 15: Added discovery MPEC issuance to the events timeline beginning with the last two close passers discovered in December: 2011 YB63 and YC63.
• 2011 Nov. 7: A/CC EBN traffic reporting resumed with no gaps in the Timeline.
• 2011 Aug. 9: Earth's Busy Neighborhood (EBN) traffic reporting came to a screeching halt when our data-querying scripts stopped working following changes in JPL's Horizons telnet interface.
• 2010 Nov. 1: Implemented extensive script changes to allow reporting optical observations published in MPECs while JPL's public orbit solution is locked down and not being updated for an object during a radar campaign or other circumstances.
• 2010 Oct. 19: Began implementing changes to adapt to the Minor Planet Center's new discovery credit policy.
• 2010 April 25: Finally isolated and 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.
• 2008 Jan. 2: Added sky charts to the EBN Traffic Report.
• 2007 Nov. 14: Inaugurated the semi-automated Traffic Report for Earth's Busy Neighborhood.

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

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