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NEO Discovery Statistics

NEAR-EARTH ASTEROID DISCOVERY STATISTICS

Some entries in the following charts and tables are dependent upon a diameter that is roughly inferred from the object’s estimated absolute magnitude (H) and its assumed reflectivity, or albedo. The absolute magnitude (H) of a near-Earth asteroid (NEA) is a measure of the object's brightness one astronomical unit from the sun and Earth and at zero phase angle (i.e., the angle between the sun and Earth, as seen from the NEA, is zero). The absolute magnitude (H) for a particular NEA is computed from the observed apparent magnitudes of the object at various times when the phase angles and the distances from the sun and Earth are known. An effective diameter is the diameter of a hypothetical spherical NEA that would provide the same apparent brightness as the observed NEA, whose actual shape is unknown.

Since most NEAs do not have a known reflectivity, or albedo, this albedo must be estimated before the H values, representing intrinsic brightness, can be converted to an approximate diameter. Pravec et al (2012) determined that, for their sample of 583 main-belt asteroids and NEAs, the mean albedos and their standard deviations are 0.057 (±0.013) for the Tholen/Bus/DeMeo C/G/B/F/P/D types and 0.197 (±0.051) for the S/A/L types. Since the albedos for NEAs are most likely to be either approximately 6% for asteroids of the C-type and associated taxonomic classes or 20% for asteroids of the more populous S-type and associated taxonomic classes, we have used an approximate mean value of 14% albedo and an H value of 17.75 to represent a one kilometer spherical NEA. Since the determined H values are uncertain, and likely biased by a few tenths (see Pravec et al., 2012, Icarus) and the single 14% albedo is only a rough mean representing a bimodal albedo distribution, the estimated numbers of one kilometer and larger sized objects in the tables below are very rough. However, these statistics are useful for monitoring the annual NEA discovery progress.

Using near-infrared data provided by the WISE spacecraft in 2010 and early 2011, Mainzer et al (2011) were able to determine diameters and albedos for 250 NEAs with a minimum uncertainty of 10% and 20% respectively. Hence they were able to determine the albedo distribution of these objects with known diameters and this distribution was then used to compute diameters for previously known NEOs with known H values but unknown diameters or albedos. They provided an estimate of 981 (±19) NEAs as the total population of NEAs one kilometer and larger. At the time of their analysis (Spring 2011), they also estimated that 911 (±17) of these large NEAs had already been discovered. While this latter estimate is both higher and more accurate than the estimated numbers given for Spring 2011 in the following tables, this statistical technique cannot be easily employed for day-to-day estimates of the population of NEAs one kilometer and larger. In the following tables, we will continue to use the simpler method described in the previous paragraph.

Mainzer, A. et al. (2011). NEOWISE observations of near-Earth objects: Preliminary Results. Astrophysical Journal. 743:156.
Pravec, P., A.W. Harris, P. Kusnirak, A. Galad, K. Hornoch (2012). Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations. Icarus (submitted 6/2012).
Stuart, J.S. (2003). Observational constraints on the number, albedos, sizes and impact hazards of the near-Earth asteroids. Ph.D. thesis, MIT.

All Asteroids

Table: Number of Near-Earth Asteroid Discoveries at Half-Year Intervals: All Asteroids

Table 1. NEAs Discovered by Site

Half Year
Intervals
LINEAR
(704)
NEAT
(566,608,644)
Spacewatch
(691,291)
LONEOS
(699)
Catalina
(703,E12,G96)
Pan-STARRS
(F51)
NEOWISE
(C51)
OtherCumulative
Total
 1995 (1)001400004334
 1995 (2)001200002348
 1996 (1)151800004376
 1996 (2)051000002393
 1997 (1)321000004412
 1997 (2)149400007446
 1998 (1)4491911007527
 1998 (2)9221562005649
 1999 (1)75012611001754
 1999 (2)8707719003877
 2000 (1)10821421130041039
 2000 (2)15014121700081240
 2001 (1)942872200021393
 2001 (2)18364152000041679
 2002 (1)15856161410061930
 2002 (2)130896700052167
 2003 (1)10230233300092364
 2003 (2)13338332170082604
 2004 (1)167194114250062876
 2004 (2)13772925600063140
 2005 (1)788292211500103402
 2005 (2)5930541919300103767
 2006 (1)44445131950034071
 2006 (2)52175461990054404
 2007 (1)3842072010034677
 2007 (2)7402552660075054
 2008 (1)7404312810055458
 2008 (2)66043028000115858
 2009 (1)50032026000186218
 2009 (2)58031031500176639
 2010 (1)29021025708797042
 2010 (2)7502203451837147553
 2011 (1)410170331683128025
 2011 (2)3001502531040238450
 2012 (1)260130352120078968
 2012 (2)2901302771310269444
 2013 (1)301302881500189916
 2013 (2)0012031520812910481
 2014 (1)0080332242164811127
 2014 (2)*0030514091911303
* Incomplete half-year (based on discovery data through 2014-Sep-02 06:05 local)

Large Asteroids

Table: Number of Near-Earth Asteroid Discoveries at Half-Year Intervals: Large Asteroids

Table 2. Large NEAs Discovered by Site

Half Year
Intervals
LINEAR
(704)
NEAT
(566,608,644)
Spacewatch
(691,291)
LONEOS
(699)
Catalina
(703,E12,G96)
Pan-STARRS
(F51)
NEOWISE
(C51)
OtherCumulative
Total
 1995 (1)00300002178
 1995 (2)00400001183
 1996 (1)02200000187
 1996 (2)02000000189
 1997 (1)01300001194
 1997 (2)23100002202
 1998 (1)74210002218
 1998 (2)242130003251
 1999 (1)160244000277
 1999 (2)230112002306
 2000 (1)322114001347
 2000 (2)382350004399
 2001 (1)238040000434
 2001 (2)235040001467
 2002 (1)304230001507
 2002 (2)1910010001538
 2003 (1)143160002564
 2003 (2)175142001594
 2004 (1)165123001622
 2004 (2)910112000645
 2005 (1)100219001668
 2005 (2)645010001694
 2006 (1)30219000709
 2006 (2)102012000724
 2007 (1)20309001739
 2007 (2)50107000752
 2008 (1)20109000764
 2008 (2)30105000773
 2009 (1)10009000783
 2009 (2)60006002797
 2010 (1)00004030804
 2010 (2)10001030809
 2011 (1)20005100817
 2011 (2)00106300827
 2012 (1)00009100837
 2012 (2)10005200845
 2013 (1)00004000849
 2013 (2)00003201855
 2014 (1)00002420863
 2014 (2)*00000100864
* Incomplete half-year (based on discovery data through 2014-Sep-02 06:05 local)
NOTE: In the year 2010, the "Other" site category was exclusively WISE.
A separate table of WISE discoveries is
available.

Data compiled by Alan Chamberlin.

NUMBER OF NEOS
With over 90% of the near-Earth objects larger than one kilometer already discovered, the NEO Program is now focusing on finding 90% of the NEO population larger than 140 meters. A separate table containing WISE discoveries for NEAs and comets is available.

The chart below shows the cumulative total known near-Earth asteroids versus time. The blue area shows all near-Earth asteroids while the red area shows only large near-Earth asteroids (those with diameters roughly one kilometer and larger).
Table: Number of Known Near-Earth Asteroids Over Time
(click on the chart above for a larger version)

The chart below shows the total known near-Earth asteroids per size bin. Diameters are estimated using an assumed average albedo for NEAs. The first size bin represents NEAs smaller than 30m in diameter. The second represents NEAs with diameters from 30m to 100m, and so on.
Known Near-Earth Asteroids by Size Bin
Data shown in the chart above represent known NEAs as of the date shown in the bottom-right corner of the chart.

The table below shows the total number of NEOs known at selected dates. The most recent date at the top of the table is generally not the date the table was updated, but rather the discovery date of the most recently discovered NEO. Numbers for large asteroids (PHA-KM and NEA-KM) are rough estimates (see introductory note above). This table is updated daily using discovery data published by the Minor Planet Center.

----------------------------------------------------------------------------
   Date      NEC  Atira  Aten Apollo  Amor  PHA-KM  PHA  NEA-KM  NEA    NEO
----------  ----  ----- ----- ------ -----  ------ ----  ------ -----  -----
2014-09-01    94     14   859   6111  4319     155 1496     864 11303  11397
2014-09-01    94     14   859   6110  4319     155 1496     864 11302  11396
2014-08-01    94     14   855   6070  4268     155 1491     863 11207  11301
2014-07-01    94     14   853   6026  4234     155 1481     863 11127  11221
2014-06-01    94     14   844   5989  4176     154 1473     859 11023  11117
2014-05-01    94     14   837   5930  4130     154 1461     857 10911  11005
2014-04-01    94     14   826   5854  4069     154 1454     856 10763  10857
2014-03-01    94     13   819   5798  4042     154 1449     856 10672  10766
2014-02-01    94     13   811   5753  4004     154 1442     856 10581  10675
2014-01-01    94     13   804   5700  3964     154 1438     855 10481  10575
2013-12-01    94     13   799   5645  3938     154 1434     855 10395  10489
2013-11-01    94     13   798   5574  3911     154 1426     855 10296  10390
2013-10-01    94     12   786   5515  3849     153 1418     851 10162  10256
2013-09-01    94     12   780   5458  3794     153 1414     850 10044  10138
2013-08-01    94     12   778   5427  3757     153 1408     850  9974  10068
2013-07-01    94     12   773   5399  3732     153 1401     849  9916  10010
2013-06-01    94     12   770   5369  3714     153 1395     847  9865   9959
2013-05-01    94     11   765   5329  3694     153 1388     847  9799   9893
2013-04-01    94     11   760   5288  3663     153 1379     846  9722   9816
2013-03-01    94     11   755   5240  3635     153 1370     846  9641   9735
2013-02-01    93     11   750   5201  3608     153 1366     846  9570   9663
2013-01-01    93     11   743   5120  3570     153 1352     845  9444   9537
2012-12-01    93     11   735   5067  3539     153 1342     845  9352   9445
2012-11-01    92     10   727   5013  3502     153 1333     842  9252   9344
2012-10-01    92     10   721   4938  3446     153 1322     840  9115   9207
2012-09-01    92     10   717   4905  3416     153 1319     839  9048   9140
2012-08-01    92     10   712   4880  3382     153 1314     838  8984   9076
2012-07-01    91     10   711   4874  3373     153 1310     837  8968   9059
2012-06-01    91     10   706   4848  3350     153 1301     834  8914   9005
2012-05-01    91     10   704   4815  3326     153 1296     831  8855   8946
2012-04-01    91     10   702   4764  3299     153 1290     830  8775   8866
2012-03-01    91     10   696   4684  3272     153 1284     828  8662   8753
2012-02-01    91     10   686   4637  3231     153 1278     828  8564   8655
2012-01-01    91     10   676   4568  3196     153 1270     827  8450   8541
2011-12-01    91     10   672   4536  3171     153 1263     823  8389   8480
2011-11-01    91     10   669   4495  3136     151 1253     820  8310   8401
2011-10-01    91     10   662   4433  3091     150 1242     819  8196   8287
2011-09-01    90     10   661   4398  3037     150 1236     818  8106   8196
2011-08-01    90     10   661   4382  3011     150 1233     817  8064   8154
2011-07-01    89     10   659   4369  2987     150 1229     817  8025   8114
2011-06-01    89     10   659   4352  2962     150 1223     816  7983   8072
2011-05-01    89     10   656   4326  2939     150 1215     814  7931   8020
2011-04-01    89     10   645   4277  2909     150 1208     812  7841   7930
2011-03-01    89     10   634   4214  2885     150 1199     810  7743   7832
2011-02-01    89     10   624   4167  2866     150 1188     810  7667   7756
2011-01-01    89     10   618   4091  2834     150 1172     809  7553   7642
2010-12-01    89      9   609   4036  2802     150 1163     808  7456   7545
2010-11-01    89      9   598   3967  2756     150 1157     808  7330   7419
2010-10-01    89      9   588   3911  2716     150 1143     808  7224   7313
2010-09-01    89      9   582   3865  2651     150 1138     807  7107   7196
2010-08-01    89      9   579   3851  2641     150 1135     805  7080   7169
2010-07-01    89      9   574   3829  2630     150 1133     804  7042   7131
2010-06-01    88      9   568   3798  2608     150 1125     803  6983   7071
2010-05-01    87      9   560   3754  2589     149 1113     801  6912   6999
2010-04-01    87      9   552   3708  2572     149 1107     801  6841   6928
2010-03-01    87      9   544   3671  2547     148 1098     800  6771   6858
2010-02-01    87      9   540   3617  2522     148 1086     799  6688   6775
2010-01-01    87      9   535   3591  2504     148 1083     797  6639   6726
2009-12-01    87      9   531   3570  2494     148 1078     795  6604   6691
2009-11-01    86      9   520   3494  2465     148 1070     792  6488   6574
2009-10-01    86      9   511   3439  2432     148 1066     790  6391   6477
2009-09-01    86      9   506   3386  2385     148 1057     788  6286   6372
2009-08-01    86      9   504   3366  2358     148 1055     787  6237   6323
2009-07-01    86      9   504   3356  2349     147 1053     783  6218   6304
2009-06-01    85      9   501   3345  2338     146 1050     782  6193   6278
2009-05-01    85      9   499   3318  2325     146 1041     781  6151   6236
2009-04-01    85      9   496   3286  2311     146 1037     778  6102   6187
2009-03-01    85      9   491   3224  2292     146 1025     778  6016   6101
2009-02-01    85      9   487   3166  2266     145 1013     775  5928   6013
2009-01-01    85      9   481   3122  2246     145 1004     773  5858   5943
2008-12-01    84      9   480   3080  2216     145  994     772  5785   5869
2008-11-01    84      9   474   3032  2194     145  986     770  5709   5793
2008-10-01    84      8   467   2970  2144     144  976     769  5589   5673
2008-09-01    83      8   464   2939  2109     144  966     768  5520   5603
2008-08-01    83      8   461   2925  2095     144  961     767  5489   5572
2008-07-01    83      8   459   2908  2083     143  952     764  5458   5541
2008-06-01    83      8   455   2897  2075     143  949     763  5435   5518
2008-05-01    83      8   451   2867  2057     143  943     762  5383   5466
2008-04-01    83      8   449   2820  2028     143  940     761  5305   5388
2008-03-01    83      7   440   2752  2003     142  930     754  5202   5285
2008-02-01    83      7   428   2692  1973     141  916     752  5100   5183
2008-01-01    83      7   426   2665  1956     141  908     752  5054   5137
2007-12-01    83      7   423   2630  1939     141  897     749  4999   5082
2007-11-01    83      7   411   2572  1903     141  887     745  4893   4976
2007-10-01    82      7   397   2523  1861     141  877     744  4788   4870
2007-09-01    82      7   390   2485  1829     140  870     743  4711   4793
2007-08-01    82      7   388   2474  1819     139  865     739  4688   4770
2007-07-01    82      7   388   2470  1812     139  864     739  4677   4759
2007-06-01    82      7   383   2448  1803     138  855     737  4641   4723
2007-05-01    82      7   382   2435  1792     138  851     735  4616   4698
2007-04-01    82      7   381   2409  1775     138  847     731  4572   4654
2007-03-01    82      6   375   2369  1752     138  840     729  4502   4584
2007-02-01    82      6   367   2336  1736     137  832     725  4445   4527
2007-01-01    82      6   359   2316  1723     137  823     724  4404   4486
2006-12-01    81      6   354   2290  1705     137  820     722  4355   4436
2006-11-01    81      5   344   2241  1682     136  808     716  4272   4353
2006-10-01    79      5   337   2211  1650     136  798     714  4203   4282
2006-09-01    79      5   330   2174  1623     135  789     710  4132   4211
2006-08-01    79      5   328   2157  1610     135  784     710  4100   4179
2006-07-01    79      5   327   2146  1593     135  782     709  4071   4150
2006-06-01    79      5   326   2135  1580     135  779     709  4046   4125
2006-05-01    79      5   325   2107  1553     135  769     705  3990   4069
2006-04-01    78      5   321   2080  1538     135  760     703  3944   4022
2006-03-01    78      5   319   2065  1519     135  759     702  3908   3986
2006-02-01    78      5   316   2030  1502     135  751     699  3853   3931
2006-01-01    78      5   312   1975  1475     134  742     694  3767   3845
2005-12-01    78      5   302   1943  1454     133  731     691  3704   3782
2005-11-01    77      5   297   1901  1428     132  721     686  3631   3708
2005-10-01    76      4   289   1845  1388     131  709     675  3526   3602
2005-09-01    76      4   286   1811  1369     131  704     672  3470   3546
2005-08-01    76      4   283   1797  1353     131  698     671  3437   3513
2005-07-01    76      4   279   1778  1341     130  691     668  3402   3478
2005-06-01    76      4   275   1763  1321     130  687     663  3363   3439
2005-05-01    75      4   274   1746  1307     128  681     660  3331   3406
2005-04-01    75      4   268   1721  1288     126  668     656  3281   3356
2005-03-01    75      4   263   1681  1263     125  658     652  3211   3286
2005-02-01    75      4   262   1657  1255     124  654     649  3178   3253
2005-01-01    75      4   258   1633  1245     124  647     645  3140   3215
2004-12-01    74      3   249   1601  1224     124  639     637  3077   3151
2004-11-01    74      3   245   1581  1218     123  630     632  3047   3121
2004-10-01    73      3   238   1553  1210     122  619     630  3004   3077
2004-09-01    72      3   230   1515  1185     122  611     629  2933   3005
2004-08-01    72      3   226   1495  1163     121  604     625  2887   2959
2004-07-01    72      3   226   1488  1159     119  601     622  2876   2948
2004-06-01    72      3   223   1458  1146     118  590     619  2830   2902
2004-05-01    72      2   218   1439  1131     118  584     615  2790   2862
2004-04-01    72      2   215   1409  1119     114  574     608  2745   2817
2004-03-01    72      2   206   1373  1101     114  567     599  2682   2754
2004-02-01    71      2   204   1358  1094     113  562     598  2658   2729
2004-01-01    71      2   202   1324  1076     111  552     594  2604   2675
2003-12-01    71      2   196   1292  1064     108  539     586  2554   2625
2003-11-01    71      2   193   1271  1051     108  532     580  2517   2588
2003-10-01    70      2   188   1244  1029     108  523     578  2463   2533
2003-09-01    70      2   185   1224   995     106  514     571  2406   2476
2003-08-01    70      2   185   1212   982     103  509     567  2381   2451
2003-07-01    69      2   184   1205   973     103  506     564  2364   2433
2003-06-01    69      2   182   1189   961     103  501     558  2334   2403
2003-05-01    67      2   180   1175   955     102  499     556  2312   2379
2003-04-01    67      2   175   1155   944     101  491     551  2276   2343
2003-03-01    67      2   170   1136   933     101  484     547  2241   2308
2003-02-01    67      1   169   1116   927     101  478     543  2213   2280
2003-01-01    67      1   167   1089   910     100  468     538  2167   2234
2002-12-01    67      1   163   1062   890     100  466     536  2116   2183
2002-11-01    67      1   160   1047   873      99  460     532  2081   2148
2002-10-01    66      1   158   1023   850      98  454     524  2032   2098
2002-09-01    64      1   155   1003   830      97  448     515  1989   2053
2002-08-01    64      1   154    987   807      95  437     512  1949   2013
2002-07-01    63      1   152    977   800      94  430     507  1930   1993
2002-06-01    63      1   148    960   791      92  422     501  1900   1963
2002-05-01    63      1   144    942   780      91  413     490  1867   1930
2002-04-01    63      1   142    924   767      91  406     488  1834   1897
2002-03-01    62      1   136    897   753      90  396     485  1787   1849
2002-02-01    62      1   131    874   737      89  387     475  1743   1805
2002-01-01    62      1   124    840   714      89  374     467  1679   1741
2001-12-01    62      1   121    804   695      85  360     458  1621   1683
2001-11-01    60      1   120    776   680      84  353     454  1577   1637
2001-10-01    60      1   114    751   656      83  344     450  1522   1582
2001-09-01    60      1   110    722   622      82  333     438  1455   1515
2001-08-01    59      1   109    700   602      82  327     435  1412   1471
2001-07-01    58      1   108    695   589      82  326     434  1393   1451
2001-06-01    57      1   108    685   579      80  323     427  1373   1430
2001-05-01    56      1   107    673   568      78  316     419  1349   1405
2001-04-01    56      1   105    661   559      77  307     415  1326   1382
2001-03-01    56      1   101    646   545      75  298     408  1293   1349
2001-02-01    56      1    98    635   534      74  295     403  1268   1324
2001-01-01    56      1    94    620   525      74  292     399  1240   1296
2000-12-01    56      1    93    606   513      73  286     392  1213   1269
2000-11-01    56      1    90    582   496      72  283     383  1169   1225
2000-10-01    56      1    87    572   482      72  279     376  1142   1198
2000-09-01    56      1    81    554   456      71  272     367  1092   1148
2000-08-01    56      1    79    536   440      69  263     358  1056   1112
2000-07-01    56      1    77    531   430      67  260     347  1039   1095
2000-06-01    56      1    76    526   424      66  256     344  1027   1083
2000-05-01    56      1    76    513   410      66  251     337  1000   1056
2000-04-01    55      1    73    498   397      65  245     330   969   1024
2000-03-01    55      1    64    482   386      63  233     318   933    988
2000-02-01    55      1    62    465   375      62  222     311   903    958
2000-01-01    55      1    57    451   368      62  216     306   877    932
1999-12-01    54      1    56    441   359      60  208     299   857    911
1999-11-01    54      1    54    428   345      60  204     289   828    882
1999-10-01    54      1    54    412   331      59  199     285   798    852
1999-09-01    52      1    54    396   315      57  192     281   766    818
1999-08-01    52      1    54    396   313      57  192     281   764    816
1999-07-01    52      1    54    391   308      56  190     277   754    806
1999-06-01    52      1    51    384   298      56  186     274   734    786
1999-05-01    51      1    49    372   292      52  178     264   714    765
1999-04-01    51      1    48    359   285      51  174     257   693    744
1999-03-01    51      1    47    349   280      51  172     256   677    728
1999-02-01    51      1    47    339   275      51  169     253   662    713
1999-01-01    51      1    45    334   269      51  166     251   649    700
1998-12-01    51      1    41    324   260      51  162     242   626    677
1998-11-01    51      1    38    310   251      49  154     237   600    651
1998-10-01    51      1    36    306   244      49  152     233   587    638
1998-09-01    51      1    29    293   231      48  140     227   554    605
1998-08-01    51      1    29    283   220      46  133     221   533    584
1998-07-01    51      1    29    279   218      44  129     218   527    578
1998-06-01    51      1    29    273   211      43  127     215   514    565
1998-05-01    51      1    29    264   205      43  124     211   499    550
1998-04-01    51      1    27    256   196      43  117     210   480    531
1998-03-01    51      1    27    244   188      43  112     206   460    511
1998-02-01    51      0    26    240   188      42  110     205   454    505
1998-01-01    51      0    26    235   185      42  108     202   446    497
1997-01-01    51      0    22    206   165      40   97     189   393    444
1996-01-01    51      0    20    178   150      38   86     183   348    399
1995-01-01    51      0    19    163   134      37   83     173   316    367
1994-01-01    49      0    15    140   114      33   70     155   269    318
1993-01-01    49      0    13    117    98      31   64     141   228    277
1992-01-01    49      0    11    103    84      29   61     123   198    247
1991-01-01    47      0     9     76    73      24   49     105   158    205
1990-01-01    47      0     8     63    62      20   42      89   133    180
1980-01-01    43      0     3     27    22      12   17      44    52     95
1970-01-01    41      0     0     13    14       8   10      24    27     68
1960-01-01    40      0     0     10    10       7    8      18    20     60
1950-01-01    40      0     0      7     6       4    5      12    13     53
1940-01-01    35      0     0      3     6       2    3       8     9     44
1930-01-01    33      0     0      0     5       0    0       5     5     38
1920-01-01    31      0     0      0     3       0    0       3     3     34
1910-01-01    29      0     0      0     1       0    0       1     1     30
1900-01-01    27      0     0      0     1       0    0       1     1     28

Note: "NEC" are Near-Earth comets. "PHA-KM" and "NEA-KM" are PHAs and NEAs with diameters roughly one kilometer and larger. Other definitions, such as Apollo, are on the NEO groups page.

Data compiled by Alan Chamberlin.

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