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NOTICE: The NEO Program Office website is being retired. Please use the new CNEOS site (update your bookmarks and links). The legacy NEO site will be available until late March 2017, after which you will be automatically redirected to the new CNEOS site.

NEO Discovery Statistics

NUMBER OF NEAR-EARTH ASTEROIDS DISCOVERED

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. Many of the charts and tables below depend on diameters that can only be roughly inferred from an asteroid's estimated absolute magnitude (H) and an assumed reflectivity, or albedo.

The absolute magnitude H is a measure of the asteroid’s intrinsic mean brightness, estimated from measurements of its apparent magnitudes at the various times it has been observed, at various distances from the Sun and Earth, and at various phase angles. Also, since the actual shape of the asteroid is usually unknown, it is simply assumed to be spherical.

To estimate the size of an asteroid, we must know its average reflectivity, or albedo, but this is usually unknown. For main-belt asteroids, Pravec et al. (2012) showed that there is a rough correlation between albedo and taxonomic spectral class: asteroids in the C/G/B/F/P/D spectral classes have mean albedos of about 6%, while those in the S/A/L classes have mean albedos of about 20%. But since the taxonomic class of most NEAs is unknown, we simply use an assumed mean albedo of 14% to estimate all NEA sizes. With this assumption, a one kilometer spherical NEA corresponds to an H value of 17.75. Since the estimated H values are uncertain, and likely biased by a few tenths (Pravec et al., 2012), and the single 14% albedo is only a rough mean representing a bimodal albedo distribution, the estimated numbers of objects larger than a given size in the tables below are very rough. Nonetheless, these statistics are useful for monitoring the annual NEA discovery progress.

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).
[read more...]

The following chart shows the cumulative number of known Near-Earth Asteroids (NEAs) versus time. Totals are shown for NEAs of all sizes, those NEAs larger than ~140m in size, and those larger than ~1km in size.

The following chart shows the current total number of known NEAs grouped according to their estimated sizes. The first size bin represents NEAs smaller than ~30m in diameter. The last bin represents NEAs with diameters larger than ~1km.

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 asteroids constrained by size (PHA-KM, NEA-KM, and NEA140) are rough estimates (see introductory note above). The "-KM" suffix indicates NEAs larger than approximately 1km, while the "140" suffix indicates NEAs larger than approximately 140m. This table is updated daily using discovery data published by the Minor Planet Center.

"NEC" are Near-Earth comets. "PHA-KM" and "NEA-KM" are PHAs and NEAs with diameters roughly one kilometer and larger. "NEA140" are NEAs with diameters roughly 140 meters and larger. Other definitions, such as Apollo, are on the NEO groups page.
-----------------------------------------------------------------------------------
   Date      NEC  Atira  Aten Apollo  Amor  PHA-KM  PHA  NEA-KM NEA140  NEA    NEO
----------  ----  ----- ----- ------ -----  ------ ----  ------ ------ -----  -----
2017-03-20   106     16  1151   8612  6035     156 1791     874   7579 15814  15920
2017-03-01   106     16  1145   8550  6015     156 1786     874   7559 15726  15832
2017-02-01   106     16  1138   8473  5974     156 1781     873   7527 15601  15707
2017-01-01   106     16  1124   8345  5922     156 1763     872   7469 15407  15513
2016-12-01   106     16  1118   8273  5887     156 1750     872   7425 15294  15400
2016-11-01   106     16  1103   8153  5833     156 1742     872   7373 15105  15211
2016-10-01   106     16  1085   8032  5757     156 1733     872   7324 14890  14996
2016-09-01   106     16  1073   7950  5680     156 1730     871   7283 14719  14825
2016-08-01   106     16  1070   7898  5600     156 1719     871   7236 14584  14690
2016-07-01   106     16  1064   7862  5541     156 1709     871   7194 14483  14589
2016-06-01   106     16  1058   7806  5503     156 1703     871   7151 14383  14489
2016-05-01   105     16  1042   7740  5459     156 1694     871   7112 14257  14362
2016-04-01   105     16  1028   7653  5402     155 1686     870   7070 14099  14204
2016-03-01   105     16  1004   7511  5341     155 1675     869   7011 13872  13977
2016-02-01   105     16   992   7405  5278     154 1660     868   6965 13691  13796
2016-01-01   105     16   979   7311  5212     154 1643     866   6899 13518  13623
2015-12-01   103     16   959   7194  5158     154 1632     865   6841 13327  13430
2015-11-01   103     16   950   7104  5109     154 1628     864   6804 13179  13282
2015-10-01   103     16   947   7032  5043     154 1613     864   6748 13038  13141
2015-09-01   103     16   940   6979  4978     154 1606     864   6714 12913  13016
2015-08-01   103     16   938   6939  4940     154 1601     864   6681 12833  12936
2015-07-01   103     16   935   6913  4908     154 1595     864   6647 12772  12875
2015-06-01   103     15   934   6873  4868     154 1591     863   6610 12690  12793
2015-05-01   103     15   922   6811  4804     154 1581     863   6573 12552  12655
2015-04-01   102     15   917   6729  4742     153 1573     862   6534 12403  12505
2015-03-01   102     15   906   6619  4704     153 1560     859   6482 12244  12346
2015-02-01   101     14   898   6536  4665     153 1548     859   6444 12113  12214
2015-01-01   100     14   889   6452  4599     153 1534     857   6374 11954  12054
2014-12-01   100     14   880   6388  4562     153 1525     855   6321 11844  11944
2014-11-01   100     14   874   6315  4497     153 1516     852   6275 11700  11800
2014-10-01    99     14   867   6225  4434     153 1511     852   6235 11540  11639
2014-09-01    99     14   861   6172  4379     153 1505     852   6203 11426  11525
2014-08-01    99     14   856   6119  4306     153 1496     852   6144 11295  11394
2014-07-01    99     14   854   6076  4274     153 1485     852   6110 11218  11317
2014-06-01    99     14   845   6039  4218     152 1477     848   6065 11116  11215
2014-05-01    99     14   838   5972  4172     152 1464     847   6020 10996  11095
2014-04-01    99     14   826   5855  4063     152 1456     846   5964 10758  10857
2014-03-01    99     13   819   5798  4038     152 1451     846   5934 10668  10767
2014-02-01    99     13   811   5753  4000     152 1444     846   5899 10577  10676
2014-01-01    99     13   804   5700  3960     152 1440     845   5865 10477  10576
2013-12-01    99     13   799   5645  3934     152 1436     845   5833 10391  10490
2013-11-01    99     13   798   5573  3908     152 1428     845   5800 10292  10391
2013-10-01    98     12   786   5514  3846     151 1420     841   5759 10158  10256
2013-09-01    98     12   780   5458  3790     151 1416     840   5722 10040  10138
2013-08-01    98     12   778   5427  3753     151 1409     840   5694  9970  10068
2013-07-01    98     12   773   5399  3728     151 1402     838   5665  9912  10010
2013-06-01    98     12   770   5370  3709     151 1396     836   5635  9861   9959
2013-05-01    98     11   765   5331  3689     151 1389     836   5605  9796   9894
2013-04-01    98     11   760   5290  3659     151 1380     836   5571  9720   9818
2013-03-01    98     11   755   5242  3631     151 1371     836   5545  9639   9737
2013-02-01    97     11   750   5203  3604     151 1368     836   5520  9568   9665
2013-01-01    97     11   743   5122  3567     151 1354     835   5467  9443   9540
2012-12-01    97     11   735   5069  3536     151 1343     835   5431  9351   9448
2012-11-01    96     10   727   5015  3500     151 1336     833   5398  9252   9348
2012-10-01    96     10   721   4940  3445     151 1325     832   5344  9116   9212
2012-09-01    96     10   717   4907  3414     151 1322     831   5317  9048   9144
2012-08-01    96     10   712   4881  3381     151 1317     830   5284  8984   9080
2012-07-01    95     10   711   4875  3372     151 1312     829   5269  8968   9063
2012-06-01    95     10   706   4850  3348     151 1303     826   5234  8914   9009
2012-05-01    95     10   704   4817  3324     151 1297     823   5208  8855   8950
2012-04-01    95     10   702   4766  3297     151 1292     822   5178  8775   8870
2012-03-01    95     10   696   4686  3271     151 1286     820   5146  8663   8758
2012-02-01    95     10   686   4639  3230     151 1281     820   5112  8565   8660
2012-01-01    95     10   676   4570  3195     151 1272     819   5076  8451   8546
2011-12-01    95     10   672   4538  3171     151 1265     816   5050  8391   8486
2011-11-01    95     10   669   4497  3138     149 1254     813   5015  8314   8409
2011-10-01    95     10   662   4435  3093     148 1243     811   4978  8200   8295
2011-09-01    94     10   661   4400  3041     148 1237     810   4942  8112   8206
2011-08-01    94     10   661   4384  3014     148 1234     808   4921  8069   8163
2011-07-01    93     10   659   4371  2990     148 1230     808   4902  8030   8123
2011-06-01    93     10   659   4353  2966     148 1224     807   4874  7988   8081
2011-05-01    93     10   656   4327  2944     148 1215     806   4845  7937   8030
2011-04-01    93     10   645   4279  2914     148 1208     803   4801  7848   7941
2011-03-01    93     10   634   4216  2890     148 1199     801   4767  7750   7843
2011-02-01    93     10   624   4171  2873     148 1188     801   4743  7678   7771
2011-01-01    93     10   618   4097  2839     147 1172     800   4695  7564   7657
2010-12-01    93      9   609   4042  2808     147 1164     800   4658  7468   7561
2010-11-01    93      9   598   3973  2764     147 1158     800   4620  7344   7437
2010-10-01    93      9   588   3917  2726     147 1144     800   4580  7240   7333
2010-09-01    93      9   582   3869  2662     147 1139     798   4547  7122   7215
2010-08-01    93      9   579   3856  2651     147 1137     795   4531  7095   7188
2010-07-01    93      9   574   3833  2640     147 1134     794   4501  7056   7149
2010-06-01    92      9   568   3802  2618     147 1126     793   4461  6997   7089
2010-05-01    91      9   560   3758  2598     146 1113     791   4420  6925   7016
2010-04-01    91      9   552   3713  2579     146 1109     790   4386  6853   6944
2010-03-01    91      9   544   3676  2553     145 1100     788   4355  6782   6873
2010-02-01    91      9   540   3622  2529     145 1088     787   4312  6700   6791
2010-01-01    91      9   535   3594  2510     145 1083     786   4290  6648   6739
2009-01-01    89      9   481   3124  2253     142 1004     761   3943  5867   5956
2008-01-01    85      7   426   2666  1963     138  910     741   3556  5062   5147
2007-01-01    83      6   359   2317  1730     134  823     714   3212  4412   4495
2006-01-01    79      5   312   1977  1480     131  740     684   2847  3774   3853
2005-01-01    76      4   258   1637  1248     122  647     634   2471  3147   3223
2004-01-01    72      2   202   1327  1080     109  552     585   2130  2611   2683
2003-01-01    68      1   167   1091   914      99  469     530   1813  2173   2241
2002-01-01    64      1   124    840   718      88  374     460   1428  1683   1747
2001-01-01    58      1    94    620   527      72  291     393   1075  1242   1300
2000-01-01    57      1    57    451   369      61  216     303    765   878    935
1990-01-01    48      0     8     63    61      20   42      88    132   132    180
1980-01-01    44      0     3     27    21      12   17      43     51    51     95
1970-01-01    41      0     0     13    14       8   10      24     27    27     68
1960-01-01    40      0     0     10    10       7    8      18     20    20     60
1950-01-01    40      0     0      7     6       4    5      12     13    13     53
1940-01-01    35      0     0      3     6       2    3       8      9     9     44
1930-01-01    33      0     0      0     5       0    0       5      5     5     38
1920-01-01    31      0     0      0     3       0    0       3      3     3     34
1910-01-01    29      0     0      0     1       0    0       1      1     1     30
1900-01-01    27      0     0      0     1       0    0       1      1     1     28
NEAR-EARTH ASTEROID DISCOVERY STATISTICS BY SURVEY

The following three charts show the number of NEA discoveries per year, by survey. The first chart shows the totals for NEAs of all sizes, the second for NEAs that are ~140m and larger, and the third for NEAs ~1km and larger. The data used to create each chart can be displayed by clicking on the button at the bottom of each chart. A separate table containing WISE discoveries for NEAs and comets is available.

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