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NEO Discovery Statistics

NOTE: The Discovery Statistics page has been revamped with a new style, and expanded to show statistics for asteroids ~140 meters in diameter and larger. The old Discovery Statistics page has been moved here and will continue to be available for a short while.

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
----------  ----  ----- ----- ------ -----  ------ ----  ------ ------ -----  -----
2016-02-05   105     16   993   7420  5278     153 1667     879   6968 13707  13812
2016-02-01   105     16   992   7405  5275     153 1666     879   6965 13688  13793
2016-01-01   105     16   979   7311  5210     153 1648     877   6900 13516  13621
2015-12-01   104     16   958   7195  5156     153 1638     876   6842 13325  13429
2015-11-01   104     16   949   7105  5107     153 1634     875   6805 13177  13281
2015-10-01   104     16   946   7035  5039     153 1619     875   6749 13036  13140
2015-09-01   104     16   939   6982  4974     153 1612     875   6715 12911  13015
2015-08-01   104     16   937   6942  4935     153 1607     874   6681 12830  12934
2015-07-01   104     16   934   6916  4903     153 1601     874   6647 12769  12873
2015-06-01   104     15   933   6876  4864     153 1597     873   6611 12688  12792
2015-05-01   104     15   922   6813  4800     153 1586     873   6574 12550  12654
2015-04-01   103     15   917   6731  4738     152 1578     872   6535 12401  12504
2015-03-01   103     15   906   6621  4700     152 1565     869   6483 12242  12345
2015-02-01   102     14   898   6538  4661     152 1553     869   6445 12111  12213
2015-01-01   101     14   889   6456  4595     152 1540     867   6375 11954  12055
2014-12-01   101     14   880   6392  4559     152 1531     865   6323 11845  11946
2014-11-01   101     14   874   6318  4495     152 1522     862   6277 11701  11802
2014-10-01   100     14   867   6228  4432     152 1517     862   6237 11541  11641
2014-09-01   100     14   861   6175  4377     152 1510     862   6205 11427  11527
2014-08-01   100     14   856   6122  4304     152 1501     862   6146 11296  11396
2014-07-01   100     14   854   6079  4272     152 1491     862   6112 11219  11319
2014-06-01   100     14   845   6042  4215     151 1483     858   6066 11116  11216
2014-05-01   100     14   838   5975  4168     151 1469     856   6020 10995  11095
2014-04-01   100     14   826   5858  4060     151 1461     855   5965 10758  10858
2014-03-01   100     13   819   5802  4034     151 1456     855   5935 10668  10768
2014-02-01   100     13   811   5757  3996     151 1449     855   5900 10577  10677
2014-01-01   100     13   804   5704  3956     151 1445     854   5866 10477  10577
2013-12-01   100     13   799   5649  3930     151 1441     854   5834 10391  10491
2013-11-01   100     13   798   5577  3904     151 1433     854   5801 10292  10392
2013-10-01    99     12   786   5518  3842     150 1425     850   5760 10158  10257
2013-09-01    99     12   780   5462  3786     150 1421     849   5723 10040  10139
2013-08-01    99     12   778   5431  3749     150 1415     849   5695  9970  10069
2013-07-01    99     12   773   5403  3724     150 1408     848   5666  9912  10011
2013-06-01    99     12   770   5373  3706     150 1402     846   5636  9861   9960
2013-05-01    99     11   765   5334  3685     150 1395     846   5605  9795   9894
2013-04-01    99     11   760   5293  3655     150 1386     846   5571  9719   9818
2013-03-01    99     11   755   5245  3626     150 1377     846   5544  9637   9736
2013-02-01    98     11   750   5206  3599     150 1374     846   5519  9566   9664
2013-01-01    98     11   743   5125  3561     150 1360     845   5465  9440   9538
2012-12-01    98     11   735   5072  3530     150 1349     845   5429  9348   9446
2012-11-01    97     10   727   5018  3494     150 1342     843   5396  9249   9346
2012-10-01    97     10   721   4943  3438     150 1331     841   5341  9112   9209
2012-09-01    97     10   717   4909  3409     150 1328     840   5315  9045   9142
2012-08-01    97     10   712   4883  3376     150 1323     839   5282  8981   9078
2012-07-01    96     10   711   4877  3367     150 1318     838   5267  8965   9061
2012-06-01    96     10   706   4852  3343     150 1309     835   5232  8911   9007
2012-05-01    96     10   704   4819  3319     150 1303     832   5206  8852   8948
2012-04-01    96     10   702   4768  3292     150 1297     831   5175  8772   8868
2012-03-01    96     10   696   4688  3266     150 1291     829   5143  8660   8756
2012-02-01    96     10   686   4641  3225     150 1286     829   5109  8562   8658
2012-01-01    96     10   676   4572  3190     150 1277     828   5074  8448   8544
2011-12-01    96     10   672   4540  3166     150 1270     825   5048  8388   8484
2011-11-01    96     10   669   4499  3132     148 1259     822   5012  8310   8406
2011-10-01    96     10   662   4437  3087     147 1248     820   4975  8196   8292
2011-09-01    95     10   661   4402  3035     147 1242     819   4939  8108   8203
2011-08-01    95     10   661   4386  3008     147 1239     817   4918  8065   8160
2011-07-01    94     10   659   4373  2984     147 1235     817   4899  8026   8120
2011-06-01    94     10   659   4355  2960     147 1229     816   4871  7984   8078
2011-05-01    94     10   656   4329  2937     147 1220     814   4841  7932   8026
2011-04-01    94     10   645   4281  2908     147 1212     812   4798  7844   7938
2011-03-01    94     10   634   4218  2884     147 1203     810   4764  7746   7840
2011-02-01    94     10   624   4172  2866     147 1191     810   4739  7672   7766
2011-01-01    94     10   618   4098  2833     147 1176     809   4691  7559   7653
2010-12-01    94      9   609   4043  2802     147 1167     809   4653  7463   7557
2010-11-01    94      9   598   3974  2757     147 1161     809   4614  7338   7432
2010-10-01    94      9   588   3918  2718     147 1147     809   4573  7233   7327
2010-09-01    94      9   582   3870  2654     147 1142     807   4540  7115   7209
2010-08-01    94      9   579   3857  2643     147 1140     804   4524  7088   7182
2010-07-01    94      9   574   3834  2632     147 1137     803   4494  7049   7143
2010-06-01    93      9   568   3803  2610     147 1129     802   4454  6990   7083
2010-05-01    92      9   560   3759  2590     146 1116     800   4413  6918   7010
2010-04-01    92      9   552   3714  2573     146 1111     800   4381  6848   6940
2010-03-01    92      9   544   3677  2546     145 1102     798   4349  6776   6868
2010-02-01    92      9   540   3623  2521     145 1090     797   4305  6693   6785
2010-01-01    92      9   535   3596  2503     145 1086     795   4285  6643   6735
2009-01-01    90      9   481   3127  2245     142 1007     770   3938  5862   5952
2008-01-01    86      7   426   2669  1955     138  911     749   3551  5057   5143
2007-01-01    84      6   359   2320  1722     134  825     721   3207  4407   4491
2006-01-01    80      5   312   1979  1474     131  742     691   2844  3770   3850
2005-01-01    77      4   258   1637  1245     121  647     642   2469  3144   3221
2004-01-01    73      2   202   1328  1076     108  552     592   2128  2608   2681
2003-01-01    69      1   167   1092   911      98  470     536   1812  2171   2240
2002-01-01    64      1   124    841   716      87  374     464   1428  1682   1746
2001-01-01    58      1    94    620   527      72  293     397   1076  1242   1300
2000-01-01    57      1    57    451   370      61  218     304    767   879    936
1990-01-01    48      0     8     63    62      20   42      89    133   133    181
1980-01-01    44      0     3     27    22      12   17      44     52    52     96
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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