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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
----------  ----  ----- ----- ------ -----  ------ ----  ------ ------ -----  -----
2016-06-29   107     16  1064   7854  5542     157 1706     872   7186 14476  14583
2016-06-01   107     16  1059   7803  5505     157 1701     872   7147 14383  14490
2016-05-01   106     16  1043   7737  5461     157 1692     872   7108 14257  14363
2016-04-01   106     16  1029   7650  5404     156 1684     871   7067 14099  14205
2016-03-01   106     16  1005   7508  5343     156 1674     870   7009 13872  13978
2016-02-01   106     16   993   7402  5280     155 1659     869   6963 13691  13797
2016-01-01   106     16   980   7308  5214     155 1642     867   6897 13518  13624
2015-12-01   104     16   959   7192  5160     155 1631     866   6839 13327  13431
2015-11-01   104     16   950   7102  5111     155 1627     865   6802 13179  13283
2015-10-01   104     16   947   7032  5043     155 1612     865   6746 13038  13142
2015-09-01   104     16   940   6979  4978     155 1605     865   6712 12913  13017
2015-08-01   104     16   938   6939  4939     155 1600     865   6678 12832  12936
2015-07-01   104     16   935   6913  4907     155 1594     865   6644 12771  12875
2015-06-01   104     15   934   6873  4868     155 1590     864   6608 12690  12794
2015-05-01   104     15   922   6811  4804     155 1580     864   6571 12552  12656
2015-04-01   103     15   917   6729  4742     154 1573     863   6532 12403  12506
2015-03-01   103     15   906   6619  4704     154 1560     860   6480 12244  12347
2015-02-01   102     14   898   6536  4665     154 1548     860   6442 12113  12215
2015-01-01   101     14   889   6453  4599     154 1535     858   6372 11955  12056
2014-12-01   101     14   880   6389  4562     154 1526     856   6319 11845  11946
2014-11-01   101     14   874   6315  4498     154 1517     853   6273 11701  11802
2014-10-01   100     14   867   6225  4435     154 1512     853   6233 11541  11641
2014-09-01   100     14   861   6172  4380     154 1506     853   6201 11427  11527
2014-08-01   100     14   856   6119  4307     154 1497     853   6142 11296  11396
2014-07-01   100     14   854   6076  4275     154 1486     853   6108 11219  11319
2014-06-01   100     14   845   6039  4218     153 1478     849   6062 11116  11216
2014-05-01   100     14   838   5972  4171     153 1465     847   6016 10995  11095
2014-04-01   100     14   826   5855  4063     153 1457     846   5961 10758  10858
2014-03-01   100     13   819   5798  4038     153 1452     846   5931 10668  10768
2014-02-01   100     13   811   5753  4000     153 1445     846   5896 10577  10677
2014-01-01   100     13   804   5700  3960     153 1441     845   5862 10477  10577
2013-12-01   100     13   799   5645  3934     153 1437     845   5830 10391  10491
2013-11-01   100     13   798   5573  3908     153 1429     845   5797 10292  10392
2013-10-01    99     12   786   5514  3846     152 1421     841   5756 10158  10257
2013-09-01    99     12   780   5458  3790     152 1417     840   5719 10040  10139
2013-08-01    99     12   778   5427  3753     152 1410     840   5691  9970  10069
2013-07-01    99     12   773   5399  3728     152 1403     839   5662  9912  10011
2013-06-01    99     12   770   5370  3709     152 1397     837   5632  9861   9960
2013-05-01    99     11   765   5331  3688     152 1390     837   5601  9795   9894
2013-04-01    99     11   760   5290  3658     152 1381     837   5567  9719   9818
2013-03-01    99     11   755   5242  3629     152 1372     837   5540  9637   9736
2013-02-01    98     11   750   5203  3602     152 1369     837   5515  9566   9664
2013-01-01    98     11   743   5122  3565     152 1355     836   5462  9441   9539
2012-12-01    98     11   735   5069  3534     152 1344     836   5426  9349   9447
2012-11-01    97     10   727   5015  3498     152 1337     834   5393  9250   9347
2012-10-01    97     10   721   4940  3443     152 1326     833   5339  9114   9211
2012-09-01    97     10   717   4906  3413     152 1323     832   5312  9046   9143
2012-08-01    97     10   712   4880  3380     152 1318     831   5279  8982   9079
2012-07-01    96     10   711   4874  3371     152 1313     830   5264  8966   9062
2012-06-01    96     10   706   4849  3347     152 1304     827   5229  8912   9008
2012-05-01    96     10   704   4816  3323     152 1298     824   5203  8853   8949
2012-04-01    96     10   702   4765  3296     152 1293     823   5173  8773   8869
2012-03-01    96     10   696   4685  3270     152 1287     821   5141  8661   8757
2012-02-01    96     10   686   4638  3229     152 1282     821   5107  8563   8659
2012-01-01    96     10   676   4569  3194     152 1273     820   5072  8449   8545
2011-12-01    96     10   672   4537  3170     152 1266     817   5046  8389   8485
2011-11-01    96     10   669   4496  3136     150 1255     814   5010  8311   8407
2011-10-01    96     10   662   4434  3091     149 1244     812   4973  8197   8293
2011-09-01    95     10   661   4399  3039     149 1238     811   4937  8109   8204
2011-08-01    95     10   661   4383  3012     149 1235     809   4916  8066   8161
2011-07-01    94     10   659   4370  2988     149 1231     809   4897  8027   8121
2011-06-01    94     10   659   4352  2964     149 1225     808   4869  7985   8079
2011-05-01    94     10   656   4326  2941     149 1216     806   4839  7933   8027
2011-04-01    94     10   645   4278  2912     149 1209     804   4796  7845   7939
2011-03-01    94     10   634   4215  2888     149 1200     802   4762  7747   7841
2011-02-01    94     10   624   4169  2870     149 1189     802   4737  7673   7767
2011-01-01    94     10   618   4095  2837     148 1173     801   4689  7560   7654
2010-12-01    94      9   609   4040  2806     148 1164     801   4651  7464   7558
2010-11-01    94      9   598   3971  2762     148 1158     801   4613  7340   7434
2010-10-01    94      9   588   3915  2724     148 1144     801   4573  7236   7330
2010-09-01    94      9   582   3867  2660     148 1139     799   4540  7118   7212
2010-08-01    94      9   579   3854  2649     148 1137     796   4524  7091   7185
2010-07-01    94      9   574   3831  2638     148 1134     795   4494  7052   7146
2010-06-01    93      9   568   3800  2616     148 1126     794   4454  6993   7086
2010-05-01    92      9   560   3756  2596     147 1113     792   4413  6921   7013
2010-04-01    92      9   552   3711  2578     147 1109     792   4380  6850   6942
2010-03-01    92      9   544   3674  2551     146 1100     790   4348  6778   6870
2010-02-01    92      9   540   3620  2526     146 1088     789   4304  6695   6787
2010-01-01    92      9   535   3593  2508     146 1084     787   4284  6645   6737
2009-01-01    90      9   481   3124  2250     143 1005     762   3937  5864   5954
2008-01-01    86      7   426   2666  1960     139  912     742   3551  5059   5145
2007-01-01    84      6   359   2318  1726     135  825     715   3207  4409   4493
2006-01-01    80      5   312   1978  1476     132  741     685   2843  3771   3851
2005-01-01    77      4   258   1636  1247     123  648     636   2469  3145   3222
2004-01-01    73      2   202   1327  1078     110  553     587   2128  2609   2682
2003-01-01    69      1   167   1091   912     100  470     531   1811  2171   2240
2002-01-01    64      1   124    840   717      89  375     460   1427  1682   1746
2001-01-01    58      1    94    620   527      73  292     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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