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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
----------  ----  ----- ----- ------ -----  ------ ----  ------ ------ -----  -----
2016-09-27   107     16  1086   8028  5755     157 1735     875   7323 14885  14992
2016-09-01   107     16  1074   7948  5684     157 1732     874   7286 14722  14829
2016-08-01   107     16  1071   7896  5603     157 1719     874   7237 14586  14693
2016-07-01   107     16  1065   7859  5543     157 1708     874   7193 14483  14590
2016-06-01   107     16  1059   7803  5505     157 1702     874   7150 14383  14490
2016-05-01   106     16  1043   7737  5461     157 1693     874   7111 14257  14363
2016-04-01   106     16  1029   7650  5404     156 1685     873   7069 14099  14205
2016-03-01   106     16  1005   7508  5343     156 1674     872   7010 13872  13978
2016-02-01   106     16   993   7402  5280     155 1659     871   6964 13691  13797
2016-01-01   106     16   980   7308  5214     155 1642     869   6898 13518  13624
2015-12-01   104     16   959   7192  5160     155 1631     868   6840 13327  13431
2015-11-01   104     16   950   7102  5111     155 1627     867   6803 13179  13283
2015-10-01   104     16   947   7032  5043     155 1612     867   6747 13038  13142
2015-09-01   104     16   940   6979  4978     155 1605     867   6713 12913  13017
2015-08-01   104     16   938   6939  4939     155 1600     866   6679 12832  12936
2015-07-01   104     16   935   6913  4907     155 1594     866   6645 12771  12875
2015-06-01   104     15   934   6873  4868     155 1590     865   6609 12690  12794
2015-05-01   104     15   922   6811  4804     155 1580     865   6572 12552  12656
2015-04-01   103     15   917   6729  4742     154 1573     864   6533 12403  12506
2015-03-01   103     15   906   6619  4704     154 1560     861   6481 12244  12347
2015-02-01   102     14   898   6536  4665     154 1548     861   6443 12113  12215
2015-01-01   101     14   889   6453  4599     154 1535     859   6373 11955  12056
2014-12-01   101     14   880   6389  4562     154 1526     857   6320 11845  11946
2014-11-01   101     14   874   6315  4498     154 1517     854   6274 11701  11802
2014-10-01   100     14   867   6225  4435     154 1512     854   6234 11541  11641
2014-09-01   100     14   861   6172  4380     154 1506     854   6202 11427  11527
2014-08-01   100     14   856   6119  4307     154 1497     854   6143 11296  11396
2014-07-01   100     14   854   6076  4275     154 1486     854   6109 11219  11319
2014-06-01   100     14   845   6039  4218     153 1478     850   6063 11116  11216
2014-05-01   100     14   838   5972  4171     153 1465     848   6017 10995  11095
2014-04-01   100     14   826   5855  4063     153 1457     847   5962 10758  10858
2014-03-01   100     13   819   5798  4038     153 1452     847   5932 10668  10768
2014-02-01   100     13   811   5753  4000     153 1445     847   5897 10577  10677
2014-01-01   100     13   804   5700  3960     153 1441     846   5863 10477  10577
2013-12-01   100     13   799   5645  3934     153 1437     846   5831 10391  10491
2013-11-01   100     13   798   5573  3908     153 1429     846   5798 10292  10392
2013-10-01    99     12   786   5514  3846     152 1421     842   5757 10158  10257
2013-09-01    99     12   780   5458  3790     152 1417     841   5720 10040  10139
2013-08-01    99     12   778   5427  3753     152 1410     841   5692  9970  10069
2013-07-01    99     12   773   5399  3728     152 1403     839   5663  9912  10011
2013-06-01    99     12   770   5370  3709     152 1397     837   5633  9861   9960
2013-05-01    99     11   765   5331  3688     152 1390     837   5602  9795   9894
2013-04-01    99     11   760   5290  3658     152 1381     837   5568  9719   9818
2013-03-01    99     11   755   5242  3629     152 1372     837   5541  9637   9736
2013-02-01    98     11   750   5203  3602     152 1369     837   5516  9566   9664
2013-01-01    98     11   743   5122  3565     152 1355     836   5463  9441   9539
2012-12-01    98     11   735   5069  3534     152 1344     836   5427  9349   9447
2012-11-01    97     10   727   5015  3498     152 1337     834   5394  9250   9347
2012-10-01    97     10   721   4940  3443     152 1326     833   5340  9114   9211
2012-09-01    97     10   717   4906  3413     152 1323     832   5313  9046   9143
2012-08-01    97     10   712   4880  3380     152 1318     831   5280  8982   9079
2012-07-01    96     10   711   4874  3371     152 1313     830   5265  8966   9062
2012-06-01    96     10   706   4849  3347     152 1304     827   5230  8912   9008
2012-05-01    96     10   704   4816  3323     152 1298     824   5204  8853   8949
2012-04-01    96     10   702   4765  3296     152 1293     823   5174  8773   8869
2012-03-01    96     10   696   4685  3270     152 1287     821   5142  8661   8757
2012-02-01    96     10   686   4638  3229     152 1282     821   5108  8563   8659
2012-01-01    96     10   676   4569  3194     152 1273     820   5073  8449   8545
2011-12-01    96     10   672   4537  3170     152 1266     817   5047  8389   8485
2011-11-01    96     10   669   4496  3136     150 1255     814   5011  8311   8407
2011-10-01    96     10   662   4434  3091     149 1244     812   4974  8197   8293
2011-09-01    95     10   661   4399  3039     149 1238     811   4938  8109   8204
2011-08-01    95     10   661   4383  3012     149 1235     809   4917  8066   8161
2011-07-01    94     10   659   4370  2988     149 1231     809   4898  8027   8121
2011-06-01    94     10   659   4352  2964     149 1225     808   4870  7985   8079
2011-05-01    94     10   656   4326  2941     149 1216     806   4840  7933   8027
2011-04-01    94     10   645   4278  2912     149 1209     804   4797  7845   7939
2011-03-01    94     10   634   4215  2888     149 1200     802   4763  7747   7841
2011-02-01    94     10   624   4170  2870     149 1189     802   4739  7674   7768
2011-01-01    94     10   618   4096  2837     148 1173     801   4691  7561   7655
2010-12-01    94      9   609   4041  2806     148 1164     801   4653  7465   7559
2010-11-01    94      9   598   3972  2762     148 1158     801   4615  7341   7435
2010-10-01    94      9   588   3916  2724     148 1144     801   4575  7237   7331
2010-09-01    94      9   582   3868  2660     148 1139     799   4542  7119   7213
2010-08-01    94      9   579   3855  2649     148 1137     796   4526  7092   7186
2010-07-01    94      9   574   3832  2638     148 1134     795   4496  7053   7147
2010-06-01    93      9   568   3801  2616     148 1126     794   4456  6994   7087
2010-05-01    92      9   560   3757  2596     147 1113     792   4415  6922   7014
2010-04-01    92      9   552   3712  2578     147 1109     792   4382  6851   6943
2010-03-01    92      9   544   3675  2551     146 1100     790   4350  6779   6871
2010-02-01    92      9   540   3621  2526     146 1088     789   4306  6696   6788
2010-01-01    92      9   535   3594  2508     146 1084     787   4286  6646   6738
2009-01-01    90      9   481   3125  2250     143 1005     762   3939  5865   5955
2008-01-01    86      7   426   2667  1960     139  912     742   3553  5060   5146
2007-01-01    84      6   359   2319  1726     135  825     715   3209  4410   4494
2006-01-01    80      5   312   1979  1476     132  741     685   2844  3772   3852
2005-01-01    77      4   258   1637  1247     123  648     636   2470  3146   3223
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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