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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
----------  ----  ----- ----- ------ -----  ------ ----  ------ ------ -----  -----
2016-07-16   107     16  1070   7882  5591     157 1714     872   7220 14559  14666
2016-07-01   107     16  1064   7860  5543     157 1707     872   7190 14483  14590
2016-06-01   107     16  1059   7804  5505     157 1701     872   7147 14384  14491
2016-05-01   106     16  1043   7738  5461     157 1692     872   7108 14258  14364
2016-04-01   106     16  1029   7651  5404     156 1684     871   7067 14100  14206
2016-03-01   106     16  1005   7509  5343     156 1674     870   7009 13873  13979
2016-02-01   106     16   993   7403  5280     155 1659     869   6963 13692  13798
2016-01-01   106     16   980   7309  5214     155 1642     867   6897 13519  13625
2015-12-01   104     16   959   7193  5160     155 1631     866   6839 13328  13432
2015-11-01   104     16   950   7103  5111     155 1627     865   6802 13180  13284
2015-10-01   104     16   947   7033  5043     155 1612     865   6746 13039  13143
2015-09-01   104     16   940   6980  4978     155 1605     865   6712 12914  13018
2015-08-01   104     16   938   6940  4939     155 1600     865   6678 12833  12937
2015-07-01   104     16   935   6914  4907     155 1594     865   6644 12772  12876
2015-06-01   104     15   934   6874  4868     155 1590     864   6608 12691  12795
2015-05-01   104     15   922   6812  4804     155 1580     864   6571 12553  12657
2015-04-01   103     15   917   6730  4742     154 1573     863   6532 12404  12507
2015-03-01   103     15   906   6620  4704     154 1560     860   6480 12245  12348
2015-02-01   102     14   898   6537  4665     154 1548     860   6442 12114  12216
2015-01-01   101     14   889   6454  4599     154 1535     858   6372 11956  12057
2014-12-01   101     14   880   6390  4562     154 1526     856   6319 11846  11947
2014-11-01   101     14   874   6316  4498     154 1517     853   6273 11702  11803
2014-10-01   100     14   867   6226  4435     154 1512     853   6233 11542  11642
2014-09-01   100     14   861   6173  4380     154 1506     853   6201 11428  11528
2014-08-01   100     14   856   6120  4307     154 1497     853   6142 11297  11397
2014-07-01   100     14   854   6077  4275     154 1486     853   6108 11220  11320
2014-06-01   100     14   845   6040  4218     153 1478     849   6062 11117  11217
2014-05-01   100     14   838   5973  4171     153 1465     847   6016 10996  11096
2014-04-01   100     14   826   5856  4063     153 1457     846   5961 10759  10859
2014-03-01   100     13   819   5799  4038     153 1452     846   5931 10669  10769
2014-02-01   100     13   811   5754  4000     153 1445     846   5896 10578  10678
2014-01-01   100     13   804   5701  3960     153 1441     845   5862 10478  10578
2013-12-01   100     13   799   5646  3934     153 1437     845   5830 10392  10492
2013-11-01   100     13   798   5574  3908     153 1429     845   5797 10293  10393
2013-10-01    99     12   786   5515  3846     152 1421     841   5756 10159  10258
2013-09-01    99     12   780   5459  3790     152 1417     840   5719 10041  10140
2013-08-01    99     12   778   5428  3753     152 1410     840   5691  9971  10070
2013-07-01    99     12   773   5400  3728     152 1403     839   5662  9913  10012
2013-06-01    99     12   770   5371  3709     152 1397     837   5632  9862   9961
2013-05-01    99     11   765   5332  3688     152 1390     837   5601  9796   9895
2013-04-01    99     11   760   5291  3658     152 1381     837   5567  9720   9819
2013-03-01    99     11   755   5243  3629     152 1372     837   5540  9638   9737
2013-02-01    98     11   750   5204  3602     152 1369     837   5515  9567   9665
2013-01-01    98     11   743   5123  3565     152 1355     836   5462  9442   9540
2012-12-01    98     11   735   5070  3534     152 1344     836   5426  9350   9448
2012-11-01    97     10   727   5016  3498     152 1337     834   5393  9251   9348
2012-10-01    97     10   721   4941  3443     152 1326     833   5339  9115   9212
2012-09-01    97     10   717   4907  3413     152 1323     832   5312  9047   9144
2012-08-01    97     10   712   4881  3380     152 1318     831   5279  8983   9080
2012-07-01    96     10   711   4875  3371     152 1313     830   5264  8967   9063
2012-06-01    96     10   706   4850  3347     152 1304     827   5229  8913   9009
2012-05-01    96     10   704   4817  3323     152 1298     824   5203  8854   8950
2012-04-01    96     10   702   4766  3296     152 1293     823   5173  8774   8870
2012-03-01    96     10   696   4686  3270     152 1287     821   5141  8662   8758
2012-02-01    96     10   686   4639  3229     152 1282     821   5107  8564   8660
2012-01-01    96     10   676   4570  3194     152 1273     820   5072  8450   8546
2011-12-01    96     10   672   4538  3170     152 1266     817   5046  8390   8486
2011-11-01    96     10   669   4497  3136     150 1255     814   5010  8312   8408
2011-10-01    96     10   662   4435  3091     149 1244     812   4973  8198   8294
2011-09-01    95     10   661   4400  3039     149 1238     811   4937  8110   8205
2011-08-01    95     10   661   4384  3012     149 1235     809   4916  8067   8162
2011-07-01    94     10   659   4371  2988     149 1231     809   4897  8028   8122
2011-06-01    94     10   659   4353  2964     149 1225     808   4869  7986   8080
2011-05-01    94     10   656   4327  2941     149 1216     806   4839  7934   8028
2011-04-01    94     10   645   4279  2912     149 1209     804   4796  7846   7940
2011-03-01    94     10   634   4216  2888     149 1200     802   4762  7748   7842
2011-02-01    94     10   624   4170  2870     149 1189     802   4737  7674   7768
2011-01-01    94     10   618   4096  2837     148 1173     801   4689  7561   7655
2010-12-01    94      9   609   4041  2806     148 1164     801   4651  7465   7559
2010-11-01    94      9   598   3972  2762     148 1158     801   4613  7341   7435
2010-10-01    94      9   588   3916  2724     148 1144     801   4573  7237   7331
2010-09-01    94      9   582   3868  2660     148 1139     799   4540  7119   7213
2010-08-01    94      9   579   3855  2649     148 1137     796   4524  7092   7186
2010-07-01    94      9   574   3832  2638     148 1134     795   4494  7053   7147
2010-06-01    93      9   568   3801  2616     148 1126     794   4454  6994   7087
2010-05-01    92      9   560   3757  2596     147 1113     792   4413  6922   7014
2010-04-01    92      9   552   3712  2578     147 1109     792   4380  6851   6943
2010-03-01    92      9   544   3675  2551     146 1100     790   4348  6779   6871
2010-02-01    92      9   540   3621  2526     146 1088     789   4304  6696   6788
2010-01-01    92      9   535   3594  2508     146 1084     787   4284  6646   6738
2009-01-01    90      9   481   3125  2250     143 1005     762   3937  5865   5955
2008-01-01    86      7   426   2667  1960     139  912     742   3551  5060   5146
2007-01-01    84      6   359   2319  1726     135  825     715   3207  4410   4494
2006-01-01    80      5   312   1979  1476     132  741     685   2843  3772   3852
2005-01-01    77      4   258   1637  1247     123  648     636   2469  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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