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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
----------  ----  ----- ----- ------ -----  ------ ----  ------ ------ -----  -----
2016-05-02   106     16  1044   7732  5458     157 1692     875   7106 14250  14356
2016-05-01   106     16  1043   7731  5458     157 1692     875   7106 14248  14354
2016-04-01   106     16  1029   7648  5404     156 1684     874   7067 14097  14203
2016-03-01   106     16  1005   7507  5343     156 1675     873   7010 13871  13977
2016-02-01   106     16   993   7401  5280     155 1660     872   6964 13690  13796
2016-01-01   106     16   980   7307  5214     155 1643     870   6898 13517  13623
2015-12-01   104     16   959   7191  5160     155 1632     869   6840 13326  13430
2015-11-01   104     16   950   7101  5111     155 1628     868   6803 13178  13282
2015-10-01   104     16   947   7031  5043     155 1613     868   6747 13037  13141
2015-09-01   104     16   940   6978  4978     155 1606     868   6713 12912  13016
2015-08-01   104     16   938   6938  4939     155 1601     867   6679 12831  12935
2015-07-01   104     16   935   6912  4907     155 1595     867   6645 12770  12874
2015-06-01   104     15   934   6872  4868     155 1591     866   6609 12689  12793
2015-05-01   104     15   922   6810  4804     155 1581     866   6572 12551  12655
2015-04-01   103     15   917   6728  4742     154 1574     865   6533 12402  12505
2015-03-01   103     15   906   6618  4704     154 1561     862   6481 12243  12346
2015-02-01   102     14   898   6535  4665     154 1549     862   6443 12112  12214
2015-01-01   101     14   889   6453  4599     154 1536     860   6373 11955  12056
2014-12-01   101     14   880   6389  4562     154 1527     858   6320 11845  11946
2014-11-01   101     14   874   6315  4498     154 1518     855   6274 11701  11802
2014-10-01   100     14   867   6225  4435     154 1513     855   6234 11541  11641
2014-09-01   100     14   861   6172  4380     154 1507     855   6202 11427  11527
2014-08-01   100     14   856   6119  4307     154 1498     855   6143 11296  11396
2014-07-01   100     14   854   6076  4275     154 1487     855   6109 11219  11319
2014-06-01   100     14   845   6039  4218     153 1479     851   6063 11116  11216
2014-05-01   100     14   838   5972  4171     153 1466     849   6017 10995  11095
2014-04-01   100     14   826   5855  4063     153 1458     848   5962 10758  10858
2014-03-01   100     13   819   5798  4038     153 1453     848   5932 10668  10768
2014-02-01   100     13   811   5753  4000     153 1446     848   5897 10577  10677
2014-01-01   100     13   804   5700  3960     153 1442     847   5863 10477  10577
2013-12-01   100     13   799   5645  3934     153 1438     847   5831 10391  10491
2013-11-01   100     13   798   5573  3908     153 1430     847   5798 10292  10392
2013-10-01    99     12   786   5514  3846     152 1422     843   5757 10158  10257
2013-09-01    99     12   780   5458  3790     152 1418     842   5720 10040  10139
2013-08-01    99     12   778   5427  3753     152 1411     842   5692  9970  10069
2013-07-01    99     12   773   5399  3728     152 1404     841   5663  9912  10011
2013-06-01    99     12   770   5370  3709     152 1398     839   5633  9861   9960
2013-05-01    99     11   765   5331  3688     152 1391     839   5602  9795   9894
2013-04-01    99     11   760   5290  3658     152 1382     839   5568  9719   9818
2013-03-01    99     11   755   5242  3629     152 1373     839   5541  9637   9736
2013-02-01    98     11   750   5203  3602     152 1370     839   5516  9566   9664
2013-01-01    98     11   743   5122  3565     152 1356     838   5463  9441   9539
2012-12-01    98     11   735   5069  3534     152 1345     838   5427  9349   9447
2012-11-01    97     10   727   5015  3498     152 1338     836   5394  9250   9347
2012-10-01    97     10   721   4940  3442     152 1327     835   5339  9113   9210
2012-09-01    97     10   717   4906  3413     152 1324     834   5313  9046   9143
2012-08-01    97     10   712   4880  3380     152 1319     833   5280  8982   9079
2012-07-01    96     10   711   4874  3371     152 1314     832   5265  8966   9062
2012-06-01    96     10   706   4849  3347     152 1305     829   5230  8912   9008
2012-05-01    96     10   704   4816  3323     152 1299     826   5204  8853   8949
2012-04-01    96     10   702   4765  3296     152 1293     825   5173  8773   8869
2012-03-01    96     10   696   4685  3270     152 1287     823   5141  8661   8757
2012-02-01    96     10   686   4638  3229     152 1282     823   5107  8563   8659
2012-01-01    96     10   676   4569  3194     152 1273     822   5072  8449   8545
2011-12-01    96     10   672   4537  3170     152 1266     819   5046  8389   8485
2011-11-01    96     10   669   4496  3136     150 1255     816   5010  8311   8407
2011-10-01    96     10   662   4434  3091     149 1244     814   4973  8197   8293
2011-09-01    95     10   661   4399  3039     149 1238     813   4937  8109   8204
2011-08-01    95     10   661   4383  3012     149 1235     811   4916  8066   8161
2011-07-01    94     10   659   4370  2988     149 1231     811   4897  8027   8121
2011-06-01    94     10   659   4352  2964     149 1225     810   4869  7985   8079
2011-05-01    94     10   656   4326  2941     149 1216     808   4839  7933   8027
2011-04-01    94     10   645   4278  2912     149 1209     806   4796  7845   7939
2011-03-01    94     10   634   4215  2888     149 1200     804   4762  7747   7841
2011-02-01    94     10   624   4169  2870     149 1189     804   4737  7673   7767
2011-01-01    94     10   618   4095  2837     148 1173     803   4689  7560   7654
2010-12-01    94      9   609   4040  2806     148 1164     803   4651  7464   7558
2010-11-01    94      9   598   3971  2762     148 1158     803   4613  7340   7434
2010-10-01    94      9   588   3915  2723     148 1144     803   4572  7235   7329
2010-09-01    94      9   582   3867  2659     148 1139     801   4539  7117   7211
2010-08-01    94      9   579   3854  2648     148 1137     798   4523  7090   7184
2010-07-01    94      9   574   3831  2637     148 1134     797   4493  7051   7145
2010-06-01    93      9   568   3800  2615     148 1126     796   4453  6992   7085
2010-05-01    92      9   560   3756  2595     147 1113     794   4412  6920   7012
2010-04-01    92      9   552   3711  2577     147 1109     794   4379  6849   6941
2010-03-01    92      9   544   3674  2550     146 1100     792   4347  6777   6869
2010-02-01    92      9   540   3620  2525     146 1088     791   4303  6694   6786
2010-01-01    92      9   535   3593  2507     146 1084     789   4283  6644   6736
2009-01-01    90      9   481   3124  2249     143 1005     764   3936  5863   5953
2008-01-01    86      7   426   2666  1959     139  912     744   3550  5058   5144
2007-01-01    84      6   359   2318  1726     135  825     717   3207  4409   4493
2006-01-01    80      5   312   1978  1476     132  741     687   2843  3771   3851
2005-01-01    77      4   258   1636  1247     123  648     638   2469  3145   3222
2004-01-01    73      2   202   1327  1078     110  553     589   2128  2609   2682
2003-01-01    69      1   167   1091   912     100  470     533   1811  2171   2240
2002-01-01    64      1   124    840   717      89  375     462   1427  1682   1746
2001-01-01    58      1    94    620   527      73  292     395   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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