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NEO Discovery Statistics

NEAR-EARTH ASTEROID DISCOVERY STATISTICS

Some entries in the following charts and tables are dependent upon a diameter that is roughly inferred from the object’s estimated absolute magnitude (H) and its assumed reflectivity, or albedo. The absolute magnitude (H) of a near-Earth asteroid (NEA) is a measure of the object's brightness one astronomical unit from the sun and Earth and at zero phase angle (i.e., the angle between the sun and Earth, as seen from the NEA, is zero). The absolute magnitude (H) for a particular NEA is computed from the observed apparent magnitudes of the object at various times when the phase angles and the distances from the sun and Earth are known. An effective diameter is the diameter of a hypothetical spherical NEA that would provide the same apparent brightness as the observed NEA, whose actual shape is unknown.

Since most NEAs do not have a known reflectivity, or albedo, this albedo must be estimated before the H values, representing intrinsic brightness, can be converted to an approximate diameter. Pravec et al (2012) determined that, for their sample of 583 main-belt asteroids and NEAs, the mean albedos and their standard deviations are 0.057 (±0.013) for the Tholen/Bus/DeMeo C/G/B/F/P/D types and 0.197 (±0.051) for the S/A/L types. Since the albedos for NEAs are most likely to be either approximately 6% for asteroids of the C-type and associated taxonomic classes or 20% for asteroids of the more populous S-type and associated taxonomic classes, we have used an approximate mean value of 14% albedo and an H value of 17.75 to represent a one kilometer spherical NEA. Since the determined H values are uncertain, and likely biased by a few tenths (see Pravec et al., 2012, Icarus) and the single 14% albedo is only a rough mean representing a bimodal albedo distribution, the estimated numbers of one kilometer and larger sized objects in the tables below are very rough. However, these statistics are useful for monitoring the annual NEA discovery progress.

Using near-infrared data provided by the WISE spacecraft in 2010 and early 2011, Mainzer et al (2011) were able to determine diameters and albedos for 250 NEAs with a minimum uncertainty of 10% and 20% respectively. Hence they were able to determine the albedo distribution of these objects with known diameters and this distribution was then used to compute diameters for previously known NEOs with known H values but unknown diameters or albedos. They provided an estimate of 981 (±19) NEAs as the total population of NEAs one kilometer and larger. At the time of their analysis (Spring 2011), they also estimated that 911 (±17) of these large NEAs had already been discovered. While this latter estimate is both higher and more accurate than the estimated numbers given for Spring 2011 in the following tables, this statistical technique cannot be easily employed for day-to-day estimates of the population of NEAs one kilometer and larger. In the following tables, we will continue to use the simpler method described in the previous paragraph.

Mainzer, A. et al. (2011). NEOWISE observations of near-Earth objects: Preliminary Results. Astrophysical Journal. 743:156.
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).
Stuart, J.S. (2003). Observational constraints on the number, albedos, sizes and impact hazards of the near-Earth asteroids. Ph.D. thesis, MIT.

All Asteroids

Table: Number of Near-Earth Asteroid Discoveries at Half-Year Intervals: All Asteroids

Table 1. NEAs Discovered by Site

Half Year
Intervals
LINEAR
(704)
NEAT
(566,608,644)
Spacewatch
(691,291)
LONEOS
(699)
Catalina
(703,E12,G96)
Pan-STARRS
(F51)
NEOWISE
(C51)
OtherCumulative
Total
 1995 (1)001400004333
 1995 (2)001200002347
 1996 (1)151800004375
 1996 (2)051000002392
 1997 (1)321000004411
 1997 (2)149400007445
 1998 (1)4491911007526
 1998 (2)9221562005648
 1999 (1)74012611001752
 1999 (2)8707719003875
 2000 (1)10821421130041037
 2000 (2)15014121700081238
 2001 (1)952872200021392
 2001 (2)18464152000041679
 2002 (1)15856161410061930
 2002 (2)130896700052167
 2003 (1)10230233300092364
 2003 (2)13338332170082604
 2004 (1)167194114240062875
 2004 (2)13772925600063139
 2005 (1)788292211500103401
 2005 (2)5930541919300103766
 2006 (1)44445131950034070
 2006 (2)52175471990054404
 2007 (1)3842072010034677
 2007 (2)7402552660075054
 2008 (1)7404312810055458
 2008 (2)66043027900115857
 2009 (1)50032026000186217
 2009 (2)58031031500176638
 2010 (1)29021025708897042
 2010 (2)7502203451838147554
 2011 (1)400170331683128025
 2011 (2)3001502531050238451
 2012 (1)260130352120078969
 2012 (2)2901302771310269445
 2013 (1)301302881500189917
 2013 (2)0012031420812910481
 2014 (1)0080332229164811114
 2014 (2)*00000186511143
* Incomplete half-year (based on discovery data through 2014-Jul-27 06:05 local)

Large Asteroids

Table: Number of Near-Earth Asteroid Discoveries at Half-Year Intervals: Large Asteroids

Table 2. Large NEAs Discovered by Site

Half Year
Intervals
LINEAR
(704)
NEAT
(566,608,644)
Spacewatch
(691,291)
LONEOS
(699)
Catalina
(703,E12,G96)
Pan-STARRS
(F51)
NEOWISE
(C51)
OtherCumulative
Total
 1995 (1)00300002177
 1995 (2)00400001182
 1996 (1)02200000186
 1996 (2)02000000188
 1997 (1)01300001193
 1997 (2)23100002201
 1998 (1)74210002217
 1998 (2)242130003250
 1999 (1)150244000275
 1999 (2)230112002304
 2000 (1)322114001345
 2000 (2)382350004397
 2001 (1)238040000432
 2001 (2)245040001466
 2002 (1)304230001506
 2002 (2)1910010001537
 2003 (1)143160002563
 2003 (2)175142001593
 2004 (1)165123001621
 2004 (2)910112000644
 2005 (1)100219001667
 2005 (2)645010001693
 2006 (1)30219000708
 2006 (2)102012000723
 2007 (1)20309001738
 2007 (2)50107000751
 2008 (1)20109000763
 2008 (2)30105000772
 2009 (1)10009000782
 2009 (2)60006002796
 2010 (1)00004030803
 2010 (2)10001040809
 2011 (1)10006100817
 2011 (2)00106400828
 2012 (1)00009100838
 2012 (2)10005200846
 2013 (1)00004000850
 2013 (2)00003201856
 2014 (1)*00002220862
* Incomplete half-year (based on discovery data through 2014-Jul-27 06:05 local)
NOTE: In the year 2010, the "Other" site category was exclusively WISE.
A separate table of WISE discoveries is
available.

Data compiled by Alan Chamberlin.

NUMBER OF NEOS
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. A separate table containing WISE discoveries for NEAs and comets is available.

The chart below shows the cumulative total known near-Earth asteroids versus time. The blue area shows all near-Earth asteroids while the red area shows only large near-Earth asteroids (those with diameters roughly one kilometer and larger).
Table: Number of Known Near-Earth Asteroids Over Time
(click on the chart above for a larger version)

The chart below shows the total known near-Earth asteroids per size bin. Diameters are estimated using an assumed average albedo for NEAs. The first size bin represents NEAs smaller than 30m in diameter. The second represents NEAs with diameters from 30m to 100m, and so on.
Known Near-Earth Asteroids by Size Bin
Data shown in the chart above represent known NEAs as of the date shown in the bottom-right corner of the chart.

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 large asteroids (PHA-KM and NEA-KM) are rough estimates (see introductory note above). This table is updated daily using discovery data published by the Minor Planet Center.

----------------------------------------------------------------------------
   Date      NEC  Atira  Aten Apollo  Amor  PHA-KM  PHA  NEA-KM  NEA    NEO
----------  ----  ----- ----- ------ -----  ------ ----  ------ -----  -----
2014-07-25    94     14   854   6038  4237     154 1493     862 11143  11237
2014-07-01    94     14   854   6022  4224     154 1489     862 11114  11208
2014-06-01    94     14   845   5990  4174     153 1483     860 11023  11117
2014-05-01    94     14   838   5931  4128     153 1469     858 10911  11005
2014-04-01    94     14   827   5855  4067     153 1462     857 10763  10857
2014-03-01    94     13   820   5799  4040     153 1457     857 10672  10766
2014-02-01    94     13   812   5754  4002     153 1450     857 10581  10675
2014-01-01    94     13   805   5701  3962     153 1446     856 10481  10575
2013-12-01    94     13   800   5646  3936     153 1442     856 10395  10489
2013-11-01    94     13   799   5575  3909     153 1434     856 10296  10390
2013-10-01    94     12   787   5516  3848     152 1426     852 10163  10257
2013-09-01    94     12   780   5460  3793     152 1422     851 10045  10139
2013-08-01    94     12   778   5429  3756     152 1416     851  9975  10069
2013-07-01    94     12   773   5401  3731     152 1409     850  9917  10011
2013-06-01    94     12   770   5371  3713     152 1403     848  9866   9960
2013-05-01    94     11   765   5331  3693     152 1396     848  9800   9894
2013-04-01    94     11   760   5290  3662     152 1387     847  9723   9817
2013-03-01    94     11   755   5242  3634     152 1378     847  9642   9736
2013-02-01    93     11   750   5203  3607     152 1374     847  9571   9664
2013-01-01    93     11   743   5122  3569     152 1360     846  9445   9538
2012-12-01    93     11   735   5069  3538     152 1350     846  9353   9446
2012-11-01    92     10   727   5015  3501     152 1341     843  9253   9345
2012-10-01    92     10   721   4940  3445     152 1330     841  9116   9208
2012-09-01    92     10   717   4907  3415     152 1327     840  9049   9141
2012-08-01    92     10   712   4882  3381     152 1322     839  8985   9077
2012-07-01    91     10   711   4876  3372     152 1317     838  8969   9060
2012-06-01    91     10   706   4850  3349     152 1308     835  8915   9006
2012-05-01    91     10   704   4817  3325     152 1303     832  8856   8947
2012-04-01    91     10   702   4766  3298     152 1297     831  8776   8867
2012-03-01    91     10   696   4686  3271     152 1291     829  8663   8754
2012-02-01    91     10   686   4639  3230     152 1285     829  8565   8656
2012-01-01    91     10   676   4570  3195     152 1276     828  8451   8542
2011-12-01    91     10   672   4538  3170     152 1269     824  8390   8481
2011-11-01    91     10   669   4497  3135     150 1258     821  8311   8402
2011-10-01    91     10   662   4435  3090     149 1247     820  8197   8288
2011-09-01    90     10   661   4400  3035     149 1241     818  8106   8196
2011-08-01    90     10   661   4384  3009     149 1238     817  8064   8154
2011-07-01    89     10   659   4371  2985     149 1234     817  8025   8114
2011-06-01    89     10   659   4354  2960     149 1228     816  7983   8072
2011-05-01    89     10   656   4328  2938     149 1219     815  7932   8021
2011-04-01    89     10   645   4279  2908     149 1212     813  7842   7931
2011-03-01    89     10   634   4216  2884     149 1203     811  7744   7833
2011-02-01    89     10   624   4169  2865     149 1192     811  7668   7757
2011-01-01    89     10   618   4093  2833     149 1176     809  7554   7643
2010-12-01    89      9   609   4038  2801     149 1167     808  7457   7546
2010-11-01    89      9   598   3969  2755     149 1161     808  7331   7420
2010-10-01    89      9   588   3913  2715     149 1147     808  7225   7314
2010-09-01    89      9   582   3867  2650     149 1142     807  7108   7197
2010-08-01    89      9   579   3853  2640     149 1139     805  7081   7170
2010-07-01    89      9   574   3831  2628     149 1137     803  7042   7131
2010-06-01    88      9   568   3800  2606     149 1129     802  6983   7071
2010-05-01    87      9   560   3756  2587     148 1116     800  6912   6999
2010-04-01    87      9   552   3710  2570     148 1110     800  6841   6928
2010-03-01    87      9   544   3673  2545     147 1101     799  6771   6858
2010-02-01    87      9   540   3619  2520     147 1089     798  6688   6775
2010-01-01    87      9   535   3593  2501     147 1086     796  6638   6725
2009-12-01    87      9   531   3572  2491     147 1081     794  6603   6690
2009-11-01    86      9   520   3496  2462     147 1074     791  6487   6573
2009-10-01    86      9   511   3441  2429     147 1070     789  6390   6476
2009-09-01    86      9   506   3388  2382     147 1061     787  6285   6371
2009-08-01    86      9   504   3368  2355     147 1059     786  6236   6322
2009-07-01    86      9   504   3358  2346     146 1057     782  6217   6303
2009-06-01    85      9   501   3347  2335     145 1054     781  6192   6277
2009-05-01    85      9   499   3320  2322     145 1045     780  6150   6235
2009-04-01    85      9   496   3288  2308     145 1041     777  6101   6186
2009-03-01    85      9   491   3226  2289     145 1029     777  6015   6100
2009-02-01    85      9   487   3168  2263     144 1017     774  5927   6012
2009-01-01    85      9   481   3124  2243     144 1008     772  5857   5942
2008-12-01    84      9   480   3082  2213     144  998     771  5784   5868
2008-11-01    84      9   474   3034  2191     144  990     769  5708   5792
2008-10-01    84      8   467   2972  2141     143  980     768  5588   5672
2008-09-01    83      8   464   2941  2107     143  970     767  5520   5603
2008-08-01    83      8   461   2927  2093     143  965     766  5489   5572
2008-07-01    83      8   459   2909  2082     142  955     763  5458   5541
2008-06-01    83      8   455   2898  2074     142  952     762  5435   5518
2008-05-01    83      8   451   2868  2056     142  946     761  5383   5466
2008-04-01    83      8   449   2821  2027     142  943     760  5305   5388
2008-03-01    83      7   440   2753  2002     141  933     753  5202   5285
2008-02-01    83      7   428   2693  1972     140  920     751  5100   5183
2008-01-01    83      7   426   2666  1955     140  912     751  5054   5137
2007-12-01    83      7   423   2631  1938     140  901     748  4999   5082
2007-11-01    83      7   411   2573  1902     140  891     744  4893   4976
2007-10-01    82      7   397   2524  1860     140  881     743  4788   4870
2007-09-01    82      7   390   2486  1828     139  874     742  4711   4793
2007-08-01    82      7   388   2475  1818     138  869     738  4688   4770
2007-07-01    82      7   388   2471  1811     138  868     738  4677   4759
2007-06-01    82      7   383   2449  1802     137  859     736  4641   4723
2007-05-01    82      7   382   2436  1791     137  855     734  4616   4698
2007-04-01    82      7   381   2410  1774     137  851     730  4572   4654
2007-03-01    82      6   375   2370  1751     137  844     728  4502   4584
2007-02-01    82      6   367   2337  1735     136  836     724  4445   4527
2007-01-01    82      6   359   2317  1722     136  827     723  4404   4486
2006-12-01    81      6   354   2291  1704     136  824     721  4355   4436
2006-11-01    81      5   344   2242  1681     135  812     715  4272   4353
2006-10-01    79      5   337   2212  1649     135  802     713  4203   4282
2006-09-01    79      5   330   2175  1621     134  793     709  4131   4210
2006-08-01    79      5   328   2158  1608     134  788     709  4099   4178
2006-07-01    79      5   327   2147  1591     134  786     708  4070   4149
2006-06-01    79      5   326   2136  1578     134  783     708  4045   4124
2006-05-01    79      5   325   2108  1551     134  773     704  3989   4068
2006-04-01    78      5   321   2081  1536     134  763     702  3943   4021
2006-03-01    78      5   319   2066  1517     134  762     701  3907   3985
2006-02-01    78      5   316   2031  1500     134  754     698  3852   3930
2006-01-01    78      5   312   1975  1474     133  744     693  3766   3844
2005-12-01    78      5   302   1943  1453     132  733     690  3703   3781
2005-11-01    77      5   297   1901  1427     131  723     685  3630   3707
2005-10-01    76      4   289   1845  1387     130  711     674  3525   3601
2005-09-01    76      4   286   1811  1368     130  706     671  3469   3545
2005-08-01    76      4   283   1797  1352     130  700     670  3436   3512
2005-07-01    76      4   279   1778  1340     129  693     667  3401   3477
2005-06-01    76      4   275   1763  1320     129  689     662  3362   3438
2005-05-01    75      4   274   1746  1306     127  683     659  3330   3405
2005-04-01    75      4   268   1721  1287     126  671     655  3280   3355
2005-03-01    75      4   263   1681  1262     125  661     651  3210   3285
2005-02-01    75      4   262   1657  1254     124  657     648  3177   3252
2005-01-01    75      4   258   1633  1244     124  650     644  3139   3214
2004-12-01    74      3   249   1601  1223     124  642     636  3076   3150
2004-11-01    74      3   245   1581  1217     123  633     631  3046   3120
2004-10-01    73      3   238   1553  1209     122  622     629  3003   3076
2004-09-01    72      3   230   1515  1184     122  614     628  2932   3004
2004-08-01    72      3   226   1495  1162     121  607     624  2886   2958
2004-07-01    72      3   226   1488  1158     119  604     621  2875   2947
2004-06-01    72      3   223   1458  1145     118  593     618  2829   2901
2004-05-01    72      2   218   1439  1130     118  587     614  2789   2861
2004-04-01    72      2   215   1409  1118     114  577     607  2744   2816
2004-03-01    72      2   206   1373  1100     114  570     598  2681   2753
2004-02-01    71      2   204   1358  1094     113  565     597  2658   2729
2004-01-01    71      2   202   1324  1076     111  555     593  2604   2675
2003-12-01    71      2   196   1292  1064     108  542     585  2554   2625
2003-11-01    71      2   193   1271  1051     108  535     579  2517   2588
2003-10-01    70      2   188   1244  1029     108  526     577  2463   2533
2003-09-01    70      2   185   1224   995     106  517     570  2406   2476
2003-08-01    70      2   185   1212   982     103  512     566  2381   2451
2003-07-01    69      2   184   1205   973     103  509     563  2364   2433
2003-06-01    69      2   182   1189   961     103  504     557  2334   2403
2003-05-01    67      2   180   1175   955     102  502     555  2312   2379
2003-04-01    67      2   175   1155   944     101  494     550  2276   2343
2003-03-01    67      2   170   1136   933     101  487     546  2241   2308
2003-02-01    67      1   169   1116   927     101  481     542  2213   2280
2003-01-01    67      1   167   1089   910     100  471     537  2167   2234
2002-12-01    67      1   163   1062   890     100  469     535  2116   2183
2002-11-01    67      1   160   1047   873      99  463     531  2081   2148
2002-10-01    66      1   158   1023   850      98  456     523  2032   2098
2002-09-01    64      1   155   1003   830      97  450     514  1989   2053
2002-08-01    64      1   154    987   807      95  439     511  1949   2013
2002-07-01    63      1   152    977   800      94  432     506  1930   1993
2002-06-01    63      1   148    959   792      92  424     500  1900   1963
2002-05-01    63      1   144    941   781      91  415     489  1867   1930
2002-04-01    63      1   142    923   768      91  408     487  1834   1897
2002-03-01    62      1   136    896   754      90  398     484  1787   1849
2002-02-01    62      1   131    873   738      89  389     474  1743   1805
2002-01-01    62      1   124    839   715      89  376     466  1679   1741
2001-12-01    62      1   121    803   696      85  362     457  1621   1683
2001-11-01    60      1   120    775   681      84  354     453  1577   1637
2001-10-01    60      1   114    750   657      83  345     449  1522   1582
2001-09-01    60      1   110    721   622      82  334     436  1454   1514
2001-08-01    59      1   109    699   602      82  328     433  1411   1470
2001-07-01    58      1   108    694   589      82  327     432  1392   1450
2001-06-01    57      1   108    684   578      80  324     425  1371   1428
2001-05-01    56      1   107    672   567      78  317     417  1347   1403
2001-04-01    56      1   105    660   558      77  308     413  1324   1380
2001-03-01    56      1   101    645   544      75  299     406  1291   1347
2001-02-01    56      1    98    634   533      74  296     401  1266   1322
2001-01-01    56      1    94    619   524      74  293     397  1238   1294
2000-12-01    56      1    93    605   512      73  287     390  1211   1267
2000-11-01    56      1    90    581   495      72  284     381  1167   1223
2000-10-01    56      1    87    571   481      72  280     374  1140   1196
2000-09-01    56      1    81    553   455      71  273     365  1090   1146
2000-08-01    56      1    79    535   439      69  264     356  1054   1110
2000-07-01    56      1    77    530   429      67  261     345  1037   1093
2000-06-01    56      1    76    525   423      66  257     342  1025   1081
2000-05-01    56      1    76    512   409      66  252     335   998   1054
2000-04-01    55      1    73    497   396      65  246     328   967   1022
2000-03-01    55      1    64    481   385      63  234     316   931    986
2000-02-01    55      1    62    464   374      62  223     309   901    956
2000-01-01    55      1    57    450   367      62  217     304   875    930
1999-12-01    54      1    56    440   358      60  209     297   855    909
1999-11-01    54      1    54    427   344      60  205     287   826    880
1999-10-01    54      1    54    411   330      59  200     283   796    850
1999-09-01    52      1    54    395   314      57  193     279   764    816
1999-08-01    52      1    54    395   312      57  193     279   762    814
1999-07-01    52      1    54    390   307      56  191     275   752    804
1999-06-01    52      1    51    383   297      56  186     272   732    784
1999-05-01    51      1    49    371   292      52  178     263   713    764
1999-04-01    51      1    48    358   285      51  174     256   692    743
1999-03-01    51      1    47    348   280      51  172     255   676    727
1999-02-01    51      1    47    338   275      51  169     252   661    712
1999-01-01    51      1    45    333   269      51  166     250   648    699
1998-12-01    51      1    41    323   260      51  162     241   625    676
1998-11-01    51      1    38    309   251      49  154     236   599    650
1998-10-01    51      1    36    305   244      49  152     232   586    637
1998-09-01    51      1    29    292   231      48  140     226   553    604
1998-08-01    51      1    29    282   220      46  133     220   532    583
1998-07-01    51      1    29    279   217      44  129     217   526    577
1998-06-01    51      1    29    273   210      43  127     214   513    564
1998-05-01    51      1    29    264   204      43  124     210   498    549
1998-04-01    51      1    27    256   195      43  117     209   479    530
1998-03-01    51      1    27    244   187      43  112     205   459    510
1998-02-01    51      0    26    240   187      42  110     204   453    504
1998-01-01    51      0    26    235   184      42  108     201   445    496
1997-01-01    51      0    22    206   164      40   97     188   392    443
1996-01-01    51      0    20    178   149      38   86     182   347    398
1995-01-01    51      0    19    163   133      37   83     172   315    366
1994-01-01    49      0    15    140   113      33   70     154   268    317
1993-01-01    49      0    13    117    97      31   64     140   227    276
1992-01-01    49      0    11    103    84      29   61     123   198    247
1991-01-01    47      0     9     76    73      24   49     105   158    205
1990-01-01    47      0     8     63    62      20   42      89   133    180
1980-01-01    43      0     3     27    22      12   17      44    52     95
1970-01-01    41      0     0     13    14       8   10      24    27     68
1960-01-01    40      0     0     10    10       7    8      18    20     60
1950-01-01    40      0     0      7     6       4    5      12    13     53
1940-01-01    35      0     0      3     6       2    3       8     9     44
1930-01-01    33      0     0      0     5       0    0       5     5     38
1920-01-01    31      0     0      0     3       0    0       3     3     34
1910-01-01    29      0     0      0     1       0    0       1     1     30
1900-01-01    27      0     0      0     1       0    0       1     1     28

Note: "NEC" are Near-Earth comets. "PHA-KM" and "NEA-KM" are PHAs and NEAs with diameters roughly one kilometer and larger. Other definitions, such as Apollo, are on the NEO groups page.

Data compiled by Alan Chamberlin.

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