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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)3842072000034676
 2007 (2)7402552660075053
 2008 (1)7404312800055456
 2008 (2)66043027900115855
 2009 (1)50032026000186215
 2009 (2)58031031500176636
 2010 (1)29021025708897040
 2010 (2)7502203451838147552
 2011 (1)400170332683128024
 2011 (2)3001502531050238450
 2012 (1)260130353120078969
 2012 (2)2901302771310269445
 2013 (1)301302881500189917
 2013 (2)0012031520812910482
 2014 (1)*0060224899510815
* Incomplete half-year (based on discovery data through 2014-Apr-15 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)240112002305
 2000 (1)322115001347
 2000 (2)382350004399
 2001 (1)238040000434
 2001 (2)255040001469
 2002 (1)324230001511
 2002 (2)1910010001542
 2003 (1)143160002568
 2003 (2)175142001598
 2004 (1)165123001626
 2004 (2)910112000649
 2005 (1)100219001672
 2005 (2)645010001698
 2006 (1)30219000713
 2006 (2)102012000728
 2007 (1)20309001743
 2007 (2)50107000756
 2008 (1)20109000768
 2008 (2)30105000777
 2009 (1)10009000787
 2009 (2)60006002801
 2010 (1)00004030808
 2010 (2)10001040814
 2011 (1)10006100822
 2011 (2)00106400833
 2012 (1)00009100843
 2012 (2)10005200851
 2013 (1)00004000855
 2013 (2)00004201862
 2014 (1)*00001100864
* Incomplete half-year (based on discovery data through 2014-Apr-15 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
----------  ----  ----- ----- ------ -----  ------ ----  ------ -----  -----
2014-04-09    94     14   834   5883  4084     154 1465     864 10815  10909
2014-04-01    94     14   827   5855  4066     154 1462     863 10762  10856
2014-03-01    94     13   820   5799  4040     154 1457     863 10672  10766
2014-02-01    94     13   812   5754  4003     154 1450     863 10582  10676
2014-01-01    94     13   805   5701  3963     154 1446     862 10482  10576
2013-12-01    94     13   800   5646  3937     154 1442     862 10396  10490
2013-11-01    94     13   799   5575  3910     154 1434     862 10297  10391
2013-10-01    94     12   787   5516  3848     153 1426     857 10163  10257
2013-09-01    94     12   780   5460  3793     153 1422     856 10045  10139
2013-08-01    94     12   778   5429  3756     153 1416     856  9975  10069
2013-07-01    94     12   773   5401  3731     153 1409     855  9917  10011
2013-06-01    94     12   770   5371  3713     153 1403     853  9866   9960
2013-05-01    94     11   765   5331  3693     153 1396     853  9800   9894
2013-04-01    94     11   760   5290  3662     153 1387     852  9723   9817
2013-03-01    94     11   755   5242  3634     153 1378     852  9642   9736
2013-02-01    93     11   750   5203  3607     153 1374     852  9571   9664
2013-01-01    93     11   743   5122  3569     153 1360     851  9445   9538
2012-12-01    93     11   735   5069  3538     153 1350     851  9353   9446
2012-11-01    92     10   727   5015  3501     153 1341     848  9253   9345
2012-10-01    92     10   721   4940  3445     153 1330     846  9116   9208
2012-09-01    92     10   717   4907  3415     153 1327     845  9049   9141
2012-08-01    92     10   712   4882  3381     153 1322     844  8985   9077
2012-07-01    91     10   711   4876  3372     153 1317     843  8969   9060
2012-06-01    91     10   706   4850  3349     153 1308     840  8915   9006
2012-05-01    91     10   704   4817  3325     153 1303     837  8856   8947
2012-04-01    91     10   702   4766  3298     153 1297     836  8776   8867
2012-03-01    91     10   696   4686  3271     153 1291     834  8663   8754
2012-02-01    91     10   686   4639  3230     153 1285     834  8565   8656
2012-01-01    91     10   676   4569  3195     153 1276     833  8450   8541
2011-12-01    91     10   672   4537  3170     153 1269     829  8389   8480
2011-11-01    91     10   669   4496  3135     151 1258     826  8310   8401
2011-10-01    91     10   662   4434  3090     150 1247     825  8196   8287
2011-09-01    90     10   661   4399  3035     150 1241     823  8105   8195
2011-08-01    90     10   661   4383  3009     150 1238     822  8063   8153
2011-07-01    89     10   659   4370  2985     150 1234     822  8024   8113
2011-06-01    89     10   659   4353  2960     150 1228     821  7982   8071
2011-05-01    89     10   656   4327  2938     150 1219     820  7931   8020
2011-04-01    89     10   645   4277  2908     150 1212     818  7840   7929
2011-03-01    89     10   634   4214  2884     150 1203     816  7742   7831
2011-02-01    89     10   624   4167  2865     150 1192     816  7666   7755
2011-01-01    89     10   618   4091  2833     150 1176     814  7552   7641
2010-12-01    89      9   609   4036  2801     150 1167     813  7455   7544
2010-11-01    89      9   598   3967  2755     150 1161     813  7329   7418
2010-10-01    89      9   588   3911  2715     150 1147     813  7223   7312
2010-09-01    89      9   582   3865  2650     150 1142     812  7106   7195
2010-08-01    89      9   579   3851  2640     150 1139     810  7079   7168
2010-07-01    89      9   574   3829  2628     150 1137     808  7040   7129
2010-06-01    88      9   568   3798  2606     150 1129     807  6981   7069
2010-05-01    87      9   560   3754  2587     149 1116     805  6910   6997
2010-04-01    87      9   552   3708  2570     149 1110     805  6839   6926
2010-03-01    87      9   544   3671  2545     148 1101     804  6769   6856
2010-02-01    87      9   540   3617  2520     148 1089     803  6686   6773
2010-01-01    87      9   535   3591  2501     148 1086     801  6636   6723
2009-12-01    87      9   531   3570  2491     148 1081     799  6601   6688
2009-11-01    86      9   520   3494  2462     148 1074     796  6485   6571
2009-10-01    86      9   511   3439  2429     148 1070     794  6388   6474
2009-09-01    86      9   506   3386  2382     148 1061     792  6283   6369
2009-08-01    86      9   504   3366  2355     148 1059     791  6234   6320
2009-07-01    86      9   504   3356  2346     147 1057     787  6215   6301
2009-06-01    85      9   501   3345  2335     146 1054     786  6190   6275
2009-05-01    85      9   499   3318  2322     146 1045     785  6148   6233
2009-04-01    85      9   496   3286  2308     146 1041     782  6099   6184
2009-03-01    85      9   491   3224  2289     146 1029     782  6013   6098
2009-02-01    85      9   487   3166  2263     145 1017     779  5925   6010
2009-01-01    85      9   481   3122  2243     145 1008     777  5855   5940
2008-12-01    84      9   480   3080  2213     145  998     776  5782   5866
2008-11-01    84      9   474   3032  2191     145  990     774  5706   5790
2008-10-01    84      8   467   2970  2141     144  980     773  5586   5670
2008-09-01    83      8   464   2939  2107     144  970     772  5518   5601
2008-08-01    83      8   461   2925  2093     144  965     771  5487   5570
2008-07-01    83      8   459   2907  2082     143  955     768  5456   5539
2008-06-01    83      8   455   2896  2074     143  952     767  5433   5516
2008-05-01    83      8   451   2866  2056     143  946     766  5381   5464
2008-04-01    83      8   449   2820  2027     143  943     765  5304   5387
2008-03-01    83      7   440   2752  2002     142  933     758  5201   5284
2008-02-01    83      7   428   2692  1972     141  920     756  5099   5182
2008-01-01    83      7   426   2665  1955     141  912     756  5053   5136
2007-12-01    83      7   423   2630  1938     141  901     753  4998   5081
2007-11-01    83      7   411   2572  1902     141  891     749  4892   4975
2007-10-01    82      7   397   2523  1860     141  881     748  4787   4869
2007-09-01    82      7   390   2485  1828     140  874     747  4710   4792
2007-08-01    82      7   388   2474  1818     139  869     743  4687   4769
2007-07-01    82      7   388   2470  1811     139  868     743  4676   4758
2007-06-01    82      7   383   2448  1802     138  859     741  4640   4722
2007-05-01    82      7   382   2435  1791     138  855     739  4615   4697
2007-04-01    82      7   381   2410  1774     138  851     735  4572   4654
2007-03-01    82      6   375   2370  1751     138  844     733  4502   4584
2007-02-01    82      6   367   2337  1735     137  836     729  4445   4527
2007-01-01    82      6   359   2317  1722     137  827     728  4404   4486
2006-12-01    81      6   354   2291  1704     137  824     726  4355   4436
2006-11-01    81      5   344   2242  1681     136  812     720  4272   4353
2006-10-01    79      5   337   2212  1649     136  802     718  4203   4282
2006-09-01    79      5   330   2175  1621     135  793     714  4131   4210
2006-08-01    79      5   328   2158  1608     135  788     714  4099   4178
2006-07-01    79      5   327   2147  1591     135  786     713  4070   4149
2006-06-01    79      5   326   2136  1578     135  783     713  4045   4124
2006-05-01    79      5   325   2108  1551     135  773     709  3989   4068
2006-04-01    78      5   321   2081  1536     135  763     707  3943   4021
2006-03-01    78      5   319   2066  1517     135  762     706  3907   3985
2006-02-01    78      5   316   2031  1500     135  754     703  3852   3930
2006-01-01    78      5   312   1975  1474     134  744     698  3766   3844
2005-12-01    78      5   302   1943  1453     133  733     695  3703   3781
2005-11-01    77      5   297   1901  1427     132  723     690  3630   3707
2005-10-01    76      4   289   1845  1387     131  711     679  3525   3601
2005-09-01    76      4   286   1811  1368     131  706     676  3469   3545
2005-08-01    76      4   283   1797  1352     131  700     675  3436   3512
2005-07-01    76      4   279   1778  1340     130  693     672  3401   3477
2005-06-01    76      4   275   1763  1320     130  689     667  3362   3438
2005-05-01    75      4   274   1746  1306     128  683     664  3330   3405
2005-04-01    75      4   268   1721  1287     127  671     660  3280   3355
2005-03-01    75      4   263   1681  1262     126  661     656  3210   3285
2005-02-01    75      4   262   1657  1254     125  657     653  3177   3252
2005-01-01    75      4   258   1633  1244     125  650     649  3139   3214
2004-12-01    74      3   249   1601  1223     125  642     641  3076   3150
2004-11-01    74      3   245   1581  1217     124  633     636  3046   3120
2004-10-01    73      3   238   1553  1209     123  622     634  3003   3076
2004-09-01    72      3   230   1515  1184     123  614     633  2932   3004
2004-08-01    72      3   226   1495  1162     122  607     629  2886   2958
2004-07-01    72      3   226   1488  1158     120  604     626  2875   2947
2004-06-01    72      3   223   1458  1145     119  593     623  2829   2901
2004-05-01    72      2   218   1439  1130     119  587     619  2789   2861
2004-04-01    72      2   215   1409  1118     115  577     612  2744   2816
2004-03-01    72      2   206   1373  1100     115  570     603  2681   2753
2004-02-01    71      2   204   1358  1094     114  565     602  2658   2729
2004-01-01    71      2   202   1324  1076     112  555     598  2604   2675
2003-12-01    71      2   196   1292  1064     109  542     590  2554   2625
2003-11-01    71      2   193   1271  1051     109  535     584  2517   2588
2003-10-01    70      2   188   1244  1029     109  526     582  2463   2533
2003-09-01    70      2   185   1224   995     107  517     575  2406   2476
2003-08-01    70      2   185   1212   982     104  512     571  2381   2451
2003-07-01    69      2   184   1205   973     104  509     568  2364   2433
2003-06-01    69      2   182   1189   961     104  504     562  2334   2403
2003-05-01    67      2   180   1175   955     103  502     560  2312   2379
2003-04-01    67      2   175   1155   944     102  494     555  2276   2343
2003-03-01    67      2   170   1136   933     102  487     551  2241   2308
2003-02-01    67      1   169   1116   927     102  481     547  2213   2280
2003-01-01    67      1   167   1089   910     101  471     542  2167   2234
2002-12-01    67      1   163   1062   890     101  469     540  2116   2183
2002-11-01    67      1   160   1047   873     100  463     536  2081   2148
2002-10-01    66      1   158   1023   850      99  456     528  2032   2098
2002-09-01    64      1   155   1003   830      98  450     519  1989   2053
2002-08-01    64      1   154    987   807      96  439     516  1949   2013
2002-07-01    63      1   152    977   800      95  432     511  1930   1993
2002-06-01    63      1   148    959   792      93  424     505  1900   1963
2002-05-01    63      1   144    941   781      92  415     494  1867   1930
2002-04-01    63      1   142    923   768      92  408     492  1834   1897
2002-03-01    62      1   136    896   754      91  398     488  1787   1849
2002-02-01    62      1   131    873   738      90  389     478  1743   1805
2002-01-01    62      1   124    839   715      90  376     469  1679   1741
2001-12-01    62      1   121    803   696      86  362     460  1621   1683
2001-11-01    60      1   120    775   681      84  354     455  1577   1637
2001-10-01    60      1   114    750   657      83  345     451  1522   1582
2001-09-01    60      1   110    721   622      82  334     438  1454   1514
2001-08-01    59      1   109    699   602      82  328     435  1411   1470
2001-07-01    58      1   108    694   589      82  327     434  1392   1450
2001-06-01    57      1   108    684   578      80  324     427  1371   1428
2001-05-01    56      1   107    672   567      78  317     419  1347   1403
2001-04-01    56      1   105    660   558      77  308     415  1324   1380
2001-03-01    56      1   101    645   544      75  299     408  1291   1347
2001-02-01    56      1    98    634   533      74  296     403  1266   1322
2001-01-01    56      1    94    619   524      74  293     399  1238   1294
2000-12-01    56      1    93    605   512      73  287     392  1211   1267
2000-11-01    56      1    90    581   495      72  284     383  1167   1223
2000-10-01    56      1    87    571   481      72  280     376  1140   1196
2000-09-01    56      1    81    553   455      71  273     367  1090   1146
2000-08-01    56      1    79    535   439      69  264     358  1054   1110
2000-07-01    56      1    77    530   429      67  261     347  1037   1093
2000-06-01    56      1    76    525   423      66  257     344  1025   1081
2000-05-01    56      1    76    512   409      66  252     337   998   1054
2000-04-01    55      1    73    497   396      65  246     330   967   1022
2000-03-01    55      1    64    481   385      63  234     317   931    986
2000-02-01    55      1    62    464   374      62  223     310   901    956
2000-01-01    55      1    57    450   367      62  217     305   875    930
1999-12-01    54      1    56    440   358      60  209     298   855    909
1999-11-01    54      1    54    427   344      60  205     288   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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