Skip Navigation: Avoid going through Home page links and jump straight to content
spacer spacer spacer
spacer spacer spacer
spacer
NASA Logo    + View the NASA Portal  
Near Earth Object Program
spacer
spacer spacer spacer
spacer
NEO Basics Search Programs Discovery Statistics Accessible NEAs News Frequently Asked Questions
spacer
spacer spacer spacer
spacer
Orbit Diagrams Orbit Elements Close Approaches Impact Risk Images Related LInks
spacer
spacer spacer spacer
spacer

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)001400004334
 1995 (2)001201002349
 1996 (1)151800004377
 1996 (2)051000002394
 1997 (1)321000004413
 1997 (2)149400007447
 1998 (1)4491911007528
 1998 (2)9221563005651
 1999 (1)75012611001756
 1999 (2)8707719003879
 2000 (1)10821421130041041
 2000 (2)15014121700081242
 2001 (1)942872200021395
 2001 (2)18364152000041681
 2002 (1)15857161410061933
 2002 (2)130896700052170
 2003 (1)10230233300092367
 2003 (2)13337332270082607
 2004 (1)167194114250062879
 2004 (2)13772925600063143
 2005 (1)778292211500103404
 2005 (2)5930541919300103769
 2006 (1)44445131950034073
 2006 (2)52175461990054406
 2007 (1)3842072000034678
 2007 (2)7402652660075056
 2008 (1)7404212800055458
 2008 (2)66043028100115859
 2009 (1)51032026000186220
 2009 (2)58031031400176640
 2010 (1)30021025808797045
 2010 (2)7502203461737147556
 2011 (1)410170328683128025
 2011 (2)2901502521040238448
 2012 (1)260130351120078965
 2012 (2)2801302771310269440
 2013 (1)301302881510189913
 2013 (2)0012031520812910478
 2014 (1)00803322411614611221
 2014 (2)0080285380243811956
 2015 (1)00203053831810912773
 2015 (2)*00201610431612914
* Incomplete half-year (based on discovery data through 2015-Sep-01 21:05 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)00300002176
 1995 (2)00400001181
 1996 (1)02200000185
 1996 (2)02000000187
 1997 (1)01300001192
 1997 (2)23100002200
 1998 (1)74210002216
 1998 (2)242130003249
 1999 (1)160244000275
 1999 (2)230112002304
 2000 (1)332114001346
 2000 (2)372350004397
 2001 (1)238040000432
 2001 (2)225030001463
 2002 (1)294230001502
 2002 (2)2010010001534
 2003 (1)133260002560
 2003 (2)175142001590
 2004 (1)155123001617
 2004 (2)910112000640
 2005 (1)100219001663
 2005 (2)645010001689
 2006 (1)30219000704
 2006 (2)102012000719
 2007 (1)20309001734
 2007 (2)50107000747
 2008 (1)20108000758
 2008 (2)30105000767
 2009 (1)10109000778
 2009 (2)60006002792
 2010 (1)10004030800
 2010 (2)10002030806
 2011 (1)20005100814
 2011 (2)00106300824
 2012 (1)00009100834
 2012 (2)00005200841
 2013 (1)00004000845
 2013 (2)00003201851
 2014 (1)00002420859
 2014 (2)00001310864
 2015 (1)00000720873
 2015 (2)*00000200875
* Incomplete half-year (based on discovery data through 2015-Sep-01 21:05 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
----------  ----  ----- ----- ------ -----  ------ ----  ------ -----  -----
2015-08-29   104     16   939   6982  4977     154 1608     875 12914  13018
2015-08-01   104     16   937   6943  4938     154 1603     873 12834  12938
2015-07-01   104     16   934   6917  4906     154 1596     873 12773  12877
2015-06-01   104     15   933   6876  4867     153 1591     871 12691  12795
2015-05-01   104     15   922   6813  4803     153 1580     871 12553  12657
2015-04-01   103     15   917   6731  4741     152 1572     870 12404  12507
2015-03-01   103     15   906   6621  4702     152 1558     866 12244  12347
2015-02-01   102     14   898   6538  4663     152 1546     866 12113  12215
2015-01-01   101     14   889   6456  4597     152 1532     864 11956  12057
2014-12-01   101     14   880   6392  4561     152 1523     862 11847  11948
2014-11-01   101     14   874   6318  4497     152 1514     859 11703  11804
2014-10-01   100     14   867   6228  4434     152 1509     859 11543  11643
2014-09-01   100     14   861   6175  4379     152 1503     859 11429  11529
2014-08-01   100     14   856   6122  4306     152 1494     859 11298  11398
2014-07-01   100     14   854   6079  4274     152 1484     859 11221  11321
2014-06-01   100     14   845   6042  4217     151 1476     855 11118  11218
2014-05-01   100     14   838   5975  4170     151 1463     853 10997  11097
2014-04-01   100     14   826   5859  4061     151 1455     852 10760  10860
2014-03-01   100     13   819   5803  4034     151 1450     852 10669  10769
2014-02-01   100     13   811   5758  3996     151 1443     852 10578  10678
2014-01-01   100     13   804   5705  3956     151 1439     851 10478  10578
2013-12-01   100     13   799   5650  3930     151 1435     851 10392  10492
2013-11-01   100     13   798   5578  3904     151 1427     851 10293  10393
2013-10-01    99     12   786   5519  3842     150 1420     847 10159  10258
2013-09-01    99     12   780   5462  3787     150 1416     846 10041  10140
2013-08-01    99     12   778   5431  3750     150 1410     846  9971  10070
2013-07-01    99     12   773   5403  3725     150 1403     845  9913  10012
2013-06-01    99     12   770   5373  3707     150 1397     843  9862   9961
2013-05-01    99     11   765   5334  3686     150 1390     843  9796   9895
2013-04-01    99     11   760   5293  3655     150 1381     842  9719   9818
2013-03-01    99     11   755   5245  3626     150 1372     842  9637   9736
2013-02-01    98     11   750   5206  3599     150 1368     842  9566   9664
2013-01-01    98     11   743   5125  3561     150 1354     841  9440   9538
2012-12-01    98     11   735   5072  3530     150 1343     841  9348   9446
2012-11-01    97     10   727   5018  3494     150 1335     839  9249   9346
2012-10-01    97     10   721   4943  3438     150 1324     837  9112   9209
2012-09-01    97     10   717   4910  3408     150 1321     836  9045   9142
2012-08-01    97     10   712   4884  3375     150 1316     835  8981   9078
2012-07-01    96     10   711   4878  3366     150 1312     834  8965   9061
2012-06-01    96     10   706   4853  3342     150 1303     831  8911   9007
2012-05-01    96     10   704   4820  3318     150 1298     828  8852   8948
2012-04-01    96     10   702   4769  3291     150 1292     827  8772   8868
2012-03-01    96     10   696   4689  3265     150 1286     825  8660   8756
2012-02-01    96     10   686   4642  3224     150 1280     825  8562   8658
2012-01-01    96     10   676   4573  3189     150 1271     824  8448   8544
2011-12-01    96     10   672   4541  3164     150 1264     820  8387   8483
2011-11-01    96     10   669   4500  3130     148 1254     817  8309   8405
2011-10-01    96     10   662   4438  3085     147 1243     816  8195   8291
2011-09-01    95     10   661   4403  3032     147 1237     815  8106   8201
2011-08-01    95     10   661   4387  3006     147 1234     814  8064   8159
2011-07-01    94     10   659   4374  2982     147 1230     814  8025   8119
2011-06-01    94     10   659   4357  2957     147 1224     813  7983   8077
2011-05-01    94     10   656   4331  2934     147 1215     811  7931   8025
2011-04-01    94     10   645   4282  2905     147 1208     809  7842   7936
2011-03-01    94     10   634   4219  2881     147 1199     807  7744   7838
2011-02-01    94     10   624   4173  2863     147 1188     807  7670   7764
2011-01-01    94     10   618   4098  2830     147 1172     806  7556   7650
2010-12-01    94      9   609   4043  2799     147 1163     806  7460   7554
2010-11-01    94      9   598   3974  2753     147 1157     806  7334   7428
2010-10-01    94      9   588   3918  2714     147 1143     806  7229   7323
2010-09-01    94      9   582   3871  2649     147 1138     804  7111   7205
2010-08-01    94      9   579   3858  2638     147 1136     801  7084   7178
2010-07-01    94      9   574   3835  2627     147 1133     800  7045   7139
2010-06-01    93      9   568   3804  2605     147 1125     799  6986   7079
2010-05-01    92      9   560   3760  2586     146 1112     797  6915   7007
2010-04-01    92      9   552   3715  2569     146 1107     797  6845   6937
2010-03-01    92      9   544   3678  2542     145 1098     795  6773   6865
2010-02-01    92      9   540   3624  2517     145 1086     794  6690   6782
2010-01-01    92      9   535   3597  2499     145 1082     792  6640   6732
2009-12-01    92      9   531   3576  2489     145 1077     790  6605   6697
2009-11-01    91      9   520   3500  2460     145 1069     787  6489   6580
2009-10-01    91      9   511   3445  2428     145 1065     785  6393   6484
2009-09-01    91      9   506   3392  2381     145 1055     783  6288   6379
2009-08-01    91      9   504   3372  2354     145 1053     782  6239   6330
2009-07-01    91      9   504   3362  2345     144 1051     778  6220   6311
2009-06-01    90      9   501   3351  2334     143 1048     777  6195   6285
2009-05-01    90      9   499   3324  2320     143 1039     775  6152   6242
2009-04-01    90      9   496   3292  2306     143 1035     772  6103   6193
2009-03-01    90      9   491   3231  2287     143 1023     772  6018   6108
2009-02-01    90      9   487   3172  2261     142 1011     769  5929   6019
2009-01-01    90      9   481   3128  2241     142 1002     767  5859   5949
2008-12-01    88      9   480   3086  2212     142  992     766  5787   5875
2008-11-01    88      9   474   3038  2189     142  984     764  5710   5798
2008-10-01    88      8   467   2976  2138     141  974     763  5589   5677
2008-09-01    87      8   464   2945  2103     141  964     762  5520   5607
2008-08-01    87      8   461   2931  2089     141  959     761  5489   5576
2008-07-01    87      8   459   2914  2077     140  950     758  5458   5545
2008-06-01    87      8   455   2903  2069     140  947     757  5435   5522
2008-05-01    87      8   451   2873  2052     140  941     757  5384   5471
2008-04-01    87      8   449   2826  2023     140  938     756  5306   5393
2008-03-01    87      7   440   2758  1998     139  928     749  5203   5290
2008-02-01    87      7   428   2698  1968     138  914     747  5101   5188
2008-01-01    86      7   426   2671  1952     138  906     747  5056   5142
2007-12-01    86      7   423   2636  1934     138  896     744  5000   5086
2007-11-01    86      7   411   2578  1898     138  886     740  4894   4980
2007-10-01    85      7   397   2529  1856     138  875     739  4789   4874
2007-09-01    85      7   390   2491  1824     137  868     738  4712   4797
2007-08-01    85      7   388   2480  1814     136  863     734  4689   4774
2007-07-01    85      7   388   2476  1807     136  862     734  4678   4763
2007-06-01    85      7   383   2454  1798     135  853     732  4642   4727
2007-05-01    85      7   382   2441  1787     135  849     730  4617   4702
2007-04-01    85      7   381   2415  1771     135  845     726  4574   4659
2007-03-01    85      6   375   2375  1748     135  838     724  4504   4589
2007-02-01    85      6   367   2342  1732     134  830     720  4447   4532
2007-01-01    85      6   359   2322  1719     134  821     719  4406   4491
2006-12-01    84      6   354   2296  1701     134  818     717  4357   4441
2006-11-01    84      5   344   2247  1678     133  806     711  4274   4358
2006-10-01    82      5   337   2217  1646     133  796     709  4205   4287
2006-09-01    82      5   330   2180  1619     132  787     705  4134   4216
2006-08-01    82      5   328   2163  1606     132  782     705  4102   4184
2006-07-01    82      5   327   2152  1589     132  780     704  4073   4155
2006-06-01    82      5   326   2141  1576     132  777     704  4048   4130
2006-05-01    82      5   325   2113  1549     132  767     700  3992   4074
2006-04-01    81      5   321   2086  1534     132  757     698  3946   4027
2006-03-01    81      5   319   2071  1515     132  756     697  3910   3991
2006-02-01    81      5   316   2036  1498     132  748     694  3855   3936
2006-01-01    81      5   312   1981  1471     131  739     689  3769   3850
2005-12-01    81      5   302   1949  1450     130  728     686  3706   3787
2005-11-01    80      5   297   1907  1424     129  718     681  3633   3713
2005-10-01    79      4   289   1851  1384     128  706     670  3528   3607
2005-09-01    79      4   286   1817  1365     128  701     667  3472   3551
2005-08-01    79      4   283   1803  1349     128  695     666  3439   3518
2005-07-01    79      4   279   1783  1338     127  688     663  3404   3483
2005-06-01    79      4   275   1768  1318     127  684     658  3365   3444
2005-05-01    78      4   274   1751  1304     125  678     655  3333   3411
2005-04-01    78      4   268   1726  1286     123  665     651  3284   3362
2005-03-01    78      4   263   1686  1260     122  654     647  3213   3291
2005-02-01    78      4   262   1663  1252     121  650     644  3181   3259
2005-01-01    78      4   258   1639  1242     121  643     640  3143   3221
2004-12-01    77      3   249   1607  1221     121  635     632  3080   3157
2004-11-01    77      3   245   1587  1215     120  626     627  3050   3127
2004-10-01    76      3   238   1559  1207     119  615     625  3007   3083
2004-09-01    75      3   230   1521  1182     119  607     624  2936   3011
2004-08-01    75      3   226   1501  1160     118  600     620  2890   2965
2004-07-01    75      3   226   1494  1156     116  597     617  2879   2954
2004-06-01    75      3   223   1464  1143     115  586     614  2833   2908
2004-05-01    75      2   218   1445  1128     115  580     610  2793   2868
2004-04-01    75      2   215   1415  1116     111  570     603  2748   2823
2004-03-01    75      2   206   1379  1098     111  563     594  2685   2760
2004-02-01    74      2   204   1364  1091     110  558     593  2661   2735
2004-01-01    74      2   202   1330  1073     108  548     590  2607   2681
2003-12-01    74      2   196   1298  1061     105  535     582  2557   2631
2003-11-01    74      2   193   1277  1048     105  528     576  2520   2594
2003-10-01    73      2   188   1250  1025     105  520     574  2465   2538
2003-09-01    73      2   185   1229   992     103  511     567  2408   2481
2003-08-01    73      2   185   1217   979     100  506     563  2383   2456
2003-07-01    72      2   184   1210   971     100  503     560  2367   2439
2003-06-01    72      2   182   1194   959     100  498     555  2337   2409
2003-05-01    70      2   180   1180   953      99  496     553  2315   2385
2003-04-01    70      2   175   1160   942      99  489     547  2279   2349
2003-03-01    70      2   170   1141   931      99  482     543  2244   2314
2003-02-01    70      1   169   1121   925      99  477     539  2216   2286
2003-01-01    70      1   167   1094   908      98  467     534  2170   2240
2002-12-01    70      1   163   1067   888      98  465     532  2119   2189
2002-11-01    70      1   160   1052   871      97  459     528  2084   2154
2002-10-01    69      1   158   1028   848      96  453     520  2035   2104
2002-09-01    67      1   155   1007   829      95  447     511  1992   2059
2002-08-01    67      1   154    991   806      93  436     507  1952   2019
2002-07-01    66      1   152    981   799      92  429     502  1933   1999
2002-06-01    66      1   148    962   791      90  421     496  1902   1968
2002-05-01    66      1   144    944   780      89  412     485  1869   1935
2002-04-01    66      1   142    926   767      89  405     483  1836   1902
2002-03-01    65      1   136    899   753      88  395     480  1789   1854
2002-02-01    65      1   131    876   737      87  386     470  1745   1810
2002-01-01    65      1   124    842   714      87  373     463  1681   1746
2001-12-01    65      1   121    806   695      83  359     454  1623   1688
2001-11-01    63      1   120    778   680      82  352     450  1579   1642
2001-10-01    63      1   114    752   657      81  343     446  1524   1587
2001-09-01    63      1   110    723   623      80  332     436  1457   1520
2001-08-01    62      1   109    701   603      80  327     433  1414   1476
2001-07-01    61      1   108    696   590      80  326     432  1395   1456
2001-06-01    60      1   108    686   580      78  323     425  1375   1435
2001-05-01    59      1   107    674   569      76  316     417  1351   1410
2001-04-01    59      1   105    662   560      75  307     413  1328   1387
2001-03-01    59      1   101    647   546      73  298     406  1295   1354
2001-02-01    59      1    98    636   535      72  295     401  1270   1329
2001-01-01    59      1    94    621   526      72  292     397  1242   1301
2000-12-01    59      1    93    607   514      71  286     390  1215   1274
2000-11-01    59      1    90    583   497      70  283     381  1171   1230
2000-10-01    59      1    87    573   483      70  279     374  1144   1203
2000-09-01    59      1    81    555   457      69  272     366  1094   1153
2000-08-01    59      1    79    537   441      67  263     357  1058   1117
2000-07-01    59      1    77    532   431      65  260     346  1041   1100
2000-06-01    59      1    76    527   425      64  256     343  1029   1088
2000-05-01    59      1    76    514   411      64  251     335  1002   1061
2000-04-01    58      1    73    499   398      63  245     328   971   1029
2000-03-01    58      1    64    483   387      61  233     316   935    993
2000-02-01    58      1    62    466   376      61  223     309   905    963
2000-01-01    58      1    57    452   369      61  217     304   879    937
1999-12-01    57      1    56    442   360      59  209     297   859    916
1999-11-01    57      1    54    429   346      59  205     287   830    887
1999-10-01    57      1    54    413   332      58  200     283   800    857
1999-09-01    55      1    54    397   316      56  192     279   768    823
1999-08-01    55      1    54    397   314      56  192     279   766    821
1999-07-01    55      1    54    392   309      55  190     275   756    811
1999-06-01    55      1    51    385   299      55  186     272   736    791
1999-05-01    54      1    49    373   293      51  178     262   716    770
1999-04-01    54      1    48    360   286      50  174     255   695    749
1999-03-01    54      1    47    350   281      50  172     254   679    733
1999-02-01    54      1    47    340   276      50  169     251   664    718
1999-01-01    54      1    45    335   270      50  166     249   651    705
1998-12-01    54      1    41    325   261      50  162     240   628    682
1998-11-01    54      1    38    311   252      48  154     235   602    656
1998-10-01    54      1    36    306   245      48  152     231   588    642
1998-09-01    54      1    29    293   232      47  140     225   555    609
1998-08-01    54      1    29    283   221      45  133     219   534    588
1998-07-01    54      1    29    279   219      43  129     216   528    582
1998-06-01    54      1    29    273   212      42  127     213   515    569
1998-05-01    54      1    29    264   206      42  124     209   500    554
1998-04-01    54      1    27    256   197      42  117     208   481    535
1998-03-01    54      1    27    244   189      42  112     204   461    515
1998-02-01    54      0    26    240   189      41  110     203   455    509
1998-01-01    54      0    26    235   186      41  108     200   447    501
1997-01-01    53      0    22    206   166      39   97     187   394    447
1996-01-01    53      0    20    178   151      37   86     181   349    402
1995-01-01    53      0    19    163   134      36   83     171   316    369
1994-01-01    51      0    15    140   114      32   70     153   269    320
1993-01-01    51      0    13    117    98      30   64     139   228    279
1992-01-01    51      0    11    103    84      28   61     122   198    249
1991-01-01    49      0     9     76    73      23   49     104   158    207
1990-01-01    49      0     8     63    62      20   42      89   133    182
1980-01-01    45      0     3     27    22      12   17      44    52     97
1970-01-01    42      0     0     13    14       8   10      24    27     69
1960-01-01    41      0     0     10    10       7    8      18    20     61
1950-01-01    41      0     0      7     6       4    5      12    13     54
1940-01-01    36      0     0      3     6       2    3       8     9     45
1930-01-01    34      0     0      0     5       0    0       5     5     39
1920-01-01    32      0     0      0     3       0    0       3     3     35
1910-01-01    30      0     0      0     1       0    0       1     1     31
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.

Menu
FIRST GOV   NASA Home Page Site Manager: Paul Chodas
Webmaster: Ron Baalke
Last Updated:
Feedback Credits Privacy Mailing List NASA