NEO Discovery Statistics

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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 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)	Other	Cumulative Total
1995 (1)	0	0	14	0	0	0	4	335
1995 (2)	0	0	12	0	0	0	2	349
1996 (1)	1	5	18	0	0	0	4	377
1996 (2)	0	5	10	0	0	0	2	394
1997 (1)	3	2	10	0	0	0	4	413
1997 (2)	14	9	4	0	0	0	7	447
1998 (1)	44	9	19	1	1	0	7	528
1998 (2)	92	2	15	6	2	0	5	650
1999 (1)	74	0	12	6	11	0	1	754
1999 (2)	87	0	7	7	19	0	3	877
2000 (1)	108	2	14	21	13	0	4	1039
2000 (2)	150	14	12	17	0	0	8	1240
2001 (1)	95	28	7	22	0	0	2	1394
2001 (2)	184	64	15	20	0	0	4	1681
2002 (1)	158	56	16	14	1	0	6	1932
2002 (2)	128	89	6	7	0	0	5	2167
2003 (1)	102	30	23	33	0	0	9	2364
2003 (2)	133	38	33	21	8	0	8	2605
2004 (1)	167	19	41	14	25	0	6	2877
2004 (2)	137	7	29	25	60	0	6	3141
2005 (1)	78	8	29	22	116	0	10	3404
2005 (2)	59	30	54	19	193	0	10	3769
2006 (1)	44	4	45	13	197	0	3	4075
2006 (2)	52	17	54	7	199	0	5	4409
2007 (1)	38	4	20	7	200	0	3	4681
2007 (2)	74	0	25	5	266	0	7	5058
2008 (1)	74	0	43	1	281	0	5	5462
2008 (2)	66	0	43	0	278	0	11	5860
2009 (1)	50	0	32	0	261	0	18	6221
2009 (2)	58	0	31	0	314	0	17	6641
2010 (1)	29	0	21	0	257	0	97	7045
2010 (2)	75	0	22	0	345	18	52	7557
2011 (1)	40	0	17	0	332	68	15	8029
2011 (2)	30	0	15	0	253	105	23	8455
2012 (1)	25	0	13	0	353	120	7	8973
2012 (2)	29	0	13	0	277	131	26	9449
2013 (1)*	3	0	4	0	105	36	7	9604

* Incomplete half-year (based on discovery data through 2013-Feb-14 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) Other Cumulative
Total

1995 (1) 0 0 3 0 0 0 2 180

1995 (2) 0 0 4 0 0 0 1 185

1996 (1) 0 2 2 0 0 0 0 189

1996 (2) 0 2 0 0 0 0 0 191

1997 (1) 0 1 2 0 0 0 1 195

1997 (2) 2 3 1 0 0 0 2 203

1998 (1) 7 4 2 1 0 0 2 219

1998 (2) 24 2 1 3 0 0 3 252

1999 (1) 15 0 2 4 4 0 0 277

1999 (2) 24 0 1 1 2 0 2 307

2000 (1) 31 2 1 1 4 0 1 347

2000 (2) 39 2 3 5 0 0 4 400

2001 (1) 24 8 0 4 0 0 0 436

2001 (2) 25 5 0 4 0 0 1 471

2002 (1) 32 4 2 3 0 0 1 513

2002 (2) 21 11 0 1 0 0 1 547

2003 (1) 15 3 1 6 0 0 2 574

2003 (2) 17 5 1 4 2 0 1 604

2004 (1) 16 5 1 2 3 0 1 632

2004 (2) 9 1 0 1 13 0 0 656

2005 (1) 10 0 2 1 9 0 1 679

2005 (2) 6 5 5 0 10 0 1 706

2006 (1) 3 0 2 1 9 0 0 721

2006 (2) 1 0 2 0 12 0 0 736

2007 (1) 2 0 3 0 9 0 1 751

2007 (2) 5 0 1 0 7 0 0 764

2008 (1) 2 0 1 0 8 0 0 775

2008 (2) 3 0 1 0 5 0 0 784

2009 (1) 1 0 0 0 9 0 0 794

2009 (2) 6 0 0 0 6 0 2 808

2010 (1) 0 0 1 0 5 0 3 817

2010 (2) 1 0 0 0 1 0 4 823

2011 (1) 1 0 0 0 6 1 0 831

2011 (2) 0 0 1 0 6 4 0 842

2012 (1) 0 0 0 0 9 1 0 852

2012 (2) 1 0 0 0 5 2 0 860

2013 (1)* 0 0 0 0 1 0 0 861

* Incomplete half-year (based on discovery data through 2013-Feb-14 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

NASA's current search program is designed to discover 90% of the NEO population. 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).

(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 ---------- ---- ----- ---- ------ ---- ------ ---- ------ ---- ---- 2013-02-12 93 12 751 5224 3617 155 1378 861 9604 9697 2013-02-01 93 12 750 5205 3608 155 1375 861 9575 9668 2013-01-01 93 12 743 5124 3570 155 1361 860 9449 9542 2012-12-01 93 12 735 5071 3539 155 1351 860 9357 9450 2012-11-01 92 11 727 5017 3502 155 1342 857 9257 9349 2012-10-01 92 11 721 4942 3446 155 1331 855 9120 9212 2012-09-01 92 11 717 4909 3416 155 1328 854 9053 9145 2012-08-01 92 11 712 4884 3382 155 1323 853 8989 9081 2012-07-01 91 11 711 4878 3373 155 1318 852 8973 9064 2012-06-01 91 11 706 4853 3350 155 1309 849 8920 9011 2012-05-01 91 11 704 4820 3326 155 1304 846 8861 8952 2012-04-01 91 11 702 4770 3298 155 1298 845 8781 8872 2012-03-01 91 11 696 4690 3271 155 1292 843 8668 8759 2012-02-01 91 11 686 4643 3230 155 1285 843 8570 8661 2012-01-01 91 11 676 4573 3195 155 1277 842 8455 8546 2011-12-01 91 11 672 4541 3170 155 1270 838 8394 8485 2011-11-01 91 11 669 4500 3135 153 1260 835 8315 8406 2011-10-01 91 11 662 4438 3090 152 1249 834 8201 8292 2011-09-01 90 11 661 4403 3035 152 1243 832 8110 8200 2011-08-01 90 11 661 4387 3009 152 1240 831 8068 8158 2011-07-01 89 11 659 4374 2985 152 1236 831 8029 8118 2011-06-01 89 11 659 4357 2960 152 1231 830 7987 8076 2011-05-01 89 11 656 4331 2938 152 1222 829 7936 8025 2011-04-01 89 11 645 4281 2908 152 1215 827 7845 7934 2011-03-01 89 11 634 4218 2884 152 1205 825 7747 7836 2011-02-01 89 11 624 4171 2865 152 1194 825 7671 7760 2011-01-01 89 11 618 4095 2833 152 1178 823 7557 7646 2010-12-01 89 10 609 4040 2801 152 1169 822 7460 7549 2010-11-01 89 10 598 3971 2755 152 1163 822 7334 7423 2010-10-01 89 10 588 3915 2715 152 1149 822 7228 7317 2010-09-01 89 10 582 3869 2650 152 1144 821 7111 7200 2010-08-01 89 10 579 3855 2640 152 1141 819 7084 7173 2010-07-01 89 10 574 3833 2628 152 1139 817 7045 7134 2010-06-01 88 10 568 3802 2606 152 1131 815 6986 7074 2010-05-01 87 10 560 3758 2587 151 1119 813 6915 7002 2010-04-01 87 10 552 3712 2570 151 1113 813 6844 6931 2010-03-01 87 10 544 3675 2545 150 1104 812 6774 6861 2010-02-01 87 10 540 3621 2520 149 1092 810 6691 6778 2010-01-01 87 10 535 3595 2501 149 1089 808 6641 6728 2009-12-01 87 10 531 3574 2491 149 1084 806 6606 6693 2009-11-01 86 10 520 3497 2464 149 1077 803 6491 6577 2009-10-01 86 10 511 3442 2431 149 1073 801 6394 6480 2009-09-01 86 10 506 3389 2384 149 1064 799 6289 6375 2009-08-01 86 10 504 3369 2357 149 1062 798 6240 6326 2009-07-01 86 10 504 3359 2348 148 1060 794 6221 6307 2009-06-01 85 10 501 3347 2338 147 1057 793 6196 6281 2009-05-01 85 10 499 3320 2325 147 1048 792 6154 6239 2009-04-01 85 10 496 3288 2311 147 1044 789 6105 6190 2009-03-01 85 10 491 3226 2292 147 1032 789 6019 6104 2009-02-01 85 10 487 3168 2266 146 1020 786 5931 6016 2009-01-01 85 10 481 3123 2246 146 1011 784 5860 5945 2008-12-01 84 10 480 3081 2216 146 1001 783 5787 5871 2008-11-01 84 10 474 3033 2194 146 993 781 5711 5795 2008-10-01 84 9 467 2972 2144 145 983 780 5592 5676 2008-09-01 83 9 464 2941 2110 145 973 779 5524 5607 2008-08-01 83 9 461 2927 2096 145 968 778 5493 5576 2008-07-01 83 9 459 2909 2085 144 959 775 5462 5545 2008-06-01 83 9 455 2898 2077 144 956 774 5439 5522 2008-05-01 83 9 451 2868 2060 144 950 774 5388 5471 2008-04-01 83 9 449 2821 2031 144 947 773 5310 5393 2008-03-01 83 8 440 2753 2006 143 937 766 5207 5290 2008-02-01 83 8 428 2694 1975 142 923 764 5105 5188 2008-01-01 83 8 426 2666 1958 142 914 764 5058 5141 2007-12-01 83 8 423 2631 1941 142 903 761 5003 5086 2007-11-01 83 8 411 2573 1905 142 893 757 4897 4980 2007-10-01 82 8 397 2524 1863 142 883 756 4792 4874 2007-09-01 82 8 390 2486 1831 141 876 755 4715 4797 2007-08-01 82 8 388 2475 1821 140 871 751 4692 4774 2007-07-01 82 8 388 2471 1814 140 870 751 4681 4763 2007-06-01 82 8 383 2449 1805 139 861 749 4645 4727 2007-05-01 82 8 382 2436 1794 139 857 747 4620 4702 2007-04-01 82 8 381 2411 1777 139 853 743 4577 4659 2007-03-01 82 7 375 2372 1753 139 846 741 4507 4589 2007-02-01 82 7 367 2339 1737 138 838 737 4450 4532 2007-01-01 82 7 359 2319 1724 138 829 736 4409 4491 2006-12-01 81 7 354 2293 1706 138 826 734 4360 4441 2006-11-01 81 6 344 2244 1683 137 814 728 4277 4358 2006-10-01 79 6 337 2214 1651 137 804 726 4208 4287 2006-09-01 79 6 330 2177 1623 136 795 722 4136 4215 2006-08-01 79 6 328 2160 1610 136 790 722 4104 4183 2006-07-01 79 6 327 2149 1593 136 788 721 4075 4154 2006-06-01 79 6 326 2138 1580 136 785 721 4050 4129 2006-05-01 79 5 325 2110 1553 136 775 717 3993 4072 2006-04-01 78 5 321 2083 1538 136 765 715 3947 4025 2006-03-01 78 5 319 2067 1519 136 764 714 3910 3988 2006-02-01 78 5 316 2032 1502 136 756 711 3855 3933 2006-01-01 78 5 312 1976 1476 135 747 706 3769 3847 2005-12-01 78 5 302 1944 1455 134 736 703 3706 3784 2005-11-01 77 5 297 1902 1429 133 726 698 3633 3710 2005-10-01 76 4 289 1846 1389 132 714 687 3528 3604 2005-09-01 76 4 286 1812 1370 132 709 684 3472 3548 2005-08-01 76 4 283 1798 1354 132 703 682 3439 3515 2005-07-01 76 4 279 1779 1342 131 696 679 3404 3480 2005-06-01 76 4 275 1764 1322 131 692 674 3365 3441 2005-05-01 75 4 274 1747 1307 129 686 671 3332 3407 2005-04-01 75 4 268 1722 1288 127 673 667 3282 3357 2005-03-01 75 4 263 1681 1264 126 663 663 3212 3287 2005-02-01 75 4 262 1657 1256 125 659 660 3179 3254 2005-01-01 75 4 258 1633 1246 125 652 656 3141 3216 2004-12-01 74 3 249 1601 1225 125 643 647 3078 3152 2004-11-01 74 3 245 1581 1219 124 634 642 3048 3122 2004-10-01 73 3 238 1553 1211 123 623 640 3005 3078 2004-09-01 72 3 230 1515 1186 123 615 639 2934 3006 2004-08-01 72 3 226 1496 1163 122 608 635 2888 2960 2004-07-01 72 3 226 1490 1158 120 605 632 2877 2949 2004-06-01 72 3 223 1460 1145 119 594 629 2831 2903 2004-05-01 72 2 218 1441 1130 119 588 625 2791 2863 2004-04-01 72 2 215 1411 1118 115 578 618 2746 2818 2004-03-01 72 2 206 1375 1100 115 571 609 2683 2755 2004-02-01 71 2 204 1360 1093 114 566 608 2659 2730 2004-01-01 71 2 202 1326 1075 112 556 604 2605 2676 2003-12-01 71 2 196 1294 1063 109 543 596 2555 2626 2003-11-01 71 2 193 1272 1050 109 535 590 2517 2588 2003-10-01 71 2 188 1245 1028 109 526 588 2463 2534 2003-09-01 71 2 185 1225 994 107 517 581 2406 2477 2003-08-01 71 2 185 1213 981 104 512 577 2381 2452 2003-07-01 70 2 184 1206 972 104 509 574 2364 2434 2003-06-01 70 2 182 1190 960 104 504 568 2334 2404 2003-05-01 68 2 180 1176 954 103 502 566 2312 2380 2003-04-01 68 2 175 1156 943 103 495 561 2276 2344 2003-03-01 68 2 170 1137 932 103 488 557 2241 2309 2003-02-01 68 1 169 1117 926 103 482 553 2213 2281 2003-01-01 68 1 167 1090 909 102 472 547 2167 2235 2002-12-01 68 1 163 1063 889 102 470 545 2116 2184 2002-11-01 68 1 160 1048 872 101 464 541 2081 2149 2002-10-01 67 1 158 1024 849 100 457 532 2032 2099 2002-09-01 65 1 155 1004 830 99 451 523 1990 2055 2002-08-01 65 1 154 988 807 97 440 518 1950 2015 2002-07-01 64 1 152 978 801 96 433 513 1932 1996 2002-06-01 64 1 148 960 793 94 424 507 1902 1966 2002-05-01 64 1 144 942 782 93 415 496 1869 1933 2002-04-01 64 1 142 924 769 93 408 494 1836 1900 2002-03-01 63 1 136 897 755 92 398 490 1789 1852 2002-02-01 63 1 131 874 739 91 389 480 1745 1808 2002-01-01 63 1 124 840 716 91 376 471 1681 1744 2001-12-01 63 1 121 804 697 87 362 462 1623 1686 2001-11-01 61 1 120 776 682 85 355 457 1579 1640 2001-10-01 61 1 114 750 659 84 346 453 1524 1585 2001-09-01 61 1 110 721 624 82 334 440 1456 1517 2001-08-01 60 1 109 699 604 82 328 437 1413 1473 2001-07-01 59 1 108 694 591 82 327 436 1394 1453 2001-06-01 58 1 108 684 580 80 324 429 1373 1431 2001-05-01 57 1 107 672 569 78 317 421 1349 1406 2001-04-01 57 1 105 660 560 77 308 417 1326 1383 2001-03-01 57 1 101 645 546 75 299 409 1293 1350 2001-02-01 57 1 98 634 535 74 296 404 1268 1325 2001-01-01 57 1 94 619 526 74 293 400 1240 1297 2000-12-01 57 1 93 605 514 73 287 393 1213 1270 2000-11-01 57 1 90 581 497 72 284 384 1169 1226 2000-10-01 57 1 87 571 483 72 280 376 1142 1199 2000-09-01 57 1 81 553 457 71 273 367 1092 1149 2000-08-01 57 1 79 535 441 69 264 358 1056 1113 2000-07-01 57 1 77 530 431 67 261 347 1039 1096 2000-06-01 57 1 76 525 425 66 257 344 1027 1084 2000-05-01 57 1 76 512 411 66 252 338 1000 1057 2000-04-01 56 1 73 497 398 65 246 331 969 1025 2000-03-01 56 1 64 481 387 63 234 319 933 989 2000-02-01 56 1 62 464 376 62 223 312 903 959 2000-01-01 56 1 57 450 369 62 217 307 877 933 1999-12-01 55 1 56 440 360 60 209 300 857 912 1999-11-01 55 1 54 427 346 60 205 290 828 883 1999-10-01 55 1 54 411 332 59 200 285 798 853 1999-09-01 53 1 54 395 316 57 193 281 766 819 1999-08-01 53 1 54 395 314 57 193 281 764 817 1999-07-01 53 1 54 390 309 56 191 277 754 807 1999-06-01 53 1 51 383 299 56 186 274 734 787 1999-05-01 52 1 49 371 294 52 178 265 715 767 1999-04-01 52 1 48 358 287 51 174 258 694 746 1999-03-01 52 1 47 348 282 51 172 257 678 730 1999-02-01 52 1 47 338 277 51 169 254 663 715 1999-01-01 52 1 45 333 271 51 166 252 650 702 1998-12-01 52 1 41 323 262 51 162 243 627 679 1998-11-01 52 1 38 309 253 49 154 238 601 653 1998-10-01 52 1 36 305 246 49 152 234 588 640 1998-09-01 52 1 29 292 233 48 140 228 555 607 1998-08-01 52 1 29 282 222 46 133 222 534 586 1998-07-01 52 1 29 279 219 44 129 219 528 580 1998-06-01 52 1 29 273 212 43 127 216 515 567 1998-05-01 52 1 29 264 206 43 124 212 500 552 1998-04-01 52 1 27 256 197 43 117 211 481 533 1998-03-01 52 1 27 244 189 43 112 207 461 513 1998-02-01 52 0 26 240 189 42 110 206 455 507 1998-01-01 52 0 26 235 186 42 108 203 447 499 1997-01-01 52 0 22 206 166 40 97 191 394 446 1996-01-01 52 0 20 178 151 38 86 185 349 401 1995-01-01 52 0 19 163 135 37 83 175 317 369 1994-01-01 50 0 15 140 115 33 70 157 270 320 1993-01-01 50 0 13 117 99 31 64 143 229 279 1992-01-01 50 0 11 103 85 29 61 125 199 249 1991-01-01 48 0 9 76 74 24 49 106 159 207 1990-01-01 48 0 8 63 63 20 42 90 134 182 1980-01-01 44 0 3 27 23 12 17 45 53 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 28 0 0 0 1 0 0 1 1 29

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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