Year Observations     Objects
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           12          6 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          213         76 
1991          856        306 
1992          656        270 
1993         1176        442 
1994         1481        553 
1995         2350        830 
1996         2614        928 
1997         2480        847 
1998        23904       8540 
1999        12798       4882 
2000        36244      14882 
2001        41357      16238 
2002        34910      14935 
2003        56786      23265 
2004        44739      17040 
2005       302564     136371 
2006       330214     147483 
2007       191450      59328 
2008       107355      30639 
2009        87727      24555 
2010       135479      36092 
2011       142225      38704 
2012       169828      36799 
2013       223561      56231 
2014       470510     116748 
2015       708234     185212 
2016       598510     154676 
2017       502502     136610 
2018       300175      84897 
2019       801403     196275 
2020       524922     133018 
2021       706378     165256 
2022       548727     157410 
2023       508339     145645 
2024       548199     157582 
2025       523119     148756 
2026       368012      87609