Year Observations     Objects
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
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          216         77 
1991          856        306 
1992          664        273 
1993         1213        455 
1994         1552        577 
1995         2576        907 
1996         2776        983 
1997         2681        914 
1998        24209       8644 
1999        13034       4966 
2000        36730      15094 
2001        41808      16423 
2002        35367      15134 
2003        57690      23610 
2004        45424      17290 
2005       305356     137441 
2006       332602     148384 
2007       193522      59877 
2008       110122      31373 
2009        90789      25368 
2010       138931      36986 
2011       146554      39857 
2012       174373      38018 
2013       230291      58051 
2014       488873     121193 
2015       738518     192737 
2016       619242     159886 
2017       518474     141033 
2018       308331      87175 
2019       813517     199376 
2020       536116     136067 
2021       725603     170217 
2022       563931     161676 
2023       516355     147894 
2024       557592     160240 
2025       535549     151407 
2026       272574      60052