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          216         77 
1991          856        306 
1992          656        270 
1993         1176        442 
1994         1490        556 
1995         2368        836 
1996         2640        937 
1997         2509        857 
1998        23954       8558 
1999        12862       4905 
2000        36408      14953 
2001        41469      16288 
2002        35045      14997 
2003        57080      23382 
2004        44934      17117 
2005       303470     136735 
2006       330831     147719 
2007       192041      59486 
2008       108228      30870 
2009        88797      24838 
2010       136566      36371 
2011       143544      39060 
2012       171087      37141 
2013       225646      56811 
2014       472784     117331 
2015       712511     186353 
2016       600645     155224 
2017       506204     137644 
2018       302205      85462 
2019       805444     197353 
2020       528946     134074 
2021       713029     166947 
2022       553784     158824 
2023       510988     146393 
2024       551221     158439 
2025       525655     149134 
2026       345482      81033