Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          468        178 
1992          740        300 
1993         1296        483 
1994         1664        611 
1995         3006       1050 
1996         2959       1046 
1997         1828        633 
1998        21610       9194 
1999        13239       5089 
2000        38497      15916 
2001        39304      15268 
2002        32254      14281 
2003        57590      23971 
2004        46193      17731 
2005        81053      24967 
2006       104574      33587 
2007       191195      59129 
2008       111754      32014 
2009        92543      26097 
2010       144921      38936 
2011       156925      43550 
2012       148299      41109 
2013       219997      62699 
2014       564552     143884 
2015       798413     210186 
2016       657674     170919 
2017       554027     149975 
2018       350673      98528 
2019       862660     210601 
2020       616026     156785 
2021       828731     196783 
2022       618987     177192 
2023       558020     159634 
2024       616373     177617 
2025       219956      62864