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          471        179 
1992          746        302 
1993         1308        487 
1994         1684        618 
1995         3093       1079 
1996         2980       1053 
1997         1866        644 
1998        22102       9359 
1999        13572       5207 
2000        38727      16011 
2001        39507      15349 
2002        31038      13889 
2003        57882      24084 
2004        46464      17827 
2005        81701      25147 
2006       105349      33806 
2007       192366      59440 
2008       113334      32433 
2009        93818      26435 
2010       124195      34092 
2011       159271      44169 
2012       150523      41706 
2013       223009      63522 
2014       567669     144602 
2015       814909     213746 
2016       663670     172156 
2017       556754     150529 
2018       354094      99456 
2019       869219     212146 
2020       621596     158245 
2021       838286     199227 
2022       625258     178958 
2023       562137     160765 
2024       624791     179948 
2025       189989      54161