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        38721      16008 
2001        39507      15349 
2002        31217      13949 
2003        57873      24081 
2004        46457      17824 
2005        81680      25141 
2006       105328      33800 
2007       192332      59430 
2008       113281      32419 
2009        93796      26429 
2010       124168      34085 
2011       159191      44147 
2012       150467      41690 
2013       222870      63486 
2014       567084     144477 
2015       797636     209691 
2016       659800     171311 
2017       555510     150331 
2018       354023      99448 
2019       868225     211902 
2020       621068     158100 
2021       837794     199092 
2022       624788     178826 
2023       561808     160679 
2024       623882     179700 
2025       188531      53783