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          743        301 
1993         1308        487 
1994         1675        615 
1995         3045       1063 
1996         2977       1052 
1997         1858        641 
1998        21674       9215 
1999        13350       5129 
2000        38586      15954 
2001        39414      15308 
2002        33269      14626 
2003        57727      24018 
2004        46273      17752 
2005        81354      25044 
2006       104978      33694 
2007       191703      59259 
2008       112175      32122 
2009        93023      26220 
2010       145446      39072 
2011       157773      43765 
2012       149018      41289 
2013       220896      62932 
2014       565365     144065 
2015       798569     210226 
2016       658532     171143 
2017       554747     150159 
2018       351339      98700 
2019       863246     210734 
2020       616513     156901 
2021       829413     196947 
2022       619520     177332 
2023       558457     159759 
2024       617227     177868 
2025       220876      63054