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         3087       1077 
1996         2980       1053 
1997         1866        644 
1998        22028       9334 
1999        13565       5204 
2000        38693      15996 
2001        39485      15339 
2002        49317      19981 
2003        57843      24069 
2004        46425      17811 
2005        81611      25121 
2006       105286      33787 
2007       192224      59401 
2008       113022      32350 
2009        93647      26388 
2010       129755      35420 
2011       158927      44076 
2012       150200      41617 
2013       222408      63362 
2014       566280     144272 
2015       797888     209880 
2016       658131     170913 
2017       554420     150061 
2018       353500      99316 
2019       866944     211650 
2020       620023     157844 
2021       836499     198719 
2022       623837     178559 
2023       560882     160429 
2024       622448     179299 
2025       197698      56409