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        22033       9336 
1999        13567       5205 
2000        38695      15997 
2001        39485      15339 
2002        49319      19982 
2003        57845      24070 
2004        46428      17812 
2005        81623      25124 
2006       105286      33787 
2007       192230      59403 
2008       113073      32363 
2009        93654      26390 
2010       129774      35425 
2011       158966      44086 
2012       150244      41628 
2013       222483      63383 
2014       566374     144298 
2015       797852     209872 
2016       657962     170866 
2017       554517     150088 
2018       353573      99337 
2019       867031     211671 
2020       620093     157862 
2021       836672     198768 
2022       623990     178602 
2023       560960     160450 
2024       622521     179320 
2025       196579      56077