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          743        301 
1993         1308        487 
1994         1681        617 
1995         3057       1067 
1996         2980       1053 
1997         1863        643 
1998        21754       9242 
1999        13541       5194 
2000        38639      15974 
2001        39462      15329 
2002        32275      14297 
2003        57783      24043 
2004        46364      17788 
2005        81486      25083 
2006       105171      33754 
2007       191948      59325 
2008       112546      32223 
2009        93314      26298 
2010       141361      38160 
2011       158399      43933 
2012       149640      41459 
2013       221607      63132 
2014       565005     143945 
2015       798177     210048 
2016       659574     171408 
2017       555212     150298 
2018       352274      98963 
2019       864701     211061 
2020       618067     157307 
2021       832219     197632 
2022       621489     177892 
2023       559362     159990 
2024       617952     178034 
2025       207429      59243