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         3069       1071 
1996         2980       1053 
1997         1863        643 
1998        21790       9254 
1999        13553       5195 
2000        38656      15981 
2001        39472      15333 
2002        32285      14301 
2003        57797      24049 
2004        46378      17794 
2005        81515      25092 
2006       105195      33761 
2007       191992      59338 
2008       112646      32249 
2009        93393      26320 
2010       138302      37460 
2011       158530      43967 
2012       149783      41499 
2013       221803      63190 
2014       565275     144007 
2015       798014     209996 
2016       659709     171435 
2017       555117     150284 
2018       352593      99054 
2019       865515     211283 
2020       618611     157457 
2021       833463     197925 
2022       622311     178127 
2023       559678     160083 
2024       618687     178241 
2025       205820      58811