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          749        303 
1993         1310        488 
1994         1692        621 
1995         3111       1085 
1996         2999       1060 
1997         1922        663 
1998        22337       9439 
1999        13620       5227 
2000        38875      16080 
2001        39657      15414 
2002        31067      13920 
2003        58249      24229 
2004        46767      17950 
2005        82198      25295 
2006       105920      33976 
2007       193631      59780 
2008       115410      32976 
2009        95094      26785 
2010       114244      31714 
2011       161761      44846 
2012       153061      42401 
2013       225780      64297 
2014       568921     145020 
2015       794467     208077 
2016       664534     172356 
2017       560791     151671 
2018       358911     100787 
2019       876098     213912 
2020       629042     160216 
2021       848767     201987 
2022       632346     181007 
2023       570525     163024 
2024       635163     182894 
2025       118761      33688