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          468        178 
1992          743        301 
1993         1308        487 
1994         1678        616 
1995         3051       1065 
1996         2980       1053 
1997         1860        642 
1998        21679       9217 
1999        13492       5177 
2000        38620      15966 
2001        39445      15321 
2002        32594      14403 
2003        57753      24029 
2004        46335      17777 
2005        81419      25063 
2006       105081      33726 
2007       191851      59298 
2008       112371      32176 
2009        93162      26259 
2010       141242      38127 
2011       158057      43842 
2012       149388      41390 
2013       221213      63021 
2014       564991     143940 
2015       798526     210159 
2016       659340     171346 
2017       554893     150194 
2018       351751      98814 
2019       863975     210885 
2020       617372     157118 
2021       830723     197264 
2022       620182     177512 
2023       558656     159789 
2024       617699     177962 
2025       213727      61093