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          740        300 
1993         1296        483 
1994         1666        612 
1995         3006       1050 
1996         2959       1046 
1997         1828        633 
1998        21610       9194 
1999        13245       5091 
2000        38509      15921 
2001        39307      15269 
2002        32281      14290 
2003        57590      23971 
2004        46199      17733 
2005        81072      24972 
2006       104586      33590 
2007       191227      59137 
2008       111802      32026 
2009        92565      26103 
2010       144970      38948 
2011       156998      43569 
2012       148372      41124 
2013       220114      62730 
2014       564765     143912 
2015       798510     210210 
2016       657849     170964 
2017       554145     150003 
2018       350731      98543 
2019       862815     210631 
2020       616072     156798 
2021       828804     196805 
2022       619027     177203 
2023       558112     159660 
2024       616459     177644 
2025       219897      62848