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          532        200 
1992          936        367 
1993         1678        613 
1994         2342        845 
1995         4448       1535 
1996         3605       1266 
1997         2340        798 
1998        23370       9850 
1999        14665       5627 
2000        40965      17015 
2001        42086      16430 
2002        33399      14904 
2003        62544      25918 
2004        49216      18892 
2005        88160      27055 
2006       114179      36403 
2007       209565      64087 
2008       130958      37184 
2009       106630      29917 
2010       123698      34280 
2011       187185      51724 
2012       173061      47860 
2013       270506      76658 
2014       670791     171084 
2015       784039     207766 
2016       569768     152814 
2017       529610     147656 
2018       412238     115729 
2019       914168     223330 
2020       725417     186310 
2021       933482     224665 
2022       701814     200760 
2023       656299     188774 
2024            3          0