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         2339        844 
1995         4439       1532 
1996         3605       1266 
1997         2340        798 
1998        23370       9850 
1999        14657       5624 
2000        40941      17005 
2001        42038      16408 
2002        33334      14875 
2003        62463      25885 
2004        49108      18848 
2005        87964      26997 
2006       113893      36319 
2007       209225      63993 
2008       130648      37100 
2009       106329      29838 
2010       123192      34146 
2011       186374      51506 
2012       172359      47669 
2013       269565      76408 
2014       669448     170723 
2015       782308     207299 
2016       573181     153631 
2017       531638     147948 
2018       411268     115446 
2019       919965     224753 
2020       723852     185882 
2021       931908     224300 
2022       697686     199588 
2023       655459     188555 
2024            4          0