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        40949      17007 
2001        42044      16411 
2002        33334      14875 
2003        62470      25888 
2004        49123      18853 
2005        87986      27002 
2006       113903      36322 
2007       209244      63998 
2008       130659      37103 
2009       106346      29842 
2010       123237      34158 
2011       186408      51515 
2012       172409      47681 
2013       269618      76423 
2014       669498     170738 
2015       782375     207314 
2016       572601     153497 
2017       531215     147849 
2018       411276     115455 
2019       919214     224554 
2020       723936     185906 
2021       931948     224311 
2022       697775     199613 
2023       656872     188964 
2024            4          0