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         4442       1533 
1996         3605       1266 
1997         2340        798 
1998        23370       9850 
1999        14657       5624 
2000        40949      17007 
2001        42048      16413 
2002        33348      14881 
2003        62478      25892 
2004        49128      18855 
2005        87988      27003 
2006       113905      36323 
2007       209259      64002 
2008       130693      37112 
2009       106352      29844 
2010       123244      34160 
2011       186458      51529 
2012       172466      47696 
2013       269717      76449 
2014       669544     170749 
2015       782475     207342 
2016       572082     153370 
2017       530975     147787 
2018       411288     115458 
2019       918399     224342 
2020       724011     185926 
2021       931998     224325 
2022       697808     199622 
2023       657043     189012 
2024            4          0