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         2337        797 
1998        23370       9850 
1999        14657       5624 
2000        40920      16996 
2001        42020      16401 
2002        33313      14866 
2003        62457      25883 
2004        49100      18845 
2005        87956      26995 
2006       113871      36313 
2007       209221      63992 
2008       130606      37089 
2009       106315      29834 
2010       123180      34143 
2011       186365      51503 
2012       172335      47662 
2013       269524      76397 
2014       669382     170707 
2015       782237     207281 
2016       573306     153665 
2017       532477     148124 
2018       411195     115430 
2019       920462     224884 
2020       723752     185856 
2021       931879     224291 
2022       697620     199568 
2023       655454     188557 
2024            4          0