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        23368       9849 
1999        14654       5623 
2000        40913      16993 
2001        42020      16401 
2002        33309      14864 
2003        62455      25882 
2004        49094      18842 
2005        87925      26985 
2006       113868      36312 
2007       209206      63988 
2008       130582      37082 
2009       106304      29831 
2010       123143      34133 
2011       186320      51491 
2012       172315      47656 
2013       269500      76391 
2014       669272     170679 
2015       782171     207264 
2016       573423     153693 
2017       533297     148286 
2018       411209     115434 
2019       921057     225046 
2020       723683     185837 
2021       931840     224279 
2022       697508     199535 
2023       653994     188136 
2024            4          0