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         1672        611 
1994         2339        844 
1995         4430       1529 
1996         3605       1266 
1997         2337        797 
1998        23345       9841 
1999        14644       5620 
2000        40811      16949 
2001        41919      16358 
2002        33128      14787 
2003        62254      25805 
2004        48889      18762 
2005        87523      26866 
2006       113352      36157 
2007       208411      63770 
2008       129622      36823 
2009       105268      29552 
2010       122349      33927 
2011       184516      51000 
2012       170954      47288 
2013       266980      75697 
2014       665342     169657 
2015       777863     206100 
2016       574887     153921 
2017       557248     152829 
2018       407576     114370 
2019       924756     225842 
2020       716642     183984 
2021       929854     223653 
2022       691806     197909 
2023       637609     183462 
2024        19962       6096