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          492        186 
1992          767        309 
1993         1356        504 
1994         1746        640 
1995         3285       1143 
1996         3171       1118 
1997         2288        782 
1998        23084       9739 
1999        14410       5524 
2000        39960      16567 
2001        40715      15861 
2002        34331      15082 
2003        59701      24801 
2004        47273      18139 
2005        82972      25529 
2006       107004      34292 
2007       196084      60438 
2008       117810      33625 
2009        97104      27337 
2010       111718      31138 
2011       165245      45785 
2012       156335      43293 
2013       230653      65650 
2014       571905     145910 
2015       745968     195332 
2016       668056     173010 
2017       570026     153991 
2018       366965     102981 
2019       889038     217171 
2020       641086     163388 
2021       861287     205167 
2022       638990     182899 
2023       578363     165548 
2024       515649     149185