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          489        185 
1992          767        309 
1993         1356        504 
1994         1746        640 
1995         3285       1143 
1996         3156       1113 
1997         2288        782 
1998        23078       9736 
1999        14410       5524 
2000        39958      16566 
2001        40709      15859 
2002        31958      14290 
2003        59681      24793 
2004        47262      18135 
2005        82934      25517 
2006       106986      34287 
2007       195981      60410 
2008       117722      33601 
2009        97022      27314 
2010       111632      31116 
2011       165154      45760 
2012       156223      43264 
2013       230387      65576 
2014       565533     144562 
2015       744662     195020 
2016       667638     172913 
2017       569742     153915 
2018       366620     102887 
2019       888643     217065 
2020       640499     163234 
2021       860942     205082 
2022       638784     182841 
2023       577795     165385 
2024       524345     151584