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          468        178 
1992          740        300 
1993         1296        483 
1994         1661        610 
1995         3000       1048 
1996         2956       1045 
1997         1822        631 
1998        21596       9189 
1999        13161       5062 
2000        38443      15891 
2001        39270      15254 
2002        32171      14246 
2003        57482      23927 
2004        46114      17702 
2005        80896      24919 
2006       104361      33524 
2007       190910      59051 
2008       111276      31886 
2009        92254      26018 
2010       144448      38820 
2011       156270      43371 
2012       147623      40921 
2013       219322      62515 
2014       563129     143527 
2015       798208     210107 
2016       656337     170570 
2017       552576     149615 
2018       349638      98241 
2019       860798     210139 
2020       613877     156225 
2021       825942     196063 
2022       617495     176765 
2023       556558     159219 
2024       613238     176680 
2025       282747      81259