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         2953       1044 
1997         1822        631 
1998        21596       9189 
1999        13152       5059 
2000        38438      15889 
2001        39268      15253 
2002        31586      14051 
2003        57482      23927 
2004        46108      17700 
2005        80889      24917 
2006       104348      33520 
2007       190894      59047 
2008       111250      31879 
2009        92243      26015 
2010       144410      38810 
2011       156252      43366 
2012       147605      40916 
2013       219276      62501 
2014       563069     143510 
2015       798747     210214 
2016       656458     170591 
2017       552474     149588 
2018       349594      98230 
2019       860823     210146 
2020       613819     156209 
2021       825729     195999 
2022       617399     176735 
2023       556509     159205 
2024       613195     176667 
2025       289046      83105