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          743        301 
1993         1308        487 
1994         1675        615 
1995         3048       1064 
1996         2977       1052 
1997         1858        641 
1998        21674       9215 
1999        13409       5149 
2000        38599      15960 
2001        39425      15313 
2002        33272      14628 
2003        57738      24023 
2004        46290      17759 
2005        81370      25049 
2006       105008      33705 
2007       191767      59276 
2008       112219      32134 
2009        93067      26232 
2010       145484      39083 
2011       157876      43793 
2012       149080      41307 
2013       220988      62958 
2014       564878     143920 
2015       798817     210262 
2016       658887     171228 
2017       554518     150094 
2018       351496      98744 
2019       863297     210747 
2020       616696     156951 
2021       829641     196992 
2022       619745     177395 
2023       558652     159814 
2024       617687     177997 
2025       219856      62881