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          735        298 
1993         1285        479 
1994         1655        608 
1995         2948       1030 
1996         2944       1041 
1997         1813        628 
1998        21562       9175 
1999        13074       5032 
2000        38264      15812 
2001        39174      15211 
2002        30679      13737 
2003        57214      23822 
2004        45901      17621 
2005        80574      24822 
2006       103918      33393 
2007       190130      58841 
2008       110151      31585 
2009        91563      25828 
2010       143438      38560 
2011       154597      42913 
2012       146150      40523 
2013       217787      62087 
2014       559074     142471 
2015       798432     210012 
2016       655204     170227 
2017       550211     148909 
2018       346036      97250 
2019       858676     209541 
2020       608199     154684 
2021       818325     194127 
2022       614122     175806 
2023       553720     158432 
2024       608077     175199 
2025       357446     102535