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         2953       1032 
1996         2947       1042 
1997         1813        628 
1998        21564       9176 
1999        13079       5034 
2000        38276      15817 
2001        39174      15211 
2002        30686      13740 
2003        57224      23826 
2004        45916      17627 
2005        80601      24829 
2006       103946      33401 
2007       190199      58859 
2008       110247      31610 
2009        91621      25843 
2010       143511      38578 
2011       154705      42943 
2012       146336      40575 
2013       217895      62118 
2014       559353     142547 
2015       798784     210103 
2016       655324     170257 
2017       550477     148981 
2018       346324      97326 
2019       858702     209549 
2020       608730     154832 
2021       818801     194246 
2022       614349     175870 
2023       553869     158473 
2024       608352     175280 
2025       353738     101341