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         1283        478 
1994         1655        608 
1995         2948       1030 
1996         2944       1041 
1997         1813        628 
1998        21556       9172 
1999        13067       5029 
2000        38245      15804 
2001        39154      15204 
2002        30669      13733 
2003        57179      23809 
2004        45864      17607 
2005        80557      24817 
2006       103893      33385 
2007       190021      58812 
2008       110023      31549 
2009        91499      25811 
2010       143296      38526 
2011       154459      42875 
2012       145866      40448 
2013       217669      62055 
2014       558605     142344 
2015       798089     209923 
2016       654869     170133 
2017       549739     148805 
2018       345767      97174 
2019       858292     209432 
2020       607546     154504 
2021       817513     193925 
2022       613834     175723 
2023       553521     158375 
2024       608306     175151 
2025       365105     104950