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          737        299 
1993         1288        480 
1994         1655        608 
1995         2973       1039 
1996         2953       1044 
1997         1815        629 
1998        21574       9180 
1999        13088       5037 
2000        38334      15842 
2001        39203      15223 
2002        30720      13754 
2003        57325      23865 
2004        45996      17657 
2005        80681      24855 
2006       104108      33448 
2007       190441      58925 
2008       110620      31711 
2009        91882      25914 
2010       143786      38650 
2011       155252      43094 
2012       146836      40712 
2013       218308      62232 
2014       561065     143009 
2015       799456     210311 
2016       656244     170512 
2017       550897     149130 
2018       347580      97674 
2019       859466     209773 
2020       610912     155403 
2021       821630     194997 
2022       615398     176167 
2023       554560     158659 
2024       609816     175703 
2025       316753      90554