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          471        179 
1992          746        302 
1993         1308        487 
1994         1684        618 
1995         3093       1079 
1996         2980       1053 
1997         1869        645 
1998        22153       9376 
1999        13578       5209 
2000        38731      16013 
2001        39522      15354 
2002        31204      13946 
2003        57922      24100 
2004        46495      17839 
2005        81737      25159 
2006       105390      33819 
2007       192444      59461 
2008       113548      32490 
2009        93902      26459 
2010       120810      33273 
2011       159520      44235 
2012       150770      41775 
2013       223358      63621 
2014       568413     144797 
2015       812714     213071 
2016       664243     172309 
2017       557223     150657 
2018       354534      99577 
2019       869928     212331 
2020       622312     158425 
2021       839651     199600 
2022       626162     179220 
2023       562510     160873 
2024       625669     180194 
2025       187420      53272