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          749        303 
1993         1308        487 
1994         1686        619 
1995         3099       1081 
1996         2986       1055 
1997         1896        654 
1998        22333       9437 
1999        13604       5221 
2000        38809      16050 
2001        39578      15378 
2002        30989      13883 
2003        58102      24171 
2004        46640      17896 
2005        81989      25232 
2006       105645      33897 
2007       193099      59638 
2008       114661      32780 
2009        94577      26645 
2010       113816      31604 
2011       160876      44604 
2012       154936      43079 
2013       227809      65022 
2014       572238     146025 
2015       801345     209944 
2016       670852     174271 
2017       562744     152356 
2018       361932     101783 
2019       875294     213822 
2020       626150     159445 
2021       845182     201053 
2022       629956     180311 
2023       566427     161978 
2024       631866     181922 
2025       138680      39268