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          740        300 
1993         1296        483 
1994         1664        611 
1995         3003       1049 
1996         2959       1046 
1997         1825        632 
1998        21599       9190 
1999        13207       5078 
2000        38491      15913 
2001        39297      15265 
2002        32242      14276 
2003        57561      23960 
2004        46184      17727 
2005        81006      24953 
2006       104521      33572 
2007       191134      59112 
2008       111683      31995 
2009        92479      26080 
2010       144844      38915 
2011       156773      43508 
2012       148164      41074 
2013       219853      62660 
2014       564203     143799 
2015       798604     210237 
2016       657317     170832 
2017       553844     149925 
2018       350515      98485 
2019       862381     210555 
2020       615879     156746 
2021       828543     196729 
2022       618795     177136 
2023       557776     159563 
2024       615695     177421 
2025       224407      64182