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        21607       9193 
1999        13216       5081 
2000        38491      15913 
2001        39302      15267 
2002        32247      14278 
2003        57568      23963 
2004        46189      17729 
2005        81039      24963 
2006       104544      33578 
2007       191167      59121 
2008       111723      32006 
2009        92505      26087 
2010       144885      38926 
2011       156856      43531 
2012       148213      41086 
2013       219946      62685 
2014       564403     143850 
2015       798432     210191 
2016       657505     170878 
2017       553887     149936 
2018       350557      98496 
2019       862538     210574 
2020       615957     156765 
2021       828677     196768 
2022       618946     177178 
2023       557965     159617 
2024       616230     177575 
2025       219525      62741