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          444        170 
1992          724        294 
1993         1283        478 
1994         1640        603 
1995         2909       1017 
1996         2898       1025 
1997         1790        620 
1998        21463       9133 
1999        12913       4975 
2000        38059      15721 
2001        39683      15369 
2002        32887      14453 
2003        56505      23549 
2004        45474      17470 
2005        80034      24662 
2006       103071      33144 
2007       188131      58305 
2008       107129      30775 
2009        89851      25367 
2010       141781      38130 
2011       151486      42068 
2012       142589      39556 
2013       215545      61463 
2014       549321     139871 
2015       794460     209015 
2016       647446     168129 
2017       544964     147500 
2018       339507      95442 
2019       851625     207837 
2020       595251     151087 
2021       805814     190757 
2022       608944     174328 
2023       549212     157180 
2024       605424     174059 
2025       507043     144533