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          721        293 
1993         1280        477 
1994         1628        599 
1995         2891       1011 
1996         2889       1022 
1997         1784        618 
1998        21444       9124 
1999        12854       4954 
2000        37864      15635 
2001        39055      15140 
2002        34805      15084 
2003        56592      23540 
2004        45066      17322 
2005        79558      24515 
2006       102442      32954 
2007       186612      57897 
2008       104716      30122 
2009        88142      24913 
2010       140609      37821 
2011       148573      41275 
2012       139411      38691 
2013       213168      60800 
2014       540713     137600 
2015       796294     209620 
2016       634301     163999 
2017       544752     147543 
2018       334216      94010 
2019       846087     206763 
2020       584400     148055 
2021       795906     188099 
2022       603536     172779 
2023       543853     155641 
2024       600149     172447 
2025       568166     162462