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          532        200 
1992          936        367 
1993         1669        610 
1994         2339        844 
1995         4430       1529 
1996         3605       1266 
1997         2334        796 
1998        23337       9838 
1999        14628       5614 
2000        40797      16942 
2001        41873      16338 
2002        33075      14765 
2003        62156      25765 
2004        48819      18734 
2005        87321      26808 
2006       113164      36100 
2007       208182      63707 
2008       129315      36738 
2009       104988      29476 
2010       122074      33854 
2011       184051      50876 
2012       170591      47190 
2013       266278      75502 
2014       662888     169036 
2015       775290     205417 
2016       575412     153938 
2017       570459     154950 
2018       407478     114324 
2019       927129     226313 
2020       715184     183610 
2021       927823     223185 
2022       697918     199461 
2023       634195     182477 
2024        48446      14045