Year Observations     Objects
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           12          6 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          216         77 
1991          856        306 
1992          656        270 
1993         1176        442 
1994         1484        554 
1995         2353        831 
1996         2623        931 
1997         2495        852 
1998        23922       8547 
1999        12830       4893 
2000        36332      14921 
2001        41423      16267 
2002        34967      14961 
2003        56899      23312 
2004        44801      17064 
2005       302928     136510 
2006       330417     147556 
2007       191687      59392 
2008       107634      30712 
2009        88160      24670 
2010       135819      36178 
2011       142717      38836 
2012       170205      36903 
2013       224215      56414 
2014       471432     116988 
2015       709658     185606 
2016       599275     154862 
2017       503746     136950 
2018       300863      85090 
2019       802910     196657 
2020       526441     133406 
2021       708640     165802 
2022       550300     157851 
2023       509271     145899 
2024       549398     157918 
2025       522438     148479 
2026       368562      87865