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          664        273 
1993         1210        454 
1994         1543        574 
1995         2521        889 
1996         2761        978 
1997         2644        902 
1998        24134       8614 
1999        12955       4938 
2000        36654      15058 
2001        41717      16390 
2002        35271      15095 
2003        57578      23562 
2004        45342      17259 
2005       304958     137295 
2006       332264     148256 
2007       193238      59803 
2008       109857      31304 
2009        90436      25274 
2010       138567      36888 
2011       146111      39741 
2012       173954      37907 
2013       229749      57904 
2014       477779     118662 
2015       722023     188952 
2016       609676     157710 
2017       516846     140588 
2018       307150      86848 
2019       811838     199003 
2020       534438     135606 
2021       723890     169838 
2022       562893     161395 
2023       515523     147668 
2024       556468     159931 
2025       532108     150853 
2026       274325      60588