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         1490        556 
1995         2368        836 
1996         2631        934 
1997         2509        857 
1998        23951       8557 
1999        12862       4905 
2000        36402      14951 
2001        41466      16286 
2002        35036      14993 
2003        57074      23379 
2004        44926      17114 
2005       303425     136718 
2006       330800     147708 
2007       191972      59468 
2008       108116      30841 
2009        88699      24813 
2010       136457      36344 
2011       143421      39027 
2012       170946      37102 
2013       225403      56745 
2014       472604     117284 
2015       712121     186248 
2016       600524     155189 
2017       505847     137544 
2018       302020      85411 
2019       805172     197277 
2020       528569     133969 
2021       712498     166800 
2022       553309     158691 
2023       510847     146355 
2024       551010     158380 
2025       525158     148995 
2026       354274      83379