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         2634        935 
1997         2509        857 
1998        23951       8557 
1999        12862       4905 
2000        36402      14951 
2001        41466      16286 
2002        35039      14994 
2003        57076      23380 
2004        44928      17115 
2005       303434     136721 
2006       330803     147709 
2007       191992      59474 
2008       108155      30851 
2009        88715      24817 
2010       136533      36364 
2011       143482      39044 
2012       170990      37114 
2013       225494      56770 
2014       472671     117302 
2015       712190     186266 
2016       600478     155177 
2017       505981     137582 
2018       302093      85432 
2019       805258     197301 
2020       528658     133994 
2021       712649     166843 
2022       553496     158745 
2023       510867     146361 
2024       551088     158403 
2025       525231     149013 
2026       352099      82854