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         2371        837 
1996         2646        939 
1997         2509        857 
1998        23957       8559 
1999        12865       4906 
2000        36438      14967 
2001        41486      16295 
2002        35058      15003 
2003        57094      23387 
2004        44982      17133 
2005       303598     136785 
2006       330951     147761 
2007       192128      59509 
2008       108304      30890 
2009        88918      24871 
2010       136692      36403 
2011       143783      39121 
2012       171283      37194 
2013       225872      56869 
2014       473163     117430 
2015       713005     186481 
2016       600878     155284 
2017       506681     137775 
2018       302480      85538 
2019       805862     197466 
2020       529293     134173 
2021       713721     167134 
2022       554321     158975 
2023       511264     146469 
2024       551551     158533 
2025       526017     149248 
2026       329547      76530