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         1481        553 
1995         2353        831 
1996         2614        928 
1997         2486        849 
1998        23910       8542 
1999        12807       4885 
2000        36263      14891 
2001        41380      16248 
2002        34927      14943 
2003        56834      23285 
2004        44744      17042 
2005       302611     136390 
2006       330245     147495 
2007       191492      59341 
2008       107384      30647 
2009        87789      24572 
2010       135525      36104 
2011       142265      38715 
2012       169851      36805 
2013       223664      56256 
2014       470796     116812 
2015       708305     185233 
2016       598586     154695 
2017       502596     136636 
2018       300255      84919 
2019       801526     196299 
2020       524991     133038 
2021       706565     165291 
2022       548843     157444 
2023       508421     145669 
2024       548368     157630 
2025       523298     148806 
2026       368160      87652