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         2617        929 
1997         2492        851 
1998        23910       8542 
1999        12815       4888 
2000        36279      14898 
2001        41397      16255 
2002        34945      14951 
2003        56857      23295 
2004        44771      17053 
2005       302730     136440 
2006       330317     147523 
2007       191544      59354 
2008       107414      30655 
2009        87848      24588 
2010       135567      36115 
2011       142370      38743 
2012       169910      36822 
2013       223776      56288 
2014       470945     116852 
2015       708529     185297 
2016       598765     154740 
2017       502868     136710 
2018       300386      84954 
2019       801782     196362 
2020       525165     133086 
2021       707026     165387 
2022       549122     157521 
2023       508621     145726 
2024       548632     157701 
2025       523457     148851 
2026       369977      88239