Year Observations     Objects
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
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          219         78 
1991          861        308 
1992          675        277 
1993         1222        458 
1994         1581        587 
1995         2705        950 
1996         2802        992 
1997         2768        943 
1998        24401       8713 
1999        13179       5023 
2000        37211      15312 
2001        42234      16608 
2002        35775      15310 
2003        58456      23916 
2004        45997      17510 
2005       308649     138844 
2006       335244     149496 
2007       195007      60267 
2008       111848      31833 
2009        92623      25863 
2010       140839      37486 
2011       149702      40702 
2012       177289      38812 
2013       233751      59012 
2014       531086     130444 
2015       756342     197040 
2016       626569     161704 
2017       525361     142812 
2018       313304      88551 
2019       821573     201362 
2020       543062     137717 
2021       737149     172769 
2022       571183     163724 
2023       522024     149512 
2024       566026     162653 
2025       547859     155223 
2026       245619      52131