Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          492        186 
1992          933        366 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2329        794 
1998        23252       9804 
1999        14522       5568 
2000        40463      16790 
2001        43022      16683 
2002        32472      14515 
2003        61188      25367 
2004        47950      18390 
2005        85303      26228 
2006       110768      35394 
2007       203892      62534 
2008       125063      35598 
2009       101708      28585 
2010       118230      32840 
2011       177263      49023 
2012       164512      45487 
2013       255411      72245 
2014       605437     155009 
2015       730817     193801 
2016       681154     176469 
2017       602372     162325 
2018       395821     110898 
2019       930913     228218 
2020       685528     175648 
2021       894098     214022 
2022       663812     189871 
2023       603103     173641 
2024       227012      65637