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          936        367 
1993         1663        608 
1994         2320        837 
1995         3368       1171 
1996         3576       1256 
1997         2329        794 
1998        23258       9806 
1999        14522       5568 
2000        40463      16790 
2001        43022      16683 
2002        32476      14517 
2003        61197      25370 
2004        47953      18391 
2005        85313      26231 
2006       110780      35398 
2007       203919      62541 
2008       125083      35603 
2009       101716      28587 
2010       118247      32844 
2011       177282      49029 
2012       164548      45497 
2013       255480      72264 
2014       605455     155025 
2015       730906     193828 
2016       664767     172795 
2017       602346     162342 
2018       395848     110906 
2019       930935     228220 
2020       685612     175671 
2021       894205     214045 
2022       663801     189870 
2023       603238     173673 
2024       222079      64203