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        40467      16792 
2001        43022      16683 
2002        32476      14517 
2003        61197      25370 
2004        47953      18391 
2005        85313      26231 
2006       110782      35399 
2007       203927      62543 
2008       125095      35606 
2009       101720      28588 
2010       118253      32846 
2011       177300      49034 
2012       164559      45500 
2013       255545      72273 
2014       605677     155047 
2015       731116     193856 
2016       652087     169849 
2017       602449     162355 
2018       395953     110922 
2019       930984     228231 
2020       685693     175694 
2021       894213     214047 
2022       663814     189874 
2023       603254     173677 
2024       220479      63727