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          770        310 
1993         1356        504 
1994         1752        642 
1995         3318       1154 
1996         3428       1205 
1997         2294        784 
1998        23133       9758 
1999        14447       5538 
2000        40069      16616 
2001        40924      15944 
2002        32701      14551 
2003        60088      24950 
2004        47436      18198 
2005        83430      25666 
2006       107768      34516 
2007       198012      60958 
2008       119456      34075 
2009        98178      27632 
2010       113182      31516 
2011       167709      46443 
2012       157945      43732 
2013       235377      66953 
2014       578878     148672 
2015       699807     185567 
2016       674682     175154 
2017       575624     155463 
2018       372748     104584 
2019       898121     219570 
2020       649485     165609 
2021       868010     206954 
2022       643270     184174 
2023       586899     168009 
2024       450263     131252