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         1755        643 
1995         3321       1155 
1996         3474       1221 
1997         2300        785 
1998        23151       9765 
1999        13533       5235 
2000        40077      16619 
2001        42117      16344 
2002        32028      14328 
2003        60134      24967 
2004        47468      18209 
2005        83515      25691 
2006       107873      34547 
2007       198234      61017 
2008       119605      34116 
2009        98301      27666 
2010       113357      31561 
2011       168023      46525 
2012       158144      43786 
2013       235857      67088 
2014       579210     148763 
2015       700339     185700 
2016       675570     175374 
2017       576252     155626 
2018       373195     104706 
2019       898885     219776 
2020       650067     165765 
2021       868566     207078 
2022       643837     184335 
2023       586824     167991 
2024       447869     130541