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          767        309 
1993         1356        504 
1994         1746        640 
1995         3291       1145 
1996         3243       1142 
1997         2288        782 
1998        23093       9743 
1999        14418       5527 
2000        39977      16575 
2001        40802      15894 
2002        32316      14412 
2003        59814      24844 
2004        47317      18155 
2005        83063      25556 
2006       107111      34324 
2007       196440      60534 
2008       118053      33691 
2009        97337      27401 
2010       111911      31187 
2011       165662      45898 
2012       156638      43374 
2013       231353      65848 
2014       575264     146720 
2015       750910     196472 
2016       669956     173468 
2017       571315     154318 
2018       367942     103250 
2019       890652     217584 
2020       643141     163947 
2021       863104     205623 
2022       639972     183180 
2023       579450     165901 
2024       513065     148313