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          503        190 
1992          936        367 
1993         1666        609 
1994         2326        839 
1995         3571       1239 
1996         3576       1256 
1997         2329        794 
1998        23263       9808 
1999        14529       5571 
2000        40476      16796 
2001        43065      16700 
2002        32502      14529 
2003        61264      25398 
2004        48003      18410 
2005        85514      26289 
2006       110932      35445 
2007       204291      62644 
2008       125425      35693 
2009       102042      28674 
2010       118547      32925 
2011       177870      49190 
2012       165728      45719 
2013       256790      72552 
2014       639544     162612 
2015       742609     196440 
2016       570845     152265 
2017       606639     163023 
2018       399876     111627 
2019       939726     230046 
2020       689783     176827 
2021       896527     214650 
2022       665342     190306 
2023       604615     174087 
2024       208310      60077