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         1669        610 
1994         2326        839 
1995         3571       1239 
1996         3576       1256 
1997         2329        794 
1998        23263       9808 
1999        14529       5571 
2000        40480      16798 
2001        43075      16703 
2002        32527      14540 
2003        61294      25410 
2004        48022      18418 
2005        85557      26302 
2006       110981      35460 
2007       204397      62673 
2008       125537      35723 
2009       102138      28701 
2010       118687      32961 
2011       178069      49244 
2012       165500      45731 
2013       256136      72541 
2014       641115     162879 
2015       743880     196691 
2016       571847     152454 
2017       607976     163238 
2018       405128     112398 
2019       940639     230283 
2020       690356     176991 
2021       897440     214868 
2022       666320     190597 
2023       605417     174313 
2024       207825      59912