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          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4107       1419 
1996         3581       1258 
1997         2331        795 
1998        23296       9821 
1999        14567       5587 
2000        40581      16845 
2001        41584      16215 
2002        32669      14604 
2003        61607      25532 
2004        48357      18550 
2005        86212      26493 
2006       111674      35663 
2007       205871      63075 
2008       126801      36064 
2009       103319      29021 
2010       119866      33266 
2011       180150      49813 
2012       167286      46287 
2013       259324      73618 
2014       645151     164536 
2015       749188     198836 
2016       575337     153567 
2017       612142     163790 
2018       406308     113854 
2019       931649     227261 
2020       697014     178952 
2021       905800     217191 
2022       675519     193245 
2023       613972     176742 
2024       155880      44604