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         4416       1524 
1996         3593       1262 
1997         2337        797 
1998        23319       9830 
1999        14590       5597 
2000        40643      16874 
2001        41657      16247 
2002        32787      14652 
2003        61720      25581 
2004        48493      18605 
2005        86598      26602 
2006       112110      35791 
2007       206713      63308 
2008       127601      36276 
2009       103871      29169 
2010       120557      33452 
2011       181535      50191 
2012       168560      46633 
2013       262233      74365 
2014       652822     166451 
2015       759533     201445 
2016       578993     154433 
2017       609171     162814 
2018       407125     114104 
2019       930840     226985 
2020       702361     180386 
2021       967225     230859 
2022       685349     195996 
2023       618558     178008 
2024       138432      39665