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          535        201 
1992          936        367 
1993         1690        617 
1994         2360        851 
1995         4496       1551 
1996         3614       1269 
1997         2362        805 
1998        23428       9871 
1999        14735       5656 
2000        41175      17110 
2001        42330      16525 
2002        33634      15009 
2003        62937      26078 
2004        49537      19012 
2005        89028      27312 
2006       115497      36776 
2007       211158      64515 
2008       132659      37643 
2009       108225      30346 
2010       125685      34816 
2011       189298      52331 
2012       176441      48784 
2013       273621      77513 
2014       675964     172453 
2015       774749     205803 
2016       552883     148839 
2017       475100     135713 
2018       407830     114590 
2019       810043     198238 
2020       721874     185445 
2021       938628     225864 
2022       713751     204186 
2023       547768     156681