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         4219       1457 
1996         3584       1259 
1997         2334        796 
1998        23298       9822 
1999        14575       5591 
2000        40624      16865 
2001        41635      16236 
2002        32738      14633 
2003        61665      25557 
2004        48430      18579 
2005        86412      26549 
2006       111929      35739 
2007       206355      63210 
2008       127276      36191 
2009       103623      29101 
2010       120212      33359 
2011       180925      50023 
2012       168025      46489 
2013       260812      73978 
2014       646596     164931 
2015       751640     199497 
2016       577089     154045 
2017       611571     163556 
2018       407630     114215 
2019       931788     227254 
2020       700240     179816 
2021       928577     222251 
2022       678328     194030 
2023       615970     177300 
2024       150333      43040