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          471        179 
1992          743        301 
1993         1308        487 
1994         1684        618 
1995         3081       1075 
1996         2980       1053 
1997         1866        644 
1998        21954       9309 
1999        13562       5203 
2000        38678      15990 
2001        39480      15337 
2002        47187      19269 
2003        57823      24060 
2004        46407      17805 
2005        81580      25112 
2006       105245      33775 
2007       192132      59376 
2008       112863      32306 
2009        93550      26363 
2010       133298      36269 
2011       158730      44021 
2012       150001      41560 
2013       222122      63279 
2014       565790     144144 
2015       798611     210087 
2016       658992     171177 
2017       554801     150211 
2018       353032      99179 
2019       866515     211534 
2020       619595     157726 
2021       834980     198291 
2022       623150     178364 
2023       560608     160348 
2024       621800     179120 
2025       206656      59059