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          532        200 
1992          936        367 
1993         1669        610 
1994         2333        842 
1995         4425       1527 
1996         3602       1265 
1997         2340        798 
1998        23330       9835 
1999        14615       5608 
2000        40721      16911 
2001        41793      16303 
2002        32930      14708 
2003        61953      25678 
2004        48644      18666 
2005        86958      26709 
2006       112642      35948 
2007       207600      63548 
2008       128489      36515 
2009       104490      29339 
2010       121441      33686 
2011       182998      50590 
2012       169706      46944 
2013       264649      75047 
2014       660313     168358 
2015       772645     204712 
2016       577985     154237 
2017       590275     158000 
2018       406556     114056 
2019       929195     226815 
2020       712196     182794 
2021       924427     222330 
2022       691686     197757 
2023       625881     180107 
2024       100985      29240