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          492        186 
1992          770        310 
1993         1356        504 
1994         2107        764 
1995         3351       1165 
1996         3564       1252 
1997         2320        791 
1998        23180       9776 
1999        14481       5552 
2000        40182      16665 
2001        41835      16260 
2002        32177      14391 
2003        60482      25099 
2004        47605      18259 
2005        83979      25833 
2006       108745      34802 
2007       199953      61477 
2008       121461      34614 
2009        99091      27878 
2010       114765      31934 
2011       170222      47123 
2012       159761      44215 
2013       240664      68380 
2014       583243     149798 
2015       705932     187256 
2016       678447     176152 
2017       578061     156237 
2018       378526     106170 
2019       905629     221688 
2020       654978     167248 
2021       872631     208100 
2022       655569     187495 
2023       598138     171144 
2024       365055     106013