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          468        178 
1992          740        300 
1993         1296        483 
1994         1661        610 
1995         3000       1048 
1996         2959       1046 
1997         1822        631 
1998        21599       9190 
1999        13168       5065 
2000        38458      15898 
2001        39285      15260 
2002        32201      14258 
2003        57512      23939 
2004        46151      17715 
2005        80929      24928 
2006       104434      33545 
2007       190978      59069 
2008       111407      31921 
2009        92321      26037 
2010       144593      38858 
2011       156427      43414 
2012       147826      40978 
2013       219450      62550 
2014       563542     143636 
2015       797900     210065 
2016       656439     170617 
2017       553065     149737 
2018       349928      98322 
2019       861373     210293 
2020       614674     156442 
2021       826719     196286 
2022       618130     176939 
2023       557341     159390 
2024       613910     176874 
2025       241907      69251