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          735        298 
1993         1283        478 
1994         1655        608 
1995         2948       1030 
1996         2944       1041 
1997         1813        628 
1998        21560       9174 
1999        13067       5029 
2000        38254      15808 
2001        39159      15206 
2002        30669      13733 
2003        57187      23812 
2004        45864      17607 
2005        80557      24817 
2006       103893      33385 
2007       190033      58815 
2008       110052      31557 
2009        91517      25816 
2010       143322      38532 
2011       154472      42879 
2012       145902      40458 
2013       217694      62062 
2014       558698     142370 
2015       798274     209974 
2016       654996     170167 
2017       549829     148829 
2018       345783      97178 
2019       858373     209454 
2020       607654     154535 
2021       817666     193969 
2022       613897     175741 
2023       553544     158382 
2024       608379     175172 
2025       365827     105115