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        38264      15812 
2001        39172      15210 
2002        30676      13736 
2003        57201      23817 
2004        45883      17614 
2005        80560      24818 
2006       103902      33388 
2007       190058      58822 
2008       110084      31566 
2009        91536      25821 
2010       143349      38538 
2011       154497      42886 
2012       146063      40490 
2013       217733      62073 
2014       558799     142397 
2015       798356     209996 
2016       655099     170192 
2017       549911     148846 
2018       345886      97205 
2019       858484     209487 
2020       607805     154575 
2021       817900     194026 
2022       613964     175761 
2023       553587     158394 
2024       608446     175192 
2025       365617     105034