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          444        170 
1992          721        293 
1993         1283        478 
1994         1634        601 
1995         2903       1015 
1996         2895       1024 
1997         1790        620 
1998        21454       9129 
1999        12875       4962 
2000        38021      15704 
2001        39360      15259 
2002        32631      14364 
2003        56397      23508 
2004        45403      17445 
2005        79980      24646 
2006       102980      33116 
2007       187823      58222 
2008       106708      30660 
2009        89618      25302 
2010       141627      38089 
2011       151030      41944 
2012       142080      39418 
2013       215231      61377 
2014       548146     139548 
2015       795519     209342 
2016       646439     167855 
2017       544681     147424 
2018       338861      95276 
2019       851836     207963 
2020       594103     150762 
2021       804554     190423 
2022       609150     174368 
2023       548880     157078 
2024       608759     174657 
2025       523505     149409