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          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         3841       1330 
1996         3578       1257 
1997         2331        795 
1998        23277       9814 
1999        14551       5581 
2000        40545      16828 
2001        45757      17604 
2002        32624      14585 
2003        61499      25490 
2004        48230      18497 
2005        86023      26435 
2006       111458      35600 
2007       205463      62962 
2008       126455      35969 
2009       103002      28931 
2010       119602      33200 
2011       179493      49633 
2012       166768      46146 
2013       258233      73324 
2014       642346     163779 
2015       746157     198002 
2016       573910     153180 
2017       611782     163925 
2018       405452     113621 
2019       934997     228305 
2020       697274     179041 
2021       904641     216847 
2022       673028     192529 
2023       611666     176100 
2024       159814      45643