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          532        200 
1992          936        367 
1993         1678        613 
1994         2342        845 
1995         4442       1533 
1996         3605       1266 
1997         2340        798 
1998        23370       9850 
1999        14657       5624 
2000        40949      17007 
2001        42058      16417 
2002        33356      14884 
2003        62484      25895 
2004        49133      18857 
2005        88023      27013 
2006       113997      36349 
2007       209317      64018 
2008       130759      37130 
2009       106428      29863 
2010       123382      34196 
2011       186670      51584 
2012       172578      47726 
2013       269933      76507 
2014       669928     170851 
2015       782817     207437 
2016       572392     153456 
2017       530667     147797 
2018       411512     115530 
2019       919048     224525 
2020       724350     186018 
2021       932272     224404 
2022       698286     199759 
2023       658726     189489 
2024            4          0