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         2348        847 
1995         4454       1537 
1996         3608       1267 
1997         2350        801 
1998        23402       9861 
1999        14699       5641 
2000        41039      17048 
2001        42173      16466 
2002        33549      14969 
2003        62700      25982 
2004        49333      18939 
2005        88612      27187 
2006       114834      36586 
2007       210255      64275 
2008       131690      37383 
2009       107258      30086 
2010       124763      34569 
2011       187983      51976 
2012       174669      48301 
2013       271915      77045 
2014       673260     171728 
2015       771414     204906 
2016       550104     148087 
2017       472264     134913 
2018       405472     113936 
2019       806690     197385 
2020       719644     184827 
2021       935924     225256 
2022       709906     203137 
2023       565411     161762