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          492        186 
1992          767        309 
1993         1356        504 
1994         1746        640 
1995         3285       1143 
1996         3171       1118 
1997         2288        782 
1998        23078       9736 
1999        14410       5524 
2000        39958      16566 
2001        40709      15859 
2002        34325      15079 
2003        59681      24793 
2004        47270      18138 
2005        82952      25523 
2006       106986      34287 
2007       196044      60427 
2008       117775      33615 
2009        97074      27329 
2010       111655      31122 
2011       165213      45776 
2012       156280      43279 
2013       230553      65622 
2014       571747     145872 
2015       744888     195084 
2016       667753     172944 
2017       569888     153954 
2018       366769     102927 
2019       888866     217122 
2020       640834     163317 
2021       861146     205127 
2022       638856     182862 
2023       578002     165446 
2024       517965     149904