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         2339        844 
1995         4439       1532 
1996         3605       1266 
1997         2337        797 
1998        23368       9849 
1999        14654       5623 
2000        40892      16984 
2001        42000      16392 
2002        33278      14850 
2003        62401      25862 
2004        49030      18817 
2005        87837      26958 
2006       113724      36267 
2007       209034      63940 
2008       130396      37032 
2009       106007      29752 
2010       122962      34088 
2011       186042      51415 
2012       171870      47534 
2013       269093      76278 
2014       668518     170486 
2015       781299     207037 
2016       573359     153670 
2017       537964     149258 
2018       411350     115449 
2019       925748     226220 
2020       722997     185656 
2021      1159180     269514 
2022       696559     199254 
2023       648117     186477