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          503        190 
1992          936        367 
1993         1666        609 
1994         2326        839 
1995         3418       1188 
1996         3576       1256 
1997         2329        794 
1998        23263       9808 
1999        14524       5569 
2000        40476      16796 
2001        43050      16693 
2002        32486      14522 
2003        61223      25380 
2004        47963      18395 
2005        85370      26248 
2006       110811      35409 
2007       204023      62569 
2008       125158      35623 
2009       101788      28604 
2010       118291      32857 
2011       177483      49083 
2012       164828      45557 
2013       256041      72345 
2014       607018     155182 
2015       729800     193434 
2016       600609     158631 
2017       603225     162484 
2018       396874     111077 
2019       931858     228386 
2020       686247     175823 
2021       894728     214182 
2022       664263     190003 
2023       603468     173761 
2024       220626      63769