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          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4422       1526 
1996         3593       1262 
1997         2337        797 
1998        23319       9830 
1999        14592       5598 
2000        40643      16874 
2001        41657      16247 
2002        32787      14652 
2003        61720      25581 
2004        48499      18607 
2005        86611      26606 
2006       112123      35795 
2007       206737      63314 
2008       127612      36279 
2009       103895      29175 
2010       120594      33462 
2011       181575      50202 
2012       168593      46643 
2013       262306      74386 
2014       653065     166512 
2015       759921     201544 
2016       578938     154412 
2017       609610     162725 
2018       406862     114024 
2019       932632     227410 
2020       705390     181017 
2021       917279     220405 
2022       686867     196418 
2023       618854     178088 
2024       139073      39836