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          770        310 
1993         1356        504 
1994         1752        642 
1995         3321       1155 
1996         3458       1215 
1997         2300        785 
1998        23137       9760 
1999        13527       5233 
2000        40077      16619 
2001        42110      16341 
2002        32024      14326 
2003        60123      24963 
2004        47463      18207 
2005        83490      25683 
2006       107839      34537 
2007       198094      60980 
2008       119528      34095 
2009        98265      27656 
2010       113279      31540 
2011       167927      46500 
2012       158068      43764 
2013       235579      67010 
2014       579086     148729 
2015       700036     185629 
2016       675249     175294 
2017       576001     155563 
2018       372979     104645 
2019       898461     219663 
2020       649797     165689 
2021       868331     207014 
2022       643598     184267 
2023       587239     168098 
2024       450069     131203