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         3452       1213 
1997         2294        784 
1998        23137       9760 
1999        14453       5541 
2000        40080      16620 
2001        42107      16340 
2002        32027      14327 
2003        60123      24963 
2004        47455      18204 
2005        83472      25678 
2006       107826      34533 
2007       198071      60974 
2008       119506      34089 
2009        98233      27647 
2010       113261      31535 
2011       167873      46486 
2012       158052      43760 
2013       235521      66994 
2014       579017     148711 
2015       699992     185617 
2016       675185     175279 
2017       575956     155549 
2018       372951     104639 
2019       898416     219650 
2020       649745     165676 
2021       868279     207000 
2022       643529     184248 
2023       587181     168080 
2024       450471     131307