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         2016        733 
1995         3339       1161 
1996         3562       1251 
1997         2320        791 
1998        23173       9774 
1999        14481       5552 
2000        40142      16648 
2001        45680      17536 
2002        32134      14373 
2003        60371      25057 
2004        47560      18242 
2005        83855      25795 
2006       108517      34736 
2007       199602      61383 
2008       121086      34512 
2009        98910      27827 
2010       114444      31850 
2011       169687      46977 
2012       159437      44127 
2013       239600      68092 
2014       582134     149517 
2015       704628     186894 
2016       677915     176045 
2017       576772     155972 
2018       377673     105930 
2019       904230     221268 
2020       653539     166847 
2021       871879     207907 
2022       646503     185105 
2023       595035     170113 
2024       372156     108211