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          444        170 
1992          724        294 
1993         1283        478 
1994         1640        603 
1995         2912       1018 
1996         2901       1026 
1997         1793        621 
1998        21472       9137 
1999        12936       4983 
2000        38079      15730 
2001        39763      15397 
2002        31880      14119 
2003        56575      23575 
2004        45500      17479 
2005        80095      24681 
2006       103174      33173 
2007       188329      58359 
2008       107443      30860 
2009        90055      25423 
2010       141921      38167 
2011       151782      42147 
2012       142975      39661 
2013       215715      61512 
2014       550421     140148 
2015       794089     208897 
2016       648306     168356 
2017       545296     147587 
2018       340249      95647 
2019       851725     207847 
2020       596457     151424 
2021       807029     191088 
2022       609378     174459 
2023       549698     157315 
2024       605848     174181 
2025       479020     136935