SILSO change of management

The International Sunspot Number is produced at the Royal Observatory of Belgium since 1981 by the team of the SILSO data center ( Recently, after significant research and refurbishment of operational procedures, the International Sunspot Number was recalibrated (Clette, F. and Lefèvre, L., 2016). SILSO has been reaffirmed in 2019 as the World Data Center for the sunspot index under co-Directorship of Laure Lefèvre and Frédéric Clette.

Due to a reshuffling of responsibilities, SILSO will from now on run under the single Directorship of Laure Lefèvre, and therefore any future questions related to the SILSO management or data should be addressed to  We  take this opportunity to thank both Frédéric Clette and Laure Lefèvre for their dedication to the SILSO operations during many years.

For any other question related to this new management structure, please don't hesitate to contact the Director General of the Royal Observatory,

International Sunspot Number



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