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The WDC-SILSO is an activity of the Operational Directorate “Solar Physics and Space Weather” also known internationally as the Solar Influences Data analysis Center (SIDC). The SIDC is a department of the Royal Observatory of Belgium. Its mission is to preserve, develop and diffuse the knowledge of the long-term variations of solar activity, as a reference input to studies of the solar cycle mechanism and of the solar forcing on the Earth’s climate.

The work realized at WDC-SILSO is under supervision from the IAU, URSI and IAGA. They provide endorsement of the World Data Center SILSO, with regard to the scientific usefulness and quality of the sunspot data produced and archived by this data center.

Transfer to Brussels

Transfer proposal

URSI Resolutions

URSI ResolutionU21, 1982
URSI SILSO Resolution

IAGA Resolution

IAGA SILSO Resolution

IAU Resulotion

IAU SILSO Resolution

SILSO Resolution

SILSO Preservation plan


ROB infrastructure

Methods and History

Sunspot Number calculation methods
Sunspot Number history