World Data Center for the Sunspot Index and Long-term Solar Observations - Royal Observatory of Belgium (ROB)
Updated 2025-10-14
What is the WDC–SILSO?
The World Data Center for the Sunspot Index and Long-term Solar Observations (WDC–SILSO) at the Royal Observatory of Belgium produces, curates, and preserves the International Sunspot Number (SN)—the longest continuous record of solar activity— supporting heliophysics research, space-weather operations, climate-adjacent studies, education, and outreach.
Cadences: EISN (preliminary) every 5 minutes from WOLF entries; provisional SN monthly; final SN quarterly (trimester consolidation). Products include daily, monthly, monthly-smoothed, and yearly SN (hemispheric and total), graphics, and short-term forecasts.
Governance, mandate & roles
WDC–SILSO operates under international mandates (IAU, IUGG/IAGA, URSI) and a Letter of Agreement with the World Data System (2012; reconfirmed 2023), with hosting and institutional support from the ROB.
Roles & responsibilities
- Direction (WDC–SILSO) — strategy, policy, approval of releases & recalibrations.
- Release Manager — configuration control (CVS), version tags, checksums, publication to web.
- Data Curator — observer onboarding & QC, trimester finalization, documentation & changelogs.
- Observer Network Coordinator — Website maintenance, WOLF content, training & support, feedback loop with observers.
- ROB ICT Operations — compute/storage/web, backups, security, monitoring; restores on request.
- Advisory Panel — external scientific & operational guidance.
Decision-making & change control
Method or pipeline changes are proposed by curator/engineer, reviewed by the Director, tested on staging, then released by the Release Manager with version tags, checksums, and a public changelog. Prior versions remain available for reproducibility, and major releases carry DOIs (e.g., SNV1, SNV2).
Organigram
Designated Community
Heliophysics & research
Python/R/MATLAB/IDL; CSV/ASCII with error bars; versioned DOIs; metadata.
Space-weather operations
Clear status labels (preliminary, provisional, final); stable URLs.
Adjacent sciences
Long-term variability & correlations; citable versions; documented methods.
Observer network
WOLF web entry with client-side checks; station codes; feedback & training resources.
Outreach & education
PNG graphics; classroom-friendly CSV extracts.
Curation levels & products
- Level B — Acquisition & QC: daily groups and spots per hemisphere via WOLF; DB constraints; cross-observer checks; EISN every 5 min.
- Level C — Standard index: homogenization and aggregation to SN (daily, monthly, monthly-smoothed, yearly; hemispheric & total). Provisional monthly; Definitives quarterly.
- Level D — Recalibration & historical reconstruction: versioned releases with DOIs (e.g., SNV1, SNV2), methods documented & peer-reviewed.
Formats & access
Base data are provided as ASCII and CSV. Download pages include schema, units, and error bars. License: CC-BY-NC. Please cite the SN version and DOI.
Preservation & integrity
Backups and long-term preservation follow ROB ICT and Smals practices. Releases include checksum manifests and undergo scheduled fixity checks. The preservation plan and data policy are public.
How to cite
“WDC–SILSO, Royal Observatory of Belgium, International Sunspot Number (SN), Version 2, DOI: 10.24414/qnza-ac80 (CC-BY-NC).”
