Historical calibration certificate issued by Kipp & Zonen for CM21 pyranometer serial number 010785. The certificate number is 024987010785. According to records maintained by the depositor, the instrument was subsequently operated at the NCAS Chilbolton Atmospheric Observatory (CAO), hosted by the Science and Technology Facilities Council (STFC). At the time its long-term measurements were supported as part of NCAS long-term science underpinning activities funded by the Natural Environment Research Council (NERC). The certificate was issued on 22 November 2021 and deposited retrospectively in 2026 to support the provenance of associated observations archived by the Centre for Environmental Data Analysis (CEDA). This record forms part of a chronological series of calibration certificates for Kipp & Zonen CM21 pyranometer serial number 010785; links to the adjacent calibration records are provided under Related works.