National Centers for Environmental Information / National Operational Model Archive and Distribution System Catalog https://www.ncei.noaa.gov/thredds/catalog/cdr-solar-spectral-irradiance/catalog.html

Dataset Size Last Modified
     Folder  Solar Spectral Irradiance: File access   --
         Folder  ancillary-data/   --
         Folder  daily/   --
         Folder  high-resolution/   --
         Folder  monthly/   --
         Folder  standard-resolution/   --
         Folder  yearly/   --

NCEI THREDDS Server at NCEI see Info
Documentation