Development and Validation of a FITS/WCS Spectral-Cube Data Product for Slit-Scanning Solar Spectroheliography

Solar slit—scanning spectroheliography produces intrinsically multidimensional data combining spatial, spectral, and temporal information. In practice, however, these data are often stored in acquisition formats tied to specific hardware or reconstruction software, limiting their reuse, comparability, and long—term archival value. This work presents the development and validation of a FITS/WCS spectral-cube data product for solar slit—scanning observations. The product is conceived as a self—contained Level—1-like representation that preserves the reconstructed spatial and spectral structure of the observation, while documenting the acquisition timing, instrumental geometry, spectral calibration, geometric corrections, and provenance needed for independent interpretation. In this context, reproducibility refers to traceability, self-contained interpretability, and software-independent reuse of the reconstructed cube, rather than to the regeneration of the raw acquisition from the final FITS file alone. The approach is not intended to define a universal standard for spectroheliographic reduction. Instead, it provides a FITS/WCS-compliant data product and a reference implementation for a representative slit—scanning configuration, with emphasis on the instrumental assumptions under which the reconstruction is valid. Quantitative validation metrics derived from a real dataset are used to assess the internal geometric, spectral, and temporal consistency of the resulting cube. The final product enables spectro—spatial analysis independently of the original acquisition software, while remaining compatible with standard astronomical FITS/WCS tools and providing a basis for future instrument-specific extensions.