Version 1.0 of the standard has now been released.
This is available within:
Hooper, David A., Brooks, Barbara J., Garland, Wendy E., & Parton, Graham A. (2022). The National Centre for Atmospheric Science Image Metadata Standard (NCAS-IMAGE) version 1.0 (1.0). Zenodo. https://doi.org/10.5281/zenodo.6368295
For filenaming conventions and associated controlled vocabularies (e.g instrument and platform names) see NCAS-General standard.