sot/eng_archive — comment on commit 6d269692767c5233f86a867c5f5659639c36d7e6
File: Ska/engarchive/derived/pcad.py line 721
By aarvai:

I'm surprised that this one is necessary. The other sun vectors (AOSUNSA* and AOSUNAC*) occasionally have a magnitude of zero (e.g. Safe Mode) since they come from the OBC. However, I can't foresee a situation where the sun vector based on ground-based ephemeris would do the same.