The ITU-R and 3GPP standards behind HAPIS, and a tracker for revisions that affect HAPS link budgets and NTN models.
The HAPIS engine implements ITU-R P.525, P.676, P.838-3, P.840 and P.2108, alongside 3GPP TR 38.811, 38.821 and 38.822.
A monitoring feed for revisions to these standards is in development and isn't live yet — we won't post updates we haven't verified.
For how each standard maps to engine output today, see the standards mapping.