Amendment 2 to Recommendation ITU-T X.1081 changes references to ISO 31 and IEC 60027 with references to the ISO/IEC 80000-series, which supersedes these two previous standards.

This amendment also replaces the term "biosphere" with "1-m radius biosphere", as "biosphere" is classically a bigger object, around planet Earth (Sol-3).

This amendment also adds a sixth modality: "CALOR".