While working on the upcoming CCSDS ODM V3 standard, I stumbled upon conventions differences in the LVLH (Local Vertical, Local Horizontal) definition.
What we used up to now, is consistent with the definition used by Vallado’s book section 3.3.3 and in AGI STK help, i.e. the X axis is radial (pointing away from central body) and the Z axis is aligned with orbital momentum. This local orbital frame is therefore the same as QSW, RIC (Radial, In-track, Cross-track), RTN (Radial, Transverse, Normal) and Gaussian coordinate system.
However, it seems to me everyone else is using a different convention for LVLH. This alternative convention sets Z to nadir and Y opposite to momentum (hence X is towards velocity). This definition is used in CCSDS standard through SANA registry, it is used in Wertz books, is used in FreeFlyer and is in fact also already supported in Orekit under the name VVLH. Vallado states other definitions for LVLH exist (but the alternative he cites is not exactly this one).
I think that it is better to be consistent with standards like CCSDS rather than only other software. Indeed, I guess that as AGI will implement ODM V3 they will probably adopt this convention too (I have not asked them yet). So I think I should rename VVLH into LVLH and remove the old definition of LVLH.
What do you think?