Needed to transform position - GEOnet Names Server

pointing toward the mean vernal equinox of date (7) . In Figure A.2, the Z2- axis is a vector perpendicular to the plane of the mean equator of date, positive toward north (or F) . The Ye-axis is in the plane of the mean equator of date, completing a right-handed orthogona 1 coordinate system (90 degrees east of X2). ................
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