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15.5.828 xys00a

xys00a, jdtt, x, y, s

[SOFA] Returns the Celestial Intermediate Pole x, y coordinates and the CIO locator s (in radians) for TT Julian Date jdtt, based on the IAU 2000A precession-nutation model. The output variables have the same dimensions as jdtt.

The x and y coordinates are those of the unit vector towards the celestial intermediate pole. They represent the combined effects of frame bias, precession, and nutation. The CIO locator positions the Celestial Intermediate Origin on the equator of the CIP.

See also: Astronomical Coordinate Calculations