Celestial Ephemeris Origin

Acronym: CEO

The CEO is the point on the true equator used to measure the rotation of the Earth and the origin of intermediate right ascension. The CEO replaces the true equinox.

The CEO was located on the true (CIP) equator of J2000.0 at a point 2.012 mas from the ICRS prime meridian (consistent the conventional definition of the Earth Rotation Angle), at right ascension 00^h 00^m 00^s.00013416 in the ICRS.

As the true equator moves in space, the path of the CEO in space is such that the point has no instantaneous east-west velocity along the true equator. In contrast, the equinox has instantaneous velocity along the equator. After 1 century, the CEO is still within 70 mas of the ICRS prime meridian, whereas the equinox has moved nearly 1.4 degrees.

The CEO is sometimes also called the Non-Rotating Origin (NRO).

Related terms:

• International Celestial Reference System (ICRS)