References

Name Description and Reference Nomenclature isDefault Units/Type
ICRFyyyy The International Celestial Reference Frame is the realization of the International Celestial Reference System per IERS conventions 2003 and 2010 (McCarthy et al.) and is the standard Barycentric reference system. The ICRF is periodically reevaluated, such that each realization must be annotated (i.e., year "yyyy" as 2000). The ICRF axes are defined as the inertial (i.e., kinematically non-rotating) axes associated with a general relativity frame centered at the solar system barycenter (often called the BCRF). The IAU (International Astronomical Union) is the authority for the definition of the ICRF. The ICRF frame is realized by its transformational algorithm between it and the Earth Fixed frame. Note that the term 'ICRF coordinate system' is not restricted to the system whose origin is at the solar system barycenter--- rather, the term describes a coordinate system whose origin is determined from context (i.e., for a central body, its center of mass location) whose axes are aligned with the axes of the BCRF. In fact, the IAU uses the term GCRF to refer to the system with origin at the geocenter (i.e Earth's center of mass location) with axes parallel to the BCRF. [Note that 'aligned' here refers to directions in Euclidean space - not in a curved space governed by general relativity.] e.g., ICRF2000
ITRFyyyy The rotating Earth-fixed frame obtained by a transformation from ICRF which includes precession, nutation, and rotation effects, as well as pole wander and frame corrections. International Terrestrial Reference Frame solution as of year "yyyy" (e.g. 1993, 1997, 2000). Standard 1.5s increments
J2000 The quasi-inertial frame Mean Equator and Mean Equinox of the J2000 epoch (JD 2451545.0 TDB which is 1 Jan 2000 12:00:00.000 TDB). The J2000 frame is realized by the transformational algorithm (also known as the FK5 IAU76 theory) between it and the Earth Fixed frame. The algorithm uses the 1976 IAU Theory of Precession, the 1980 Nutation model, and the Greenwich Mean apparent Sidereal Time (expressed as a function of time in UT1), updated by IERS Technical Note No. 21 to include an adjustment to the equation of the equinoxes.

Note that the term 'J2000 coordinate system' is not restricted to the system whose origin is at Earth's center--- rather, the term describes a coordinate system whose origin is determined from context (i.e., for a central body, its center of mass location) whose axes are parallel to the axes of the J2000 system defined at the Earth.

Standard N/A