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GCRF: Geocentric Celestial Reference Frame is the Earth-centered counterpart of the International Celestial Reference Frame. MOD: a Mean of Date (MOD) frame is defined using the mean equator and equinox on a particular date.
The Geocentric Celestial Reference Frame (GCRF) is the geocentric equivalent of the International Celestial Reference Frame (ICRF). Its primary direction is the equinox of J2000.0, and does not move with precession and nutation, but it is otherwise equivalent to the above systems.
The International Celestial Reference System (ICRS) is the current standard celestial reference system adopted by the International Astronomical Union (IAU). Its origin is at the barycenter of the Solar System, with axes that are intended to "show no global rotation with respect to a set of distant extragalactic objects".
The Hipparcos Celestial Reference Frame (HCRF) was similar to ICRF, but earlier, used in association with the Hipparcos satellite, which functioned between 1989 and 1993. That satellite took copious stellar parallax measurements at accuracies exceeding anything otherwise available at the time, thus producing a catalog of stars still in wide use ...
GNSS systems: [2] Galileo Terrestrial Reference Frame (GTRF), ITRF2005; own implementation using IGS sites.; GPS just uses WGS 84, ITRF2020 since January 2024 (but used many versions of WGS 84 before), a little modified with International GNSS Service (IGS) implementation, IGS20.
A new study suggests that intermittent fasting is more effective than calorie-counting for weight loss and belly fat burn. A dietitian explains how to start.
The Earth-centered, Earth-fixed coordinate system (acronym ECEF), also known as the geocentric coordinate system, is a cartesian spatial reference system that represents locations in the vicinity of the Earth (including its surface, interior, atmosphere, and surrounding outer space) as X, Y, and Z measurements from its center of mass.
The IERS has various components located in the United States, Europe and Australia.Among its other functions, the IERS is responsible for announcing leap seconds.. The Sub-bureau for Rapid Service and Predictions of Earth Orientation Parameters of the IERS, located at the United States Naval Observatory, monitors the Earth's rotation.