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Reference Frames

Reference Frames

Reference frames used in CelestLab

Several reference frames are used in CelestLab. Inertial reference frames are needed for the definition of orbits (integration of the equations of motion) whereas rotating frames (i.e. tied to planets) are convenient for many purposes (when visibility with ground locations is involved).

Terrestrial Reference Frame (ITRF)

Inertial Geocentric Reference Frame: J2000 Reference Frame

This reference frame called J2000 in CelestLab follows the definition of the International Celestial Reference Frame (ICRF) in the IERS 1996 conventions. It is a standard inertial Earth centred, equatorial, mean of epoch Reference system. This inertial reference frame is defined as follows:

Transformation from ITRF to ICRF

In CelestLab, the transformation from ITRF to ICRF (J2000 in CelestLab) is achieved through a succession of rotations:

G50 Veis

The advantage of this "quasi-inertial" reference frame is to allow a transformation from a Terrestrial Reference Frame (RF) to a Celestial Reference Frame using only a single rotation around the Z-axis (Veis Sidereal time). This reference frame can be very useful for mission analysis because of its simplicity.

The G50 Veis is defined as follows:

H0-n frame

H0-n is a planetocentric inertial frame that is essentally a terrestrial frame frozen at some time. More specifically, it is defined by:

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