Local frames

Several local frames are defined in CelestLab:

- Local orbital frames: "qsw", "tnw" and "lvlh".

- Local frames tied to a ground location: "topocentric North" local frame.

The "qsw" local orbital frame is defined as follows:

X axis: unit vector from the planet center to the satellite
Z axis: unit vector in the same direction as the orbit's angular momentum vector (that is, perpendicular to the orbit plane)
Y axis: unit vector chosen so that the (X,Y,Z) trihedral is direct.

The "tnw" local orbital frame is defined as follows:

X axis: unit vector in the direction of satellite's velocity vector
Z axis: unit vector in the same direction as the orbit's angular momentum vector, that is, perpendicular to the orbit plane
Y axis: unit vector chosen so that the (X,Y,Z) trihedral is direct.

The "lvlh" local orbital frame is defined as follows:

Z axis: unit vector from the satelite to the planet center
Y axis: unit vector in the opposite direction as the orbit's angular momentum vector
X axis: unit vector so that the (X,Y,Z) trihedral is direct (if the orbit is circular, X is in the same direction as the velocity vector)

The "topocentric North" local frame is defined as follows:

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