Rosetta - Ephemeris - cruise

Coordinate systems used for cruise phase:
* HCI (Heliocentric Inertial Frame) : All vectors are geometric: no aberration corrections are used. The solar rotation axis is the primary vector: the Z axis points in the solar north direction.The solar ascending node on the ecliptic of J2000 forms the X axis.The Y axis is Z cross X, completing the right-handed reference frame.
* HEE (Heliocentric Earth Ecliptic Frame) : All vectors are geometric: no aberration corrections are used. The position of the Earth relative to the Sun is the primary vector: the X axis points from the Sun to the Earth. The northern surface normal to the mean ecliptic of date is the secondary vector: the Z axis is the component of this vector orthogonal to the X axis. The Y axis is Z cross X, completing the right-handed reference frame.
* HEEQ (Heliocentric Earth Equatorial Frame) : All vectors are geometric: no aberration corrections are used. The solar rotation axis is the primary vector: the Z axis points in the solar north direction. The position of the Sun relative to the Earth is the secondary vector: the X axis is the component of this position vectororthogonal to the Z axis. The Y axis is Z cross X, completing the right-handed reference frame.

巡航阶段所采用的坐标系包括：
* 天心惯性坐标系 (HCI，Heliocentric Inertial Frame)：所有向量均为几何向量，不使用光行差校正。太阳自转轴为主要向量，其中Z轴指向太阳北极方向。2000年黄道上的太阳升交点构成X轴。Y轴为Z轴与X轴的叉积，从而完成右手坐标系。
* 天心地球黄道坐标系 (HEE，Heliocentric Earth Ecliptic Frame)：所有向量均为几何向量，不使用光行差校正。地球相对于太阳的位置为主要向量，其中X轴从太阳指向地球。日期平均黄道上的北面法线构成次要向量，Z轴为该向量的X轴正交分量。Y轴为Z轴与X轴的叉积，从而完成右手坐标系。
* 天心地球赤道坐标系 (HEEQ，Heliocentric Earth Equatorial Frame)：所有向量均为几何向量，不使用光行差校正。太阳自转轴为主要向量，其中Z轴指向太阳北极方向。太阳相对于地球的位置为次要向量，X轴为该位置向量的Z轴正交分量。Y轴为Z轴与X轴的叉积，从而完成右手坐标系。