Three Body Rotating Coordinate System Type
A Three Body Rotating Coordinate System is one that is associated with two different three-body systems. For example, the Sun-Earth-spacecraft system and the Earth-Moon-spacecraft system. The lunar coordinate systems are primarily used when operating in close proximity to the Moon. There are, however, a few additional coordinate systems that are also useful when analyzing (and depicting) trajectories in the vicinity of the Earth-Moon system. The Sun-Earth and Earth-Moon rotating coordinate frames are defined as follows: The pole vector or Z-axis of the coordinate frame is set equal to the instantaneous orbit normal of the secondary (smaller) body about the primary (larger) body. The X-axis is set equal to the vector from the primary body center of mass (CM) to the secondary body CM. The X-axis rotates at a rate equal to the instantaneous rotation rate of the secondary body about the primary body.