Coordinate systems in lunar ranging

Three distinct coordinate systems are required in the interpretation of the lunar range observations: a celestial frame and two-body-fixed frames. However, there is no coordinate system that is uniquely, or even preferentially, related to the observations themselves. Effectively, one specifies the coordinate systems by the procedures used in data reduction and parameter improvement. Each of the three systems affects the others in some way, and internal inconsistencies are quite possible. The discussion examines some of the more important aspects of this problem.