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LRO in Earth Centered and Moon Centered Coordinates

This visualization shows the Lunar Reconnaissance Orbiter (LRO) orbit insertion from two different coordinate systems (think of it as being from two different points of view): Earth centered inertial coordinates and moon centered coordinates. Orbit trails are shown in bright colors where the orbits have been and in darker colors for where the orbits will be. At any particular time, LRO is exactly at the intersection of the two orbit trail curves. The Earth centered coordinates are in blue and the moon centered coordinate are in orange. Why are there two different trails? Because the moon is moving; therefore, the moon centered coordinate system is moving. If the moon was stationary with respect to the Earth, both trails would look the same, but since the moon is moving, the moon's trail is always moving and the trails look different. Think of LRO orbiting the moon. From the moon's perspective, it's just going in an ellipse around the moon. In this case, the observation point (the moon) is moving with LRO. But, from the Earth's perspective, if you plotted out the trail of LRO, you would get a series of loops as LRO goes around the moon and as the moon moves through the sky. Visualizing an orbit trail that shows a history of here the orbit has been that changes between two discrete coordinate systems is a challenge. A discontinuity arises if you just switch over from one trail to another. To create a smooth transition one solution is to carefully select sections of the Earth centered and moon centered curves and then morph from the Earth centered curve section to the moon centered curve section while the visualization is playing. That is technique that was used here. Visualizers: Greg Shirah (lead), Ernie Wright For more information or to download this public domain video, go to https://svs.gsfc.nasa.gov/3618#9476