Planets and Moons  ID: 3618

LRO in Earth Centered and Moon Centered Coordinates

This visualization shows the Lunar Reconnaissance Orbiter (LRO) orbit insertion from two different points of view (i.e., coordinate systems): Earth centered inertial coordinates and moon centered fixed 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, 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.

Animating an orbit trail that changes between two discrete coordinate systems is a challenge. A discontinuity arises if you just switch over from one trail to another. To animate 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 animation was playing. This technique was used here as well.

Visualization Credits

Greg Shirah (NASA/GSFC): Lead Animator
Ernie Wright (UMBC): Animator
Please give credit for this item to:
NASA/Goddard Space Flight Center Scientific Visualization Studio The Blue Marble Next Generation data is courtesy of Reto Stockli (NASA/GSFC) and NASA's Earth Observatory.

The Blue Marble data is courtesy of Reto Stockli (NASA/GSFC).

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LRO (Lunar Reconnaissance Orbiter)

Data Used:
Hipparcos/Telescope/Tycho 2 Catalogue
Terra and Aqua/MODIS/Blue Marble: Next Generation May
LRO-Simulated Ephemeris November 2008
CPC (Climate Prediction Center) Cloud Composite
Note: While we identify the data sets used in these visualizations, we do not store any further details nor the data sets themselves on our site.

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