{
    "count": 4,
    "next": null,
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    "results": [
        {
            "id": 3621,
            "url": "https://svs.gsfc.nasa.gov/3621/",
            "result_type": "Visualization",
            "release_date": "2009-07-27T00:00:00-04:00",
            "title": "LRO Transition from Earth-Centered to Moon-Centered Coordinates",
            "description": "This animation illustrates the solution to a human factors problem in the visualization of an orbit path, in this case the launch and lunar orbit insertion of the Lunar Reconnaissance Orbiter satellite.The visualization (found HERE) shows LRO orbiting the Earth, traveling from the Earth to the moon, and entering lunar orbit. Throughout the visualization, a trail is drawn to show LRO's path. This trail is a history of LRO's motion.The viewer's expectation is that LRO first travels in a circular orbit centered on the Earth, then follows a smoothly curving path connecting the Earth to the moon, and finally enters an elliptical orbit around the moon. The problem for the animator is that an accurate trail satisfying all of these expectations is impossible to draw in a single coordinate system. A trail drawn in Earth-centered coordinates forms a looping, spring-like path when LRO enters lunar orbit, and a trail drawn in moon body-fixed coordinates becomes disconnected from the Earth and precesses through space.Simply switching from one coordinate system to the other would make the trail appear to jump suddenly and dramatically. Creating a hybrid trail would leave a visually confusing elbow in LRO's path.The solution illustrated here is to morph the trail from one coordinate system to the other. The blue trail is the Earth-centered path, the orange trail is the moon body-fixed path, and the white trail is the morph between the two. In the visualization, the Earth trail shortens, disconnecting it from the Earth, and then morphs over about 400 frames into the moon body-fixed trail. With careful timing, the result is a visually seamless transition from one coordinate system to the other.Notice that the difference in coordinate systems creates no ambiguity about the present position of LRO at any given time. LRO is always at the intersection of the trails. The problem arises when attempting to depict the history of its motion. That history takes different shapes in coordinate systems that move relative to one another.An animation showing LRO's entire path in both coordinate systems simultaneously can be found HERE. || ",
            "hits": 141
        },
        {
            "id": 3618,
            "url": "https://svs.gsfc.nasa.gov/3618/",
            "result_type": "Visualization",
            "release_date": "2009-07-17T00:00:00-04:00",
            "title": "LRO in Earth Centered and Moon Centered Coordinates",
            "description": "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. || ",
            "hits": 190
        },
        {
            "id": 3603,
            "url": "https://svs.gsfc.nasa.gov/3603/",
            "result_type": "Visualization",
            "release_date": "2009-07-08T00:00:00-04:00",
            "title": "Lunar Reconnaissance Orbiter (LRO) Orbit Insertion - Stereoscopic Version",
            "description": "This visualization shows an example of how the orbit insertion for the Lunar Reconnaissance Orbiter (LRO) might look. LRO launches from Cape Canaveral, then flies around the Earth and on to the moon. Time speeds up during the journey to the moon, then slows again as LRO approaches the moon. LRO begins orbiting the moon and, through a series of several \"burns\", moves in closer to its desired orbit. LRO's initial orbit plane around the moon is parallel to the direction of the moon's travel.This visualization was created before launch using simulated ephemeris data. The ephemeris data driving this visualization was based on a simulated night time launch on 11/24/2008; but, the actual launch may happen during the daytime. In this page the visualization content is offered in two different modes to accomodate stereoscopic systems as: Left and Right Eye separate and Left and Right Eye side-by-side combined on the same frame. || ",
            "hits": 81
        },
        {
            "id": 3612,
            "url": "https://svs.gsfc.nasa.gov/3612/",
            "result_type": "Visualization",
            "release_date": "2009-05-08T00:00:00-04:00",
            "title": "Lunar Reconnaissance Orbiter (LRO) Orbit Insertion",
            "description": "This visualization shows an example of how the orbit insertion for the Lunar Reconnaissance Orbiter (LRO) might look. LRO launches from Cape Canaveral, then flies around the Earth and on to the moon. Time speeds up during the journey to the moon, then slows again as LRO approaches the moon. LRO begins orbiting the moon and, through a series of several \"burns\", moves in closer to its desired orbit. LRO's initial orbit plane around the moon is parallel to the direction of the moon's travel.This visualization was created before launch using simulated ephemeris data. The ephemeris data driving this visualization was based on a simulated nighttime launch on 11/24/2008; but, the actual launch may happen during the daytime.A stereoscopic version of this visualization can be found HERE.  For more information on the coodinate systems in the animation see HERE. || ",
            "hits": 263
        }
    ]
}