November 21, 2012

Animation Gives Future Glimpse Of Moon Phases For 2013

[ Watch the Video: Moon Phase & Libration 2013 ]

Lee Rannals for - Your Universe Online

The Lunar Reconnaissance Orbiter (LRO) has helped to create an animation showing hourly intervals of the moon's surface throughout next year.

Topographic measurements by the Lunar Orbiter Laser Altimeter aboard LRO makes it possible to simulate shadows on the Moon's surface.

"Thanks to Lunar Reconnaissance Orbiter, we now have excellent terrain maps of the Moon that can tell us the elevation at any point on the surface," said Ernie Wright, author of the new video from the Scientific Visualization Studio (SVS). "I use those maps to make the Moon sphere bumpy in all the right places. That allows the rendering software to realistically simulate all the shadows and the ragged terminator (the dividing line between day and night)."

The animation shows the geocentric phase, libration, position angle of the Moon's axis, and apparent diameter of the Moon.

The studio which made the animation used the same software that Hollywood uses to create 3D animation and special effects. This tool helped Wright to arrange virtual cameras, lights, and objects into a scene.

He started out by calculating the position of the Earth and the direction of the Sun for every hour of the year. After this, he wrote the program that tells the animation software to put the camera where the Earth is, and to point light in the same direction from which the Sun is shining.

Wright said the Moon is motionless at the center of the scene as the camera and light fly around it. Each frame of the animation represents an hour, and the program helped to set the positions and directions of each frame.

Due to the Moon's tilt and shape, people on Earth see the Moon from slightly different angles over the course of a month. When a month is compressed into 24 seconds, the changing view of the Moon makes it look like its wobbling.

The most noticeable variation in the Moon's appearance is the cycle of phases, which is caused by the changing angle of the Sun as the Moon orbits the Earth. This cycle begins with the waxing crescent Moon visible in the west just after sunset. After the first quarter, the Moon is high in the sky at sunset, and sets around midnight.

The full Moon rises at sunset and is high at midnight. The third quarter Moon is often surprisingly conspicuous in the western sky after sunrise.