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Name: John
Status: educator
Grade: 6-8
Location: AL
Country: N/A
Date: 9/5/2005


Question:
When you track the space station, the graphic shows the orbit following an oscillating track similar to a sine wave. Is this the actual track or is it just an illusion due to the spinning of the earth. If this is the actual track, why does it follow this oscillating motion? This is a result of the tilt of the Earth (about 28.5 degrees) about its axis of rotation, while the satellite is generally moving in a circular path. When this orbit is transformed to a flat surface, the satellite trajectory moves above and below the equator. On a flat map this trasforms into a sine-like wave.

NASA has an educational site:

http://media.nasaexplores.com/lessons/01-004/5-8_1.pdf that has an exercise you can do with pencil and paper, or just do the "thought"experiment.

Vince Calder


If by oscillating you mean the gradual divergence of the orbit around the globe, then that is caused by the rotation of the Earth.

HOWARD BARNES


John,

The space station, and other things in orbit, circle the earth in an elliptical orbit. It appears to be a sine wave because you are looking at it on a 2 dimensional map. When the sine wave reaches the upper peak, the orbit is actually passing over the earth and "coming down" the other side until it reaches the lower peak, etc.

Bob Hartwell



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