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Sine Track Depicting Satellite Orbits
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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Update: June 2012
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