Why do satellite's orbits appear to be curved on earth charts? For instance:?

Question

Like This:
http://upload.wikimedia.org/wikipedia/commons/3/3f/Satellite_Orbital_Elements_ISS_Groundtrack.png

I'm pretty naive about all this. Can someone explain this to me? I thought the satellites made complete circular or elliptical orbits around earth.

This one also confuses me a bit:
http://www.rap.ucar.edu/~djohnson/satellite/figures/cycle_map.gif

Answer 1

They do make circular orbits. Why it looks like they curve on the maps is because you are projecting the orbit on a flat surface, and the Earth is curved. To see this clearly, trace your finger straight on the surface of a globe, and note how the direction that your finger takes changes direction with respect to the surface of the globe.

Answer 2

The second illustration is NOT the paths of the orbits of the satellites. Each circle is the area of Earth's surface that is covered by the satellite positioned above the red dot at the center of the circle.



To answer your first question, the orbit only appears to be curved up and down because the map shows the entire surface of Earth "unfolded" and shown on a flat surface. If you looked at a globe, and traced the orbit on the globe you would see that it is just tilted, with half of the orbit being north of tthe equator and half of the orbit being south of the equator. The reason each orbit is a little off to the side of the previous orbit is because that's how far Earth spins during one orbit of the satellite.

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Answer 3

The problem is with the map. You can't accurately represent the curved surface of the Earth on a flat plane. For example, look at this representation of the orbit of ISS: http://www.heavens-above.com/orbit.aspx?satid=25544 You can see by the countries over which the satellite passes that the paths are the same.

Your second link shows satellite coverage areas or footprints, in other words, the area of the Earth which each satellite can 'see'.

Answer 4

If you watch the orbital motion from above the plane of the orbit itself, you will see it is circular. When you change to the reference plane of a map representing the Earth rotating under that orbit, it looks like this, or something similar. Part of this is the stretching of the Earth's surface view because of the map plot, or projection.



The second picture is a map of the points that represent the Earth's horizon as seen by the satellites, and these would be circles on the surface of the Earth, but they are distorted by the map projection as well.

Answer 5

it is from the direction of the satelite and the

Earths revolving that makes the orbit

look like a sine wave on a map

take an old globe and a pencil.draw a line from the

equator at a consistant angle and rotate the globe

the results will look like the sine wave

Answer 6

because of the fact the earth is around and that they've pealed it like an orange and flattened it out so which you would be able to look on the completed earth all of sudden. in case you prefer to work out what is going on print that image and wrap it around a golf ball see what occurs to the lines.

Answer 7

I'm not sure. I know what your talking about though. ISSTracker.com and u can see this.