SPACE MATH @ NASA: The Ground Track of the International Space Station

As the ISS orbits Earth every $90$ minutes, Earth rotates ‘underneath’ the orbit of the ISS once every $24$ hours. This means that each ISS orbit advances in longitude by a fixed amount in longitude. The figure above shows the ground track of the ISS for two orbits. 

Each square is $10$ degrees on a side, with the Equator running horizontally across the middle of the diagram. The squares are shown at intervals of $5$ minutes.

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