Planning a Shuttle mission to rendezvous and dock with the Russian Space Station MIR is all in the timing. There is only about a 5-10 minute launch window each day that can get the Shuttle in the correct position to rendezvous with the Russian Mir space station. It boils down to simple geometry. When a spacecraft is in orbit around the Earth, its path defines what is known as the orbital plane - and that's the plane it stays in unless it is changed by firing the spacecraft's engines.
Plane changes are the most fuel-expensive orbit adjustments that can be made.
When you see the familiar track of the Shuttle plotted on a world map, you see a trace of the Shuttle's movement in it's orbital plane projected onto the two-dimensional map. A ground track of the Mir space station can likewise be plotted. Its trace, like all low altitude, easterly-launched Earth satellites, looks like a sine wave. N latitude and 51.6 deg S latitude. The wave is in a different place on the map on each successive trace, mainly because the earth has rotated.