The missile was launched when a target satellite's ground track rises above the launch site.

The three separate orbits are spaced equally around the Earth, but share a common ground track.

It was the longest X-15 flight in both time and distance from the ground track.

A common characteristic of all the orbits was that the ground track nearly repeated every few days.

Scale is true along the ground track, varying 0.01 percent within the normal sensing range of the satellite.

To make a u-turn, which is what he was attempting, you should turn into the wind to keep the ground track as small as possible.

In this manner, the satellite could observe long term changes at the points along the ground track.

The "ground track" in this case consists of a single point on the Earth's equator, above which the satellite sits at all times.

In other words, the greater the inclination of a satellite's orbit, the further north and south its ground track will pass.

The pilot must adjust heading to compensate for the wind, in order to follow the ground track.