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Sub-satellite latitude/longitude over an equirectangular world map. The track's turning latitude equals the inclination; each successive pass shifts west as the Earth turns beneath the orbit.
period—turning lat—
The path a satellite traces over the rotating Earth. First-cut: circular orbits — the classic sinusoid that drifts westward each rev.
Sub-satellite latitude/longitude over an equirectangular world map. The track's turning latitude equals the inclination; each successive pass shifts west as the Earth turns beneath the orbit.
A satellite’s ground track is the path of the point directly beneath it — its footprint projected onto the surface. For a circular orbit the latitude oscillates sinusoidally between +i and −i, where i is the inclination: an orbit inclined 51.6° (the ISS) reaches 51.6° north and south and no farther, which is why inclination sets a mission’s coverage limits.
Longitude is where Earth’s rotation enters. In one orbital period the planet turns eastward beneath the orbit, so each successive pass crosses the equator farther west — the track drifts westward by the number of degrees Earth rotates per orbit (about 22.5° for a ~90-minute low orbit). When the period is a rational fraction of a day the track closes on itself into a repeat ground track, the basis of repeating reconnaissance and revisit orbits. A special case, the sun-synchronous orbit, uses J2 nodal precession to hold a constant local solar time.
This first cut assumes a circular orbit and takes the ascending node as the longitude origin; eccentric orbits, the argument of perigee, and J2 drift are natural extensions.