Which orbital parameter best describes the GPS constellation?

Which orbital parameter best describes the GPS constellation?

• A. Medium Earth Orbit around 20,200 km altitude with about 55-degree inclination.
• B. Geostationary orbit at about 35,786 km.
• C. Low Earth Orbit around 700 km.
• D. Highly elliptical orbit with varying inclination

Answer: (A)

The GPS constellation is designed to provide global, continuous navigation coverage by placing satellites in a middle-range orbit with a fixed, modest tilt. That combination—an orbit around 20,200 km above Earth with about 55-degree inclination—gives a broad, stable geometry so users nearly anywhere on the planet can see enough satellites at once for accurate positioning, with about a 12-hour repeat cycle. Why this fits best: the altitude is high enough to minimize atmospheric effects and provide good signal travel time characteristics, yet not so high that geometry becomes poor or the spacecraft require excessive power. The 55-degree tilt lets satellites sweep over mid- to high-latitudes, ensuring good visibility for users near the poles as well as near the equator. Together, this arrangement supports a robust, evenly distributed constellation (multiple planes and several satellites per plane) so at least a handful are above the horizon at any time. Why the other options don’t fit: a geostationary orbit would keep satellites fixed over the equator, which creates poor geometry for users at higher latitudes and reduces the overall coverage quality. a low Earth orbit around 700 km would demand many more satellites and face greater atmospheric drag, with rapid ground-track shifts and less stable signal geometry. a highly elliptical orbit with varying inclination would lead to inconsistent visibility and timing, undermining reliable global navigation. So, the best description is a medium Earth orbit around 20,200 km altitude with about 55-degree inclination.

The GPS constellation is designed to provide global, continuous navigation coverage by placing satellites in a middle-range orbit with a fixed, modest tilt. That combination—an orbit around 20,200 km above Earth with about 55-degree inclination—gives a broad, stable geometry so users nearly anywhere on the planet can see enough satellites at once for accurate positioning, with about a 12-hour repeat cycle.

Why this fits best: the altitude is high enough to minimize atmospheric effects and provide good signal travel time characteristics, yet not so high that geometry becomes poor or the spacecraft require excessive power. The 55-degree tilt lets satellites sweep over mid- to high-latitudes, ensuring good visibility for users near the poles as well as near the equator. Together, this arrangement supports a robust, evenly distributed constellation (multiple planes and several satellites per plane) so at least a handful are above the horizon at any time.

Why the other options don’t fit: a geostationary orbit would keep satellites fixed over the equator, which creates poor geometry for users at higher latitudes and reduces the overall coverage quality. a low Earth orbit around 700 km would demand many more satellites and face greater atmospheric drag, with rapid ground-track shifts and less stable signal geometry. a highly elliptical orbit with varying inclination would lead to inconsistent visibility and timing, undermining reliable global navigation.

So, the best description is a medium Earth orbit around 20,200 km altitude with about 55-degree inclination.