GPS satellite orbits — approximate orbital radius from Earth’s centre In satellite navigation (GPS), the medium Earth orbit is characterised by an orbital radius (distance from Earth’s centre) of roughly 26,600 km. Choose the closest approximate orbital radius for GPS satellites.

Introduction / Context:
Global Positioning System (GPS) satellites operate in medium Earth orbit (MEO). Understanding their orbital radius (measured from Earth’s centre, not the surface) helps in grasping geometry for visibility, dilution of precision, repeat periods, and signal travel times critical to positioning accuracy.

Given Data / Assumptions:

• We need the approximate orbital radius of GPS satellites.
• Orbital radius = Earth’s mean radius + satellite altitude.
• Earth’s mean radius is about 6,371 km; GPS altitude is about 20,200 km above mean sea level.

Concept / Approach:
Convert altitude to orbital radius by adding Earth’s radius. GPS satellites are not in geostationary orbit (~35,786 km altitude; ~42,164 km orbital radius) and not in low Earth orbit (a few hundred to ~2,000 km altitude); they sit between these regimes in MEO to balance coverage, constellation size, and signal strength.

Step-by-Step Solution:

Verification / Alternative check:
Using orbital period ~11 hours 58 minutes (half a sidereal day) corroborates MEO parameters; a ~26,600 km radius yields this period under standard gravitational parameter for Earth.

Why Other Options Are Wrong:

• 15,200 km and 18,400 km: Too small; closer to some MEO constellations but below GPS standards.
• 36,000 km: Confuses with geostationary orbit altitude (radius ~42,164 km), not GPS.
• None of these: Incorrect since 26,600 km is correct.

Common Pitfalls:
Confusing altitude (above surface) with orbital radius (from Earth’s centre) and mixing up MEO with GEO or LEO values.

Final Answer:
26,600 km