Definition check: Which statement best defines a geostationary satellite from the ground observer’s perspective?

Introduction / Context:
A geostationary satellite is a special case of a geosynchronous orbit aligned with the equator such that its angular velocity matches Earth’s rotation, making it seem fixed in the sky to ground observers—vital for fixed Earth station pointing.

Given Data / Assumptions:

• Altitude ~35,786 km over the equator (mean).
• Orbital period matches Earth’s sidereal day (~23 h 56 min).
• Inclination ≈ 0°, eccentricity ≈ 0.

Concept / Approach:

The correct defining characteristic for users is the apparent stationarity relative to Earth’s surface. While the satellite is in constant orbital motion, its ground track is a fixed point when orbit is circular, equatorial, and geosynchronous.

Step-by-Step Solution:

Verification / Alternative check:

Any inclination/eccentricity causes apparent north–south or east–west drift (analemma), violating strict “stationary” appearance.

Why Other Options Are Wrong:

• “Hangs motionless” / “stops moving”: physically incorrect—orbital velocity is required.
• “Travels around Earth in 24 hours”: necessary but not sufficient; must be equatorial and circular.
• “Remains stationary above the Earth”: ambiguous; better is “appears stationary to observers.”

Common Pitfalls:

• Equating geosynchronous (any inclination) with geostationary (equatorial, circular).

Final Answer:

It appears stationary to everybody on Earth.