Geosynchronous satellite dynamics: which statement correctly describes the apparent position of a satellite in geosynchronous (specifically, geostationary) orbit relative to observers on Earth?

Introduction:
Satellite orbits determine how a spacecraft appears to move across the sky to an observer on Earth. A special case, the geostationary orbit, is frequently used for communications and weather satellites because it simplifies ground antenna pointing. This question tests understanding of what observers see for satellites in geosynchronous (specifically, geostationary) orbit.

Given Data / Assumptions:

• Geosynchronous means the satellite's orbital period equals Earth's rotational period (~24 hours).
• A geostationary orbit is a circular, equatorial geosynchronous orbit.
• Ground antennas are fixed (no continuous tracking) for geostationary satellites.

Concept / Approach:
In a geostationary orbit, the satellite orbits at approximately 35,786 km altitude in the equatorial plane with zero inclination and zero eccentricity. Because its angular velocity matches Earth's rotation and it is above the equator, the satellite appears motionless with respect to a point on the Earth's surface (fixed azimuth and elevation). This property allows continuous line-of-sight service with stationary ground dishes.

Step-by-Step Solution:

Verification / Alternative check:
Communications satellites such as those used for television and VSAT services park at longitudes on the geostationary belt. Ground antennas are pointed once and remain fixed, confirming the "appears stationary" property.

Why Other Options Are Wrong:

• Fixed position to fully cover Earth: even from GEO, a single satellite cannot cover the entire Earth due to line-of-sight and elevation constraints.
• Moves faster than Earth: would not be geosynchronous and would not appear stationary.
• Moves simultaneously: meaningless description.
• None of the above: incorrect because one statement is correct.

Common Pitfalls:
Confusing geosynchronous with geostationary; assuming one satellite at GEO sees the entire globe; overlooking that non-zero inclination geosynchronous orbits trace an analemma (figure-eight) in the sky and are not strictly stationary.

Final Answer:
It remains in a fixed position relative to a point on Earth (appears stationary in the sky).