Correct Option (a):
A geostationary orbit is a specific type of geosynchronous orbit that is circular, lies in the equatorial plane, and has an altitude such that the satellite appears stationary relative to a fixed point on the Earth's surface. For a satellite to be in a geostationary orbit, the following conditions must be met:
- Statement 1 is correct: The orbit must be geosynchronous. This means the satellite's orbital period must match Earth's sidereal rotation period (approximately 23 hours, 56 minutes, 4 seconds). This ensures the satellite remains above the same longitude.
- Statement 2 is correct: The orbit must be circular. A circular orbit ensures a constant altitude and uniform orbital velocity, which is necessary for the satellite to appear stationary from the ground.
- Statement 3 is correct: The orbit must lie in the plane of the Earth's equator (i.e., have zero inclination). This condition is crucial for the satellite to appear fixed in the sky relative to an observer on the equator, as any inclination would cause it to drift north and south.
Incorrect Options:
- Statement 4 is incorrect: The correct altitude for a geostationary orbit is approximately 35,786 km above the Earth's surface (or about 42,164 km from the Earth's center). At this specific altitude, the satellite's orbital period precisely matches the Earth's rotational period. An altitude of 22,000 km would result in a different orbital period, preventing the satellite from being geostationary.
- Options (b), (c), and (d) are incorrect because they either include statement 4 as a correct condition or omit essential correct conditions. Since statement 4 provides an incorrect altitude for a geostationary orbit, any option that includes it cannot be the correct answer.