Satellites used for telecommunication relay are kept in a geostationary orbit. A satellite is said to be in such an orbit when: 1) The orbit is geosynchronous. 2) The orbit is circular. 3) The orbit lies in the plane of the Earth's equator. 4) The orbit is at an altitude of 22,236 km Select the correct answer using the codes given below:

The correct answer is A. A geostationary orbit is a special case of the geosynchronous orbit. Statements 1, 2 and 3 are its defining conditions, and statement 4 is the one that fails.

• Statement 1 (correct): The orbit is geosynchronous, meaning the satellite completes one revolution in one sidereal day (about 23 h 56 min), so it keeps pace with Earth's rotation.
• Statement 2 (correct): The orbit must be circular. An elliptical orbit would make the satellite drift across the sky through the day.
• Statement 3 (correct): The orbit must lie in the equatorial plane. Any inclination would make the satellite appear to move north and south.
• Statement 4 (wrong): The altitude is about 35,786 km above the equator (roughly 42,164 km from Earth's centre), not 22,236 km. The figure in the statement is a distractor built by altering the real value.

The core concept is orbital mechanics. By Kepler's third law, an orbit at about 35,786 km has a period equal to one sidereal day. Mains connection: GS-III on space technology, DTH broadcasting, INSAT and GSAT missions, and the growing congestion of the geostationary arc.

Trap: Candidates who remember the altitude loosely may accept 22,236 km as plausible and pick B or D. Fix 35,786 km firmly in memory.