Prelims 2011 · archive
MediumSatellites 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:
Answer & explanation
Answer: (a) 1, 2 and 3 only
A geostationary orbit is a circular, equatorial orbit whose period equals Earth's rotation period, so it is geosynchronous. Its altitude is 35,786 km. The figure 22,236 is that same height in miles, so statement 4 is wrong.
- ✓ 1. The satellite's orbital period equals Earth's rotational period (about 23 h 56 min 4 s). This is the meaning of geosynchronous, so a geostationary orbit is geosynchronous.
- ✓ 2. A geostationary orbit is circular. ESA describes GEO as a circular orbit above the equator.
- ✓ 3. The satellite must lie directly above the equator, moving west to east. Combined with a circular orbit and a period matching Earth's rotation, this makes it appear fixed over one spot on Earth.
- ✗ 4. The altitude is 35,786 km above the equator. The number 22,236 is the same height expressed in miles, not kilometres.
Remember · Geostationary orbit: circular, in the equatorial plane, period equal to Earth's rotation (a special case of geosynchronous), at 35,786 km (about 22,236 miles) altitude.
Sources
- ESA – Orbits (Connectivity and Secure Communications) ↗ “GEO is a circular orbit 35 786 kilometres above Earth's equator and follows the direction of Earth's rotation. An object in GEO has an orbital period equal to Earth's rotational period”
- ESA – Types of orbits ↗ “Satellites in geostationary orbit (GEO) fly above Earth’s equator, moving from west to east, exactly matching Earth’s rotation: taking 23 hours 56 minutes and 4 seconds to complete one full orbit”
Question: UPSC Civil Services (Preliminary) 2011, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·