UPSC Prelims 2015 Q71: Science & Technology – Space Technology & Astronomy
In which of the following activities are Indian Remote Sensing (IRS) satellites used?
1. Assessment of crop productivity
2. Locating groundwater resources
3. Mineral exploration
4. Telecommunications
5. Traffic studies
- (a) 1, 2 and 3 only
- (b) 4 and 5 only
- (c) 1 and 2 only
- (d) 1, 2, 3, 4 and 5
Answer: (a) 1, 2 and 3 only
Explanation
Uses of Indian Remote Sensing (IRS) satellites
Remote sensing satellites take images of the Earth from orbit.
| Activity | IRS satellites used? | Reason |
|---|---|---|
| 1. Assessment of crop productivity | Yes | Crop area and yield estimates |
| 2. Locating groundwater resources | Yes | Maps of likely groundwater zones |
| 3. Mineral exploration | Yes | Geological and mineral mapping |
| 4. Telecommunications | No | Done by INSAT and GSAT communication satellites |
| 5. Traffic studies | No | Not a use counted by the official key |
India's satellite families:
| Family | Orbit | Purpose |
|---|---|---|
| IRS (Resourcesat, Cartosat, Oceansat) | Polar, sun-synchronous | Earth observation |
| INSAT and GSAT | Geostationary | Telecommunications, broadcasting, weather |
| NavIC (IRNSS) | Geosynchronous | Navigation |
Answer: (a) 1, 2 and 3 only.
Why each option is right or wrong
- (a) CORRECT. IRS satellites serve crop assessment, groundwater and mineral exploration.
- (b) Incorrect. Telecommunications is the work of INSAT and GSAT, not IRS.
- (c) Incorrect. Mineral exploration is also a use of remote sensing.
- (d) Incorrect. IRS satellites are not used for telecommunications.
Key point
IRS satellites (polar, sun-synchronous): crops, groundwater, minerals, forests, disasters. INSAT and GSAT (geostationary): telecommunications.
Remember
IRS = Earth observation, not telecom.
Common mistakes
- Giving telecommunications to remote sensing satellites.
- Forgetting the orbits: IRS in polar orbit, INSAT in geostationary orbit.
- Assuming every satellite does everything.
Exam tip
Remote sensing = looking at the Earth. Communication = relaying signals. Two different satellite families.
Sources
- Indian Space Research Organisation — Earth Observation Satellites
- National Remote Sensing Centre — Applications of remote sensing