In which of the following activities, are Indian Remote Sensing (IRS) satellites used? 1). Assessment of crop productivity 2) Locating ground water resources 3) Mineral exploration 4) Telecommunications 5) Traffic studies Select the correct answer using the codes given below:

The correct answer is A. IRS satellites are earth observation satellites built for resource survey, so they serve statements 1, 2 and 3.

• 1. Crop productivity: Multispectral IRS data, such as LISS sensors, support crop acreage and yield estimation through vegetation indices, which is the basis of the crop-monitoring programmes run under the Department of Space and Ministry of Agriculture.
• 2. Groundwater: Remote sensing identifies lineaments, geomorphology and land-use patterns that point to groundwater potential zones.
• 3. Mineral exploration: Spectral and structural mapping helps identify geological formations and alteration zones that may host minerals.
• 4. Telecommunications: Wrong. This is the job of INSAT, the geostationary communication satellite system, which is a separate programme from the IRS series.
• 5. Traffic studies: Not part of the standard IRS application set in the key. High-resolution imagery can help map road networks, but traffic flow studies are not what IRS is designed for.

The core concept is the distinction between IRS (resource monitoring) and INSAT (communication and broadcasting). This links to the Mains theme of space technology applications in agriculture, water and disaster management.

Trap: Candidates see "satellite" and pick option D, assuming all satellites do everything. Keep the IRS and INSAT roles separate.