UPSC Prelims 2019 Q32: Science & Technology – Space Technology & Astronomy
- (a) 1 only
- (b) 2 and 3 only
- (c) 3 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Remote Sensing / Satellite Imagery Applications
| Parameter | Measurable by Satellite? | Sensor/Method |
|---|---|---|
| 1. Chlorophyll content in vegetation | YES | NDVI, EVI using red + near-infrared bands (Landsat, Sentinel-2, Resourcesat) |
| 2. Greenhouse gas emissions from rice paddies | YES | Hyperspectral / SAR sensors detect methane plumes (GOSAT, TROPOMI, MethaneSAT); rice-paddy flooded extent tracked by SAR |
| 3. Land surface temperature | YES | Thermal Infrared (TIR) bands - Landsat TIR, MODIS, Sentinel-3 SLSTR |
All three parameters are routinely measured / estimated using satellite imagery and remote sensing. Answer: (d) 1, 2 and 3.
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Statements 2 (GHG emissions) and 3 (LST) are also measurable by satellite.
- (b) Incorrect. Chlorophyll estimation (NDVI) is a classic satellite application.
- (c) Incorrect. Chlorophyll and GHG emissions are also monitored by satellites.
- (d) CORRECT. Chlorophyll (NDVI), GHG emissions (GOSAT, TROPOMI), and LST (thermal IR) - all three are routinely measured by satellite remote sensing.
Key point
Remote sensing measures: (1) Vegetation chlorophyll via NDVI, (2) GHG emissions via hyperspectral sensors (GOSAT, TROPOMI), (3) Land surface temperature via thermal IR bands. All three are yes.
Remember
Satellite imagery and remote sensing data are used for measuring chlorophyll content in vegetation (NDVI, EVI), greenhouse gas emissions from rice paddies (GOSAT, TROPOMI, MethaneSAT), and land surface temperature (thermal infrared bands from Landsat, MODIS, Sentinel-3). All three are yes.
Common mistakes
- Assuming GHG emissions cannot be measured from space - modern satellites (GOSAT, TROPOMI, MethaneSAT) do exactly this.
- Confusing land surface temperature (thermal IR from surface) with air temperature (meteorological stations).
- Not knowing India's Resourcesat and Cartosat series contribute NDVI and thermal data.
Exam tip
Satellite band applications: Visible (RGB) - land use. NIR - vegetation health (NDVI). SWIR - moisture, minerals. Thermal IR - LST. Microwave (SAR) - all-weather imaging, floods, methane. Hyperspectral - GHG/pollutant plumes.
Sources
- ISRO - Bhuvan and NRSC applications catalogue
- IPCC AR6 - Remote sensing of the Earth system