Question 63 from UPSC CSE 2019 - Science & Technology

Question

For the measurement/estimation of which of the following are satellite images/remote sensing data used?
1. Chlorophyll content in the vegetation of a specific location
2. Greenhouse gas emissions from rice paddies of a specific location
3. Land surface temperatures of a specific location
Select the correct answer using the code given below.

IASCODEX · Accepted Answer

Correct Option: D. 1, 2, and 3

Strategy: Identify which statements involve measurable or observable properties detectable via satellite. Chlorophyll content can be gauged using spectral indices like NDVI through satellite sensors. Land surface temperature is a classic application of infrared satellite remote sensing. Greenhouse gas emissions measurement may seem less obvious, but satellites equipped with hyperspectral sensors can estimate CO2/CH4 concentrations even from localized sources. All three are valid, so select option D.

Key Info: Satellite remote sensing leverages sensors that detect reflected or emitted energy from Earth's surface and atmosphere in various spectral bands.

- **Chlorophyll Content:** Chlorophyll absorbs red and blue wavelengths and reflects green and near-infrared light. Remote sensing platforms such as Landsat, MODIS, and Sentinel-2 use vegetation indices like NDVI (Normalized Difference Vegetation Index) to estimate chlorophyll levels and vegetation health over large areas, aiding agriculture and ecological monitoring.
- **Greenhouse Gas Emissions:** Advanced satellites (e.g., GOSAT, OCO-2) utilize hyperspectral and hyperfine band sensors to detect gases like CO2 and CH4 by analyzing the absorption patterns in sunlight reflected from Earth. Remote sensing allows estimation and mapping of greenhouse gas concentrations over agricultural landscapes, such as rice paddies, which emit significant methane (CH4).
- **Land Surface Temperature:** Thermal infrared sensors aboard satellites like MODIS, Landsat, and Sentinel-3 measure emitted thermal energy from the ground, enabling the estimation of land surface temperature (LST) at various scales. These data contribute to hydrology, climate studies, urban heat island mapping, and agriculture.

Applications: Remote sensing data assist in large-scale crop monitoring, climate impact analysis, drought assessment, precision agriculture, and international environmental reporting. Multiple agencies, including NASA and ISRO, provide open-access remote sensing datasets supporting scientific research and policy formulation.

IASCODEX · Answer

Option A: 1 only

IASCODEX · Answer

Option B: 2 and 3 only

IASCODEX · Answer

Option C: 3 only