Q. For the measurement/estimation of which of the following are satellite images/remote sensing data used?
- Chlorophyll content in the vegetation of a specific location
- Greenhouse gas emissions from rice paddies of a specific location
- Land surface temperatures of a specific location
Select the correct answer using the code given below. (UPSC Prelims 2019)
Answer:
1, 2 and 3
Notes: The correct answer is
[D] 1, 2 and 3.Remote sensing involves gathering information about an object or phenomenon without making physical contact, primarily through satellites equipped with specialized sensors (optical, thermal, and microwave).
- Chlorophyll content (Statement 1 – Correct): Satellite sensors, such as those on Landsat or Sentinel, measure reflectance in the visible and near-infrared spectrum. Since chlorophyll absorbs red light and reflects near-infrared light, scientists use indices like the Normalized Difference Vegetation Index (NDVI) to estimate chlorophyll concentration and overall plant health.
- Greenhouse gas emissions (Statement 2 – Correct): Advanced satellite sensors (e.g., GHGSat, TROPOMI, or GOSAT) can detect the spectral "signatures" of gases like methane (CH4) and carbon dioxide (CO2). Since rice paddies are major sources of methane due to anaerobic decomposition in flooded fields, remote sensing is used to monitor these emissions at specific locations.
- Land surface temperatures (Statement 3 – Correct): Thermal infrared (TIR) sensors measure the long-wave radiation emitted from the Earth's surface. This data is used to estimate the Land Surface Temperature (LST), which is crucial for studying urban heat islands, volcanic activity, and soil moisture.