Question

In remote sensing, the parameter(s) that can be estimated in the Thermal Infrared region (3 - 14 \(\mu\)m) is/are

• A. Forest fire
• B. Rainfall pattern
• C. Ground surface temperature
• D. Emissivity

Hint:

TIR senses emitted heat energy, not reflected sunlight, so think about which of these four depend on surface heat rather than clouds or precipitation.

Answer 1

The Correct Option is A, C, D

Step 1: Recall what the thermal infrared region senses.
The thermal infrared (TIR) band covers wavelengths from about 3 to 14 \(\mu\)m. In this range, sensors do not record reflected sunlight. They record energy that the earth's surface and objects on it emit because of their own heat. This emitted energy follows Planck's law, so its strength depends on the temperature and the emissivity of the surface.

Step 2: Check forest fire detection.
An active fire is far hotter than the ground around it, so it radiates strongly in the mid-wave part of the TIR band (near 3-5 \(\mu\)m). Fire monitoring satellites such as MODIS pick out these hot pixels using TIR channels. So forest fire is a parameter that TIR can estimate. Option (A) is correct.

Step 3: Check rainfall pattern.
Rainfall is mapped using microwave sensors, which detect scattering and emission from raindrops and ice inside clouds, or from visible and near infrared images that track cloud growth and movement. TIR only gives the temperature of the cloud top, which is a weak, indirect clue and not a direct estimate of rainfall. So rainfall pattern is not a TIR-derived parameter. Option (B) is incorrect.

Step 4: Check ground surface temperature.
Land surface temperature is calculated directly from the radiance a TIR sensor records, using Planck's law and an estimate of surface emissivity. This is one of the most common products from TIR data. Option (C) is correct.

Step 5: Check emissivity.
Different rocks, soils, and vegetation emit thermal energy with slightly different efficiency depending on wavelength. Multi-band TIR sensors, such as ASTER, use this fact to separate temperature from emissivity and map surface emissivity, which helps identify minerals and land cover. Option (D) is correct.

Step 6: Final answer.
Forest fire, ground surface temperature, and emissivity can all be estimated in the thermal infrared region, while rainfall pattern needs microwave or visible data instead.
\[ \boxed{\text{(A), (C), (D)}} \]