• Blackbody Thermal Radiation Principles:
• By definition, an ideal blackbody has an emissivity of unity across all wavelengths:

• Radiant temperature ($T_{\text{rad}}$) and kinetic temperature ($T_{\text{kin}}$) are related by Stefan-Boltzmann's law:

• Conclusion: If kinetic temperature is 27.0 °C, the radiant temperature of the blackbody is exactly 27.0 °C. (Correct answer: Option 1)

• Radiometric Sensor Calibration Equation:

• Sensor Parameters:
• The linear regression slope relating digital numbers (DN) to spectral radiance ($L$) measured by the sensor is defined as the Gain ($A$).
• The intercept represents the offset or bias. (Correct answer: Option 1)

• Assertion (A) is True: In a Real Aperture Radar (RAR) system, azimuth (along-track) resolution is determined by the physical beamwidth ($\theta \approx \frac{\lambda}{L}$) and slant range ($R$): $R_a = R \cdot \theta = \frac{R \lambda}{L}$. As distance (range $R$) from the aircraft increases, the angular beam spreads and azimuth resolution size increases (i.e., spatial resolution degrades).
• Reason (R) is False: In a Synthetic Aperture Radar (SAR) system, azimuth resolution is independent of range distance and wavelength: $R_a = \frac{L}{2}$, where $L$ is physical antenna length; hence, azimuth resolution size does NOT increase with distance in SAR.
• Conclusion: (A) is true but (R) is false (Option 3).

Correct option: (3) (A) is true but (R) is false.