Definition of active remote sensing Name the type of remote sensing in which the system generates electromagnetic radiation of a specific wavelength to illuminate a target and then measures the scattered/backscattered radiance.

Introduction / Context:
Remote sensing techniques differ in whether the sensor provides illumination. Active systems transmit energy and record the return, enabling control over wavelength, polarisation, and timing—vital for all-weather or night-time operations (e.g., radar, LiDAR).

Given Data / Assumptions:

• System emits EMR of a chosen wavelength.
• Target is illuminated intentionally by the sensor.
• Backscatter or reflectance is measured at the sensor.

Concept / Approach:
By generating its own signal, an active sensor decouples imaging from solar illumination and can penetrate clouds (microwave SAR) or measure precise ranges (LiDAR). The definition in the stem exactly matches “active remote sensing”.

Step-by-Step Reasoning:

Verification / Alternative check:
Examples include SAR missions (Sentinel-1, RISAT) and LiDAR altimetry (ICESat). Passive imagers lack this transmitter.

Why Other Options Are Wrong:

• passive remote sensing: uses natural illumination (primarily Sun), not emitted by the sensor.
• neutral remote sensing: not a standard term.
• None/All of these: Do not match the precise definition.

Common Pitfalls:
Assuming “active” implies only radar; LiDAR is also active but in optical wavelengths.

Final Answer:
active remote sensing