Understanding Bounced Radiation Measurement in Remote Sensing

Remote Sensing involves observing the Earth's surface from a distance, typically using sensors on satellites or aircraft. These sensors interact with the Earth's surface by sending out signals (like microwaves or laser pulses) or by passively detecting naturally occurring radiation. A key aspect is how the surface reflects, scatters, or "bounces" this energy back towards the sensor.

The question asks to identify the device used specifically to measure this bounced radiation. Let's analyze the options:

Analyzing Remote Sensing Devices

1. Laser Altimeter

A Laser Altimeter uses laser pulses to measure the precise distance between the sensor and the Earth's surface. It sends a laser pulse down and measures the time it takes for the reflected pulse to return. While it detects bounced laser light, its primary purpose is measuring altitude or surface elevation, not characterizing the scattering properties of the surface based on general radiation bounce.

2. Radiometer

A Radiometer measures the intensity of electromagnetic radiation within specific wavelength bands. It can detect radiation emitted by the Earth or reflected solar radiation. While it measures radiation that has interacted with the surface, it doesn't specifically focus on the directional scattering (the pattern of bouncing) of the radiation, which is crucial for understanding surface characteristics like roughness.

3. Eco Sounder

An Eco Sounder (or Echo Sounder) is primarily used for measuring water depth in oceans and seas. It uses acoustic (sound) waves, not electromagnetic radiation, to determine the distance to the seabed. This device is not used in the context of measuring bounced radiation in typical remote sensing applications.

4. Scatterometer

A Scatterometer is specifically designed to measure the amount and pattern of energy (usually microwaves) that is scattered or bounced back from a surface towards the sensor. It transmits microwave pulses and measures the intensity of the signal that is reflected off the surface (backscatter). By analyzing this returned energy at different angles, a scatterometer can provide valuable information about surface properties, such as roughness, texture, and orientation. In oceanography, it's vital for measuring wind speed over water by detecting the roughening effect on the sea surface.

Conclusion on Bounced Radiation Measurement

Based on the functions of these devices, the Scatterometer is the instrument purpose-built for measuring the characteristics of bounced radiation (specifically backscattered energy) from surfaces in Remote Sensing.