Laser for Measurement of Atmospheric Effect

Laser for Measurement of Atmospheric Effect

The atmosphere is rhe ability to study its components including cloud, aerosols ,ozone and water vapour. Lase based system called LIDARS (light detection and ranging) is used to study the atmosphere with high precision. A LIDAR can penetrate thin or broken clouds in the lower atmosphere. The space based LIDAR can provide global measurement of the vertical structure of clouds and atmospheric gases. Both ozone and water vapour are involved in many important atmospheric processes that can affect life on earth, climate changes, weather , global pollution levels etc.,

1. Types of LIDAR

i.           Satellite borne LIDARS

Provides global coverage but at lower horizontal resolution

ii.           Ground borne LIDARS

Reveal the fine detail required for atmospheric process research .

2. Construction And Working:

A powerful laser transmits a short and intense pulse of light. The pulse is expanded to minimize its divergence and is directed by a mirror into the atmosphere. As the pulse travels upward, it is scattered by atmospheric constitutes and aerosol particulates. Light that is back scattered in the field of view of a co-aligned telescope is collected and channeled towards detector by an optical fiber. Filter \s are used to eliminate light away from the laser’s wavelength an d a mechanical shutter can be used to block the intense low attitude returns. The amount of light received is measured as a function of time or distance using sensitive photo detectors and the signals are digitized for storage on a computer’s hard disk.

Coordination of the experiments is performed by a timing unit. When each laser pulse exists the atmosphere, another pulse is transmitted and the process is repeated.

3. LIDAR Applications:

Atmospheric science

Pollution detection and characterization

Dynamic measurements: temperature,waves and winds

Topographic mapping

Erosion Monitoring

Bathymetery

Harbor profiling for marine safety.

Mineshaft mapping.

Allows cavern monitoring for safety workers.