External Guide

Mr.Y.Bhavani Kumar

Scientist/Engineer-‘SE’

NARL, Gadanki

Tirupati.

Development Of Analysis Software for LAMP System

Internal Guide

Mr.G.Karunakar

Associate Professor

GIT, GITAM UNIVERSITY

Visakhapatnam-45.

Introduction1. Atmosphere

2. Atmospheric Measurementsi. In-situ measurementsii. Remote sensing observations

3. Concept of remote sensingi. Passive Remote sensingii. Active Remote sensing

4. Introduction to Lidar

1. LIDAR – Light Detection and Ranging

2. LIDAR is optical analogue to RADAR

3. Similar principle to RADAR – pulses of light emitted into the atmosphere and scattered back by clouds, aerosols or air molecules

4. Light collected by a telescope

5. Spectrometers or interference filters isolate wavelength concerned

6. Time-of-flight gives scattering height

Basic Principles

1. Cloud Geometry

2. Aerosol Studies

3. Boundary Layer Studies

4. Water vapour

5. Minor constituents e.g. ozone, hydrocarbons

6. Temperature

7. Wind (by Doppler-shifting) etc…

Applications

Primary objectives of this project are:

1. Analyzing the work done using the Ground based Monostatic LAMP (Lidar for Atmospheric Measurement and Probing) system.

2. Extracting data from the output binary file.

3. Development of different algorithms to determine various parameters of the atmospheric constituents and their variations with respect to temperature.

4. Development of Analysis Software using user-friendly MATLAB codes for scientific application purpose.

Objective

Block Diagram

1. Laser: Short pulses with lengths of few nsec and Specific Spectral properties are generated by Laser.

2. Beam Expander: To reduce the divergence of light beam before it is sent into the atmosphere.

3. Steering Mirror: Laser beam is made to fall on the mirror.

4. Control Unit: Microprocessor based system providing hardware interface.

Transmitter Section

1. Telescope: Collects the photons backscattered from the atmosphere followed by an optical analyzer.

2. Detector: Received signal is converted into an electrical signal. Generally the detector can be PMT.

3. Interference Filter: To reduce background light.

Receiver Section

Back Scattered photons

Laser pulse

trigger

Head on type photomultiplier tube

operate in photon counting mode

Pulse discriminator

amplifier

comparator

Pulse Shaper

Pulse counter

Sweep channel analyzer memory

Dwell time

control

Photon count profile

Data acquisition & Signal Processing

Laser : Diode Pumped Q Switched Nd:YAG Laser

Operating Wavelength : 532nm.

Output energy Per Pulse : 2 to 25Microjoules

Pulse Repetition Frequency: 2500Hz

Beam Divergence : <1.5mrad.

Pulse Width : 2nsec.

Transmitter Specifications

Telescope : Schmidt Cassegrain Type.

Diameter : 150mm.

Field of view : 400mrad.

IF filter Bandwidth(FWHM) : 0.5nm

Telescope F-ratio : 9

Receiver Specifications

Quantum Efficiency : <10%

Gain : 2.5*10^7

Data Acquisition System Specifications Type : Single Photon Counting

Maximum Counting Rate: 150MHz

Dwell Time : 100 to 1300ns

PMT Specifications

Raw Photon Count Data

Noise RemovedSignal

Range SquaredSignal

Algorithm For LAMP Data Analysis

Application on Single Profile(Raw Data)

Noise Removed Data

Range Squared Data

Temporal Variation Of Range Corrected Signal

Algorithm For Cloud Base and Cloud Top

Plot of Range, Time,

RCS

Determine Duration of Cloud

Average corresponding RCS w.r.t Range

Plot Range vs Avg. RCS

Cloud Base and Cloud Top

Boundary Layer Detection Techniques

1. Gradient Method: Mostly used to find boundary layer top.

Gradient=

Disadvantage: this method strongly suffers from noise.

2. Wavelet Covarience Transform:

Boundary Layer Top Using Gradient Method

Temporal Variation Of The Boundary Layer From Time To Time Using WCT

Data Inversion Algorithm(Klett Method)Raw Data

Noise Corrected Data

Range Corrected Data

Range Normalization

Number Density Calculation

Estimating Back Scatter Cross Section

Attenuated Back Scatter Coefficient

Averaged RCS(10min Profile)

Backscattering Coefficient

Scattering Ratio

1. The functioning of the currently working LAMP system was observed.

2. Various atmospheric parameters have been derived and plotted using MATLAB user-friendly software codes.

3. The code has been tested under different atmospheric conditions for retrieving the signal information.

4. The developed code has the potential to apply the code for different lidar systems with minimal changes to the program.

Conclusion

Future Work1. This work can be extended in several ways by developing the software

further, by using different algorithms.

2. Those include the determination of timely variation of the cloud base with respect to time, determination of extinction coefficient and aerosol optical thickness values by further analyzing the klett method, comparison of variation of night time AOT values and day time AOT values etc.

3. In case of clouds, the scattering parameters can be determined by using klett forward or backward algorithm methods.

4. With the addition of these features to the developed software, by using different algorithms make it more efficient and reliable software for atmospheric observations.

1. Lidar Range-Resolved Optical Remote Sensing of the Atmosphere, by Claus Weitkamp, 2004.

2. Elastic Lidar by Vladimir Kovalev, William E.Eichinger.

3. Laser Remote Sensing by Takashi Fujii, 2005.

4. Laser Remote Sensing Fundamentals and Applications, by Raymond M.Measures,1992.

5. Technology Development for Atmospheric Research & Applications, by B.Manikiam, T.G.K.Murthy, Atmospheric Science programme, ISRO, june 2008.

6. Portable Lidar system for atmospheric boundary layer Measurements, Author: Mr.Yellapragada Bhavani Kumar, Optical Engineering 45(7),1(July 2006).

7. Resonance Lidar system for mesospheric Sodium measurements, Authors: Mr.Y.Bhavani Kumar, Mr.D.Narayana Rao, Mr.M.Sundara Murthy, Mr.M.Krishnaiah, Optical Engineering 46(8),086203(August 2007).

8. Getting Started with MATLAB 7, A Quick introduction to Scientists and Engineers, Rudra Pratap, Eight edition, 2008.

References

Thank You