CE376

Compact Automatic Aerosol LiDAR

Remote sensing instruments

Overview

Features


Applications

The CE376 is the cost effective solution for automatic aerosol monitoring within an operational network as well as for field campaigns. It provides key information on aerosol layers, boundary layers and cloud layers, for numerous applications:
      • Volcanic ash watch
      • Sand dust storm watch
      • Air quality monitoring and forecast
      • Climate change
      • Airport flight operation
      • Atmospheric sciences
      • Aerosol modeling
      • Numericable Weather Prediction (NWP)
 

User benefits

Enriched aerosol data
      • Aerosol measurements up to the top of the troposphere (typically higher than 13 km by night time)
      • Very short blind zone (<100m)
      • Measurement of the aerosol optical properties in the visible (G models)
      • Non visible beam in the near infrared (N models)
      • Information on aerosol shape for each layer (P options)
      • Information on aerosol size for each layer (GN models)
      • Automatic calibration of extinction (on molecular signal)
Real time analysis
      • Automatic extinction and backscatterring profiles
      • Automatic calibration of concentrations by coupling with CE318 photometer
      • Automatic stratification analysis
      • Real time "quicklook" visualizations
Enhanced reliability
      • More than 1 year operation without technical maintenance
      • Low maintenance costs
      • High stability even in outdoor operation (from - 20°C to 45°C with optional thermal enclosure)
High flexibility of implementation
      • Eye safety compliance with EN-60825/ANSI Z136 (no need for airplane RaDAR that automatically shuts down the laser)
      • Automatic unattented operation
      • Easy transportation
      • Outdoor/ indoor/ mobile operation
      • Compliance for airborne operation

Technology

The CE376 takes advantage of the most recent advances in laser and sensor technologies. Lasers
      • 1 ou 2 low power and high frequency pulsed lasers (Green and/or NIR)
      • More than 1 year life time without any maintenance
      • Integrated output power monitoring on each laser
Optical head
      • Bi-axial design for each wavelength
      • Depolarization reception channel for each wavelength (options)
Reception
      • Up to 4 reception lines depending on the models and options
      • Detection in photon counting mode with high quantum efficiency (QE) avalanche photodiode
The whole system is integrated within a single compact housing that can be easily handled. It operates indoor or outdoor (protection against rain) in the 10°C to 30°C temperature range. The thermal enclosure should be used for more variable temperatures.

Operation

Measurement principle
      • The laser emits a light pulse that is scattered by the particles present in the atmosphere
      • A tiny part of the pulse light is directed backward towards the instrument (backscatter)
      • The time of flight of the pulse between emission and reception indicates the distance of the scattering particles
      • The amount of backscattered light received at each distance depends on the quantity and type of the particles
      • The depolarization reception channel measures only the light that has been depolarized, indicating the presence of non spherical particles
      • In aerosol free regions, the light received measures the "molecular" backscatter (due to the clean atmosphere molecules)
      • The backscatter light is converted to an electronic signal (in the control unit) and then processed (on the PC) to deliver vertical profiles
PC based data processing The supplied software may be installed on any PC with recent Windows operating system. It performs automatic signal acquisition and preprocessing
      • Noise detection and correction
      • Overlap and range correction
      • Automatic detection of a reference (aerosol free) layer for automatic calibration of the extinction coefficient on the molecular backscatter
and real time analysis and visualization of the following parameters
      • Raw data (signal)
      • Range corrected signal (averaging time between 1 min and several hours)
      • Planetary boundary layer detection
      • Extinction and backscattering profiles, optionally using external AOD/LiDAR Ratio data for automatic calibration
      • Depolarization ratio (indicator of non spherical particles)
      • Vertical stratification analysis, including cloud detection
Visualisation modes include both range profile graphs and range-time color charts (Quicklooks)

Technical features

Specification

 

Parameter

Value

Source

Laser type

Green laser: frequency doubled Nd:YAG

NIR laser: pulsed laser diode

 

Wavelengths

Green : 532 nm .  NIR <850 nm

 

Pulse energy

Green: 5-10 µJ, NIR: 3-5  µJ

 

Repetition rate

5 kHz

 

Pulse width

<15 ns

Optics

Telescope type

Galilean

 

Telescope diameter

100 mm for both emission and reception

 

Effective focal length

200 mm

 

Total beam divergence

Emission: Green: 100 µrad, NIR: <250 µrad 

Reception : Green: 200 µrad, NIR: <300 µrad 

 

Instrument configuration

Biaxial

 

Eye safety

Yes

Detection

Detector type

APD QE 55% / 70%

Power supply

Voltage, power

110/230 V AC and 28 V DC, <300 W

Automatic switching

 

Autonomy

10 min with uninterruptible power supply option

Data acquisition

Data acquisition mode

Photon counting

 

Continuous acquisition

Yes

 

Data counting rate

25 Mc/s

 

Electronic range resolution

15 m gates

 

Electronic range

From 100 m up to 30 km (2048 gates).

 

Data transfer  to PC

USB or Ethernet

Measurement range*

Molecular Detection Range in typical conditions (AOD 0.2) with 10 min averaging

By night time: 13 km

By day time: 7 km

Retrieved products

PR2 / Ln(PR2) data (after instrumental corrections)

Yes

 

Stratification analysis

Yes: aerosols, boundary layers, clouds

 

Extinction & backscatter coefficients

Yes (using external data : AOD or LiDAR Ratio)

 

Depolarization ratio

Yes

Environmental conditions

Operation without thermal enclosure 

+10°C to +30°C , 0 to 90% RH

 

 

Operation inside thermal enclosure

-20°C to +45°C, 0-100% RH and rain

General

Transportability

Yes

 

LiDAR size

L 650 mm x W 450 mm x H 710 mm

 

LiDAR weight

25 kg

* Measurement range The detection range of a high altitude layer of particles (aerosols or cloud) strongly depends on its concentration. The more concentrated the layer, the farther its detection. Therefore, to define the performance of a LiDAR in terms of measurement range, it is usual to rather refer to the Molecular Detection Range: The distance (in the absence of clouds) up to which the LiDAR is able to measure the small "molecular" signal of an aerosol free atmosphere (with a Signal to Noise Ratio superior to 1). This Molecular Detection Range only depends on measurement conditions (total aerosol loading, averaging time , night/day). For any given measurement condition, the LiDAR will detect particle layers above the corresponding Molecular Detection Range, the maximal height depending on layer's concentration.

Options

CE376 Models

Model Name

Description

Detection of non spherical particles

(ashes, sand, cirruses…)

Information on vertical distribution of particle size

CE376-G

Green (532 nm)

-

-

CE376-GP

Green with depolarization

YES

-

CE376-N

NIR (invisible)

-

-

CE376-NP

NIR with depolarization

YES

-

CE376-GN

Green + NIR

-

YES

CE376-GPN

Green with depolarization + NIR

YES

YES

Thermal enclosure (Emission antenna up the mast)

Specification

Value

Outdoor operation

YES

Outdoor temperature operation range

-20°C à +45°C

Relative humidity operation range

0-100%

Power supply (max)

800 W

Wheels

YES

Positioning

4 leveling feet

Size

950 x 950 mm

 

H 1400 mm

Weight

90 kg

 

Outputs

Vertical profile of Ln (PR2) (range corrected) signal with indication of the total Noise  (dots)(left). Time graph of background noise (top). Quicklook of range corrected signal (right bottom)