Indian Lidar technologies

LIDAR technologies
for atmospheric
remote sensing
Y.Bhavani Kumar
NARL, Gadanki
Presentation at
Laboratory for Electro-Optics systems (LEOS), ISRO,
Peenya, Bangalore
On 23 May 2012

---

Atmosphere is a
relatively thin gaseous
layer surrounding the
planet earth
It is characterized by its structure,
composition and dynamics

---

Structure and dynamics of the tropical
atmosphere
Cumulus draw
air from beneath
via buoyancy-
generated
pressure forces
Troposphere is considered as
highly dynamical region

---

Composition of the Atmosphere
Trace
Mean composition
volume
constituents
of dry air
content
Meteorite
in %
entry
nitrogen
78.08
Mesospheric
oxygen
20.95
metal layer
argon
0.934
Na, K, Fe , Ca
carbon dioxide
0.035
neon
0.0018
helium
0.0005
Stratospheric
methane
0.00017
ozone layer
UTLS aerosol
krypton
0.0001
layer
xenon
0.000009
hydrogen
0.00005
High
ABL- rich in
altitude
aerosols
dinitrogen monoxid
0.00003
clouds
carbon monoxide*
0.00002
Water vapor is a variable from 1 to 4%

---

Importance of measurement
To predict or model the atmospheric behavior,
the atmospheric parameters like temperature,
humidity, visibility ..... are need to be measured
on continuous basis.
Atmospheric measurements are of two types
In situ or direct contact type
Remote sensed - non contact type
Advantage with active remote sensing
is its
capability
to
provide
range
resolved
measurement with good spatial and temporal
resolution.

---

Active remote sensing methods
Active remote sensing methods are
of three different types
1.RADAR - Radio detection and
ranging
2.SODAR - Sonic detection and
ranging
3.LIDAR - Light detection and
ranging

---

LIDAR stands for :
Light Detection And Ranging
also called as
Laser radar or optical radar
It is an optical remote sensing technology
that measures properties of scattered light
to find range and/or other information of a
distant target.
It uses the principle of RADAR except that
it uses a laser instead of radio waves.
Lidars use lasers in
IR, Visible and UV
spectral ranges for profiling the atmosphere

---

Principles of LIDAR
R=c t/2,
C: light speed, 3108 m/s

---

Light scattering mechanisms
When the laser fires, photons travel through the
atmosphere
and
interact
with
the
basic
constituents of the atmosphere such as air
molecules and particles.
Their interaction causes scattering and
absorption
Scattering is three types, namely
1. Elastic,
2. Inelastic or Raman and
3. Resonance scattering

---

TYPES OF SCATTERING
Elastic scattering
Inelastic scattering
Measures, 1984

---