Prominence of “modis” in understanding global dynamics
By: vaibhav sharma(ece 5th semester)
Bit mesra
Abstract:

In the present scenario, the rapid
change in the global dynamics needs to
be captured by the various devices in
order to have a better understanding of
the earth and its surroundings. One
such device is Moderate Resolution
Imaging Spectroradiometer (MODIS).it
is a kind of a payload scientific
instrument which capture data in 36
spectral bands. These data will
improve our understanding of global
Keywords:




dynamics and processes occurring on
the land, in the oceans, and in the
lower atmosphere. Here, we will
understand how MODIS is playing a
vital role in the development of
validated, global, interactive Earth
system models able to predict global
change accurately enough to assist
policy makers in making sound
decisions concerning the protection of
our environment.
Global dynamics
Spectral bands
Wavelength
Radiometry
Introduction:
Figure :various sub-sustems of modis
Function:
MODIS ( Moderate Resolution Imaging
Spectroradiometer ) is a key instrument whiach
is a part of the the Terra ( known as EOS AM1) and aqua (originally known as EOS PM-1)
satellites. Terra's orbit around the Earth is
timed so that it passes from north to south
across the equator in the morning, while Aqua
passes south to north over the equator in the
afternoon. Terra MODIS and Aqua MODIS
are viewing the entire Earth's surface every 1 to
2 days, acquiring data in 36 spectral bands, or
groups of wavelengths (see MODIS Technical
Specifications). These data will improve our
understanding of global dynamics and
processes occurring on the land, in the oceans,
and in the lower atmosphere. MODIS is
playing a vital role in the development of
validated, global, interactive Earth system
models able to predict global change accurately
enough to assist policy makers in making sound
decisions concerning the protection of our
environment.
modis design:
The MODIS instrument provides high
radiometric sensitivity (12 bit) in 36 spectral
bands which range in wavelength from 0.4 µm
to 14.4 µm. The responses are customised as
per the individual needs of the user community
and provide prodigiously low out-of-band
response. Two bands are imaged at a nominal
resolution of 250 m, with five bands at 500 m,
and the remaining 29 bands at 1 km. A ±55degree scanning pattern at the EOS orbit of
705 km achieves a 2,330-km swath and
provides global coverage every one to two days.
The Scan Mirror Assembly uses a continuously
rotating double-sided scan mirror to scan ±55degrees and is driven by a motor encoder built
to operate at 100 percent duty cycle throughout
the design life of the instrument which is six
years. The optical system consists of a twomirror off-axis afocal telescope, which directs
energy to four refractive objective assemblies;
one for each of the VIS, NIR, SWIR/MWIR
and LWIR spectral regions to cover a total
spectral range of 0.4 to 14.4 µm.
A high-performance passive radiative cooler
provides cooling to 83K for the 20 infrared
spectral bands on two HgCdTe Focal Plane
Assemblies (FPAs). Novel photodiode-silicon
readout technology for the visible and near
infrared provide unsurpassed quantum
efficiency and low-noise readout with
exceptional dynamic range. Analogue
programmable gain and offset and FPA clock
and bias electronics are located near the FPAs
in two dedicated electronics modules, the
Space-viewing Analogue Module (SAM) and the
Forward-viewing Analogue Module (FAM) . A
third module, the Main Electronics Module
(MEM) provides power, control systems,
command and telemetry, and calibration
electronics.
The system also includes four on-board
calibrators as well as a view to space: a Solar
Diffuser (SD), a v-groove Blackbody (BB), a
Spectroradiometric calibration assembly
(SRCA), and a Solar Diffuser Stability Monitor
(SDSM). The first MODIS Flight Instrument,
ProtoFlight Model or PFM, is integrated on the
Terra (EOS AM-1) spacecraft. Terra successfully
launched on December 18, 1999. The second
MODIS flight instrument, Flight Model 1 or
FM1, is integrated on the Aqua (EOS PM-1)
spacecraft; it was successfully launched on May
4, 2002. These MODIS instruments offer an
unprecedented look at terrestrial, atmospheric,
and ocean phenomenology for a wide and
diverse community of users throughout the
world.
parameter used - “aerosol optical depth (a.o.d):
aerosols and their affects:
Tiny solid and liquid particles
suspended in the atmosphere are called
aerosoles. Examples of aerosols include
windblown dust, sea salts, volcanic ash,
smoke from fires, and pollution from
factories. These particles are important
to the scientists because they can affect
climate, weather, and people’s health.
Aerosols affect climate by scattering
sunlight back into the space and
cooling the surface. Aerosolsalso help
cool earth in another way – they act
like “seeds” to help form clouds. The
particles give water droplets something
to cling as the droplets form and gather
in the air to make clouds. Clouds give
shade to the surface by reflecting
sunlight back into space. People’s
health is affected when hey breathe in
smoke or pollution particles. Such
aerosols in our lungs can cause cancer
and serious other problems. But
scientists do not fully undestand all the
ways that the aerosols affect the earth
environment.
FIGURE: A.O.D variation throughout the world
Aerosol optical depth is a measure of the
extinction of the solar beam by dust and
haze. In other words, particles in the
atmosphere (dust, smoke, pollution) can
block sunlight by absorbing or by scattering
light. AOD tells us how much direct
sunlight is prevented from reaching the
ground by these aerosol particles. It is a
dimensionless number that is related to the
amount of aerosol in the vertical column of
atmosphere over the observation location.
A value of 0.01 corresponds to an
extremely clean atmosphere, and a value of
0.4 would correspond to a very hazy
condition. An average aerosol optical depth
for the U.S. is 0.1 to 0.15.
Data analysis:
1) Time averaged map of combined data target and deep blue aerosol optical depth(A.O.D)
over India:
(FROM APRIL 2009 – MARCH 2016)
Here, light blue colour indicates the least
A.O.D and then gradually increasing to
dark blue and then to red , finally yellow
being the highest concentration of A.O.D.
we can easily see that most over the land is
covered with dark blue colour, thereby
indicating the moderate concentration of
A.O.D. In the IGT belt we prominently see
the red colour indicating more than
moderate amount of A.O.D. We only see
few yellow spots.
2)from april 2015-may 2015 [pre- monsoon period]
Here also, we see most of the land covered
with dark blue colour indicating the
moderate amount of A.O.D. Then in the
western rajasthan and north-west region
and the eastern region we see red colour
thereby indicating more than moderate
A.O.D concentration. Finally , yellow
colour can be seen in the eastern region of
the country and north-west rajasthan over a
short area indicating the high
concentration of A.O.D. This period of
April-May is called as Pre- Monsoon period.
It is determined by the situation shown in
the map as per the concentration of A.O.D.
3)from december 2014-january 2015 [winter season]
Here, this map also consists of the maximum portion covered by the dark blue colour. We can
see the red area over the I.G.T spread along the edges which are surrounded by the yellow
colour which indicates high concentration of A.O.D. This period between December and
January marks the winter season. This contrasts from the previous map that is the map of PreMonsoon as it contains large amount of area covered with the yellow colour in comparison to
the previous map thus indicating more amount of A.O.D concentration in the I.G.T region.
Conclusion:
The MODIS gives a more precise and accurate idea of the weather and other global dynamics.
Thus, it’s a significant step in determining the weather conditions prevailing over a region with
a high accuracy.
ACKNOWLEDGEMENT:
I would like to express my special thanks of gratitude to B.I.S.R (Birla Institute of Scientific
Research) and “Dr. Swagata Pyra” and “Dr. Sunita Pyra” who gave me the opportunity to do
this wonderful project and enlightened me throughout.
REFRENCES:




http://google.co.in
http://wikipedia.com
http://terra.nasa.gov
http://nsidc.org