A new instrument makes the task of monitoring ozone levels easier
The ozone layer, which shields life on
earth from the Sun's harmful ultraviolet radiation, is slowly disappearing
from the upper reaches of the atmosphere, especially over the South Pole.
Hence the need to monitor this loss.
However, there are problems with
the ozone-measuring devices. Satellites and ground-based instruments,
for instance, sketch a very general picture of the ozone profile - the total
ozone lost over a span of 40 km. To
get a more refined record, layer by
layer, scientists use balloon-borne
instruments. But keeping balloons
steady in Antarctica, which experiences gales with speeds up to 300
kmph, is not easy.
To tide over this problem, scientists at Delhi's National Physical
Laboratory (NPL), in collaboration
with French scientists from the
Meudon Observatory near Paris, have
devised an instrument that can record
a layer-by-layer profile of ozone sitting on earth. The instrument, called a
laser heterodyne, was recently used
by the Indian scientists in Antarctica
to monitor not only ozone but also
various other trace gases over the icy
continent.
The device uses a carbon dioxide
laser, which is tuned to the frequency
of the molecule sought to be detected,
and blended with sunlight carrying
the signature of the molecule in the
form of its absorption spectrum.
The bledded signal is then passed
through a grid that diffracts or splits
the light. The diffracted portion of the
light is picked up by a detector and an
analysis of its spectrum gives the precise level of the compound sought.
Says 8 M Reddy, the head of
the radiosciences division at NPL
"There is nothing earthshaking aboLe
the technology used in this instr
ment. Western nations did not nug
an attempt to produce it, simpor
because it was a very expenstim
proposition, in terms of labour- it
required about 5-6 scientists com
pletely dedicated to it for 4 years
it was well worth the effort as the
machine allows extremely precrw
measurements of several diffe
atmospherivc6ristituents."
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