Improved Limb Atmospheric Spectrometer (ILAS)
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Observation Cencept
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| ILAS Observation Concept
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Improved Limb Atmospheric Spectrometer (ILAS) developed by the Environment
Agency of Japan is a sensor to monitor the polar stratospheric ozone. The object
of ILAS is to monitor and study changes in the stratosphere which are triggered
by emissions of Chloro Fluoro Carbons (CFC), and to check the effectiveness of
world-wide emission controls of CFCs.
ILAS is a spectrometer which observes the atmospheric limb absorption
spectrum from the upper troposphere to the stratosphere using sunlight (solar
occultation technique). This covers the infrared region (850-1610cm-1) and the
near visible region (753 to 781nm). ILAS is designed based on LAS (Limb
Atmospheric infrared Spectrometer), which was aboard EXOS-C (Ohzora,
ISAS). It was developed to improve observation accuracy and also to detect
minor constituents related to ozone hole chemistry. ILAS's observations are
focused on the high latitude regions because of the geometrical relation of the
solar occultation events with the sun-synchronous orbit. From these spectral
observations, ILAS can measure the vertical profile of ozone hole related
components: ozone (O3), nitrogen dioxide (NO2), aerosols,
water vapor (H2O), CFC11, methane (CH4),
nitrous oxide (N2O), temperature, and pressure.
This dataset covers the key physical and chemical parameters which
characterize ozone hold events: the cooling at the polar lower stratosphere, PSC
formation, the removal of nitrogen reservoirs, and the ozone reduction by
activated chemical chain reactions. ILAS will continue to contribute to research
into stratospheric ozone changes into the late 1990's.
ILAS Main Characteristics
| Spectral Coverage | IR (850-1610cm, 6.21-11.77um)
Visible
(753-784nm)
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| Spectrometer | Gratung Spectrometer with Lonear Linear Array
Detector
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| Spectral Data Sampling Rate | 12MHz
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| IFOV | 2km Vertical x 13km Horizontal
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| Observation Parameters | O3, NO2,
H2O), CFC11, CH4, N2O, aerosols,
temperature, and pressure
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| Observation Region | N57-70 degree, S60-85 degree
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| Weight | 140kg
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| Power | <100W
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| Size | 800x1600x550mm
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ILAS measures the sequence of the limb atmospheric absorption spectrum which
pass the various tangent heights, in 12Hz. The absorption (concentration) of
each layer is derived from this spectral data stream. ILAS tracks the
radiometric center of the solar disk. ILAS also has an IFOV position sensor
which measues the angle between IFOV and the top edge of the sun.
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| ILAS Overview
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Earth Observation Research Center