Improved Limb Atmospheric Spectrometer-II (ILAS-II), Version 2

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The Improved Limb Atmospheric Spectrometer (ILAS)-II is a satellite-borne sensor that measures ozone and its related chemical species in the high-latitude stratosphere on the basis of the solar occultation technique. There are approximately 14 measurements a day for each of the hemispheres, at sunrise seen from the satellite in the Northern Hemisphere and at sunset seen from the satellite in the Southern Hemisphere.
The retrieval algorithm is based on an onion-peeling method that uses a nonlinear least squares fitting for observed and theoretically calculated transmittance spectra (spectral fitting) at every 1 km downward from an altitude of 70 km to ~10 km to determine the volume mixing ratios of ten different trace gases (O3, HNO3, NO2, N2O, CH4, H2O, CFC-11, CFC-12, ClONO2, and N2O5). In practice, the sunset and sunrise data are retrieved by the version 2.0 and 2.1 algorithms, respectively, but this data set is distributed as the version 2.


Release date
Temporal coverage
2003/01/21 - 2003/10/24
Data provider
Email: cgerdb_admin(at)
File format
Data volume
89.0 MiB
V2 (Last updated: 2008/02)

Data Set

O3, HNO3, N2O, H2O, CH4, ClONO2, Aerosol Extinction Coefficient at 780nm, and other data
Observation period
From January 2003 to October 2003 (Ended)
Spatial coverage
[Northern Hemisphere] Latitude: 57°~ 71°, Longitude: -180°~ 180°
[Southern Hemisphere] Latitude: -64°~ -88°, Longitude: -180°~ 180°
Vertical: ~10 km - 70 km
Time resolution
1 profile per ~100 min in each hemisphere
Spatial resolution
Latitude: Depends on season
Longitude: ~25 degrees
Vertical: 1.3-2.9 km at tangent heights of 15-55 km
Depends on species and altitude
Measurement method
ILAS-II was a satellite-borne solar-occultation sensor on board the satellite ADEOS-II. ILAS-II consisted of four spectrometers: an infrared spectrometer (between 6.21 µm to 11.76 µm); a mid-infrared spectrometer (between 3.0 µm and 5.7 µm); a high-resolution infrared spectrometer (between 12.78 µm and 12.85 µm); and a visible spectrometer (between 753 nm and 784 nm).
Calculation method
Vertical profiles of gases were retrieved by applying both the onion-peeling method and the non-linear least-squares fitting method.
Earth observation satellites > ADEOS > ADEOS-II
Atmosphere > Atmospheric Chemistry > Trace gases/Trace species
[Free keywords]
Stratosphere, Ozone, O3, Nitric Acid, HNO3, Nitrous Oxide, N2O, Water Vapor, H2O, Methane, CH4, Chlorine Nitrate, ClONO2, Aerosol Extinction, Polar Vortex, Ozone Hole, CC BY
Update history
All Version 2 data are released. V2.


Readme file
Griesfeller, A., von Clarmann, T., Griesfeller, J., Höpfner, M., Milz, M., Nakajima, H., Steck, T., Sugita, T., Tanaka, T., and Yokota, T.: Intercomparison of ILAS-II version 1.4 and version 2 target parameters with MIPAS-Envisat measurements, Atmos. Chem. Phys., 8, 825-843,, 2008.
Yokota, T. H. Nakajima, T. Sugita, H. Kawasaki, M. Horikawa, H. Matsuda, N. Uemura, H. Kanzawa, H. Kobayashi, and Y. Sasano (2006), Improved Limb Atmospheric Spectrometer-II (ILAS-II) Version 1.4 algorithm for retrieval of gas and aerosol profiles in the stratosphere (unpublished manuscript).
Nakajima, H., T. Sugita, T. Yokota, T. Ishigaki, Y. Mogi, N. Araki, K. Waragai, N. Kimura, T. Iwazawa, A. Kuze, J. Tanii, H. Kawasaki, M. Horikawa, T. Togami, N. Uemura, H. Kobayashi, and Y. Sasano (2006), Characteristics and performance of the Improved Limb Atmospheric Spectrometer-II (ILAS-II) onboard the ADEOS-II satellite, 111, doi:10.1029/2005JD006334.
Other publications

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Citation format
When this data set is referred to in publications, it should be cited in the following format.
Sugita, T., H. Nakajima, and T. Yokota (2018), Improved Limb Atmospheric Spectrometer-II (ILAS-II), Version 2, Center for Global Environmental Research, NIES, DOI:10.17595/20180628.003. (Reference date*: YYYY/MM/DD)
* As the reference date, please indicate the date you downloaded the files.

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