| ILAS-II Project | Organization | Ozone Layer Depletion |
| ADEOS-II | ILAS-II | Principle of Observation |

Outline of ILAS-II

The Improved Limb Atmospheric Spectrometer-II (ILAS-II), on board the Advanced Earth Observing Satellite-II (ADEOS-II "Midori-II", launched in December 2002 and in operation until October 2003), is an atmospheric observation sensor developed by the Ministry of the Environment to monitor and study the ozone layer in the high latitude stratosphere in the Northern and Southern Hemispheres.
ILAS-II, an improved version of ILAS, which is on board ADEOS "Midori," was designed to cover wider spectral ranges and improve the accuracy of observations. ILAS-II can measure vertical distributions of atmospheric trace species and aerosols as well as temperature and pressure.

ILAS-II incorporates a 3rd channel (with a spectral range from 12.78 to 12.85 µm) for measuring ClONO2, which may function as a chemical reservoir of reactive chlorine compound. It is an important substance for understanding the mechanism of ozone layer depletion and its conditions. A mid-infrared channel below 6 µm, while ILAS has only an infrared channel above 6 µm, is also added for ILAS-II. This will improve the accuracy of evaluations of the characteristics of aerosol/PSCs (Polar Stratospheric Clouds) particles. It is generally understood that aerosol/PSCs particles contribute to ozone layer depletion. Therefore, it is necessary to extract useful information from the compositions and profiles of aerosol/PSCs.

ILAS-II has the following major functional improvements over ILAS:
  • A 3rd channel was added in order to monitor ClONO2.
  • A 2nd channel below 6 µm was added to monitor a spectrum in the infrared band, and the accuracy of particle observation of aerosol/PSCs was improved.
  • Vertical resolution was improved from 2 km to 1 km.
  • Solar surface scan method was adopted.
  • Highly accurate orbit data based on GPS data was adopted. (A function of ADEOS-II)

Main Characteristics of ILAS-II
Spectral coverage (Wave number) Ch.1: 6.21 - 11.76 µm (1,610 - 850 cm-1)
Ch.2: 3.0 - 5.7 µm (3,333 - 1,754 cm-1)
Ch.3: 12.78 - 12.85 µm (782 - 778 cm-1)
Ch.4: 753 - 784 nm (13,280 - 12,755 cm-1)
Observation parameters O3, HNO3, NO2, N2O, CH4, H2O, ClONO2, aerosol, temperature, pressure, CO2 (for pressure measurement)
Altitudal coverage 10 - 60 km (continuous observation from the cloud top to 250 km)
Target accuracy Altitudal resolution 1km
Concentration at each tangent height 1 % for ozone, 5 % for trace constituents other than ClONO2 and under study for ClONO2.
Measurement areas (latitude range) Northern Hemisphere: 57 -73 degrees
Southern Hemisphere: 64 -90 degrees
Spectrometers Ch.1 - Ch.3: Grating spectrometer with array detectors (Element number Ch.1:44, Ch.2:22, Ch.3:22)
Ch.4: Grating spectrometer (Element number: 1024 )
Data rate 453.7 kbps (10 Hz sampling)
Weight 138 kg (max)
Power consumption 120 W (during operation)

| ILAS-II Project | Organization | Ozone Layer Depletion |
| ADEOS-II | ILAS-II | Principle of Observation |