The Improved Limb Atmospheric Spectrometer‐II (ILAS‐II) monitored components associated with Polar ozone depletion. ILAS‐II was on board the Advanced Earth Observing Satellite‐II (ADEOS‐II, “Midori‐II”), which was successfully launched on 14 December 2002 from the Tanegashima Space Center of the Japan Aerospace Exploration Agency (JAXA). ILAS‐II used a solar occultation technique to measure vertical profiles of ozone (O3), nitric acid (HNO3), nitrogen dioxide (NO2), nitrous oxide (N2O), methane (CH4), water vapor (H2O), chlorine nitrate (ClONO2), dinitrogen pentoxide (N2O5), CFC‐11, CFC‐12 and aerosol extinction coefficients at high latitudes in both the Northern and Southern hemispheres. ILAS‐II included Sun‐tracking optics and four spectrometers, a Sun‐edge sensor, and electronics. The four spectrometers measured in the infrared (channel 1) between 6.21 and 11.76 μm, in the midinfrared (channel 2) between 3.0 and 5.7 μm, at high resolution in the infrared (channel 3) between 12.78 and 12.85 μm, and in the visible (channel 4) between 753 and 784 nm. The vertical height of the entrance slit was 1 km at the tangent point. A Sun‐edge sensor accurately registered tangent height. After an initial check of the instruments, ILAS‐II recorded routine measurements for about 7 months, from 2 April 2003 to 24 October 2003, a period that included the formation and collapse of an Antarctic ozone hole in 2003 that was one of the largest in history. All of the ILAS‐II data were processed using the version 1.4 data‐processing algorithm. Validation analyses show promising results for some ILAS‐II measurement species, which can be used to elucidate mechanisms of Polar ozone depletion. Studies are ongoing on ozone depletion, on the formation mechanisms of Polar stratospheric clouds, on denitrification, and on air mass descent. A state‐of‐the‐art data retrieval algorithm that is currently being developed will yield more sophisticated data sets from the ILAS‐II data in the near future.

The Improved Limb Atmospheric Spectrometer-II (ILAS-II) is a satellite-borne solar occultation sensor onboard the Advanced Earth Observing Satellite-II (ADEOS-II). The ILAS-II succeeded the ILAS. The ILAS-II used four grating spectrometers to observe vertical profiles of gas volume mixing ratios of trace constituents and was also equipped with a Sun-edge sensor to determine tangent heights geometrically with high precision. The accuracy of gas volume mixing ratios depends on the accuracy of the tangent height determination. The combination method is a tangent height registration method that was developed to give appropriate tangent heights for the ILAS-II Version 1.4 data retrieval algorithm. This study describes the method used in the ILAS-II Version 1.4 retrieval algorithm to register tangent heights. The root-sum-square total random error is estimated to be 30 m, and the total systematic error is 180 m at an altitude of 30 km. The influence of the tangent height errors on the vertical profiles of gas volume mixing ratios in ILAS-II Version 1.4 is estimated by using the relative difference. The relative difference for each species is within 7% (20%) for an altitude shift of +/-100 m(+/-300 m).

The successor of the Improved Limb Atmospheric Spectrometer (ILAS), ILAS-II, aboard the Advanced Earth Observing Satellite-II (ADEOS-II) measured atmospheric absorption spectra at a wavelength region from 753 nm to 784 nm, including the molecular oxygen (O 2 ) A-band centered at 762 nm, with a FWHM spectral resolution of 0.06 nm. Temperature and pressure profiles between ~10 km and 80 km were retrieved from the solar occultation measurements of the O 2 A-band spectra during the operational period of ADEOS-II in 2003. Based on the actual measured data during the smallest atmospheric variability, the repeatability of the measurement, which is a measure of the measurement precision, for temperature and pressure was estimated to be 1-2 K and 0.5-2%, respectively. Comparisons between ILAS-II and the U.K. Met. Office (UKMO) stratospheric analyses or the NASA's UARS/HALOE and TIMED/SABER temperature data are performed. Regardless of the good precision, it is found that the ILAS-II temperatures are systematically lower in the stratosphere and significantly higher in the lower mesosphere.

In order to investigate the alignment of CH3F in para-H2 crystals, high resolution polarization spectroscopy of the ν3 vibrational band is studied using a quantum cascade laser at 1040 cm(-1). It is found that the main and satellite series of peaks in the ν3 vibrational band of CH3F have the same polarization dependence. This result supports the previously proposed cluster model with ortho-H2 in first and second nearest neighbor sites. The observed polarization dependence function is well described by a simple six-axis void model in which CH3F is not aligned along the c-axis of the crystal but tilted to 64.9(3)° from it.

The absorption spectrum of the ν 3 (C-F stretching) mode of CH 3 F in solid para-H 2 by FTIR showed a series of equal interval peaks a . Their interpretation was that the n-th peak of this series was due to CH 3 F-(ortho-H 2 ) n clusters which were formed CH 3 F and n's ortho-H 2 in first nearest neighbor sites of the para-H 2 crystal with hcp structure. In order to understand this system in more detail, we have studied these peaks, especially n = 0 -3 corresponding to 1037 -1041 cm −1 , by using high-resolution and high-sensitive infrared quantum cascade (QC) laser spectroscopy. Before now, we found many peaks around each n-th peak of the cluster, which we didn't know their origins b . We observed photochromic phenomenon of these peaks by taking an advantage of the high brightness of the laser c . In this study, we focus on satellite series consisting of six peaks which locate at the lower energy side of each main peak. All the peaks showed a common red shouldered line profile, which corresponds to partly resolved transitions of orthoand para-CH 3 F. The spectral pattern and time behavior of the peaks may suggest that these satellite series originate from a family of CH 3 F clusters involving ortho-H 2 in second nearest neighbor sites. A model function assuming this idea is used to resolve the observed spectrum into each Lorentzian component, and then some common features of the satellite peaks are extracted and the physical meanings of them will be discussed.