Katsunori Waragai

Electrical Switching in Evaporated Lead Phthalocyanine Films

The switching characteristics of a sandwich cell having a Au-lead phthalocyanine-Au structure were studied. Switching was observed in a film which was evaporated at a rate of 10 A/s and consisted of a mixture of grains of monoclinic structure and amorphous fraction. The presence of moisture was necessary for switching.

Characteristics and performance of the Improved Limb Atmospheric Spectrometer‐II (ILAS‐II) on board the ADEOS‐II satellite

[1]xa0The 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.

Characteristics and performance of the Improved Limb Atmospheric Spectrometer (ILAS) in orbit

[1]xa0The Improved Limb Atmospheric Spectrometer (ILAS) was a satellite-based solar occultation sensor that was developed by the Environment Agency of Japan (EA) to monitor and study the stratospheric ozone layer. This paper describes the characteristics of the ILAS instrument and its performance in orbit. ILAS measured the vertical distribution of ozone, nitric acid, nitrogen dioxide, nitrous oxide, methane, water vapor, temperature, pressure, and aerosol extinction coefficients at 1.6-km vertical resolution. ILAS was equipped with two spectrometers: an infrared (IR) spectrometer with an uncooled pyroelectric linear array detector to sense between 6.21 and 11.76 μm and a visible spectrometer to monitor 753–784 nm. In addition, a Sun-edge sensor (SES) assigned the tangent height of the instantaneous field-of-view (IFOV). A two-axis gimbals control system on ILAS used two Sun position sensors to track the center of brightness of the Sun during occultation measurements. Before launch onboard the Advanced Earth Observing Satellite (ADEOS), the performance of ILAS was checked on the ground using several methods, including gas-cell measurements, time response measurements, Sun-tracking tests, and hollow-cathode lamp measurements. After the launch of ADEOS on 17 August 1996, ILAS functioned successfully for 8 months of routine operation, from 30 October 1996 to 30 June 1997, collecting more than 6700 solar occultation measurements, after which time the satellite failed due to a failure in a solar paddle. The time delay response of the IR channel was characterized using stepwise IR input. Instrument functions of the ILAS IR and visible spectrometers were determined by combining theoretical optical calculations, experimental measurements using a gas-cell before launch, and in-orbit data. The signal-to-noise ratio (SNR) of each element in the IR channel was estimated to be 400–1200. In the visible channel, it was 1600–1800 for a 100% direct Sun signal. At sunset occultation, ILAS was able to track the Sun below a tangent height of 10 km in some cases. The method of determining the solar edges from the SES data worked correctly, giving adequate tangent height information for observations. Output signal levels of the SES, visible channel, and IR channel showed slight degradation during the period that ILAS was operational, which is attributed to space-borne contaminants. However, changes in absolute signal levels do not affect data retrieval, because the solar occultation technique was self-calibrating. Overall, ILAS worked as designed during its operation in orbit and gathered valuable data for ozone layer studies.

Tangent height registration for the solar occultation satellite sensor ILAS: A new technique for Version 5.20 products

[1]xa0The Improved Limb Atmospheric Spectrometer (ILAS) was a solar occultation satellite sensor that was developed by the Environment Agency of Japan to monitor the stratospheric ozone layer. This paper describes methods of registering tangent heights for ILAS vertical profiles of gas mixing ratio and aerosol extinction coefficient. Accurate tangent height registration is crucial for the retrieval of accurate gas mixing ratios from atmospheric absorption spectra. Three methods for tangent height registration have been applied to retrieved ILAS data. The first method is the transmittance spectrum method (TS-M), which uses absorption spectra of oxygen molecules at around 760 nm (O2A band) measured by the ILAS visible channel and compares the average transmittance with that calculated theoretically from temperature and pressure using meteorological data. A tangent height is derived from these data. Version 3.10 ILAS data products use the TS-M. A second method is the Sun-edge sensor method (SES-M). This method for registering tangent heights was in mind when ILAS was originally designed. The SES-M geometrically determines the direction of the instantaneous field-of-view (IFOV) of the spectrometer from the angular difference between the top edge of the Sun determined with the SES and the spectrometers IFOV. Information on the satellites orbital position and solar position relative to the center of the Earth is used to register the tangent height. Version 4.20 ILAS data products use SES-M. The third method is a hybrid method (Hybrid-M) that was developed to correct for seasonal differences in tangent heights computed by the SES-M. The Hybrid-M assumes that the TS-M can correctly determine the tangent height at 30 km. Version 5.20 ILAS data products (the latest version) use Hybrid-M. Random and systematic errors in the Hybrid-M tangent height registration were estimated. The root-sum-square (RSS) total random error is 30 m, while the total systematic error is +300 ± 360 m in tangent height. Actual errors in tangent height registration in Version 5.20 algorithm are considered to be small judging from the results of comparisons with independent validation data sets. The Hybrid-M gives good estimates of tangent heights in Version 5.20 of the ILAS data processing algorithms.

Temperature and pressure retrievals from O2 A-band absorption measurements made by ILAS: retrieval algorithm and error analyses

A visible grating spectrometer of the Improved Limb Atmospheric Spectrometer (ILAS) aboard the Advanced Earth Observing Satellite (ADEOS) measured atmospheric absorption spectra at a wavelength region from 753 nm to 784 nm, including the molecular oxygen (O2) A-band centered at 762 nm, with a spectral resolution of 0.17 nm. Temperature and pressure profiles throughout the stratosphere were retrieved from the satellite solar occultation measurements of the O2 A-band absorption spectra. Based on simulation studies, root-sum-square errors associated with several systematic uncertainties in spectroscopic databases and instrument functions were estimated to be 4 K for temperature and 4% for pressure in the stratosphere. Current problems in this retrieval are also presented through comparisons with correlative temperature measurements.

Introduction of SOFIS/FTS calibration system

The Solar Occultation FTS for Inclined-orbit Satellite (SOFIS) is a solar occultation Fourier transform spectrometer (FTS), developed by the Ministry of the Environment (MOE) of Japan, that will be onboard the Global Change Observation Mission-A1 (GCOM-A1) satellite. GCOM-A1 will be placed in a 650km non-sun-synchronous orbit, with an inclination angle of 68 deg. SOFIS is the successor of ILAS-II, which will be onboard the Advanced Earth Observing Satellite-II (ADEOS-II). SOFIS measures atmospheric constituent vertical profiles with 0.24 cm-1 spectral resolution in 3-13 μm and 1 km vertical resolution. SOFIS will measure the global distribution of O3, HNO3, NO2, N2O, CH4, H2O, CO2, CFC-11, CFC-12, CIONO2, aerosol extinction, atmospheric pressure, and temperature. SOFIS uses a double-pass dual-pendulum type FTS with diode laser sampling system to reduce the size and weight. Two photo-voltaic (PV) MCT (HgCdTe) detectors and a pulse-tube cooler will achieve high linearity and low-noise performance. In addition, it has a visible (O2, A band) grating spectrometer for pressure and temperature retrieval and a sun-edge sensor for the tangent height position detection. We present the test results of FTS and detector assembly engineering model and describe the SOFIS/FTS calibration system.