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 (O2) 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 O2A-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.
The Improved Limb Atmospheric Spectrometer-II (ILAS-II) onboard the Advanced Earth Observing Satellite-II (ADEOS-II) was successfully launched on 14 December, 2002 from Japan Aerospace Exploration Agency (JAXA)'s Tanegashima Space Center. ILAS-II is a solar-occultation atmospheric sensor which measures vertical profiles of O3, HNO3, NO2, N2O, CH4, H2O, ClONO2, aerosol extinction coefficients etc. with four grating spectrometers. After the checkout period of the ILAS-II, ILAS-II started its routine operation since 2 April 2003 until 24 October 2003, when ADEOS-II lost its function due to solar-paddle failure. However, about 7 months of data were acquired by ILAS-II including whole period of Antarctic ozone hole in 2003 when ozone depletion was one of the largest up to now. ILAS-II successfully measured vertical profiles of ozone, nitric acid, nitrous oxide, and aerosol extinction coefficients due to Polar Stratospheric Clouds (PSCs) during this ozone hole period. The ILAS-II data with the latest data retrieval algorithm of Version 1.4 shows fairly good agreement with correlative ozonesonde measurements within 15% accuracy.
The Improved Limb Atmospheric Spectrometer-II (ILAS-II) onboard the Advanced Earth Observing Satellite-II (ADEOS-II) was successfully launched on 14 December, 2002 from National Space Development Agency of Japan (NASDA)’s Tanegashima Space Center. ILAS-II is a solar-occupation atmospheric sensor which will measure vertical profiles of O3, HNO3, NO2, N2O, CH4, H2O, ClONO2, aerosol extinction coefficients, etc. with four grating spectrometers. After the checkout period of the ILAS-II which is scheduled in January-February, 2003, ILAS-II will make routine measurements from early April. An initial checkout (ICO) operation was done on 20-23 January, 2003. Data taken during the ICO period suggest that ILAS-II was functioning normally as designed. Signal-to-noise ratio (SNR) for each channel showed good quality of the ILAS-II data except for Ch.3. Preliminary comparison of ILAS-II O3 profiles with ozonesondes showed good agreements. A validation campaign is scheduled to be taken place in Kiruna, Sweden in 2003, when several balloon-borne measurements are planned.
The Improved Limb Atmospheric Spectrometer on board the Advanced Earth Observing Satellite first detected the onset of denitrification in the 1996/1997 Arctic winter stratosphere. Box model calculations along back trajectories are used to estimate the degree of denitrification caused by the formation of nitric acid trihydrate (NAT) particles followed by their growth and sedimentation. The calculated loss of reactive nitrogen explains well the observed loss, identifying the mechanism of large NAT particle formation causing Arctic denitrification.
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.
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 satellite. We describe the performance test results of the laboratory model and present the instrument and engineering model test results.
Considering global increase in greenhouse-gases, observation and monitoring of the earth's atmosphere with space-borne instruments are essential. Satellite measurement offers the advantage of global and long-term monitoring. In the short wave infrared (SWIR) region of 1.5-1.9 micrometers , major greenhouse gases (carbon dioxide (CO2), water vapor (H2O), and methane (CH4)) have absorption spectra of moderate strength without interference by other molecule absorption. In addition, we can use the un-cooled detector for this wavelength region. Two different types of observation geometry will be discussed; one is nadir-looking with sun glint light source for the column amount retrieval and the other is limb-looking with scattered light source for the vertical profile retrieval. We propose the four- ports Fourier transform spectrometer (FTS) for this application. One input port is for nadir-looking measurements and the other input port is for limb-looking measurements. One output port is used for greenhouse gases measurements and the other port is used for the oxygen (O2) absorption spectra measurement for the optical path length calibration. The instrumentation of the FTS, retrieval algorithm and expected performance are discussed, and ground test results are also presented.
The Solar Occultation FTS for Inclined-orbit Satellite (SOFIS) is a solar-occultation Fourier-transform spectrometer developed by the Environment Agency of Japan (EA). SOFIS onboard the Global Change Observation Mission-Al (GCOM-Al) satellite will be put into a 650 km non-sun-synchronous orbit with an inclination angle of 69 deg. GCOM-Al is scheduled to be launched in spring 2006. SOFIS is the successor of the Improved Limb Atmospheric Spectrometer-II (ILAS-II), which with travel onboard the Advanced Earth Observing Satellite-II (ADEOS-II). SOFIS will measure vertical profiles of atmospheric constituents with 0.2 cm-1 spectral resolution at 3 - 13 micrometer with 1 km vertical resolution. The scientific objective of SOFIS is to measure global vertical distributions of O3, N2O, CH4, CO2, H2O, HNO3, NO2, aerosols, CFC-11, CFC-12, and ClONO2. SOFIS uses a double-pass dual-pendulum type Fourier transform spectrometer (FTS) and a diode laser sampling system to reduce the size and weight of the apparatus. Two photovoltaic (PV) HgCdTe (MCT) detectors and a pulse-tube cooler will provide high linearity and low-noise performance. SOFIS also has a visible (O2 A band) grating spectrometer for pressure and temperature retrieval and a sun- edge sensor for detecting the tangent height position. This paper describes the characteristics of SOFIS and test results of laboratory models of the FTS and the detector.
Reanalysis was made for quantitative chemical ozone loss rates in the Arctic stratospheric vortex by using ozone profile data (Version 5.10) obtained with the Improved Limb Atmospheric Spectrometer (ILAS) for the spring of 1997. The analysis method is based on the Match technique. In this study we calculated additional trajectories and set very strict criteria to identify a double-sounded air mass more reliably. The result shows that the integrated ozone loss during February and Match was 1.9 ppmv at 492 - 450 K levels (about 60% losses) and the column ozone loss during two months was 94 DU. The ozone loss rate of the present study was larger than that of the sonde-Match analysis.
We present detection methods for polar stratospheric clouds (PSCs) from the Environment Agency of Japan's Improved Limb Atmospheric Spectrometer (ILAS) instrument during the arctic winter of 1996/1997. The PSC detection methods are based on ILAS visible channel measurements in and around the oxygen A absorption band. They involve either full nonlinear or simple linear fitting of the spectra to obtain aerosol optical thickness as a function of tangent height. PSC optical thickness is determined from a subsequent linear fit to aerosol optical thickness as a function of altitude. Results for PSC optical thickness from the two methods agree reasonably well for all cases considered in this study, but only the nonlinear fitting approach allows the definitive identification of PSC events. Comparisons with operational ILAS data products show denitrification, removal of water vapor, and generally low temperatures over the vertical region of the PSC. Finally, we present a fast and simple method for the identification of possible PSC candidates from ILAS measurements.
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.
The Improved Limb Atmospheric Spectrometer (ILAS) on board the Advanced Earth Observing Satellite (ADEOS) successfully observed atmospheric profiles over the Arctic and Antarctic from November 1996 through June 1997. It revealed the frequent occurrence of Polar Stratospheric Clouds (PSCs) over the Arctic between January and mid-March 1997. The ILAS provides a unique data set, including aerosol extinction at 780 nm, nitric acid, water vapor, and nitrous oxide, simultaneously. This paper demonstrates the validity of the ILAS aerosol data and presents an approach to estimate the chemical composition of PSCs. Comparisons are made with data from the Stratospheric Aerosol and Gas Experiment (SAGE) II.
The Improved Limb Atmospheric Spectrometer-II (ILAS-II) is a satellite-borne solar occultation sensor developed by the Environment Agency of Japan for measuring ozone, other gas species, and aerosols/PSCs that are related to the ozone chemistry in the stratosphere. The ILAS-II instrument will be installed on board the ADEOS-II satellite that will be put into a sun-synchronous polar orbit by the National Space Development Agency of Japan (NASDA) in November 2001. The ILAS-II measurement is a continuation of that of ILAS on board ADEOS, which obtained data from November 1996 to June 1997. The main components of ILAS-II are four spectrometers and a sun-edge sensor. The spectrometers include an infrared spectrometer to cover about 6 to 12 micrometer in wavelength, a mid-infrared spectrometer 3 to 5.7 micrometer, a narrow band spectrometer around 12.8 micrometer, and a visible spectrometer 753 to 784 nm. The first two spectrometers are used for measuring gas and aerosol/PSC profiles, while the third is for ClONO2 measurements. The visible spectrometer is used for pressure/temperature measurements as well as aerosol/PSC extinction coefficients. The ILAS_II instrument has already completed its development and environment tests, and now is undergoing satellite system environment tests at NASDA. This paper outlines the characteristics and performance results from laboratory tests along with the present status of development of its data processing algorithm and operational software.
The Solar-Occultation FTS for Inclined-orbit Satellite (SOFIS) is an instrument for the next atmospheric remote sensing project proposed by the Environment Agency of Japan. The grating infrared spectrometer used by its predecessors (ILAS/ILAS-II) will be replaced with a Fourier-transform spectrometer (FTS) for higher spectral resolution. The three- dimensional distributions of greenhouse gases as well as those of atmospheric species related to stratospheric ozone depletion will be measured by solar occultation from an inclined-orbit satellite. A preliminary study was carried out to clarify the underlying problems in satellite-borne FTS measurement and to seek a proper method for processing the FTS data recorded by SOFIS.
A new multi-FOV space-borne lidar named "A-lidar" is being studied by the National Space Development Agency of Japan (NASDA) for the earth radiation mission proposed as a joint program with the European Space Agency (ESA). The mission is named "EarthCARE". It was formerly called ATMOS-B1 or ERM. The lidar has a two-wavelength transmitter (1064 nm and 532 nm), a dual polarization receiver at 1064 nm, and a multi-field-of-view (multi-FOV) receiver at 532 nm. The multi- FOV feature of A-lidar will enable us to solve the multiple scattering problems with space lidar measurements of profiles of clouds and aerosols. The multi-FOV feature can also be used for characterization of aerosols.
The Solar Occultation FTS for Inclined-orbit Satellite (SOFIS) is a solar occultation Fourier transform spectrometer developed by the Environmental Agency of Japan, and onboard the Global Change Observation Mission-AI (GCOM- A1) satellite. GCOM-AI will be placed in a 650 km non-sun- synchronous orbit in 2006, with an inclination angle of 69 deg. SOFIS is the successor of the Improved Limb Atmospheric Spectrometer-II, which is onboard the Advanced Earth Observing Satellite-II (ADEOS-II). SOFIS measures the vertical profile of the atmospheric constituents with 0.2 cm-1 spectral resolution at 3 - 13 micrometers and 1 km vertical-resolutions. The target of SOFIS measurements is a global distribution of O3, HNO3, NO2, N2O, CH4, H2O, CO2, CFC-11, CFC-12, ClONO2, aerosol extinction, atmospheric pressure and temperature. SOFIS uses a double-pass flexible blade Fourier transform spectrometer (FTS) and a diode laser sampling system to reduce the size and weight of the apparatus. Two photovoltaic HgCdTe detectors and a pulse-tube cooler will provide high linearity and low-noise performance. SOFIS also has a visible (O2 A-band) grating spectrometer for pressure and temperature retrieval and a sun-edge sensor for detecting the tangent height position. This paper describes the conceptual design of the instrument and examines the test results of laboratory models of the FTS and the detector.
A laboratory model of the space borne compact FTS was manufactured and tested. This type of compact FTS with medium spectral resolution (approximately 0.8 cm-1) and high spectral scan rate (approximately 10 Hz) is suitable for the observation of the vertical distribution of atmospheric constituents, especially for the observation of solar occultation. The rapid vertical velocity of tangent points requires a high spectral scan rate of the instrument. One of the candidates of platforms is the International Space Station (ISS). The results of a sensitivity study show that a moderate spectral resolution of approximately 1 cm-1 is sufficient for measuring vertical distributions of the trace gases with a measurement error less than 10%. The laboratory model is based on the Bomem/MR series with balanced rotary scan action and a frictionless flex blade at the center of rotation. For data sampling, a diode laser is utilized instead of a He-Ne gas laser. This technique provides the compactness and longevity in FTS needed for the satellite borne system. For this instrument, a vibrational environment test was conducted and it was proved to be well-balanced and to be a stable structure with a high resonance frequency. This paper also proposes a space borne interferometer.
ClONO2 is one of the most important species governing the chemistry of stratosphere, especially ozone depletion, particularly in the polar regions. A compact echelle grating spectrometer (f equals 200 mm) with 0.2 cm-1 spectral resolution around the 780.2 cm-1 chlorine nitrate (ClONO2) absorption band has been designed and tested. This is a part of the flight model of the Improved Limb Atmospheric Spectrometer-II (ILAS-II) mission onboard Advanced Earth Observing Satellite II (ADEOS-II). Using an off axis parabolic collimator and two cylindrical off axis parabolic collecting mirrors, this spectrometer is a compact space-borne instrument optimized for solar occultation measurements. The solar absorption spectra measured with the array detector on the ground are consistent with the designed spectral resolution and the resolution simulated with the Code V optical performance simulator. Radiometric and spectrometric pre-launch calibration results of the spectrometer are discussed. The instrument slit function measurement with a tunable diode laser and integrating sphere is also discussed.
In the Mission Demonstration Satellite Lidar (MDS-lidar) Project, the National Space Development Agency of Japan (NASDA) has started development of a satellite-borne lidar system for experiments in space, which is called Experimental Lidar-In-Space Equipment (ELISE). Its main purposes are to demonstrate technical feasibility of a space-borne lidar and its key components, and also to get scientific data on clouds/aerosols distribution for better understanding of the earth climate system. Presentation will be made on the ELISE development plan, scientific goals and their implementation plan.
The experimental lidar in space equipment (ELISE), one of NASDA's lidar programs, means the two-wavelength backscatter lidar. It is planned to be loaded onto the mission demonstration satellite (MDS)-2 planned to be launched early in 2001. One of the special features of ELISE is to be developed in short period using two models called the Basic Test Model and the demonstration model (DM). Through this program, we try to demonstrate some key devices, such as a lightweight laser diode (LD)-pumped high power LASER, a large diameter telescope an a photon counting detector using silicon avalanche photo diode, which are required for future spaceborn lidars. The experimental data of key devices in the space environment will be obtained. Furthermore, ELISE will observe clouds in the high altitude, multi-layered clouds, aerosols and the atmospheric density through one year. This observation will reveal the scientific value and the availability of spaceborn lidars. The collection of the information on clouds, aerosols and the density will be a great help to the design of future spaceborn lidars.
Experiments on the earth-satellite-earth laser long-path absorption measurements of atmospheric trace species will be carried out with the retroreflector in space (RIS) for the Advanced Earth Observing Satellite (ADEOS). The RIS is a single-element hollow retroreflector with an effective diameter of 0.5 m, which was designed for spectroscopic measurement in the infrared region. The ground system for the experiment employs two single-longitudinal-mode pulsed CO2 lasers. High-resolution atmospheric absorption spectra are measured by using the Doppler shift of the return beam caused by the satellite movement. Vertical profiles of O3 and CH4, and column contents of CFC12, HNO3, CO, N2O, etc. will be obtained from the measured spectra.
Ozone layer observation will be conducted with the solar occultation sensor ILAS (improved limb atmospheric spectrometer) on board the ADEOS (Advanced Earth Observing Satellite; to be launched in August 1996) to provide vertical profiles of ozone, methane, water vapor, nitrogen dioxide, nitric acid, and nitrous oxide from absorption measurements in the infrared region, and temperature and pressure profiles from measurements of absorption due to oxygen molecules in the visible region. Optical properties of stratospheric aerosol and polar stratospheric clouds (PSCs) are also derived from visible and infrared extinction measurements. Using the ILAS flight model, optical performance data was obtained from the experiments with a gas cell and a black body light source. Field experiments have been planned for the post-launch validation, which includes field campaigns using large balloons at Kiruna (Sweden) and ground-based remote sensors at Kiruna, Alaska, Syowa Station and other locations. This paper briefly describes the ILAS instrument, its performance evaluation, laboratory experiments to determine the instrument function, data processing algorithms and validation plans.
Results of conceptual design study of a solar occultation infrared sensor, improved limb atmospheric spectrometer-II (ILAS-II) which will be onboard ADEOS-II spacecraft, is discussed. The ILAS-II will have four grating spectrometers for solar occultation measurement: two are identical to the spectrometers of the ILAS onboard ADEOS to be launched in 1996. To observe ClONO2, which is a key species that controls catalytic destruction of ozone, an echelle grating spectrometer with 0.14 cm-1 resolution for the 780.2 +/- 1 cm-1 region will be added to the ILAS-II. Another new spectrometer will cover the 3 to 5.7 micrometers region to characterize the aerosols such as sulfuric acid aerosols and PSCs as well as to observe the chemical species.
Lidar in space have been featuring as a high sensitive active sensor for global observations of aerosol, cloud, water vapor, wind vector etc. Numerous efforts have been carried out toward realization of those by many researchers. NASDA also started a space lidar program from 1990. A present status of this program is a Phase A. The Phase A was highly directed to resolve system parameters of bookstore lidars, DIAL for measurements of global aerosol density, cloud height, vertical and horizontal distribution of water vapor concentration etc. and to develop an airborne lidar system, including high power diode-pumped Nd:YAG, Nd:YLF lasers, to obtain data for simulation of space lidar. This paper will describe the airborne lidar system with diode-pumped Nd:YAG, Nd:YLF lasers under development.
Program overview, scientific targets and instrument design of the Improved Limb Atmospheric Spectrometer (ILAS) is described. The ILAS has two grating spectrometers for solar occultation measurement: one is for measurement of infrared band (850-1610 cm-1, 11.76 micrometers - 6.21 micrometers ) for O3, HNO3, NO2, N2O, H2O, CH4 and CFC11, and the other is for visible band (753-784 nm, O2 A band) for aerosols, temperature and air density measurement. ILAS will be onboard the ADEOS spacecraft and will observe high-latitude (N55-70, S63-87) ozone layer after February 1996 over 3 years with high vertical resolution (less than or equal to 2 km).
The ILAS and RIS instruments for Advanced Earth Observing Satellite intended to perform laser absorption measurements are described. The ILAS measurements will provide vertical profiles of ozone and ozone-related species in the polar regions. The RIS will obtain vertical profiles of ozone, carbon dioxide and methane as well as column density of some greenhouse gases based on laser absorption measurements.
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