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 Solar Occultation FTS for Inclined-orbit Satellite (SOFIS) is a solar occultation Fourier transform spectrometer developed by the Ministry of the Environment (MOE) in Japan for the Global Change Observation Mission-A1 (GCOM-A1) satellite. GCOM-A1 will be placed in a 650 km non-sun-synchronous orbit, with an inclination angle of 69 degrees. ABB-Bomem is a sub-contractor of NTSpace (NEC-Toshiba Space) for the design and manufacturing of the FTS Engineering Model of SOFIS. SOFIS measures the vertical profile of the atmospheric constituents with 0.2 cm-1 spectral resolution for the spectral range covering 3-13 μm. The atmospheric vertical resolution of SOFIS is 1 km. 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. NTSpace in Japan is the prime contractor of SOFIS. The spectrometer is an adapted version of the classical Michelson interferometer using an optimized optical layout and moving retro-reflectors. A solid-state laser diode operating at 1550 nm is used as metrology source of the interferometer. Its highly folded optical design results in a high performance instrument with a compact size. SOFIS FTS implements high performance control techniques to achieve outstanding speed stability of the moving mechanism. This paper describes the test activities of the SOFIS-FTS Engineering Model (EM) and preliminary results. The performances of the FTS are presented in terms of key parameters like signal-to-noise ratio, modulation efficiency and stability. Spectra acquired are shown and test methodology and analyses are presented. Lessons learned during assembly, integration and testing are described as well as improvements planned to be implemented in the Flight Model.
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 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.
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 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.
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 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.
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