On 29th of October, 2018, GOSAT-2 was launched as the successor to GOSAT which is the first satellite dedicated to the greenhouse gases observation..
After the about 16 hours critical phase, GOSAT-2 moved to the commissioning phase and the functional and performant checkout of the bus system in November was followed by the one of the mission instruments in December.
The first light of the TANSO-CAI-2 was taken in the beginning of November along with the bus system checkout and the checkout of the TANSO-CAI-2 stared in the beginning of December.
The checkout of the TANSO-FTS-2 started in the middle of December. The first light of the FTS-2 was taken in the middle of December as part of the checkout of itself because the about three weeks of outgas to avoid the contamination had been needed. Though a few anomalies had been found in the checkout, it confirmed that FTS-2 and CAI-2 had worked well and all performances and functions met the requirements and the differences from the design were little except the temperature of the band 4 and 5 of FTS-2.
All data acquisition was completed at end of December except the system total operation test which is the test using all relevant systems including the ground system and this test was performed in the beginning of January of 2019.
The Greenhouse gases Observing SATellite (GOSAT) was developed to contribute to monitoring of carbon dioxide and methane from space [1]. The mission objectives are global greenhouse gas measurements from space with precision of 1 % for CO2 and 2 % for CH4 in seasonal mean. The GOSAT carries Thermal And Near infrared Sensor for carbon Observation (TANSO) for precise measurement of greenhouse gases. Main instrument is Fourier Transfer Spectrometer (TANSO-FTS) to observe atmospheric absorption spectra of CO2 and CH4 with high spectral resolution of 0.2 cm-1, broad wavelength coverage of 0.76 − 14.3 microns, wide swath of 790 km and frequent revisit of 3 days. Cloud and Aerosol Imager (TANSO-CAI) is simultaneously on board for cloud detection and correction of optical thin cirrus and aerosol interference within the FTS instantaneous field of view. The GOSAT satellite was launched by H2A-15 rocket on January 23, 2009. The Level 1B products of calibrated spectra were released from September 2009 in public. The Level 2 products of CO2 and CH4 column densities were released from February 2010 [2]. The normal observation data is acquired over one year regularly from April 2009. The mission lifetime is 5 years.
In January of 2009, GOSAT which is the first satellite dedicated to observing greenhouse gases, that is Carbon Dioxide and Methane was launched. GOSAT stands for Greenhouse Gases Observing Satellite.
To observe the global column concentration of carbon dioxide (CO2) and methane (CH4) from space, the Greenhouse gases Observing SATellite (GOSAT) was launched on January 23, 2009, and has started the operational observation. Thermal and Near Infrared Sensor for Carbon Observation – Fourier Transform Spectrometer (TANSO-FTS) has been continuously measuring CO2 and CH4 distributions globally, and supporting the global carbon cycle elucidation. It is important to monitor the greenhouse gases in long-term period with same data quality. During 7.5 years operational periods, GOSAT passed the designed lifetime, which is 5 years, and some components report the change of characteristic in-orbit. The pointing mechanism, which has a capability of change a line of scene both of along track and cross track, is equipped on GOSAT. To keep the quality of spectra from TANSO-FTS and try to ambitious observation plan, the pointing mechanism is switched to the backup one in January 2015. In addition, the spectral resolution is degraded due to the bias of ZPD position science 2014. The compensation algorithm is developed and implemented on the operational system and completed the reprocessing for all passed observation data. The pointing mechanism, observation pattern, and processing algorithm were renovated, and GOSAT can provide the long-term and consistent quality spectra.
GOSAT (Greenhouse Gases Observing Satellite) is a Japanese Earth observation satellite dedicated to the monitoring of total column amount of carbon dioxide and methane over different locations on the planet. The main instrument of GOSAT is the TANSO Fourier Transform Spectrometer (TANSO FTS). NEC-Toshiba Space Systems was the prime integrator of the TANSO FTS. ABB provided the interferometer and its control electronics. The satellite was launched in January 2009. The mission, planned for five years, has exceeded its design life-time. This paper presents an overview of the interferometer and of its development. Special emphasis is accorded to the life time qualification activities. Analysis of the health of the interferometer on-orbit is also presented.
Fourier transform spectrometer (FTS) has many advantages, especially for greenhouse gases and air pollution
detection in the atmosphere, because a single instrument can provide wide spectral coverage and high spectral
resolution with highly stabilized instrumental line function for all wavenumbers. Several channels are usually
required to derive the column amount or vertical profile of a target species. Near infrared (NIR) and shortwave
infrared (SWIR) spectral regions are very attractive for remote sensing applications. The GHG and CO of
precursors of air pollution have absorption lines in the SWIR region, and the sensitivity against change in the
amounts in the boundary layer is high enough to measure mole fractions near the Earth surface. One disadvantage
of conventional space-based FTS is the spatial density of effective observation.
To improve the effective numbers of observations, an imaging FTS coupled with a two-dimensional (2D)-camera
was considered. At first, a mercury cadmium telluride (MCT)-based imaging FTS was considered. However, an
MCT-based system requires a calibration source (black body and deep-space view) and a highly accurate and
super-low temperature control system for the MCT detector. As a result, size, weight, and power consumption are
increased and the cost of the instrument becomes too high. To reduce the size, weight, power consumption, and
cost, a commercial 2D indium gallium arsenide (InGaAs) camera can be used to detect SWIR light. To
demonstrate a small imaging SWIR-FTS (IS-FTS), an imaging FTS coupled with a commercial 2D InGaAs camera
was developed. In the demonstration, the CH4 gas cell was equipped with an IS-FTS for the absorber to make the
spectra in the SWIR region. The spectra of CH4 of the IS-FTS demonstration model were then compared with
those of traditional FTS. The spectral agreement between the traditional and IS-FTS instruments was very good.
GOSAT which is dedicated to monitor the column concentration of carbon dioxide and methane was launched almost 3 and half years ago, and the data processing algorithm have been improved a few times based on the calibration and validation, and the precision of the concentration data have been increased. These data gave us a realization of the availability of the GHG observation from space. And it has been required to expand this mission to make it useful for mankind. So we have investigated the requirements for the next generation greenhouse gases observations from space and have defined the mission requirements for GOSAT-2. The measurement accuracy target of Carbon Dioxide concentration defined in this mission requirement is 0.5 ppm at 500km and 2,000km mesh spatial resolution over the land and ocean, respectively and 1 month average. To achieve this target, GOSAT-2 will adopt the Fourier Transform Spectrometer (FTS) and the imager along with GOSAT, but the functions and performances will be improved. For example, the CO observation band will be added and the grating spectrometer for UV band of CAI will be adopted to measure NO2 and to improve the aerosol retrievals. Following the presentation of the GOSAT observation results, the concept of GOSAT-2 will be shown.
To observe the global column concentration of carbon dioxide (CO2) and methane (CH4) from space, the Greenhouse gases Observing SATellite (GOSAT) was launched on January 23, 2009, and has started the operational observation. Thermal and Near Infrared Sensor for Carbon Observation– Fourier Transform Spectrometer (TANSO-FTS) has been continuously measuring CO2 and CH4 distributions globally, and the retrieved column CO2 and CH4 data have been distributed to the public. Over three-years operational periods, the useful scientific data sets and interesting articles for carbon source/sink evaluation were produced and published, and these results have been supporting to well understanding of carbon cycle. Currently, the importance of space-based carbon observation has been approved and desired the continuous observation in toward. Through the TANSO-FTS operation with the radiometric, geometric and spectroscopic characterizations, we learned how to improve the accuracy of XCO2 and XCH4 based on short-wavelength FTS. The correction procedures for micro-vibration from companion components, non-linear response of analogue and digitizing circuit are key role on the current on-board operating TANSO-FTS. On instrumental aspects, the robustness and improvements will be required on the future mission. To elucidate the carbon cycle more precisely, our experiences have to be summarized and applied in the future missions. In this presentation, the detail of lessons and learned from TANSO-FTS operation will be presented.
To monitor the global column concentration of carbon dioxide (CO2) and methane (CH4) from space, the Greenhouse
gases Observing SATellite (GOSAT) was launched on January 23, 2009. The Thermal And Near infrared Sensor for
carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) and Cloud and Aerosol Imager (TANSO-CAI) are
onboard GOSAT to derive the precise amount of CO2 and CH4 in the earth's atmosphere. The first high spectral
resolution SWIR spectra by TANSO-FTS and the image by TANSO-CAI were acquired on Feb. 7, 2009. TANSO has
been continuously measuring CO2 and CH4 distributions globally every three days, and data distribution to the public has
started from Feb. 16, 2010. Over two year operation periods, the radiometric, geometric and spectroscopic
characterizations of TANSO have been continuously conducted with updating the Level-1 processing algorithm. Timeseries
of radiometric, geometric and spectroscopic response were determined and performed with on-orbit and vicarious
calibrations. In the updated Level-1 processing, the newly developed correction algorithm for micro-vibration effects is
operationally installed and improved the accuracy of medium gain condition. In this presentation, the detail of on-orbit
characterization and the current status of TANSO will be described..
To monitor the global column concentration of carbon dioxide (CO2) and methane (CH4) from space, the Greenhouse
gases Observing SATellite (GOSAT) was launched on January 23, 2009, and has started the operational observation.
Thermal and Near Infrared Sensor for Carbon Observation- Fourier Transform Spectrometer (TANSO-FTS) has been
continuously measuring CO2 and CH4 distributions globally every three days, and data distribution to the public started
from Feb. 16, 2010. During two years operational periods, the radiometric, geometric and spectroscopic characterizations
of TANSO have been continuously conducted with updating the Level-1 processing algorithm. To make a precise
spectroscopic observation, correction algorithms were newly developed, demonstrated and installed on operational
processing. Two major corrections are discussed. One is correction of the scan-speed instability caused by microvibration
from satellite. Through the on-orbit data analysis, degrading spectroscopic accuracy caused by periodically
micro-vibrations was found, and these distortion effects were compensated with applying the re-sampling technique for
interferogram. The other is non-linearity correction in the electronics. In this presentation, the detail of on-orbit
characteristics and the current status of Level-1procesing for TANSO will be presented.
To map the global column dry mole fractions of carbon dioxide (CO2) and methane (CH4), the Green house gases
Observing SATellite (GOSAT) was launched on January 23, 2009. The Thermal And Near infrared Sensor for carbon
Observation Fourier-Transform Spectrometer (TANSO-FTS) and Cloud and Aerosol Imager (TANSO-CAI) are onboard
on GOSAT to derive the precise amount of CO2 and CH4 in atmosphere measuring the solar light intensity reflected and
scattered on the earth's surface and the thermal radiation. The first high spectral resolution Short Wave Infrared (SWIR)
spectra by TANSO-FTS and the image by TANSO-CAI were acquired on February 7, 2009. TANSO has been
continuously measuring CO2 and CH4 distributions in global every three days periods, and data distribution for public
users was started from February 16, 2010. After the launch, the on-orbit characterization of performance, calibration, and
health monitoring of TANSO has been continuously conducted with updating the Level-1 and -2 processing algorithm.
During the over one-year operation period, a few anomalies such as instability of pointing mechanism, varying offset of
pointing position, small wave-number shift and Zero Path Difference position change, were observed. The radiometric
responses for FTS and CAI are also slightly changing. To minimize these effects in data using, quality flags were
additionally included in product, response functions are updated and the regular operation procedure was slightly
changed. In this presentation, the detail of on-orbit status of TANSO will be reported.
The greenhouse gas observing satellite (GOSAT) was launched on 23 January 2009. Its main sensor, the "thermal and
near infrared sensor for carbon observation Fourier transform spectrometer (TANSO-FTS)", is functioning normally. It
can measure a wide spectrum including three CO2 absorption bands at 1.6 μm and 2.0 μm (Short Wavelength InfraRed,
SWIR band), and 15 μm (Thermal InfraRed, TIR band). The former two bands are used to estimate columnar
concentrations of CO2. The latter is used to retrieve the vertical profile of CO2 concentration in the upper troposphere.
Simulation studies show that high radiometric calibration accuracy of 0.3 K in brightness temperature Tbb is necessary to
retrieve a CO2 concentration profile with accuracy of 1% in the upper atmosphere. The sensor's fundamental
performance was evaluated during the initial checkout period, which continued for six months. Results show that most of
the radiometric performance is achieved as designed. However, results also show that some systematic biases exist in the
TIR spectrum because of the opacity of the dichroic mirrors of SWIR bands obstructing the field of view of the TIR
band. These biases can be mostly removed by explicitly considering radiation--that emitted from inside of the optics and
multiple scattering of target signals--in the calibration procedure. Using a three-day global composite of the clear sky
spectrum, CO2 concentrations in the upper atmosphere were retrieved preliminarily. Results show a convincing
hemispheric concentration gradient, which agrees well with the climatologic distribution of CO2.
The Greenhouse gases Observing SATellite (GOSAT) monitors carbon dioxide (CO2) and methane (CH4) globally from
space. It is a joint project of Japan Aerospace Exploration Agency (JAXA), Ministry of the Environment (MOE) and
National Institute for Environmental Studies (NIES). GOSAT is placed in a sun-synchronous orbit of 666km and 12:48
local time, with an inclination angle of 98 deg. It was launched on January 23, 2009 from Tanegashima Space Center.
There are two instruments on GOSAT. The Thermal And Near infrared Sensor for carbon Observation Fourier-
Transform Spectrometer (TANSO-FTS) detects the Short wave infrared (SWIR) reflected on the earth's surface as well
as the thermal infrared (TIR) radiated from the ground and the atmosphere. TANSO-FTS is capable of detecting wide
spectral coverage; three narrow bands (0.76, 1.6, and 2 μm) and a wide band (5.5-14.3 μm) with 0.27 cm-1 spectral
resolution. The TANSO Cloud and Aerosol Imager (TANSO-CAI) is a radiometer of ultraviolet (UV), visible, and
SWIR to correct cloud and aerosol interference. For three months after the launch, the on-orbit function and
performance have been checked out. Now level 1A (raw interferogram) and level 2B (spectra) are now being processed
and provided regularly with calibration data.
Radiometric calibration accuracy of 0.3 K in Tbb is necessary to retrieve CO2 concentration profile with accuracy of 1 %
in the upper atmosphere. In case of the thermal infrared (TIR) band (band 4) of GOSAT-TANSO-FTS, interferometric
phase correction procedure is very important because the total transmittance of the optics at the band is about 70 %
because of opacity of dichroic mirrors of band 1-3 placed obstructing the field of view of band 4, and the mirrors reflect
the radiation emitted from inside of the optics. Based on the results from the thermal vacuum tests (TVTs) of the sensor,
it is found that interferometric signal is almost zero when the sensor view a target of which temperature is about 280-
300K because the radiation emitted from inside of the spectrometer controlled at about 296 K has completely opposite
phase to that of the target. It is also found that the interferometric final phase of the calibrated signal varies when the
total signal is almost zero because of weak signals that have phases differ from both of those of targets and calibrators. A
candidate phase correction procedure is proposed based on that adopted for a previous space FTS sensor, IMG/ADEOS.
Non-linearity correction for the detector and polarization efficiency correction are also desccussed.
In order to validate and calibrate TANSO-FTS data of the GOSAT satellite, and also to develop the retrieval algorism
for deriving the column density of CO2 and CH4 from spectra, the airborne SWIR (Short Wave Infrared Region) FTS
(Fourier transform spectrometer) has been developed, characterized and demonstrated. This instrument is named as
TSUKUBA model. The basically performance test of TSUKUBA model was carried out in our laboratory, and the
measured modulation efficiencies are 70% (Band1), 85% (Band2) and 88% (Band3), respectively. The measured values
of SNR with the equivalent black body temperature for 30% surface albedo are 190 (13050cm-1), 148 (6200cm-1), and
165 (5000cm-1) without polarization measurement. The measured values of full width at half maximum (FWHM) of
instrumental line shape functions are 0.38cm-1, 0.26cm-1, 0.25 cm-1 of band 1, 2, and 3, respectively. This instrument is
also able to measure the scene flux with P and S polarization, simultaneously, as TANSO-FTS SWIR measures. In 2007,
the first and second flight campaigns were arranged and the sunlight reflected spectra over the earth's surface was
obtained. This instrument was mounted on high-altitude airplane with image motion compensator and damping platform,
and flied over southern Australia and Siberia. The instrumental design and the results of performance tests as well as the
flight campaign are presented.
In order to characterize the pre-launch performance of
Thermal And Near infrared Sensor for carbon Observation
Fourier-Transform Spectrometer (TANSO-FTS) and Cloud and Aerosol Imager (TANSO-CAI) on the Green house
gases Observing SATellite (GOSAT) under the environmental condition on orbit as well as in the laboratory, the Proto
Flight Model (PFM) for TANSO-FTS and CAI have been developed. TANSO-FTS has three narrow bands of 0.76, 1.6
and 2.0 micron (Band 1, 2 and 3) with +/-2.5cm maximum optical path difference, and a wide band of 5.5 - 14.3 micron
(band 4) in thermal near infrared region. TANSO-CAI is a radiometer for detection and correction of clouds and aerosol
effects which might degrade the column concentration retrieval of CO2 and CH4. It has four spectral band regions;
ultraviolet (UV), visible, near IR and SWIR.
The basic character of TANSO-FTS and CAI, such as the Signal to Noise Ratio (SNR), the polarization sensitivity
(PS), Instantaneous Field Of View (IFOV), spectral response, and also Instrumental Line Shape Function (ILSF)
have been characterized by introducing the light emitted from the black body, halogen lamp and the tunable diode laser.
In addition to these characterizations, micro vibration effect on orbit has been investigated on TANSO-FTS. There prelaunch
test results demonstrated that TANSO will provide data for high accuracy CO2 and CH4 retrieval on orbit.
KEYWORDS: Calibration, Fourier transforms, Signal to noise ratio, Sensors, Polarization, Short wave infrared radiation, Black bodies, Clouds, Satellites, Pulmonary function tests
TANSO-FTS (Thermal And Near infrared Sensor for carbon Observation Fourier Transform Spectrometer) and
TANSO-CAI (Cloud and Aerosol Imager) are a space-born optical sensor system mainly oriented for observation of
greenhouse gases (GHGs). TANSO will be installed on the Greenhouse gases Observing SATellite "GOSAT" and
launched in early 2009. The TANSO-FTS is a Fourier transform spectrometer which has 3 SWIR bands (0.76, 1.6 and
2.0 μm) and 1 TIR band (5.5 - 14.3 μm) for observation of scattering light and thermal radiation from the earth, mainly
focused on CO2 absorption spectra. The TANSO-CAI is an imager for detection and correction of clouds and aerosol
effects to determine GHGs quantities. The instrument characteristics of TANSO-FTS are high SNR (~300), quick
interferogram scan (1.1 ~ 4.0 s) with moderate wave-number resolution (~0.2 cm-1), and polarization measurement. Now,
integration and test of proto-flight model of TANSO have been completed. In this paper, the results of performance test
such as SNR, ILS, polarization sensitivity, etc. are described.
Greenhouse gases Observing SATellite (GOSAT) is designed to monitor the carbon dioxide (CO2) and the methane
(CH4) globally from orbit and is scheduled to be launched in 2008. Two instruments are accommodated on GOSAT.
Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) detects the
Short wave infrared (SWIR) reflected on the earth's surface as well as the thermal infrared (TIR) radiated from the
ground and the atmosphere. TANSO-FTS is capable of detecting wide spectral coverage, specifically, three narrow
bands (0.76, 1.6, and 2 micron) and a wide band (5.5-14.3 micron) with 0.2 cm-1 spectral resolution. As the second
sensor, TANSO Cloud and Aerosol Imager (TANSO-CAI) is a radiometer of ultraviolet (UV), visible, and SWIR to
correct cloud and aerosol interference.
Since the contaminant deposition onto these optical sensors significantly affects the sensing capability, the spectroscopic
contamination control over wide spectral range is exercised from the initial phase of GOSAT development to on-orbit
operation.
This paper presents overview of GOSAT contamination control plan and test results from contamination environment
monitoring during thermal vacuum test using satellite system Structure and Thermal Model "STM". The result from
on-going contamination environment monitoring of clean room at the spacecraft test and assembly building is also
presented in launch site.
KEYWORDS: Fourier transforms, Sensors, Signal to noise ratio, Atmospheric modeling, Stray light, Near infrared, Infrared sensors, Polarization, Black bodies, Satellites
In order to estimate and demonstrate the performance of Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) and Cloud and Aerosol Imager (TANSO-CAI) under the environmental
condition on orbit, the Engineering Model (EM) for TANSO-FTS and CAI have been developed and demonstrated. The
TANSO-FTS has three narrow bands detectable regions; 0.76, 1.6 and 2micrion (Band1, 2 and 3) with +/⊥2.5cm
maximum optical path difference, and a wide band (5.5 − 14.3micron in thermal near infrared region. The TANSO-CAI
is a radiometer of ultraviolet (UV), visible, and SWIR, which has 4 spectral band regions with 1 dimensional array CCDs.
The initial performance tests have been carried out in the laboratory and the thermal vacuum chamber. The Signal to Noise Ratio (SNR), the polarization sensitivity (PS), Instantaneous Field Of View (IFOV) and response for FTS and CAI,
and also the Instrumental Line Shape Function (ILSF) for FTS have been characterized in this test by introducing the
light emitted from the black body, halogen lamp and the tunable diode laser. As a results of these experiments, it is
appeared that the some modification of system for manufacturing the proto flight model (PFM) is required, and now in
progressing.
In addition to these characterizations, the newly developed tests, such as the stray light measurement and micro
vibration test, are applied on TANSO-FTS to estimate the effect on orbit. These tests methods and results are presented in
this paper.
In order to validate and calibrate the GOSAT satellite data, and also to develop the retrieval algorism for deriving the
column density of CO2 and CH4 from spectra, the airborne SWIR (Short Wave Infrared Region) FTS (Fourier transform
spectrometer) has been developed and characterized. This instrument is called as TSUKUBA model. The initial
performance test of TSUKUBA model was carried out in our laboratory, and the measured modulation efficiencies are
70% (Band1), 85% (Band2) and 88% (Band3), respectively. The measured values of SNR with the equivalent black
body temperature for 30% surface albedo are 190 (13050cm-1), 148 (6200cm-1), and 165 (5000cm-1). The measured
values of full width at half maximum (FWHM) of instrumental line shape functions are 0.38cm-1, 0.26cm-1, 0.25 cm-1 for
band 1, 2, and 3, respectively. The instrumental design and the results of performance tests are presented.
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