Japan Aerospace Exploration Agency (JAXA), Japan Meteorological Agency (JMA) and Japan Space Systems (JSS) are operating major Earth Observation Satellites. Ibuki (GOSAT) carrying TANSO-CAI and -FTS, GOSAT-2 carrying TANSO-CAI2 / -FTS2, Shizuku (GCOM-W) carrying AMSR2, Daichi-2 (ALOS-2) carrying PALSAR-2, DPR on GPM-core satellite of NASA and Shikisai (GCOM-C) carrying SGLI, are being operated by JAXA under cooperation with some domestic agencies, such as Ministry of Environment (MoE), National Institute of Information and Communications Technology (NICT). JMA is operating weather satellite Himawari-8 and -9 on geostationary orbit. JSS are operating ASTER on EOS-Terra satellite of NASA. For coming satellites or instruments, JAXA is going to operate CPR on EarthCARE satellite of ESA, ALOS-3 carrying the “wide-swath and high-resolution optical imager” and ALOS-4 carrying PALSAR-3. JSS is going to have HISUI on ISS. JAXA proposed to Japanese government, its Earth Observation program along with new mid-term plan which started from April 2018 for seven years. In addition to follow-on mission studies, several new studies are underway for near future missions, such as Lidar missions, Super low orbit missions and new geostationary missions with large segmented telescope for land observation.
Accurate measurements of forest biomass are important to evaluate its contribution as a source of CO2 absorption. Forest biomass correlates with forest canopy height, and thus global measurements of canopy heights lead to a better understanding of the global carbon cycle. Space-borne lidar has the unique capability of measuring forest canopy height. A vegetation lidar named MOLI (Multi-footprint Observation Lidar and Imager) has been designed to observe canopy heights more accurately, and MOLI is currently being studied in the Japan Aerospace Exploration Agency (JAXA). This paper introduces an overview of MOLI and its current status.
A feasibility study was conducted for an optical imager system assumed to be mounted on a geostationary orbit satellite for Earth observation. The targeted spatial resolution was less than 10 meters for panchromatic mode at nadir observation conditions, and the observation area was assumed to 100 × 100 square kilometers. The optical system was designed based on a Korsch three mirror anastigmat; the primary mirror was 3.5 meters in diameter, and the focal length was approximately 45 meters. The worst wavefront error was estimated at less than 0.017 λrms in the field of view. As the next step, the primary mirror was segmented, and a trade-off study was conducted on two types of segmented mirror configurations. The optical performance of each configuration was compared in terms of PSF and MTF. Moreover, the deterioration of optical performance due to the misalignment and distortion of the segmented mirror was discussed and numerically estimated by using the Monte Carlo method. The sensitivity of the wavefront error was consequently estimated for the segmented mirror assembly.
Currently, Japan Aerospace Exploration Agency (JAXA), Japan Meteorological Agency (JMA) and Japan Space Systems (JSS) are operating major Earth Observation Satellites. Ibuki (GOSAT) carrying TANSO-CAI and -FTS, Shizuku (GCOM-W) carrying AMSR2, Daichi-2 (ALOS-2) carrying PALSAR-2, DPR on GPM-core satellite of NASA and Shikisai (GCOM-C) carrying SGLI, are being operated by JAXA under cooperation with some domestic agencies, such as Ministry of Environment (MoE), National Institute of Information and Communications Technology (NICT). JMA is operating weather satellite Himawari-8 and -9 on geostationary orbit. JSS are operating ASTER on EOS-Terra satellite of NASA. For coming satellites or instruments, JAXA is going to operate CPR on EarthCARE satellite of ESA, GOSAT-2 carrying TANSO-CAI2 / -FTS2, ALOS-3 carrying the “wide-swath and high-resolution optical imager” and ALOS-4 carrying PALSAR-3. JSS is going to have HISUI on ISS. JAXA is restructuring its program along with new mid-term plan which started from April 2018 for seven years. Adding to follow-on mission studies, several new studies are underway for near future missions, such as Lidar missions, Super low orbit missions and new geostationary missions with large segmented telescope for land observation.
Accurate measurements of forest biomass are important to evaluate its contribution to the global carbon cycle. Forest biomass correlates with forest canopy height; therefore, global measurements of canopy height enable a more precise understanding of the global carbon cycle. A vegetation lidar named “MOLI” which is designed to measure accurate canopy height has been studied by the Japan Aerospace Exploration Agency (JAXA) in cooperation with some researchers. MOLI stands for Multi-footprint Observation Lidar and Imager.
The feature of MOLI is to set multi-footprints for improving the precision of canopy height, and we can find out whether ground surface is flat or slope because an angle of inclination affects the estimation of canopy height.
MOLI is going to be mounted on the Exposed Facility (EF) of the Japanese Experiment Module (JEM, also known as “Kibo”) on the International Space Station (ISS). Now, we are carrying out a feasibility study and some experiments. We introduce an overview and a status of MOLI.
We are developing high-strength reaction-sintered silicon carbide (RS-SiC) mirror as one of the new promising candidates for large-diameter space-borne optics.
In order to observe earth surface or atmosphere with high spatial resolution from geostationary orbit, larger diameter primary mirrors of 1-2 m are required. One of the difficult problems to be solved to realize such optical system is to obtain as flat mirror surface as possible that ensures imaging performance in infrared - visible - ultraviolet wavelength region. This means that homogeneous nano-order surface flatness/roughness is required for the mirror.
The high-strength RS-SiC developed and manufactured by TOSHIBA is one of the most excellent and feasible candidates for such purpose. Small RS-SiC plane sample mirrors have been manufactured and basic physical parameters and optical performances of them have been measured. We show the current state of the art of the RS-SiC mirror and the feasibility of a large-diameter RS-SiC mirror for space-borne optics.
JAXA developed the ground test model of DIAL, Differential absorption Lidar, to measure the quantities of the carbon dioxide for the calibration and the validation of the data acquired by the one instrument, TANSO-FTS, aboard on the GOSAT, Greenhouse gases observing satellite. FTS is the Fourier Transform Spectrometer. In addition to using for the calibration and the validation, this DIAL system has the purpose to take the data for the study of the space-borne DIAL. Our CO2 DIAL system adopted the 1.6 micron CW laser, incoherent detection and all fiber optical circuit. The transmitted on-line and off-line signals are coaxial and have the same field of view and the same time oscillation. And the transmitted laser is modulated doubly, intensity modulation by micro wave and phase modulation. This double modulation is adopted to detect the distance between the DIAL system and the target. JAXA is now performing the test of this DIAL to confirm the accuracy of the measurement of the carbon dioxide. This ground test model can be aboard on an airplane, therefore JAXA is planning the test using an airborne as a part of the test of the ground test model. In addition the comparison with the other CO2 DIAL systems is under consideration. Now JAXA does not have the plan to develop the space-borne LIDAR, however the space-borne LIDAR system has been under study recently, therefore JAXA intends to take the data which will be reflected in the design of the space-borne CO2 DIAL system through this test of the ground test model of DIAL.
One of JAXA’s future missions, using an imaging Fourier Transform Spectrometer (FTS), requires the focal plane array (FPA) that has high sensitivity up to the very long-wavelength infrared (VLWIR) region. Since a Type-II superlattice (T2SL) is the only known infrared material to exhibit performance that is theoretically predicted to be higher than that of HgCdTe additionally the cutoff wavelength can be tailored in the wavelength region of 3-30 μm, we started the research and development of the T2SL detector in 2009. In order to confirm our final goal, which is to realize the FPA with a cutoff wavelength of 15 μm, we first fabricated the 320 × 256 (QVGA format) InAs/GaInSb T2SL FPA with a cutoff wavelength of 15 μm, and the large-format 640 × 512 (VGA format) T2SL FPA is followed because the other missions, using an infrared imager, require the large-format FPA. The noise-equivalent delta temperature measured with F1.4 optics was 0.15 K for QVGA format T2SL FPA at 77 K. It was 0.35 K for VGA format T2SL FPA at 77 K, but there is non-uniformity, and further improvements are necessary to achieve high performance FPAs.
Multi-footprint Observation LIDAR and Imager (MOLI) is a candidate mission for International Space Station – Japanese Experiment Module. The mission objective MOLI is to manage forest and to be a good calibrator for evaluation of forest biomass using satellite instrument such as L-band SAR. SAR is the powerful tool to evaluate biomass globally. However it has some signal saturation over 100 t/ha biomass measurement, whereas Vegetation LIDAR is expected to measure higher mass precisely. MOLI is designed to evaluate forest biomass with high accuracy. An imager, that is equipped together in good registration with LIDAR, will help to understand the situation of target forest. Also two simultaneous Laser beams from MOLI will calibrate the relief effect, which affects the precision of canopy height extremely. Using together with L-band SAR observation data or multispectral image, it is expected to have a good “wall to wall” biomass map with its phonological information. Such MOLI observation capability is so important, because both quantity and quality evaluation of biomass are essential for carbon circulation system understandings. Currently, as a key technical development, LASER Transmitters for MOLI is under test in vacuum condition. Its power is 40mJ and PRF is 150Hz. Pressure vessel design for LIDAR transmitter is supressing Laser induced contamination effect. MOLI is now under study towards around 2020 operation.
One of JAXA’s future missions, using an imaging Fourier Transform Spectrometer (FTS), require the focal plane array (FPA) that has high sensitivity and a very long-wavelength infrared (VLWIR) cutoff wavelength. Since a Type-II superlattice (T2SL) is the only known infrared material to have a theoretically predicted performance superior to that of HgCdTe and the cutoff wavelength can be tailored in the wavelength region of 3-30 μm, we started the research and development of the T2SL detector in 2009. In order to confirm our final goal which is to realize an FPA with a cutoff wavelength of 15 μm, we fabricated InAs/GaInSb T2SL infrared detectors with a cutoff wavelength of 15 μm. We show the results of the dark current and responsivity measurement of single pixel detectors and the development status of FPAs including the image taken by a 320 × 256 InAs/GaInSb T2SL FPA with a cutoff wavelength of 15 μm.
Accurate measurements of forest biomass are important to evaluate its contribution to the global carbon cycle. Forest
biomass correlates with forest canopy height; therefore, global measurements of canopy height enable a more precise
understanding of the global carbon cycle. Space-borne lidar has the unique capability of measuring forest canopy height.
A vegetation lidar named Multi-footprint Observation Lidar and Imager (MOLI) has been designed to make accurate
measurements of canopy height and is currently being studied in the Japan Aerospace Exploration Agency. This papers
introduces an overview of MOLI and its current status.
Compact Infrared Camera (CIRC) is a technology demonstration instrument equipped with an uncooled infrared array detector (microbolometer) for space application. Microbolometers have an advantage of not requiring cooling system such as a mechanical cooler and are suitable for resource-limited sensor systems. Another characteristic of the CIRC is its use of an athermal optical system and a shutterless system. The CIRC is small in size (approximately 200 mm), is light weight (approximately 3 kg), and has low electrical power consumption (<20 W) owing to these characteristics. The main objective of CIRC is to detect wildfires, which are major and chronic disasters affecting various countries of Southeast Asia, particularly considering the effects of global warming and climate change. One of the CIRCs was launched in May 24, 2014 as a technology demonstration payload of the Advanced Land Observation Satellite-2 (ALOS- 2). Since the initial functional verification phase (July 4–14, 2014), the CIRC has demonstrated functions according to its intended design. We also confirmed that the noise equivalent differential temperature of the CIRC observation data is less than 0.2 K, the temperature accuracy is within ±4 K, and the spatial resolution is less than 210 m in the calibration validation phase after the initial functional verification phase. The CIRC also detects wildfires in various areas and observes volcano activities and urban heat islands in the operational phase. The other CIRC will be launched in 2015 onboard the CALorimetric Electron Telescope (CALET) of the Japanese Experiment Module (JEM) of the International Space Station. Installation of the CIRCs on the ALOS-2 and on the JEM/CALET is expected to increase the observation frequency. In this study, we present the on-orbit performance including observational results of the CIRC onboard the ALOS-2 and the current status of the CIRC onboard the JEM/CALET.
IPCC Fifth Assessment Report says that there are still large uncertainties of carbon flux estimations in the interaction between ground and atmosphere. That is because of the uncertainties of “change of land use”, in other words, “change of biomass” such as deforestation. Biomass estimation needs not only area of the forest but also its height information with topological features. In that sense, active sensors are highly expected for precise height measurement. Laser Altimeter or simply LIDAR is able to measure the height of dense forest, where SAR has salutation. ICESat / GLAS is firstly used to measure biomass as satellite LIDAR. However it was reported that there is uncertainty where terrain relief exists. To calibrate terrain relief using multi footprints, a Vegetation LIDAR named MOLI (Multi Observation LIDAR and Imager) was studied by JAXA. The unique points of MOLI are the dual beams with enough small and close footprints to determine terrain relief. Full wave analysis technique is also under development to distinguish canopy heights, crown depth and other forest features. Co-aligned imager will be used for determination of positions where LIDAR measured and observation of phonology. MOLI system design is about to finalize. Regarding Laser Transmitter, Bread Board Model with pressure vessel is being tested under vacuum condition. Target launch year of MOLI is around 2019.
We have developed the Compact Infrared Camera (CIRC) with an uncooled infrared array detector (microbolometer) for space application. Microbolometers have an advantage of not requiring cooling system such as a mechanical cooler, and is suitable for resource-limited sensor system. Another characteristic of the CIRC is its use of athermal optics. The athermal optics system compensates for defocus owing to temperature changes. We also employ a shutter-less system which is a method to correct non-uniformity of the detector without a mechanical shutter.
The CIRC achieves a small size (approximately 200 mm), light mass (approximately 3 kg), and low electrical power consumption (<20 W) by employing athermal optics and a shutterless system.
The CIRC is launched in May 2014 as a technology-demonstration payload of Advanced Land Observation Satellite-2 (ALOS-2). Since the initial functional verification phase (July 4-14, 2014), the CIRC was demonstrated a function according to its intended design. We also confirmed the temperature accuracy of the CIRC observation data is within ±4K in the calibration validation phase after the initial functional verification phase. The CIRC also detected wildfires in various areas and observed the volcano activities in the operational phase.
In this paper, we present the on-orbit performance of the CIRC onboard ALOS-2.
The Earth, Clouds, Aerosols and Radiation Explorer (EarthCARE) mission is joint mission between Europe and Japan
for the launch year of 2015. Mission objective is to improve scientific understanding of cloud-aerosol-radiation
interactions that is one of the biggest uncertain factors for numerical climate and weather predictions. The EarthCARE
spacecraft equips four instruments such as an ultra violet lidar (ATLID), a cloud profiling radar (CPR), a broadband
radiometer (BBR), and a multi-spectral imager (MSI) to observe aerosols, clouds and their interactions simultaneously
from the orbit. Japan aerospace exploration agency (JAXA) is responsible for development of the CPR that will be the
first space-borne W-band Doppler radar. The CPR is defined with minimum radar sensitivity of -35dBz, radiometric
accuracy of 2.7 dB, and Doppler velocity measurement accuracy of 1m/s. These specifications require highly accurate
pointing technique in orbit and high power source with large antenna dish. JAXA and National Institute of Information and Communications Technology (NICT) have been jointly developed this CPR to meet these requirements. In addition, new ground calibration technique is also being progressed for the launch of EarthCARE/CPR. This evaluation method will also be the first use for spacecraft as well as Doppler cloud radar. This paper shows the summary of the CPR design and verification status, and activity status of development of ground calibration method with a few results of experiment using current space-borne cloud radar (CloudSat, NASA).
The EarthCARE mission has been jointly proposed by European and Japanese scientists with the mission objective of
improving the understanding of cloud-aerosol-radiation interactions so as to include them correctly and reliably in
climate and numerical weather prediction models. This EarthCARE mission has been defined as an international
cooperative spacecraft mission between European Space Agency (ESA) and Japan Aerospace Exploration Agency
(JAXA) for the planned launch year of 2013th. The EarthCARE spacecraft equips four instruments, such as a cloud
profiling radar (CPR), an atmospheric backscatter lidar (ATLID), a multi-spectral imager (MSI) and a broadband
radiometer (BBR) to perform very accurate synergy observation to observe cloud and aerosol vertical profiles and
simultaneous radiative flux at the top of atmosphere. In this cooperation, JAXA is responsible for development of the
CPR which will be the first space-borne W-band radar with Doppler measurement capability. JAXA has developed this
Doppler radar for several years with Japanese National Institute of Information and Communications Technology
(NICT). The last year, preliminary design was finished and then fabrication and testing have been started. This
presentation shows the summary of the CPR preliminary design and reports the test status of the CPR engineering model
Global three-dimensional cloud distributions and their properties are important information to estimate the earth
radiation budget more precisely. The interactions between cloud particles and aerosols are also focused to improve
accuracies of climate model. In order to meet expectations of scientists developing climate models for global warming
problem, European and Japanese space agencies plan to launch a satellite called EarthCARE. The Cloud Profiling Radar
(CPR), which will be the first millimeter-wave Doppler radar in space, is installed on this satellite as one of main sensors
to observe clouds. This paper describes the latest design and development status of EarthCARE CPR.
EarthCARE mission has objectives to reveal aerosol and cloud interaction and to reveal relationships with radiation
budget. For this purpose, the EarthCARE satellite has four instruments, which are Atmospheric LIDAR (ATLID), Multi
Spectral Imager (MSI) and Broad Band Radiometer (BBR) in addition to Cloud Profiling Radar (CPR). CPR is
developed under cooperation of Japanese Aerospace Exploration Agency (JAXA) and National Institute of Information
and Communications Technology (NICT) in Japan.
The requirement of sensitivity is -35dBZ, therefore CPR uses W-band frequency and needs a large (2.5m) antenna
reflector. The large antenna has small footprint and is to give up antenna scanning. From this, some difficulty of external
calibration using active radar calibrator (ARC) is recognized.
One solution of external calibration is using scattering from natural distributed target, such as sea surface. Then the
measurement of sea surface scattering using airborne cloud radar was performed. The sea surface scattering property is
being prepared. Second solution is that ARC puts on exact location of sub-satellite track. Precise sub-satellite track
prediction is necessary. We focus second solution in this paper. The test experiment was demonstrated using CloudSat of
NASA/JPL, which is provided CPR using W-band frequency. The feasibility of this calibration method is discussed.
A new concept of DIAL (DIfferential Absorption Lidar) system for global CO2 monitoring using microwave
modulation is introduced. This system uses quasi-CW lights which are intensity modulated in microwave region and
receives a backscattered light from the ground. In this system, ON/OFF wavelength laser lights are modulated with
microwave frequencies, and received lights of two wavelengths are able to be discriminated by modulation frequencies
in electrical signal domain. Higher sensitivity optical detection can be realized compared with the conventional
microwave modulation lidar by using direct down conversion of modulation frequency. The system also has the
function of ranging by using pseudo-random coding in modulation. Fiber-based optical circuit using wavelength region
of 1.6 micron is a candidate for the system configuration. After the explanation of this configuration, feasibility study
of this system on the application to global CO2 monitoring is introduced.
One of the series of satellite for the Global Change Observation Mission (GCOM) is the GCOM-W that will carry the Advanced Microwave Scanning Radiometer (AMSR) follow-on instrument. To keep the continuous observation by the current AMSR for the EOS (AMSR-E) on the Aqua satellite, an earliest launch date is desired. Current proposed launch year is 2010 in Japanese fiscal year. The AMSR-E instrument has been successfully operated for about 4-years and expected to continue providing measurements with high-spatial resolution and in C-band channels that are used to estimate all-weather sea surface temperature and land surface soil moisture. The total dataset period will be over 20-years if the AMSR-E observation can last until the GCOM-W launch. Among the GCOM mission objectives, GCOM-W will focus on the long-term observation of variations in water and energy circulation. In addition, further practical uses including numerical weather forecasting, maritime and meteorological monitoring, and ice applications will be promoted. The AMSR follow-on instrument will be a six-frequency, dual polarized passive microwave radiometer system to observe water-related geophysical parameters. It takes over the basic sensor concept of the AMSR-E instrument with some essential improvements on the calibration system and mitigation of radio-frequency interference (RFI) in C-band channels. Regarding the calibration system, some issues particularly for the warm load target will be investigated and improved based on the AMSR and AMSR-E experiences. Although mitigating the RFI problem is a difficult issue, some preliminary aircraft measurements of anthropogenic radio emissions have performed in Japan and used for assessing the possibilities of sub-band configuration in C-band. Prototyping the several critical components including the above has already started in the last Japanese fiscal year.
EarthCARE Phase-A study was successfully conducted in collaboration between ESA and Japan (JAXA and NICT). In this study, high sensitivity Cloud Profiling Radar (CPR) design with Doppler capability was studied and demonstrated that the CPR satisfies mission requirements, system resource and launcher constraint. As a result of the study, a nadir looking CPR at 94 GHz with a 2.5 m diameter antenna reflector is designed with sensitivity exceeding -36 dBZ of requirement at TOA with 10 km horizontal integration. The Doppler measurement is a new challenge to attain velocity accuracy less than 1 m/s in vertical direction. In parallel to the CPR system design, algorithm development efforts have been conducted through field campaign. A suite of measured quantities that are very similar combination to the EarthCARE data was collected and applied to the retrieval algorithm test.
Japan Aerospace Exploration Agency (JAXA) is proposing the Global Change Observation Mission (GCOM). The GCOM mission will take over the Advanced Earth Observing Satellite-II (ADEOS-II or Midori-II) mission and develop into long-term monitoring. The GCOM mission will consist of two series of medium size satellites: GCOM-W and GCOM-C (these names are provisional). Three consecutive generations of satellites with one year overlap will result in over 13 years observing period in total. Two observing instruments are proposed for the GCOM-W satellite: the Advanced Microwave Scanning Radiometer (AMSR) follow-on instrument and hopefully the scatterometer for measuring ocean vector winds like SeaWinds onboard Midori-II. To keep the continuous observation by AMSR-E on Aqua, the earliest launch date is desired by science community. Current proposed launch year is 2010. The AMSR follow-on instrument will be a multi frequency, dual polarized passive microwave radiometer that observes water-related geophysical parameters supporting the GCOM concept. To keep the earliest launch date, only minimum but essential modifications from AMSR-E are now being examined. Combination of AMSR follow-on instrument and the scatterometer will provide unique opportunity to generate a synergistic effect of the active and passive microwave measurement. This combination can provide some instrument-level advantages including attenuation and scattering correction for scatterometer. Furthermore, simultaneous measurements of water vapor, SST, precipitation, and sea surface winds are effective for investigating various time-space scale phenomena.
Regarding climate change, we have still large uncertainties to predict long-term variation, such as the global average temperature after 100 years. According to the report by Inter-governmental Panel for Climate Change (IPCC), one of the main factors of the uncertainties are from lack of understanding the process between aerosols and clouds. In order to accelerate the understandings of the process, observation of the aerosol over land is crucial. On the other hand, from the monitoring point of view, we do not have sufficient data to distinguish the effect of human activities on and near the land. The results of previous mission; ADEOS-2 Global Imager (GLI) suggests the 1 km ground resolution is not enough for distinguish the effect of human activities, such as deforestation, land cover change, pollution in coastal area, and so on. In this study, we designed a new sensor of which main ground resolution is 250 m, has wide spectral range (0.38~12 miron), rather wide swath for global observation and polarimetry function. The sensor named Second generation GLI (SGLI) consists of two sensors. The first one is conventional push broom type imager for visible and near infrared region with polarimetry channels. The second one is whisk broom sensor for shortwave and thermal infrared. SGLI has 11 channels in VNIR and 6 channels in infrared at nadir position, 2 channels with 3 polarization angles for polarimetry. The total mass of the sensor is around 400 kg. The new JAXA standard bus will carry it on the sun synchronous polar orbit at 10:30, Local Time of Descending Node. The proposed launch year is 2011.
The EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) mission has been recently selected as the 6th ESA's Earth Explorer Mission. The mission objective is to determine, in a radiatively consistent manner, the global distribution of vertical profiles of cloud and aerosol field characteristics. A major innovation of the EarthCARE mission is to include both active and passive instruments on a single platform, which allows for a complete 3-D spatial and temporal picture of the radiative flux field at the top of the atmosphere and the Earth's surface to be developed. While the active instruments provide vertical cloud profiles, the passive instruments (mainly the multi-spectral imager) provide supplementary horizontal data to allow for the extrapolation of the 3-D cloud and aerosol characteristics.
The EarthCARE payload is composed of four instruments: an Atmospheric backscatter Lidar, a Cloud Profiling Radar, a Multi-Spectral Imager and a Broad Band Radiometer. The mission baseline is a sun-synchronous orbit with an altitude around 450 km. The EarthCARE mission is a cooperative mission with Japan (JAXA and NiCT), which will provide the Cloud Profiling Radar. ESA will provide the ground segment and the rest of the space segment including the lidar, the imager and the broadband radiometer. The launch is planned for 2012.
Newly developed high-strength reaction-sintered silicon carbide, called New-Technology Silicon Carbide (NT-SiC) is an attractive material for lightweight optical mirror with two times higher bending strength than other SiC materials. The material has advantages in its fabrication process. The sintering temperature is significantly lower than that of pure silicon carbide ceramics and its sintering shrinkage is smaller than one percent. These advantages will provide rapid progress to fabricate large structures. The characteristics of the material are also investigated. The polish of the test piece demonstrated that the polished surface has no pore and is suited to visible region as well as infrared without CVD SiC coating. It is concluded that NT-SiC has potential to provide large lightweight optical mirror.
Japanese satellite for climate change observation, named ADEOS-II, was lost in October 2003. A quick concept study to compensate the loss of ADEOS-II was made. Regarding climate change study, we found the importance to monitor human activity effect for climate change is important as well as to study the natural climate system and variation by global observation. Moreover, the results from previous satellite ADEOS-II suggests the possibility of global observation and human activity monitoring, which requires certain resolution to distinguish regional change. Thus, the concept of the mission objectives is focusing human activity effect on climate change. The new system, named Global Change Observation Mission: GCOM, consists of two satellites. One satellite carrying microwave radiometer: AMSR2 and a scattarometer, and another satellite carrying multi-spectral imaging radiometer: SGLI. These satellites are named GCOM-winds: GCOM-W and GCOM-climate: GCOM-C, respectively. This system will be continued for over 13 years to observe climate change together with other specific Japanese or Japanese joined satellites, namely, Greenhouse gas observation satellites: GOSAT, Global precipitation measurement: GPM with NASA and Earth cloud aerosol and radiation explorer: EarthCARE with ESA. GCOM-W and GCOM-C are proposed to be launched in 2009 and 2010, respectively.
The high-strength reaction-sintered silicon carbide (RS-SiC) developed and manufactured by Toshiba and NEC-Toshiba Space Systems, NT-SiC, is one of the most promising, excellent and feasible candidates for light-weighted large-diameter space-borne optics that are applied to geostationary earth observations and astronomical observations. Small NT-SiC sample mirrors were manufactured to study basic physical parameters and features, and optical performances of the material, such as the surface conditions of polished NT-SiC, the condition of inner crystal grains, the correlation between the surface roughness and polishing, scattering characteristics, absorbance of solar light and infrared emissivity, and adhesiveness of metal coating. The current state of the art of the development of the NT-SiC mirror and the feasibility of light-weighted large-diameter NT-SiC mirrors for space-borne optics are described. Although technical challenges to achieve the surface roughness that is applicable to ultraviolet mirrors still remain, the optical performance and the physical properties of the present NT-SiC show that it is one of the most excellent mirror material in optical-infrared wavelength region.
The concept study of new multi spectral imager has been showed. Multi spectral imager is the basic sensor for Earth remote sensing. The result of Global Imager (GLI) of Advanced Earth Observation Satellite -2 (ADEOS-2) showed us the various change of climate system. However, according to the progress of climate system change study, the reconsideration of observation channels is necessary. First, we studied the requirements of the next generation imager on the basis of GLI design considering the less observed parameters of the climate change. Then we found the necessity of the parameters related the human activities. Several parameters of each area, i.e., atmosphere, ocean, land, cryosphere, are selected. For the atmosphere, aerosol over land is emphasized. For the ocean, coastal change observation is proposed. For the land, advanced vegetation index is proposed. For the cryosphere, impurity of snow is emphasized. For the observation purposes, the proposed imager requirements are including the multi-angle polarization observation. And the resolution requirements of most channels are changed from 1 km to 250m. As the result of preliminary engineering study, the imager consists of a push broom imager for Visible and Near Infrared (VNIR) region, and a whisk broom imager for Shortwave Infrared (SWIR) and Thermal Infrared (TIR) region. Among the all channels, two channels, center wavelength 678 nm and 865 nm, are defined as multi-angle polarization observation channels. Each channel has fore, nadir, aft angles, also three polarization angles. The satellite orbit is about 800 km height sun-synchronous polar orbit to cover global area. The new sensor was named Second generation of Global Imager (SGLI). We are proposing to launch SGLI around 2010 on a satellite of Global Change Observation Mission (GCOM).
EarthCARE(Earth Clouds, Aerosols and Radiation Explorer) project is a candidate of the ESA (European Space Agency) Earth Explorer Core Missions. EarthCARE is the joint proposal between ESA, National Space Development Agency of JAPAN (NASDA) and Communications Research Laboratory (CRL). THe Phase-A study is started in NOvember 2001. The EarthCARE satellite has five sensors, CLoud Profiling Radar (CPR), ATmospheric LIDar (ATLID), Multi-Spectral Imager (MSI), Broad Band Radiometer (BBR) and Fourier Transform Spectromter (FTS). Main objective of EarthCARE FTS is to provide spectrally resolved outgoing radiance. Another objecitve of EarthCARE FTS is to retrieve temperature and water vapor profiles in clear air and above the clouds. NASDA is carrying out the Phase A study of EarthCARE. Preliminary Concept Review (PCR) was held at March 2003. We describe the objectives and instrument design concept of EarthCARE FTS in this paper.
The whiskbroom scanner Global Imager (GLI) was launched in December 2002 on the Advanced Earth Observation Satellite 2 (ADEOS-2). The sensor provides remotely sensed data from the Earth surface in the visible to the thermal infrared part of the spectrum. Since the Earth observation data require careful post-launch calibration, different on-board calibration tools have been integrated in the GLI hardware design. For the VIS-SWIR spectral range a special calibration device allows solar and lamp calibration. In this paper we describe first results on solar calibration of GLI.
EarthCARE (Earth Clouds, Aerosol and Radiation Explorer) project is a candidate of the ESA (European Space Agency) Earth Explorer Core Missions. There are many uncertainties mainly caused by aerosols, clouds and their interaction with radiation in predictions of climate change using numerical models. EarthCARE will provide vertical and horizontal distributions and physical characteristics of clouds and aerosols, and also provide the Earth radiation budget. EarthCARE is the joint proposal between ESA, National Space Development Agency of JAPAN (NASDA) and Communications Research Laboratory (CRL). The Phase-A study is going on. The EarthCARE satellite has five sensors, Cloud Profiling Radar (CPR), ATmospheric LIDar (ATLID), Multi-Spectral Imager (MSI), Broad Band Radiometer (BBR) and Fourier Transform Spectrometer (FTS). NASDA is studying FTS design. Main objective of EarthCARE FTS is to provide spectrally resolved outgoing radiance. This spectrum has many useful signatures from the surface/cloud/aerosol/water which can not get from spectrally integrated measurement. Another objective of EarthCARE FTS is a compact Michelson interferometer, which covers from 5.6 µm to 25 µm with 0.5 cm-1 spectral resolution. The FOV (Field Of View) is 10km so that the data can be used in conjunction with BBR.
IPCC third report says that we have still a lot of uncertainties to predict global warming even using latest GCMs. Regarding atmospheric radiation, uncertainty of the radiative forcing is still large, which is mainly caused by aerosols, clouds, and water vapor interacting among them. National Space Development Agency of JAPAN (NASDA) and Communications Research Laboratory (CRL) started Phase-A study with European Space Agency (ESA) in the EarthCARE project. The objectives of EarthCARE project are to observe vertical and horizontal distributions and physical characteristics of aerosols and clouds from a satellite, and also to measure the precise Earth radiation budget simultaneously. Finally we will be able to evaluate physical processes of clouds and aerosols regarding the radiative budget and forcing. The EarthCARE satellite carries 5 sensors, namely Cloud Profiling RADAR (CPR), Atmospheric LIDAR (ATLID), Multi-Spectral Imager (MSI), Broad Band Radiometer (BBR) and Fourier Transform Spectrometer (FTS). The result of the pre-Phase A study shows the synergy observation benefits using some compensative combinations of sensors, such as CPR/ATLID for clouds, ATLID/MSI for aerosols, BBR/FTS for the radiation budget. NASDA and CRL are studying FTS and CPR, respectively. CPR is a 94GHz RADAR using 2.5m diameter reflector with Doppler measurement mode. The sensitivity is -38dBZ. The vertical and horizontal resolution is 100 m, 1 km, respectively. FTS is a Michelson interferometer of which spectral measurement range is from 5.7 μm to 25 μm with 0.5 cm-1 unapodized spectral resolution. FOV is 10 km by 10 km. EarthCARE is planned to be launched in 2008 for 2 years mission. Phase-A study will continue until the end of 2003.