The second-generation global imager (SGLI) was launched in December 2017 onboard the global change observation mission-climate (GCOM-C) and has been observing daily global data in 23 different channels using three sensor units: the visible and near-infrared radiometer with nonpolarization (VNR-NP), one with polarization (VNR-PL), and the infrared scanning radiometer (IRS). The VNR-NP uses a push-broom scanner to observe 11 spectral bands with 250-m and 1-km spatial resolutions. The VNR-PL collects the polarization data for three angles in two spectral bands with a spatial resolution of 1 km by a push-broom scanner. The IRS observes six spectral bands with spatial resolutions of 250 m, 500 m, and 1 km by a whiskbroom scanner. Their geometric processing was one of the technical challenges, where the 23-channel data acquired by the three independent sensors have different geometric characteristics. For their calibration, the imageries of the Advanced Visible and Near-Infrared Radiometer Type-2 (AVNIR-2) were used as the ground control points (GCPs). Their finer resolution, geolocation accuracies, and global distribution made the calibration more detailed. A systematic strategy was conducted in the calibration, which combines the absolute errors from GCPs and the relative errors among different channels. The errors were measured by the image-matching technique between different spectral bands based on their image correlations. As a result, the geolocation accuracies have satisfied the specification of 0.5 pixels (rms) for over six years since launch. This article describes the geolocation approach and the geometric calibration of the SGLI.

The COVID-19 pandemic has brought difficulties to our daily lives and caused various changes in socio-economic activities and the natural environment. To monitor and record the changes in socio-economic activities and the environment before and during the COVID-19 pandemic, JAXA has collaborated with NASA and ESA in developing a trilateral dashboard to provide socio-economic activities and natural environmental change information derived from earth observation data. JAXA also has analyzed Earth observation data, for example, ALOS-2, GCOM-C, GOSAT and GOSAT-2 and opened at a special website “JAXA for Earth on COVID-19” in the categories of airports, industry, shipping, agriculture, greenhouse gasses and water quality.

In order to control the spread of the pandemic of Corona-Virus Disease 2019 (COVID-19), lockdowns of various durations and intensities have been established in many countries over the world all through the year 2020. The trilateral dashboard jointly implemented by NASA, JAXA and ESA aims at exploiting remote-sensing data to evaluate the impact of these restrictions, and subsequent recovery phases on many different environmental, agriculture and economic indicators. More specifically, this paper presents the indicators implemented to monitor the impact of COVID-19 restrictions on Water Quality, together with preliminary analysis results over a few Areas of Interest.

The Global Change Observation Mission (GCOM) consists of two satellite missions, GCOM-W (Water) and GCOM-C (Climate), and aims to provide comprehensive information of the Essential Climate Variables (ECVs) of atmosphere, ocean, land, cryosphere and ecosystem. The GCOM-W "SHIZUKU" satellite was launched in May 2012, which carries the Advanced Microwave Scanning Radiometer 2 (AMSR2). It achieved its 5-year designed mission life in May 2017 and is currently in extended mission phase. The GCOM-W satellite is joining in the A-train orbit to provide synergies with the other A-train satellites, such as Aqua and Cloudsat. The GCOM-C "SHIKISAI" satellite was launched in December 2017, which carries the Second generation Global Imager (SGLI). SGLI data has been released to public since December 20, 2018. Both AMSR2 and SGLI data are used in operational numerical weather prediction and environmental monitoring to reduce meteorological disasters. Because of its observation capability and observation local time, both GCOM satellites have synergies with the Joint Polar Satellite System (JPSS) program and can contribute to objectives of JPSS.

Japanese geostationary meteorological satellite "Himawari-8" was launched in October 2014. Japan Meteorology Agency (JMA) started its official operation of Himawari-8 satellite in July 2015. Japan Aerospace Exploration Agency (JAXA) has been developing the geophysical retrieval algorithms from Himawari observation data and has been generating the products since August 2015 in an attempt to seek synergies between Himawari and JAXA’s Earth observation satellites, especially with the Global Change Observation Mission – Climate (GCOM-C), which was launched in December 2017. Several algorithms developed for GCOM-C was applied to Himawari data to produce consistent dataset, taking the opportunity of both satellites loading a multispectral imaging sensor. Application of Himawari products in numerical models and synergies with GCOM – Water (GCOM-W) are also shown.

GCOM-C/SGLI is a multi-wavelength optical radiometer launched on December 23, 2017. The data provision has started from December 20, 2018. In this research, we briefly introduce standard Level 2 products and their validation results based on in situ data. Mean absolute percentage differences are 16.3 - 69.6% for NLW between 380 - 670 nm, 39 and 64.5% for AOT at 670 nm and 865 nm, 27.9% for CHL and 44.2% for aCDOM. Although the number of in situ validation data are still scare for a few ocean color products, the accuracy of GCOM-C/SGLI data will be improved by our future efforts of calibration/validation activities.

We developed a scheme to improve hourly estimates of aerosol optical thickness (AOT) from the Advanced Himawari Imager (AHI) onboard Himawari-8, the Japan Meteorological Agency's latest geostationary satellite. Taking advantage of the sampling characteristics of the AHI (10-min temporal and subkilometer spatial resolution), we quantify temporal and spatial variability of AOT from the observations (AOToriginal) and utilize this information to develop an hourly algorithm that produces two sets of derived AOTs: AOTpure, derived by the application of strict cloud screening to AOToriginal, and AOTmerged, derived from spatial and temporal interpolations of AOTpure. The AOTs thus obtained from the hourly algorithm were validated against measurements from the aerosol robotic network. The root-mean-square errors (RMSEs) of the AOTpure and AOTmerged products were 0.14 and 0.11, respectively, providing improvement over an RMSE of 0.20 for AOToriginal.

The SGLI instrument, which is to be launched by JAXA in March 2017 aboard GCOM-C satellite, conducts ocean color observation in 250 m spatial resolution (SST in 500 m resolution) over coastal region, in addition to the global ocean observation in 1 km resolution. We first describe here the SGLI Level 2 (L2) ocean standard products, which consist of 6 ocean color parameters and 1 SST parameter, and then briefly describe the product generation data flow together with the algorithms implemented in the production system. The required time and memory size of the Level-2 data generation was evaluated over a simulated SGLI data scene, which indicates that the modules meet the standard L2 data generation system requirements, although further optimization in the processing code will be pursued.

The Advanced Land Observing Satellite (ALOS, nicknamed `Daichi') was launched on January 2006, and has operated very well. However, its operation moved to the low load mode (LLM) since April 22, 2011, and was subsequently followed by an official termination on May 12, 2011. Notwithstanding, approx. 6,500,000 scenes of archived data covering the entire globe are available to users. Therefore the calibration result is still important information for users. This paper describes calibration results of two optical instruments called PRISM and AVNIR-2 onboard ALOS are summarized during whole mission period. The previous result has been published in 2009, which was explained an overview of calibration and validation plan, and their results at that time. As the updated calibration results, we confirmed 6.1 m (root mean square error, RMSE) for PRISM nadir-looking radiometer and 21.9 m (RMSE) for AVNIR-2 0 deg. pointing of absolute geometric accuracies, and no significant degradation on radiometric accuracy.

The Japan Aerospace Exploration Agency (JAXA) is pursuing the Global Change Observation Mission (GCOM) that will inherit the Advanced Earth Observing Satellite-II (ADEOS-II) mission and develop into long-term monitoring. GCOM is not the name of a single satellite, but of a mission that consists of two series of medium-size satellites, GCOM-W (Water) and GCOM-C (Climate), and three generations of each satellite series to continue the observations for 10 to 15 years. The Advanced Microwave Scanning Radiometer-2 (AMSR2) will be the single instrument on the GCOM-W1 satellite, which is the first satellite of the GCOM series. The second satellite will be GCOM-C1, which will carry the Second-generation Global Imager (SGLI). GCOM-W will mainly contribute to the observations related to global water and energy circulation, while GCOM-C will contribute to the measurements related to the carbon cycle and radiation budget. Current target launch years are calendar year 2011 for GCOM-W1 and 2014 for C1.

The proper depiction of water vapor distribution in the upper troposphere and the related radiative properties is critical for the accuracy of climate and atmospheric circulation model predictions. In the present study, differences between satellite observations (Terra-MODIS) and atmospheric models' simulations are examined. The models are: the National Center for Environmental Protection/Department Of Energy (NCEP-DOE) reanalysis-2 data and the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The models' outputs (atmospheric temperature and humidity profiles) are used in this study to simulate the upper tropospheric brightness temperature (UTBT) and relative humidity (UTRH) at clear sky and low cloud areas. The results obtained show the contribution of atmospheric instability due to heat movements of the lower troposphere clear sky, cloud convection and low cloud radiative properties in the discrepancies between model and observation results. These differences tend to increase with the increase of the proportion of unstable pixels in the clear sky areas. Heat movements from cloud convection and low clouds examined through the convective clouds' distribution and the cloud effective emissivity respectively, show that cloud convection mostly affects the NICAM model results (existence of a positive correlation between the latter model error and the amount of convective clouds) and, discrepancies are stronger in broken clouds than continuous clouds.

The Advanced Land Observing Satellite (ALOS, nicknamed ¿Daichi¿) was successfully launched on January 24, 2006, and continues to work very well. In this paper, we introduce the updating calibration results and their time trends of the standard products for two optical instruments onboard ALOS, the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2). Geometric calibration is important in generating a precise digital surface model (DSM) by a stereo pair image of PRISM. Relative geometric calibration of both PRISM and AVNIR-2 are conducted by evaluating accuracies within one scene and evaluating sensor alignments as absolute calibration. For absolute geometric accuracies, we achieved 7.8 m for nadir-, 8.0 m for forward-, 18.7 m for backward-looking images of PRISM, and 114.2 m for AVNIR-2, respectively.

The Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) on-orbit radiometric performance has been improved through the comparison of cross-calibration and onboard lamp calibration. We proposed a new cross-calibration scheme which uses top-of-atmosphere reflectance functions of satellite zenith angle at temporally and spatially stable ground sites. Each function is made from Moderate Resolution Imaging Spectroradiometer (MODIS) 500-m resolution data over 16 days, which includes AVNIR-2 observation dates. The results showed that the radiances of AVNIR-2 bands 1 (463 nm), 2 (560 nm), and 3 (652 nm) agreed with the radiances of Aqua and Terra MODIS within 3% accuracy (standard deviation of 2%). AVNIR-2 band 4 (821 nm) had a difference of about 7% (AVNIR-2< MODIS) due to water-vapor absorption which could explain more than half of the 7%. Using many samples from this scheme, we found dependences of radiometric calibration errors within the field of view (FOV) and for different gain modes. The lamp calibration system onboard AVNIR-2 unveiled these dependences over the FOV and time. Furthermore, for the gain mode, consistent results could be retrieved using the cross-calibration scheme. The retrieved radiometric correction factors (over the FOV and gain modes) have been applied to the Japan Aerospace Exploration Agency AVNIR-2 processing scheme. The subsequent validation of the correction showed, for polar snow areas, an improved radiometric performance over the entire FOV.

The Advanced Land Observing Satellite [(ALOS); nicknamed ldquoDaichirdquo] was successfully launched on January 24, 2006, and it continues to work very well. This paper describes the calibrations of two optical instruments onboard ALOS, which are the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and Advanced Visible and Near-Infrared Radiometer type 2 (AVNIR-2). PRISM consists of three panchromatic radiometers and is used to derive a digital surface model (DSM) with high spatial resolution, which is an objective of the ALOS mission. AVNIR-2 has four radiometric bands from blue to near infrared, which are used for investigating regional environment issues such as land-use and land-cover classifications, and disaster monitoring. In this paper, we introduce the calibration and validation plan, methodologies, accuracy assessments of the standard products, image quality evaluations for PRISM and AVNIR-2, and their results. Geometric calibration is important in generating a precise DSM by a stereo pair image of PRISM. The relative geometric calibrations of both PRISM and AVNIR-2 are conducted by evaluating accuracies within one scene and evaluating sensor alignments as absolute calibration. For absolute geometric accuracies, we achieved 8.1 m for nadir-looking images and 9.3 m for forward- and backward-looking images of PRISM; we also achieved 114.2 m for AVNIR-2. PRISM is also radiometrically calibrated both relatively and absolutely. PRISM relative radiometric calibration is accomplished by using acquired images over homogeneous targets, such as oceans, deserts, ice, and snow areas, as well as nighttime observation. Simultaneously observed images with calibrated AVNIR-2 are used for absolute radiometric calibration by cross-calibration. The absolute radiometric accuracy of the PRISM nadir-looking radiometer is similar to that of AVNIR-2.

A cross-calibration scheme which uses top-of-atmosphere (TOA) reflectance functions of satellite zenith angle at temporally and spatially stable ground sites is proposed. Each function is made from MODIS 500m-channel observations over 16 days which includes AVNIR-2 observation dates. The results showed that radiances of AVNIR-2 channels 1 (463 nm), 2 (560 nm), and 3 (652 nm) agreed to the radiances of Aqua and Terra MODIS channels 3 (466 nm), 4 (554 nm) and 1 (646 nm) respectively within 5% accuracy. AVNIR-2 channel-4 (821 nm) decreased more than 5% by water-vapor absorption in some cases. Using many samples from this scheme, we found possible gain dependencies on Field Of View (FOV) and gain-modes. Lamp calibration system onboard AVNIR-2 showed dependencies on FOV, time change of the FOV error, and gain-mode consistent with the cross-calibration results. After correction of the identified errors, inter-channel consistency of FOV in the polar-snow scenes was improved.

The Advanced Land Observing Satellite (ALOS, nicknamed "Daichi") was successfully launched on January 24, 2006 and it continuously working very well. This paper introduces the updated results of calibration for two optical sensors of ALOS i.e. the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2). PRISM consists of three panchromatic radiometers, and is using to derive a digital surface model (DSM) that is topography and terrain height information with high spatial resolution. Therefore, geometric calibration is important in generating a highly accurate DSM by stereo pair image of PRISM. The radiometric calibration is also important for PRISM as well as AVNIR-2. This paper describes the updated results of geometric and radiometric calibrations and image quality evaluation of PRISM and AVNIR-2 in the operational phase, which are including stability or time trend of accuracies during 2.5 years since launch the ALOS.

We have developed a global vicarious calibration scheme for spaceborne ocean-color sensors, simulating top-of-atmosphere radiance globally using a radiative transfer model, SeaWiFS Level 3 eight-day mean products, and an in-water optical model. This is a relative calibration against two channels used to detect aerosol properties; however, it enables us to determine the spatial and temporal characteristics of the vicarious calibration coefficients (Kvc) without in situ observations. We applied this scheme to the NASDA Global Imager (GLI), which operated from January 25, 2003 to October 24, 2003. Kvc exhibited the following properties: (1) channel characteristics of 1.0-1.1 (GLI was lower than the simulation) in channels 1-9 (380-565 nm), nearly 1.0 in channels 10-19 (625-865 nm), and 0.91-0.98 in channels 24-29 (1050-2210 nm); (2) scan-angle dependency and its temporal changes in channels 1-3; and (3) scan-mirror side differences and temporal changes. Applying Kvc to GLI ocean-color processing produced outputs consistent with the ground observation data. This scheme is also useful for generating consistent products from different ocean-color sensors in orbit.

We conducted vicarious calibration of the Global Imager (GLI) in visible to near-infrared channels over different targets. For calibration over the ocean, we used the normalized water-leaving radiance derived from the Marine Optical Buoy (MOBY) and the aerosol optical properties (aerosol optical depth, size distribution, and refractive index) obtained through the Aerosol Robotic Network (AERONET). For calibration over land, we used the ground-based measurement data at Railroad Valley Playa. The following GLI characteristics are recognized from the calibration results. First, GLI underestimates the radiance in channels 1, 2, 4, and 5. Next, in the near-infrared channels, there is good agreement between the observed and simulated radiance over bright targets. On the other hand, it is suggested that the GLI overestimates the radiance over dark targets (e.g., on the order of 15% at 4.0 W/m/sup 2///spl mu/m/sr in channels 18 and 19). Furthermore, we evaluated these calibration results over different targets taking into account the difference in the target radiance and in the accuracy between the two results. This combined evaluation of vicarious calibration results suggests the possibility that the GLI-observed radiance has offset radiance versus the simulated radiance.

After ADEOS-2 launch on 14 December 2002, GLI ocean group has investigated vicarious calibration, algorithm improvement and product validation, and released version-1 products on 24 December 2003. Although we lost ADEOS-2/GLI on 24 October 2003, we continue product evaluation and algorithm revision toward the future product updates. For example, we are investigating absorptive aerosol correction and 250-m ocean color image processing. The absorptive aerosol correction is very important especially in the East Asia where is surrounded by the fast developing countries and influenced frequently by a kind of carbon aerosols. The 250-m products are made using GLI 250-m channels from blue to near-infrared, and enable to detect fine spatial structures in the coastal areas.

Calibration results of the ocean color and temperature scanner (OCTS) on board the Advanced Earth Observing Satellite (ADEOS) are presented. The authors have evaluated the OCTS responses to internal calibration sources (i.e., lamps, electric voltages, and sunlight), natural targets (i.e., night data and uniform targets in the daytime), external calibration source (i.e., underflight of a calibrated airborne sensor), and a theoretical calibration source modeled for the atmospheric radiation. The authors then compared the acceptability of these calibration sources.

Topography is a fundamental Earth characteristic that can be measured for studies of the land surface. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard the EOS-AM1 platform will acquire along-track stereo data for topographic mapping. ASTER is capable of recording 771 digital stereo pairs per day, each covering 60/spl times/60 km on the ground, at 15-m resolution, with a base-to-height ratio of 0.6. According to present plans, approximately 30 digital elevation models (DEMs), accurate to within /spl plusmn/7 to /spl plusmn/50 m (RMSE/sub z/) will be produced daily by processing facilities in Japan and the United States. The Land Processes Distributed Active Archive Center (LP-DAAC) at the United States Geological Survey's (USGS's) EROS Data Center (EDC) will emphasize the use of automated stereocorrelation procedures to produce absolute DEMs tied to ground control. During the six-year mission, ASTER has the potential to provide a coherent, digital stereo data set covering all of the Earth's land surface. At minimum, ASTER DEMs will augment topographic data from other sources. Results of simulations of ASTER stereo data using existing satellite and aircraft data over validation sites in Huntsville, AL, and Iguala, Mexico, illustrate the value of high-resolution ASTER DEMs and how actual ASTER DEMs will be validated.