The Second-generation global imager (SGLI) empowers surface and atmospheric measurements related to the carbon cycle and radiation budget, with two radiometers of Visible and Near Infrared Radiometer (VNR) and Infrared Scanning Radiometer (IRS) which perform a wide-band (380 nm - 12 μm) optical observation not only with as wide as 1150-1400 km FOV but also with as high as 250 - 500 m resolution. Also, polarization and along-track slant view observation are quite characteristic of SGLI. SGLI provides the earth observing data for more than 28 standard products and 23 research products including clouds, aerosols, ocean color, vegetation, snow and ice, and other applications. SGLI-VNR has several on-board calibration methods, such as solar, LED and lunar calibration. In this paper, methodologies and results of solar and LED calibration of SGLI-VNR Non-Polarization (NP) telescopes with a deployable diffuser to illuminate the uniformly scattered solar and LED light to telescope and photo diode stability monitor (PD) are provided, respectively. In addition, inter-comparison of the solar and the LED calibration is conducted with NP-Nadir telescope, PD2 and PD4. The calibration area of the telescope and the PDs are less affected by the UV degradation, so that the PD2 and the PD4, as an independent calibrator, can correct the solar diffuser reflectance degradation for the NP-Nadir telescope. As a result, each trend of the solar and the LED calibration of the NP-Nadir’s VN5, 10, and 11 bands agrees 1% or less. It concludes that the response change in the NIR spectral regions (VN10 and 11 with wavelength of 868.5 nm) is stable and that in the shorter wavelength band (VN5 with wavelength of 530 nm) is less than 2 % over a year. Lessons learned of on-board calibrations are also stated for the next generation's global imager.
JAXA's Global Change Observation Mission for Climate (GCOM-C) spacecraft called "SHIKISAI", which means colorfulness in Japanese, was successfully launched on December 23, 2017 by H-IIA launch vehicle, Flight 37 (F37). GCOM-C is sun-synchronous polar orbit satellite with wide field of view (FOV) and 19 channels optical imager, Second Generation Global Imager (SGLI). The essential satellite operation to establish the satellite basic function to be used for the house keeping was successfully completed after the one day critical phase operation. The three months initial commissioning activities for the both satellite bus and sensor has been conducted before the calibration and verification phase to ensure the sensor observation product accuracy. This paper describes the commissioning of SGLI that we have performed during the first several months of in-orbit operation to confirm the system integrity. The technical aspects to the lunar calibration and the thermal infrared performance are specially described.
The Global Change Observation Mission (GCOM) aims to establish and demonstrate a global, long-term satelliteobserving
system to measure essential geophysical parameters to facilitate understanding the global water circulation and
climate change, and eventually contribute to improving future climate projection through a collaborative framework with
climate model institutions. GCOM consists of two polar orbiting satellite observing systems, GCOM-W (Water) and
GCOM-C (Climate). The first satellite, GCOM-W with Advance Microwave Radiometer -2 (AMSR-2), was already
launched in 2012 and has been observing continuously. The follower satellite, GCOM-C with Second Generation Global
Imager (SGLI), will be launched in Japanese fiscal year 2017. SGLI enables a new generation of operational moderate
resolution-imaging capabilities following the legacy of the GLI on ADEOS-II (Advanced Earth Observing Satellite-II)
satellite. The SGLI empowers surface and atmospheric measurements related to the carbon cycle and radiation budget,
with two radiometers of Visible and Near Infrared Radiometer (VNR) and Infrared Scanning Radiometer (IRS) which
perform a wide-band (380nm-12μm) optical observation not only with as wide as 1150-1400km FOV (field of view) but
also with as high as 250-500m resolution. Also, polarization and along-track slant view observation are quite
characteristic of SGLI, providing the sensor data records for more than 28 standard products and 23 research products
including clouds, aerosols, ocean color, vegetation, snow and ice, and other applications. Sensor instrument proto-flight
tests including optical characterization tests such as radiometric and geometric were completed, and satellite system
proto-flight tests have finished including thermal vacuum, vibration and acoustic test. In this paper, the pre-launch phase
instrument characterization of SGLI flight model and status of GCOM-C satellite system flight model along with the
overview of them will be described. Especially we focus on the pre-launch geometric and radiometric performance test
results, in-orbit calibration activities and methodologies: VNR's on-board calibrator, IRS's on-board calibrator and
calibration maneuver, and in-orbit verification plan during a commissioning phase lasting approximately 3 months.
The hyper-multi spectral mission named HISUI (Hyper-spectral Imager SUIte) is the next Japanese earth observation
project that will be on board ALOS-3 satellite. This project is the follow up mission of the Advanced Spaceborne
Thermal Emission and reflection Radiometer (ASTER). HISUI is composed of hyperspectral radiometer with higher
spectral resolution and multi-spectral radiometer with higher spatial resolution. The functional evaluation model is under
development to confirm the spectral and radiometric performance prior to the flight model manufacture phase. This
model contains the VNIR and SWIR spectrograph, the VNIR and SWIR detector assemblies with a mechanical cooler
for SWIR, signal processing circuit and on-board calibration source.
Fast and small foot print lossless image compressors aiming at hyper-spectral sensor for the earth observation satellite
have been developed.
Since more than one hundred channels are required for hyper-spectral sensors on optical observation satellites, fast
compression algorithm with small foot print implementation is essential for reducing encoder size and weight resulting in
realizing light-weight and small-size sensor system. The image compression method should have low complexity in
order to reduce size and weight of the sensor signal processing unit, power consumption and fabrication cost. Coding
efficiency and compression speed enables enlargement of the capacity of signal compression channels, which resulted in
reducing signal compression channels onboard by multiplexing sensor signal channels into reduced number of
The employed method is based on FELICS1, which is hierarchical predictive coding method with resolution scaling. To
improve FELICS's performance of image decorrelation and entropy coding, we applied two-dimensional interpolation
prediction and adaptive Golomb-Rice coding, which enables small footprint. It supports progressive decompression
using resolution scaling, whilst still delivering superior performance as measured by speed and complexity.
The small footprint circuitry is embedded into the hyper-spectral sensor data formatter. In consequence, lossless
compression function has been added without additional size and weight.
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.
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.