Spacecraft and Instruments
The GOSAT-GW satellite is a medium-sized (2.9 t) spacecraft with a power generation capability of 5.0 kW and will be launched by the H-IIA rocket from JAXA's Tanegashima Space Center in Japan's fiscal year 2023. Its orbit is sun-synchronous at an altitude of 666 km with a repeat cycle of 3 days, same as GOSAT. It will ascend from south-east to north-west in the daytime, and its local equator crossing time will be 1:30 pm.
Figure 2: GOSAT-GW spacecraft, artist’s rendition
Figure 3: TANSO-3, illustration
GOSAT-GW will carry a grating imaging spectrometer named TANSO-3. GOSAT and GOSAT-2 carry Fourier Transform Spectrometer (FTS) in favor of the high spectral resolution in the wide spectral range from the near infrared to the thermal infrared regions. In the case of TANSO-3, gratings were chosen instead of FTS to realize imaging of greenhouse gas concentrations with a smaller footprint and a wider swath than FTS, which is necessary for emission source observations.
TANSO-3 will observe CO2 and CH4, two major greenhouse gases, and NO2. The NO2 information will be utilized to locate CO2 emission sources by fossil fuel burning and obtain the precise shape of plumes emitted from the sources.
TANSO-3 will have three spectral bands: Band 1 at around 0.45 µm for NO2, Band 2 at around 0.76 µm for O2, and Band 3 at around 1.6 µm for CO2 and CH4. These gases cause distinct absorption features in the sunlight reflected at the land or ocean surface and observed by TANSO-3. Through the detailed characterization of these physical features using mathematical methods such as "optimal estimation," the column abundances of these gases (CO2 and CH4) and surface pressure will be obtained. These data will be finally converted to column-averaged dry-air mole fractions of CO2 and CH4 (XCO2 and XCH4, respectively). The column amount of NO2 will be calculated from the conventional Differential Optical Absorption Spectroscopy (DOAS) approach. Bands 1 and 2 will also be used for cloud detection. Solar Induced chlorophyll Fluorescence (SIF), an important indicator of photosynthetic activity of the terrestrial vegetation, will be obtained from Band 2 data.
Table 1: Specification overview of GOSAT Series satellites
|Launch / lifetime
||2009 / 5 years
||2018 / 5 years
||FY2023 / 7 years
|Satellite mass / power
||1.75 t / 3770 W
||1.8 t / 5000 W
||2.9 t / 5200 W
||666 km, 3 days,
|613 km, 6 days,
|666 km, 3 days,
||CO2, CH4, CO
||CO2, CH4, NO2
||0.7 / 1.6 / 2 µm + TIR
||0.7 / 1.6 / 2 µm + TIR
||0.45 / 0.7 / 1.6 µm
(≈ 0.01 nm @ 0.7 µm, ≈ 0.05 nm @ 1.6 µm)
|< 0.5 nm @ 0.45 µm, <0.05 nm @ 0.7 µm,
< 0.2 nm @ 1.6 µm
||Discrete, 1 – 9 points
||Discrete, 5 points
||Selectable, 911 km (Wide) or 90 km (Focus)
|Footprint size, nadir
||Selectable, 10 km (Wide) or 1 – 3 km (Focus)
||±20 /±35 deg (AT/CT)
||±40 /±35 deg (AT/CT)
||±40 /±34.4 deg (AT/CT)
||CAI (Cloud and Aerosol Imager)
||CAI-2 (Cloud and Aerosol Imager 2)
||AMSR3 (Advanced Microwave Scanning Radiometer 3)
GOSAT-GW will also carry AMSR3, a sensor for observing microwave signals emitted from the land, ocean, and atmosphere. It is a successor to AMSR, AMSR-E, and AMSR2 which were launched on board JAXA's ADEOS-II (2002–2003), NASA's Aura (2002–), and JAXA's GCOM-W1 (2012–) satellites respectively. The obtained data will be used to estimate temperature and water-related parameters of the Earth, such as precipitation, water vapor profiles, sea ice, and soil water content. For more details, see below.
Status of GCOM-W and GOSAT-GW/AMSR3: