Over ten years observation of GOSAT (alias “IBUKI”) launched on January 23, 2009, have made the importance and availability of the measurements of the greenhouse gases from space points to us.
On the other hand, although GOSAT has accomplished the accuracy targets which is highest ever for any observations from space with involvement of the information of the boundary layer, the accuracies were not enough for the political use, and in addition the scientists had required to improve the accuracy. So it was desired to improve the measurement accuracies. Through the GOSAT operation, we learned a lot of things on the instrument, software, processing algorithm and operation; and we have recognized what we should improve in the following mission. To elucidate the carbon cycle more precisely, our experiences regarding observation performances as well as hardware design were reflected on the mission requirements on GOSAT-2.
The development of GOSAT-2 had started in April of 2014 after the nominal operation phase of GOSAT is complete, and the development of TANSO-FTS-2 which is the instrument to measure the greenhouse gases such as Carbon Dioxide and Methane has been completed in January of 2018 and TANSO-CAI-2 has been completed in February of 2018. And the development of GOSAT-2 has been completed in August of 2018.
The principal requirements are measuring the CO2 concentration with the accuracy of 0.5 ppm at 500km and 2,000km mesh spatial resolution over the land and ocean, respectively and 1 month average, estimating the net flux with the error of 100% and measuring the Carbon Monoxide as the correlated matter of the anthropogenic emission of the greenhouse gases to study the detection of that.

To improve the measurement accuracy, the signal to noise ratio was increased by the extension of the aperture size and cooling the after optics as well as the thermal detectors. And to increase the number of the useful data, TANSO-FTS-2 has been equipped with the function to avoid the clouds using the images obtained by the monitor camera in FTS.
To observe the carbon monoxide, spectral range of the 2.0m band was extended to 2.3m.
The pointing angle in the along track direction was extend from 20 degrees of GOSAT to 40 degrees to expand the observation area over the ocean where the sun glint is observed.
The cloud and aerosol imager (TANSO-CAI) data have been used to eliminate the FTS data contaminated with the clouds and the function to measure the aerosols of TANSO-CAI-2 was enhanced to detect the flow of the PM2.5 which is the critical issues not only in Japan but also in the world. New observation channels are added and the viewing angles were changed to + and - 20 degrees from nadir of GOSAT.
In addition, the GSD of the 1.6m band is twice of the one of GOSAT.

GOSAT-2 was launched on 29th of October, 2018 and after the critical phase of about 16 hours the initial performance test on orbit started and will be completed in middle of January. The results of the initial performance test will be shown compared with the results of the pre-launch test in this presentation.

The Orbiting Carbon Observatory 3 (OCO-3) will continue and extend global CO₂ and solar-induced chlorophyll fluorescence (SIF) using the flight spare instrument from OCO-2. The instrument has been through ground testing and thermal vacuum, and is packaged for installation on the International Space Station (ISS), currently scheduled for launch in February 2019, with no significant delay to be expected. This talk will focus on the post-launch mission status, science objectives, science data products, early operations plan, and data availability.
The low-inclination ISS orbit lets OCO-3 sample the tropics and sub-tropics across the full range of daylight hours with dense observations at northern and southern mid-latitudes (+/- 52°). The combination of these dense CO₂ and SIF measurements provides continuity of data for global flux estimates as well as a unique opportunity to address key deficiencies in our understanding of the global carbon cycle. The instrument utilizes an agile, 2-axis pointing mechanism, providing the capability to look towards the bright reflection from the ocean and validation targets. In addition to the nadir-, glint-, and target-mode geometries familiar from OCO-2, OCO-3 includes a new observation mode dedicated to mapping out larger spatial-scale emitters like cities. This Snapshot Area Map (SAM) mode will be used to map areas of up to 80x80 km² on the Earth surface with the standard OCO-3 ground footprints of 2x3 km², providing unprecedented high spatial resolution coverage of large-scale CO₂ emitters worldwide. Measurements over urban centers could aid in making estimates of fossil fuel CO₂ emissions. Similarly, the snapshot mapping mode can be used to sample regions of interest for the terrestrial carbon cycle. In addition, there is potential to utilize data from the currently operating ISS instruments ECOSTRESS (ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station) and GEDI (Global Ecosystem Dynamics Investigation), which measure other key variables of the control of carbon uptake by plants, to complement OCO-3 data in science analysis.
In mid-May 2019 OCO-3 will have been in orbit for about two months. We will report updates on mission status and detailed simulations of planned operations and data quality, along with the instrument characterization from thermal vacuum and on-orbit testing. The specific nature of the ISS orbit track produces spatial and temporal coverage that is something of a paradigm shift compared to low-earth-orbiting satellites like OCO-2, which provide observations at fixed overpass times and repeat cycles. OCO-3 observations will necessitate re-evaluation and adaptation of the current approaches of how satellite data are being used in model evaluation and science studies.

Figure: Example of an OCO-3 snapshot area map coverage over Los Angeles, CA, drawn over a nightlights image to highlight the urban area. Red circles represent the center of OCO-3 soundings at 0.3 second intervals; gray lines show an approximation of the eight across-track ground pixels for each sounding.

MicroCarb is a space mission designed to monitor the atmospheric load of Carbon Dioxide with the aim of improving our understanding of the Carbon cycle. It therefore has similar mission and monitoring objectives as the currently flying GOSAT, OCO-2 or TANSAT satellites.
The project is conducted by the CNES in partnership with the UK Space Agency, and involves the scientific community from both France and UK.
Compared to similar ongoing space mission, MicroCarb includes an additional spectral band at 1.27 µm. It is expected that this additional band will allow a better estimate of the surface pressure and atmospheric scattering, despite its contamination by airglow. Radiative transfer simulations and analysis indicate that the airglow emission and the oxygen absorption can be distinguished despite their similar (but not identical) spectral signatures. The oxygen absorption at 1.27 µm may be easier to interpret and the impact of aerosol may be easier to extrapolate to the CO2 absorption bands than from the oxygen 1 band that is used in the other similar missions. This, together with the high spectral resolution, may help to reduce the current difficulties of the CO2 monitoring from space.
The instrument will be carried onboard a microsatellite that allows some pointing to target of opportunities. A mirror in the optical design makes it possible to scan cross-track, and then to acquire successive observations that are more independent from each other than for continuous nadir sampling.
The MicroCarb operating modes aim at an optimal science return, with glint, nadir, target, scan and imagery modes. The later makes it possible to acquire dense sampling over a target of opportunity, such as a power plant or a large city.
The project is currently completing its detailed definition phase (phase C) and the launch is scheduled for 2021
The MicroCarb spectra shall be processed by a retrieval code currently under development. It relies on an-priori information on the atmospheric CO2, water vapor and aerosol profiles, and the surface pressure, that are modified through the inversion.
The presentation will describe the instrument design, the operating modes, the data processing and the expected scientific impact.

The European Commission is considering to expand the space component of the Copernicus programme with a constellation of CO2 imaging spectrometers to support the global monitoring of anthropogenic CO2 emissions. The imaging capability would allow for observing CO2 plumes of individual strong point sources and quantifying their emissions. However, since the enhancements in total column CO2 (XCO2) will only be small and potentially obscured by biospheric signals, measurements of auxiliary trace gases such as CO and NO2 were proposed to help detecting the plume and separating anthropogenic from biospheric signals.
We present results from the ESA study SMARTCARB on the potential synergies of CO and NO2 measurements as well as first results from the EU project CHE. In SMARTCARB, we simulated realistic CO2, CO and NO2 fields considering anthropogenic and biospheric fluxes at very high resolution (1 km × 1 km) using the GPU-accelerated mesoscale model COSMO-GHG. The simulations were conducted for the full year 2015 over a domain covering the city of Berlin and several power plants. The simulations were then used to generate synthetic XCO2, CO and NO2 satellite observations (2 × 2 km2 pixel size with 250-km swath) with parameterized noise for constellations of up to six satellites. The CO2 plumes of Berlin and the power station Jänschwalde were detected using CO2 alone or in combination with CO or NO2 observations. CO2 emissions were then quantified by inverse modeling and mass-balance methods.
Although a constellation of six satellites was sufficient to cover Berlin on a daily basis, only about 60 out of 365 plumes per year could be observed due to frequent cloud cover. The CO2 instrument could detect only 6 to 14 of these 60 plumes with high (σVEG50 = 1.0 ppm) and low noise (σVEG50 = 0.5 ppm), respectively, because the CO2 enhancements were often too weak with respect to instrument noise and background variability. A CO instrument performed worse than the CO2 instrument, while the number of detectable plumes could be significantly increased to 39 plumes with an NO2 instrument, assuming instrument specifications similar to Sentinel-5P. The NO2 instrument also greatly helped to estimate the background XCO2 levels required to quantify the local enhancements within the plumes. The CO2 instrument alone could only detect a small fraction of the real plume, so that the background, estimated from the values surrounding the plume, contained significant amounts of XCO2 emitted from Berlin. Consequently, the XCO2 background within the plume was overestimated and Berlin's emissions were correspondingly underestimated by about 15-25%. The NO2 instrument detected a much larger portion of the plume which enabled an almost unbiased estimation of the background and of the emissions of the city (<10%). The emission uncertainties for single overpasses were about 5-10 Mt yr-1 (30%-60%) and, for a constellation of six satellites, the RMSDs of the annual mean estimate were 4-7 Mt yr-1 for the CO2 instrument and about 2 Mt yr-1 when also using the NO2 instrument. In conclusion, an NO2 instrument on the same platform as a CO2 instrument has the potential to greatly improve CO2 emission estimation by increasing the number of detectable plumes and by reducing biases and scatter of the estimates.
Similar simulations are currently being conducted in the project CHE with further improvements regarding nesting strategy (from global to European to regional) and improved biospheric and anthropogenic fluxes. Since the simulations are conducted with four different transport models and at different resolutions, they will allow investigating transport model uncertainties as well as the influence of model resolution on the representation of individual plumes.

Recent advances in space-based remote sensing methods provide new tools for measuring atmospheric carbon dioxide (CO2) and methane (CH4) from space. Space agencies have exploited these capabilities by supporting a series of pioneering space-based instruments including the ESA’s ENVISAT SCIAMACHY, Japan’s GOSAT TANSO-FTS and GOSAT-2 TANSO-FTS-2, NASA’s OCO-2, China’s TanSat AGCS, Feng Yun-3D GAS and Gaofen-5 GMI, and the Copernicus Sentinel 5 Precursor TROPOMI. These sensors collect high resolution spectra of reflected sunlight, which are analyzed to estimate the column-averaged dry air mole fractions of CO2 and/or CH4 (hereinafter XCO2 and XCH4, respectively) over the globe. Data from these space-based sensors has fostered the development of end-to-end modelling systems for estimating surface CO2 and CH4 fluxes from atmospheric measurements on scales ranging from urban to global scales. Based on this progress, several additional missions are currently being developed by government space agencies, private companies, and non-governmental organizations. The most ambitious of these include operational CO2/CH4 constellations that are currently being considered by the Copernicus Program and by China.
The Committee on Earth Observation Satellites (CEOS) recognized that XCO2 and XCH4 estimates from a constellation of space-based sensors will be an essential component of an integrated global GHG observing system. To address this goal, they plan to work with stakeholders in the greenhouse gas inventory community to refine the requirements for an atmospheric CO2 and CO2 flux product. They will then coordinate efforts by their member agencies and partners to integrate XCO2 and XCH4 estimates from existing and near-term space-based platforms with data from surface and airborne CO2 and CH4 networks to develop a prototype global atmospheric CO2 and CH4 flux product. By exploiting ongoing efforts in the atmospheric measurement and modeling communities, the objective is to produce and validate this prototype atmospheric flux product by 2021, so that it is available in time to support inventory builders in their development of GHG emission inventories for the 2023 global stocktake. Lessons learned from this effort will be used to refine plans for future, operational constellations of space-based CO2 and CH4 sensors. This presentation summarizes these objectives and describes the rapidly evolving implementation approach and near-term plans.

The Atmospheric Imaging Mission for Northern Regions (AIM-North) is satellite mission concept undergoing Phase 0 study for the Canadian Space Agency (CSA). AIM-North would observe greenhouse gases (GHGs) and air quality (AQ) species using a pair of satellites in a highly elliptical orbit (HEO) formation. Since the proposed AIM-North mission has commonalities with ideas considered by ESA for an Arctic and Nordic mission, it could be useful to explore potential synergies, partnerships or cooperation scenarios.

Low Earth Orbit (LEO) satellite missions for atmospheric composition continue to improve our understanding of the carbon cycle and air quality by providing globally-distributed observations. However, revisit rates from a single LEO satellite range from days to weeks and more frequent revisits are desirable for a better understanding of some geophysical processes or for applications such as anthropogenic emissions monitoring. Geostationary (GEO) satellites can give sub-daily revisits for latitudes up to approximately 50-55°N/S, beyond which viewing angles become too large. An international GEO constellation for air quality is planned for the early 2020’s with the coordination of the Committee on Earth Observation Satellites (CEOS) Atmospheric Composition Virtual Constellation (AC-VC) group. The CEOS AC-VC recently completed a report to space agencies (http://ceos.org/ourwork/virtual-constellations/acc/) recommending a constellation architecture for monitoring CO₂ and CH₄ from space consisting of LEO, GEO and HEO components, since the HEO vantage point enables ‘quasi-geostationary’ observations of higher northern latitudes.

AIM-North would make ultraviolet-visible (UV-vis) and near to shortwave infrared (NIR-SWIR) spectroscopic observations to enable retrieval of CO₂ CH₄, CO, O₃, NO₂, BrO, HCHO, SO₂, aerosols and solar induced fluorescence (SIF) from vegetation with requirements that are consistent with the coming generation of LEO and GEO missions planned by ESA and other international space agencies. Equipping AIM-North with a cloud imager would enable an intelligent pointing approach, where knowledge of cloud coverage would inform pointing to focus observing time only on regions with low enough cloud for successful observing. The resulting AIM-North observations would span land from ~40-80°N with ~3x3 km² pixels and a revisit of 90 minutes or less during daylight where clouds permit, thus delivering data of unprecedented frequency, density and quality for the North. We will present an overview and status update for the AIM-North mission and using CO₂ as an example, demonstrate how such observations could assist in understanding and quantifying aspects of the northern carbon cycle (boreal forest, permafrost and northern anthropogenic CO₂ fluxes) based on simulation studies in support of Phase 0.