# Review of Satellite Remote Sensing of Carbon Dioxide Inversion and Assimilation
## 2 CO2 Observation, Datasets, Global Related Research
### Satellite Remote Sensing Observations  
Nowadays, satellite remote sensing detection technology is one of the most advanced means of obtaining CO\({}_{2}\) data. Sensors onboard satellites are used to acquire the spectral characteristics of atmospheric CO\({}_{2}\), which are then inverted by inversion algorithms to obtain CO\({}_{2}\) concentration data. Satellite remote sensing offers more continuous data compared to other observation instruments, with notable advantages such as continuity, uniformity, and wide coverage. Satellite observation methods for monitoring CO\({}_{2}\) concentrations are mainly divided into two types: one based on Thermal Infrared Radiation (TIR) detection, which is sensitive to CO\({}_{2}\) concentrations in the upper atmosphere and can provide vertical contour distributions of CO\({}_{2}\) using TIR spectra; the other based on Shortwave Infrared (SWIR) detection. The thermal infrared bands, sensitive to the mid to upper troposphere but less to near-surface CO\({}_{2}\) changes, contrast with shortwave infrared bands, which are sensitive to near-surface CO\({}_{2}\). Inversion channels are selected based on CO\({}_{2}\) absorption bands (strong: 15, 4.3, 2.06 \(\upmu\)m; weak: 10, 5, 1.6, 1.4 \(\upmu\)m) and are chosen according to regional and seasonal contexts. The primary inversion method uses the O\({}_{2}\)-A  
Figure 4: Distribution of stations of the Total Carbon Column Observation Network (from [[https://tccon-wiki.caltech.edu/Main/TCCONsites](https://tccon-wiki.caltech.edu/Main/TCCONsites)]([https://tccon-wiki.caltech.edu/Main/TCCONsites](https://tccon-wiki.caltech.edu/Main/TCCONsites)), accessed on 23 August 2023).  
band at 0.76 \(\upmu\)m and CO\({}_{2}\) absorption bands at 1.61 \(\upmu\)m and 2.06 \(\upmu\)m to infer light scattering and related information. For detecting atmospheric CH\({}_{4}\), the method utilizes absorption near 1.65 \(\upmu\)m. Inversion using the 1.65 \(\upmu\)m and 2.06 \(\upmu\)m bands retains over 90% of CH\({}_{4}\), CO\({}_{2}\), and temperature information, and more than 85% of H\({}_{2}\)O information. Since both near-infrared and shortwave infrared are used for CO\({}_{2}\) inversion, the choice of wavelength range and spectral resolution is crucial. This decision depends on factors such as CO\({}_{2}\) absorption features, atmospheric sensitivity, spectral resolution requirements, atmospheric conditions, mission objectives, and sensor capabilities. Strong absorption bands such as 4.3 \(\upmu\)m and 2.06 \(\upmu\)m are typically used to improve measurement accuracy, while high spectral resolution helps differentiate closely spaced absorption features and enhances precision. However, the chosen bands also need to account for atmospheric factors like water vapor and the mission's needs for temporal resolution and geographic focus. These factors collectively determine the final wavelength range and resolution to achieve accurate CO\({}_{2}\) measurements. Currently, operational satellites for detecting atmospheric CO\({}_{2}\) concentrations include GOSAT, SCIAMACHY, OCO-2, and TanSat.  
In this paper, the development of carbon-monitoring technology is divided into three stages in Figure 5 based on the degree of progress of satellite remote sensing technology and the demand for carbon-monitoring applications: the initial stage (1996-2008), the rapid development stage (2009-2018) and the full-scale application stage (2019-present).