## 5 Conclusions  
To investigate the impact of spatial resolution, spectral resolution, and SNR on methane plume estimation accuracy. We simulated methane plumes with different emission rates and generated TOA radiance datasets. Sensitivity analysis was conducted on the instrument parameters using the IMAP-DOAS retrieval algorithm and the IME model. To evaluate the effects of varying spatial resolutions, we also simulated radiance within hybrid pixels. Regarding the impact of individual parameters, fine spectral resolution and high SNR are the keys to accurately retrieve single-pixel XCH\({}_{4}\). Meanwhile, the spatial resolution is an important prerequisite for identifying emission point locations as well as small plume emission. In addition, according to the quantification results of the three instrument parameters, the estimated error has a certain relationship with the emission rates. Specifically, for plumes with large emission rates (10,000 kg/h), the estimated error is generally below 50% within the parameter range of most current hyperspectral imagers. In contrast, for plumes with an emission rate of approximately 100 kg/h, the estimated error can reach around 100%. Based on the three-dimensional estimation matrix built from instrument parameters, we found that although spatial resolution degradation decreases XCH\({}_{4}\) in the pixel, larger emission rates (1000 kg/h or 10,000 kg/h) remain distinguishable from the background, and quantifiable even at 120 m resolution. Notably, finer spatial resolution captures plume details and improves small-emission plume (100 kg/h) detection capabilities. Since small emission rates account for the majority of plumes, achieving high spatial resolution observations should be an important priority for future satellite missions. In addition, regardless of the spatial scale, finer spectral resolution (2 nm or 5 nm) is vital for accurately estimating methane plumes, as it enhances single-pixel retrieval precision. Therefore, designing instruments to achieve fine spectral resolution is a key consideration. The dispersive spectrometers or Fabry-Perot interferometers are well-suited to meet current detection needs. Moreover, increasing the SNR from 400 to 800 does not significantly improve the overall quantification accuracy. To verify the feasibility of the established matrix, we interpolated it to span the parameter range of existing satellite instruments. In addition, pseudo-observations convolved with the current satellite response function were generated for comparison. Due to the slight difference in spectral sampling rate, the estimation results are slightly different. Nevertheless, these results sufficiently demonstrate that the constraint relationships between the simulated instrument parameters are representative. In total, enhancing the spectral resolution can markedly improve the quantification performance. Increasing spatial resolution can significantly increase the accuracy of small emission plume estimation, provided that high spectral resolution is maintained. A scientific SNR helps reduce estimation errors, but there is no need to pursue an extremely high SNR. Our future research will consider a wider spectral range and more satellite instruments, as well as various surface types. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/rs17040634/s1](https://www.mdpi.com/article/10.3390/rs17040634/s1)]([https://www.mdpi.com/article/10.3390/rs17040634/s1](https://www.mdpi.com/article/10.3390/rs17040634/s1)). Conceptualization, Y.J., L.Z. ([PERSON]) and X.Z. ; Methodology, Y.J. ; Software, Y.J. ; Validation, Y.J., L.Z. ([PERSON]) and X.C. ; Formal analysis, Y.J., L.Z. ([PERSON]) and X.C. ; Investigation, Y.J., H.D. and L.Z. ([PERSON]); Resources, L.Z. ([PERSON]), Y.W., Y.S. and B.C. ; Data curation, Y.J., H.D. and L.Z. ([PERSON]); Writing--original draft, Y.J. ; Writing--review & editing, L.Z. ([PERSON]), X.Z. and X.C. ; Visualization, Y.J. ; Supervision, L.Z. ([PERSON]), X.Z. and H.Y. ; Project administration, X.Z.