According to a study published in remote sensing recently, a research team led by Prof. XIONG Wei from Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS) conducted a series of research to verify and calibrate the Greenhouse Gases Monitoring Instrument (GMI), a satellite payload that provides data on greenhouse gases.
China's carbon neutrality goals require accurate monitoring and evaluation of carbon emissions.
In this research, a mobile satellite-ground verification system was developed to address the issues including low verification frequency and large space-time differences, with authenticity verification using the Global Carbon Column Observation Network (TCCON).
The system, which is called high-resolution Fourier transform spectrometer (HRFTS), enhanced the precision of greenhouse gas satellite remote sensing. To achieve a spectral resolution of 0.26 cm-1 that is compatible with on-orbit greenhouse gas satellite loads, the HRFTS employed dynamic collimation technology, gas absorption, and band scanning methods to evaluate the absorption spectrum and instrument line shape.
There have been cross-comparison studies using the portable verification equipment EM27/SUN, and the data from the instrument has been processed to address baseline correction, spectral fine registration, and environmental parameter profile reconstruction. The GMI sensor on the GF5-02 satellite was recently tested using the HRFTS, and the results showed the CO2 column concentration retrieval error around 1.5 ppm and the CH4 column concentration retrieval error about 11.3 ppb.
Prior to this research, the team also designed a global digital calibration field network with 11 fields to meet the high-frequency and large dynamic range calibration requirements, for the characteristics of GMI like large field of view, non-imaging, and hyperspectral, and with which the calibration experiments were carried out, and the results showed that the performance of the GMI is stable on orbit with the standard deviation of variation not exceeding 3%.
This innovation in satellite ground synchronization verification enables satellite inversion algorithm optimization and systematic error correction, improving global carbon source and sink monitoring.
In-orbit calibration results of greenhouse gas satellite payload GMI (Image by SHI Hailiang)