Cross comparison of the Gaofen-5 AHSI and VIMI sensors

The Advanced HyperSpectral Imager (AHSI) and the Visual and Infrared Multispectral Imager (VIMI) are the two sensors onboard China's Gaofen-5 remote sensing satellite. These two sensors provide images of different spectral and spatial resolutions. To date, the quantitative relationship between the two sensors' data has not been investigated in detail. To understand the quantitative relationship and the calibration agreement between AHSI and VIMI, date-coincided image pairs of the two sensors from the Dunhuang calibration site as well as the Tengzhou area were used to conduct a cross comparison. The approach was achieved by evaluating the consistency of the at-sensor radiance data between the two sensors. The results were then validated to those of near-simultaneous Landsat-8 OLI sensor. This study finds that the at-sensor radiance data of VIMI is overall lower than that of AHSI, with a mean absolute percentage error (MAPE) of 32% and an R² of 0.817. Among the corresponding bands, the red band has the greatest difference between the two sensors, with a MAPE of more than 40%. The validation to Landsat-8 OLI shows that AHSI's radiance data is close to that of OLI with a MAPE of less than 5%, while the MAPE of VIMI is more than 20%. Given the differences between VIMI and AHSI radiance data revealed in this study, it is suggested to correct VIMI data if both data need to be used together. The conversion using the model developed in this study based on the Dunhuang site shows that the difference between the VIMI and the AHSI radiance data can be greatly reduced after conversion. A synergistic use of AHSI and calibrated VIMI data can greatly benefit the science community by proving a high-quality observation of the Earth.