Environment-2 (HJ-2) A/B satellites will be launched in 2020, which are expected to work as the successors of Environment-1 (HJ-1) satellites in Chinese Environment and Disaster Monitoring and Prediction Satellite Constellation. A new space-borne instrument called Polarized Scanning Atmospheric Corrector (PSAC) also will be onboard HJ-2 satellites, aiming to provide the atmospheric properties for synchronous atmospheric correction of the main sensors, such as the charge-coupled device cameras onboard the same satellite. PSAC is a cross-track scanning polarimeter with polarized channels from near-ultraviolet to shortwave infrared, centered in 410, 443, 555, 670, 865, 910, 1380, 1610 and 2250 nm. In order to test the performance of inversion algorithms and software modules, synthetic data simulated by the vector radiative transfer is indispensable. In this paper, the regional simulation of PSAC multispectral measurements are preliminarily studied, and the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) has been used as the forward model. For the observation geometries, the viewing zenith angles are calculated by the linear interpolation over the cross-track scanning angle range from west to east, while the viewing azimuth angle are simulated by following the azimuth angle distribution of other corresponding satellite. By taking the vegetated surface type as an example, the multispectral Lambertian surface reflectance and wavelength-independent BPDF model are used in the forward simulation, and different aerosol optical depth with fine-dominated and coarse-dominated aerosols are considered. In this way, the multispectral measurements can be obtained by the forward simulations over a regional grid with the predefined latitude and longitude, and further analysis are carried out based on the synthetic data. Thus, this study can provide key support to the testbed of inversion algorithms and software modules before and after the satellite launch.
Environment-2 (HJ-2) satellites will be launched after 2019, which are designed as the successor of Environment-1 (HJ- 1) satellites in Chinese Environment and Disaster Monitoring and Prediction Satellite Constellation. Different from HJ-1 satellites, a new multispectral single-viewing polarimetric instrument called Polarized Scanning Atmospheric Corrector (PSAC) will be onboard on HJ-2 satellites, and further provide the aerosol properties for synchronous atmospheric correction of the main sensors, such as the multispectral charge-coupled device (CCD) cameras onboard the same satellite. In this way, the multispectral surface reflectance could be further obtained from the remote sensing measurements of CCD cameras by the atmospheric correction with the retrieved aerosol properties from PSAC. In this paper, based on the optimal estimation (OE) theory and information content analysis method, we have a preliminary study on the propagation errors from the retrieved aerosol properties to multispectral surface reflectance in the process of synchronous atmospheric correction. The priori information and errors for the analysis are assumed based on the measurement noise of CCD cameras and a priori error of retrieved aerosol optical depth (AOD), as well as typical multispectral reflectance from USGS and ASTER spectral library. For the simulation of synthetic measurements of CCD cameras, Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) has been used as the forward model. By this means, the posterior errors of multispectral surface reflectance are calculated, and the errors propagations can be evaluated theoretically, which can further provide key support for the study of synchronous atmospheric correction in HJ-2 satellites.
In the design of the interferometric spectrometer, if the spectral range of filters in the instrument is not significantly greater than the output spectral range of the spectrometer, there exists a problem of mismatch between the spectral range of the filter and the spectrometer, resulting in a significant weakening of the edge spectral response and affecting the spectral accuracy of the edge spectrum. This paper makes a theoretical analysis of the weakening of the edge spectral response, and proposes a method to reduce this phenomenon. The core idea of this method is to simulate the interference data of the edge spectrum through the spectrum and phase data, overlapped with the interference information of the spectrometer to obtain the interference data, which is compensated by the edge spectrum. The data of HJ-1A satellite hyperspectral imager are processed and analyzed by this method. As a result, the image quality of the edge bands improved. In the end, the interference simulation data of the spectrometer are generated and they are analyzed and processed by this method. The results prove that the method can make the edge spectral quality significantly improved.