## 1 Introduction
The time-sharing measurement method of a rotating polarizer runner faces the bottleneck of time resolution. Because it scans different polarization states with the rotating polarizer, it takes a long time to complete a scanning cycle and cannot be completed instantaneously. Taking the observation of a cloud by DPC as an example, when considering the factors such as cloud movement, Earth rotation and satellite operation, the imaging range change caused by cloud movement (speed 20 m/s) accounts for 14% of a single pixel in the single measurement time of the rotating manipulator structure. Moreover, after the manipulator rotates for one week, the cloud layer is likely to have exceeded the imaging range of the detector. In the face of the rapid dynamic changes of the Earth target, this measurement method can easily miss the key polarization information, resulting in a lack of information in the time dimension. It is difficult to meet the needs of high frequency monitoring of the polarization characteristics of the Earth target, and there are obvious limitations in capturing the rapidly changing polarization characteristics. In addition, airborne and ground-based polarization imagers have obvious shortcomings. The observation range of the two is limited, and they are greatly interfered with by the ground environment and atmospheric boundary layer. There is a certain gap between the observation breadth, accuracy and environmental adaptability and the satellite-borne polarization imager. Based on the demand for Earth observations and the shortcomings of the existing load, we designed new observation equipment, the Multispectral Earth Polarization Imager(MEPI), which performs multi-spectral and polarization information synchronous with observations of the whole Earth from the Earth-Moon L1 point. We used the advantages of the sub-aperture structure to image multiple polarization states on a single detector at the same time, and adopted a new method of coating the surface of the detector to replace the moving component of the traditional filter to split the light, eliminating vibrations, stray signals, beam drift and other problems. The MEPI has the nature of a snapshot. In addition to its compact structure, the MEPI can also dynamically capture rapidly changing information such as clouds, aerosol and water, effectively improve the real-time performance of satellite remote sensing detection, and provide high-precision and multi-dimensional data support for in-depth study of the characteristics and changes of clouds and aerosols, surface vegetation and soil, so as to help achieve important scientific goals such as a more comprehensive and accurate understanding of the operating mechanism of the Earth's ecosystem and climate change laws. By accurately obtaining the polarization signal of the whole Earth, it can provide a solid theoretical and data basis for further exploring the key aspects of the atmospheric composition structure and surface physical characteristics of extrasolar terrestrial planets. In this paper, a new instrument concept combining mosaic coating and simultaneous polarization measurement is proposed, which breaks through the limitations of the asynchronous imaging of polarization information and spectral information in the past. Nine types of spectral information covering three polarization states are simultaneously imaged on a detector so as to realize the simultaneous acquisition of the five-dimensional information of polarization, spectrum and imaging. Figure 1 shows a schematic diagram of the overall system structure. The polarization instrument with a split-aperture structure [11] not only shows the characteristics of being light, small and compact at the structural level, but also significantly improves the real-time performance of satellite remote sensing detection in the functional dimension, which effectively solves the problems of time-sharing imaging of traditional rotating manipulators and imaging calibration and synchronization caused by multiple detectors.