Through the combination of active and passive detection, the marine science mission will realize the integrated remote sensing of marine dynamic and ecological parameters, fill the gap of sub-mesoscale perspective observation, and take a key step toward three-dimensional remote sensing of "transparent ocean". The satellite will operate in a sun-synchronous orbit and will be equipped with lidar and a light-weighted multispectral camera. Among them, the camera has 8 multispectral bands with a spatial resolution of 20m and a width of 160km. In this paper, the simulation calculation of the sun glints area is carried out for the two installation methods, which are formal and oblique, and the four typical simulation time nodes are spring equinox, summer solstice, autumn equinox, and winter solstice. The results show that the proportion of single-track sun glints area on the summer solstice is about 37.5% and 34.0%, respectively, which is the highest time point of the year, and the equator, tropic of Capricorn and tropic of cancer regions will produce 100% of the sun glints area at different time points. Compared with the formal form, the total proportion of sun glints area is reduced by about 10% for the oblique form, which will improve the effective data rate in orbit and improve the efficiency of satellite imaging. At the same time, this paper briefly describes the satellite calibration mode according to the combination of active and passive imaging. It will guide the subsequent satellite design and application.
The lunar is a stable radiation source, which can be used as an ideal source for in-orbit calibration of remote sensors and evaluation of detector degradation performance. A passive lunar calibration method is proposed for Chinese ocean color satellite, which reuses field of view of cryogenic-deep-space calibration, periodically achieves monthly lunar calibration tasks. This work enriches ocean color satellite in-orbit calibration methods and improves data accuracy of products. The start and stop angle vector of cryogenic-deep-space, satellite-lunar pointing vector and imaging observation model are established in simulation software. The satellite and payload parameters are used as input conditions to carry out the simulation of the lunar calibration timing. The lunar calibration timing of payload COCTS (Chinese Ocean Color and Temperature Scanner) is simulated 00:00:00~24:00:00UTC on June 28, 2020. The result shows that lunar calibration was carried out for twice. The starting UTC (Universal Time Coordinated) time was 15:16:44 and 16:56:37, respectively. The duration was two seconds. Through analyzing the 0-level products of in-orbit satellite received by the application system, the cryogenic-deep-space data showed abnormal changes at 15:16:45 and 16:56:38 on June 28, 2020, and the DN (Digital Number) values dropped from 300 to 62 and 73, respectively. The in-orbit calibration timing is basically the same as the simulation results, and the numerical anomalies of cryogenic-deep-space data are consistent with the principle design, indicating that the simulation model can be used to predict the in-orbit lunar calibration timing of ocean color satellite. The analysis method can be used for cryogenic-deep-space imaging mission mode and payload design of the follow-up ocean color satellites.
Coastal Zone Imager(CZI) was designed for coastal water body and islands. To analyze the potential application of Chinese
ocean color satellite in coastal zone area and evaluate the image quality, we used subjective and objective evaluation
method and took a comparison between Chinese ocean color satellite and Gaofen series satellite. Subjective evaluation
showed that Chinese ocean color satellite images had a better performance than Gaofen series satellite images in water
bodies. Based on statistical information ,objective evaluation showed that each band gray distribution of Chinese ocean
color satellite images was more dispersed and had a higher separability feature. Applying evaluation showed that Chinese
ocean color satellite also performed better in terms of texture property and classification accuracy. Overall Chinese ocean
color satellite had a high image quality and potential applications in coastal areas.
Sun light reflected from sea surface forms a high intensity solar ray. Sun-glint is created by Fresnel reflection which contaminates ocean color products. It covers up the real physical characteristics of water bodies and interferes with the inversion of ocean remote sensing data precision. In this paper, sun glint regional characteristics are simulated and analyzed in consideration of the different satellite attitude angles and time phases based on Cox–Munk model. The numerical simulation shows that through the satellites adjust attitude dynamically, the contamination area decreases by 11.8%.Onorbit test data are used to evaluate the method precision and it will contributes to the estimation of sun glint regional characteristics and strategy of on-orbit use.
The multi-angle polarization technique, which uses the intensity of polarized radiation as the observed quantity, is a new remote sensing means for earth observation. With this method, not only can the multi-angle light intensity data be provided, but also the multi-angle information of polarized radiation can be obtained. So, the technique may solve the problems, those could not be solved with the traditional remote sensing methods. Nowadays, the multi-angle polarization technique has become one of the hot topics in the field of the international quantitative research on remote sensing. In this paper, we firstly introduce the principles of the multi-angle polarization technique, then the situations of basic research and engineering applications are particularly summarized and analysed in 1) the peeled-off method of sun glitter based on polarization, 2) the ocean color remote sensing based on polarization, 3) oil spill detection using polarization technique, 4) the ocean aerosol monitoring based on polarization. Finally, based on the previous work, we briefly present the problems and prospects of the multi-angle polarization technique used in China’s ocean color remote sensing.
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