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 existing space-based remote sensing has problems such as weak collaboration, slow response, and long links, which cannot meet the application requirements of real-time anomaly detection, recognition, and transmission. This article studies the characteristics of existing surface anomaly classification, establishes a demand matrix for anomaly remote sensing, establishes a new surface anomaly real-time detection system, and proposes a working mode for anomaly real-time recognition, using the constellation system task and information flow design combined with the on-board intelligent processing unit, improve the anomaly recognition and service capability of the space-based system, design the mission flow and information flow of the constellation system, and finally analyze the communication link and timeliness of the system. The simulation analysis results show that the system can achieve minute level efficient anomaly recognition and early warning, effectively improving the service capability to users, this provides an overall idea and architectural reference for the construction of future space-based surface anomaly real-time detection systems.
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.
In recent years, the emerging global navigation satellite system reflectometry (GNSS-R) technology has become a research hotspot for its lightweight, high sensitivity and rich technology application scenarios. It has broad application prospects in the field of remote sensing detection and navigation technology. The role of GNSS-R remote sensing satellite in the field of marine remote sensing is becoming increasingly prominent. The acquisition of data and information and the observation performance of GNSS-R remote sensing satellite are not only constrained by the remote sensing equipment itself, but also affected by the satellite orbit. Based on the technical characteristics of GNSS-R remote sensing satellite, this paper proposes a grid based coverage efficiency statistical method, analyzes some influencing factors of GNSS-R remote sensing satellite efficiency based on the remote sensing task, and analyzes the influence of each factor on GNSS-R remote sensing satellite efficiency by modeling -It can provide theoretical reference for GNSS-R satellite orbit selection and optimization, onboard load design optimization and large-scale system construction.
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 precisely extraction of construction areas in remote sensing images can play an important role in territorial planning, land use management, urban environments and disaster reduction. In this article, we propose a method for extracting construction areas using Gaofen-1 panchromatic remote sensing images by adopting the improved Pantex[1] (a procedure for the calculation of texture-derived built-up presence index) and unsupervised classification. First of all, texture cooccurrence measures of 10 different directions and displacements are calculated. In this step, we improve the built-up presence index that we use the windows size of 21*21 to calculate the GLCM contrast measure instead of 9*9 according to the spatial resolution of Gaofen-1 panchromatic image. Then we use the intersection operator “MIN” to combine the 10 different anisotropic GLCM contrast measure to generate the final built-up presence index result. At last, we use the unsupervised classification method to classify the Pantex result into two classes and the one with larger cluster center is the construction area class. Confusion matrix of Beijing-Tianjin-Hebei region experiment shows that this method can effectively and accurately extract the construction areas in Gaofen-1 panchromatic images with the overall accuracy of more than 92%.
Satellite telemetry is the vital indicators to estimate the performance of the satellite. The telemetry data, the threshold
range and the variation tendency collected during the whole operational life of the satellite, can guide and evaluate the
subsequent design of the satellite in the future. The rotational parts on the satellite (e.g. solar arrays, antennas and
oscillating mirrors) affect collecting the solar energy and the other functions of the satellite. Visualization telemetries
(pictures, video) are captured to interpret the status of the satellite qualitatively in real time as an important supplement
for troubleshooting. The mature technology of commercial off-the-shelf (COTS) products have obvious advantages in
terms of the design of construction, electronics, interfaces and image processing. Also considering the weight, power
consumption, and cost, it can be directly used in our application or can be adopted for secondary development. In this
paper, characteristic simulations of solar arrays radiation in orbit are presented, and a suitable camera module of certain
commercial smartphone is adopted after the precise calculation and the product selection process. Considering the
advantages of the COTS devices, which can solve both the fundamental and complicated satellite problems, this
technique proposed is innovative to the project implementation in the future.
Based on the maximum detection range, the detection capability of space-based camera for space debris is analyzed in the paper. We perform grid generation method on the debris target and analyze the shadowing effects among the grids, building the geometry modeling of cone target sequentially. The calculation model of optical infrared characteristics is established, taking into consideration the target self-radiation and radiation reflection characteristics of the material on surface. The radiation energy of the target is only depended on the reflection of earth’s radiation and its self-radiation in the simulation proposed in the paper. Based on the maximum detection range formula, the numerical simulation presented shows that when the space-based target radiation intensity is 21.54W/sr and optical system aperture is 0.5m, the maximum detection range is 17279km. The simulation results theoretically contribute to the estimation of camera parameters and analysis on the detection capability.
The freeform optics is extensively applied in the fields of aerospace, aviation, lighting, medical treatment, et al.. For the linearly push-broom space-borne imager, integration time of different field of view can be affected by the optical system design of the imager, orbits of the satellite, maneuver of the attitudes, rotation of the Earth, light delay due to the refraction and transmission of the atmosphere, terrain error and so on. The dynamically imaging quality should be affected by the accuracy and adjusting mode of the integration time. In this paper, a new method which is especially appropriate to imaging model simulating and integration time calculating for the wide-field-of-view remote sensor is proposed. Then, the integration time of specified viewing direction for the imager with a single projection center and a super-wide field of view based on freeform mirror, which is mounted on a sun-synchronous orbit satellite, is calculated. And influence on imaging quality of adjusting integration time of different grouping modes for the focal plane assembly is analyzed. The results indicate that with the constraint condition of satellite roll angle and the modulation transfer function (MTF) influence factor no more than 20°and 2% respectively, integration time of all CCDs for the whole focal plane assembly divided into two groups with each adopting the uniform integration time, can fulfill the requirements of the imaging quality for the imager.
KEYWORDS: LIDAR, Space telescopes, Telescopes, Signal to noise ratio, Atmospheric modeling, Atmospheric optics, Solid state lasers, Laser systems engineering, Pulsed laser operation, Atmospheric sensing
Many studies have indicated that the optimum measurement approach for winds from space is a pulsed coherent wind lidar, which is an active remote sensing tool with the characteristics that high spatial and temporal resolutions, real-time detection, high mobility, facilitated control and so on. Because of the significant eye safety, efficiency, size, and lifetime advantage, 2μm wavelength solid-state laser lidar systems have attracted much attention in spacebased wind lidar plans. In this paper, the theory of coherent detection is presented and a 2μm wavelength solid-state laser lidar system is introduced, then the ideal aperture is calculated from signal-to-noise(SNR) view at orbit 400km. However, considering real application, even if the lidar hardware is perfectly aligned, the directional jitter of laser beam, the attitude change of the lidar in the long round trip time of the light from the atmosphere and other factors can bring misalignment angle. So the influence of misalignment angle is considered and calculated, and the optimum telescope diameter(0.45m) is obtained as the misalignment angle is 4 μrad. By the analysis of the optimum aperture required for spacebased coherent wind lidar system, we try to present the design guidance for the telescope.
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