Design And Implementation Of Information Processing System Of Spaceborne Lightning Imager

Lightning is an important natural phenomenon that directly causes a lot of casualties and economic losses every year, so the research of lighting is of great significance. The existing ground-based detection technology can hardly give the lightning maps of the earth in a global scope of the lightning maps due to the limitations of its distribution. Nevertheless, the spaceborne lightning detection has the advantages of wide coverage and more lighting information detection ability. Especially the geostationary orbit satellite-based lightning detection is able to observe a large specific area of the earth throughout the day, thus it is considered to be an ideal platform for lightning observation. Currently, there is no geostationary orbit meteorological satellite that equipped with lightning detection equipment launched into space in the world. FY-4, being developed by China, is a geostationary orbit meteorological satellite equipped with special lightning detection equipment Lightning Imager.The Lightning Imager is an optical detection equipment used to detect lightning events on satellite. It mainly includes an optical imaging system, a lightning information processing systems and a management system. This paper, according to the FY-4meteorological satellite general technical requirements, develops the lightning information processing system which is the nucleus of the Lightning Imager. The lightning information processing system has three modes. The first mode is lightning detection mode. It receives image data from focal plane, identifies the lightning events from the image data, encodes the lightning events and outputs the encoding data. The second mode is landmark observation mode. It receives focal plane image data and transfers the whole image to the ground. The third mode is orbit injection mode. It receives the terrestrial transmission program data and updates the lightning detection algorithm. Since the satellite is difficult to maintain after the launch of satellite, this paper puts forward some reliability design idea and method, and analyses the board circuit of the lightning information processing system by way of Failure Mode and Effects Analysis. To be specific, in this paper, the research work is as follows:1) On the basis of in-depth analysis of the functional requirements and technical specifications of the lightning information processing system, the whole scheme of the lightning information processing system is proposed. The paper designs the hardware platform, including the lightning identification circuit, the encoding circuit, the filter circuit and the motherboard. The system employs the picture-in-board structure. The communication among the lightning recognition circuit, the encoding circuit and the filter circuit is through the motherboard.2) Since the lightning information processing system is difficult to maintain after launch of satellite, the system reliability is particularly important. This paper establishes a reliable model for the lightning information processing system and proposes a simplified system model through which the reliability of the design is verified. Failure Mode and Effects Analysis (FMEA) is an important method for reliability designing. According to the system requirement that a single board's fault should not lead to disastrous consequence, by analyzing the board circuit of the lightning information processing system using FMEA, it is convinced that a single board's fault has no calamitous effect.3) The FY-4meteorological satellite is the first satellite that employs SpaceWire bus in China. This paper analyzed the characteristics of the SpaceWire bus and the data rate of the satellite payloads, a communication system based on the AT7911E chip that adopts the Space Wire bus is designed. The bus system has the features of adjustable logical address and node rate. By testing with the other satellite payloads and the tube subsystem network, it is validated that the system meets the requirement of the satellite bus communication.4) Since no geostationary orbit satellite equipped with a Lightning Imager has been launched, It has no access to take any lightning image on the geostationary orbit, thus it is unable to develop a mature lightning detection algorithm. The proposed system adds the orbit injection function to the existing lightning detection algorithm in FPGA program. By utilizing the real lightning images taken by the launched satellite in the landmark observation mode, new lightning detection algorithm could be simulated and designed. Furthermore, the orbit injection function is adopted to update the lightning detection algorithm.Taking into consideration that the amount of data transmitted by the orbit injection function is large and any bit error can lead to the orbit injection failure, this paper proposes a highly reliable orbit injection process. The process consists for instructions:program injection mode, program injection mode begins, program transmission in packets and program injection mode ends. With the four instructions, the switching and the beginning or ending of the injection mode can be effectively controlled. Apart from this, some data checking methods such as ED AC, CRC and so on are utilized to guarantee the safety and reliability of the orbit injection.5) Given the fact that the frame-frame background removal algorithm in the lightning identification circuit requires the cache of seven frames background, this paper puts forward a reading and writing method in a pipelined utilizing seven chips of SRAM. In this way, input image data in one channel is expanded to seven sequentially.6) To test the performance of the proposed lightning information processing system before the satellite launching, this paper builds a test platform. The test platform is made up of a power supply device, a simulated lightning image source, a device that receives and displays the lightning events and a remote control and telemetry equipment. With the test platform, the paper conducts a complete test for the lightning information processing system including the hardware test, the lightning detection mode test, the landmark observation mode test and the program orbit injection mode test. The lightning information processing system is proved to meet all the requirements of the satellite through the test.