Research And Application Of Storage Manangement Technology For Spaceborne Solid State Reocorder

Chinese space missions have experienced an outstanding progress with its growing mission numbers, expanding exploration region and increasing task diversity, ranges from the near-Earth satellite missions to deep space exploration, from manned space flight project to the global positioning system, and from Lunar rover to the space station. Large amount of various priceless data has been obtained from or by the spacecrafts. The data recorder is one of the core equipment in data transmission and management system. The recorder works as a buffer before the data being send to earth from the spacecrafts, and its performance, reliability and applicable condition have decisive influences on the data acquisition ability of space missions. The Solid State Recorder(SSR) based on semi-conductor has many advantages such as high shock resistance, large capacity and abundant reserved technologies. Therefore it has become the mainstream of spacecraft storage device. Especially the NAND Flash based SSR is used more and more widely because of its non-volatile features, high storage density and low power consumption.On the basis of laboratory technology accumulation, the research and application of the Flash based SSR technology focus in the respects of performance, architecture, data management method and data reliability. All the works come from the development or pre-research project of specific space missions. The main research contents include the following aspects.Generally the SSR improvement depends on the progress of core logic device, storage medium, bus and interface and data management technology. With the development work of a certain scientific experiment satellite, the SSR design has taken 4-pipeline writing and bus expansion techniques to guarantee the basic performance in need. The storage control system is consist of a FPGA, a Loogson CPU, a storage address management software and a 1553 B bus remote terminal, controlling the MRAM, SDRAM and Flash array on board to accomplish the data storage task. The adopted data management method with fixed partition is quite mature. A new hardware architecture is designed and certificated, providing a platform for the SSR research.Data management is difficult in SSR upon the request of high performance and reliability, and also the unique features of Flash lead to some problems like long-time-cost initiation and so on. Thus the data management level is low and a lot of inconveniences are brought to practical use. With the development work of a certain satellite, the SSR design focuses on the research of the file-like dynamic management method with collaborative design with software and hardware following the linked list structure file system. Meanwhile, a SSR quick start scheme is proposed in the use of MRAM with its non-volatilization and simplicity in operation.Space missions has an extreme demand in data reliability. The comprehensive EDAC technologies should be used to guarantee the reliability in data storage, processing and transmission. A fault tolerant mechanism to cover different demands in various situations from the aspects of protecting the management information, the data bit stream and the data channel between spacecraft and ground is proposed and analyzed. Hamming Code is used against the bit errors in Flash cluster information brought by Single Event Upsets(SEUs). R-S Code is used against the errors in the data in store brought by SEUs, Flash retention effect and electronic interfere. Low Density Parity-Check Code(LDPC) is used to achieve a high channel gain in space. With the development of data management file system, the Auto Repeat Request(ARQ) strategy application with secure mode of CCSDS File Delivery Protocol(CFDP) is feasible.Space missions are highly specific, thus the SSR standardization and modularization are very important as the SSR has become one standard allocation for spacecrafts gradually. The pre-research project of the integrating electronic system aims at providing one standard, configurable and extensible satellite electronic platform. The research of the SSR within the system includes dividing the internal modules rationally, streamlining the external interfaces of data and command, developing the unified data management with multiple SSRs and improving the scalability. Furthermore, advanced storage structure upon the modularization research has been explored to meet the growing demand of space missions in future.This paper has summarized the important factors and the development trend of SSR through its background and history. In order to continuously meet the needs of space missions, high speed hardware architecture and data management methods are studied and prompted, which are useful for upgrading data transmission system.