A Proposal of Integrated
Construction of Multi-Satellite Earth Observation System to Meet
Requirements of Fast Response to Flood And Waterlogging Monitoring
Pan Xizhe Li Chanrong Kou
Lianquan Tang Lingli Abstract:( Remote sensing satellite ground station, Chinese Academy of Scineces) In some particular time periods, fast response to flood and waterlogging monitoring is an issue of the first priority for satellite remote sensing or Earth observation satellite remote sensing. From the point of view of technology, at the same time when developing and utilizing multi-satellite data to resolve the problem of too long intervals of revisit and low resolution in order to make improvements in these affaires, it is key issue to lay emphasis on the integrated construction of system of data receiving and processing, so that intermediate procedures can be minimized, non -compatibility between different data and processing system, caused by various factors can be avoided. Thus, the time effect ( delay of time ) to the delivery of final merged/fused image products can be improved, making the image products be readable and usable for end-users with the particular requirements of fast response, which is very important and key issue, to which attention should be paid continuously. Take the flood and waterlogging monitoring by satellite remote sensing in 1988 as an example, the effectiveness of satellite Earth observation technology was proved in respect of fast response of flood and waterlogging monitoring, i.e. goals of timely understanding of overall flood and waterlogging situation, accurate analysis after floods, dynamic monitoring construction of water conservancy facilities; forest drainage areas, preservation of water and soil were achieved. It is pointed in this paper that in order to achieve the above mentioned goals actually, under the realistic conditions of our country, the construction of multi-satellite Earth observation data receiving and processing systems must be intensified. In this paper, it is taken as an example how China RSGS, the only one civilian satellite remote sensing station, functioned during the flood and waterlogging in 1998. analysis was made, taking in to account the key technique an system requirements of multi-satellite observation, data receiving, processing and correction, data fusing, and production of final image products. An idea of further integrated system construction to meet the requirements of flood and waterlogging mitigation and prevention is presented. 1. Foreword Along with the very fast development of system of Earth observation technology, continuous improvement of satellite Earth observation operational systems , improvement of performance of sensors an there are more kinds of sensors, satellite Earth observation technology is playing more and more important role in areas of environment, resources, etc., and more concerns are shown by all sides of the society. Take the fast response to flood and waterlogging monitoring as example, satellite Earth observation technology can play role in respect of
When we start ot consider practical situation and take the fast response of flood and waterlogging monitoring to be implemented by a business operational system, we must analyze the problem in more details; is the problem of fast response to flood and waterlogging monitoring resoled, if we have got SAR satellites operational ? Besides factors, such as band selection, polarization, a and interference, which we are not going to discuss in this paper the key point is the length if interval of revisit time. Of course, from here, a great many of suggestions can be proposed, for example, if a constellation of 4 SAR satellites =, transmitting images of 100km width is operational, due to the feature of data acquisition of all weather and for all time of day a given place can be revisited one to two times per day. If we consider the problem in more depth, it will be required , for whatever plan adopted, that the satellites and their sensors must be reliable. Their abnormality cannot appear quite often due to problem of technology, planning, and administration. It is so called commercialized operation . as pointed in [4], commercialized operation reflects a responsible commitment in respect of product delivery , quality control, turnaround time of products, technical services, etc. If we consider the problem more comprehensively , we also need ground receiving and processing system, the capability of which can match that of the satellite observation . of courser, the system should not be abnormal due to any problem of any technical component, planning, and management. 2. Operational system and operation of system. " Operational system and operation of system " includes tow aspects of a business engineering operational system : stability and reliability , and effectiveness . a system of high " Operationalizaiton " is a basis of reliable operation while high level of operation techniques is a guarantee of reliable operation. The combination of high system " Operationalization " and high level of operation techniques is the necessary condition of technical support to meet the requirements of fast response to flood and waterlogging monitoring etc. The operational characteristics of a system are first of all reflected on the capability of uninterrupted, stable, and reliable operations with a meaning of being industrialized. From the stand point of view of technology, included are factors of various components of the system, such s the value of mean time between failure over a long period of time, reasonable configuration, design with redundancy, capability to fix problems, etc. second, for an operational system, quality control must be there to ensure quality of its products. What more important is, an operational system must also ensure that, in the entire work procedures, all of the links in the process must match and coordinate with each other orderly, so as to increaser the work efficiency of the entire system . Take the work of China RSDS for flood and waterlogging monitoring in 1998 as a n example for the first step, our station achieved to cover a given are with a revisit period of 3-4 days, and we spent 4 hours (including 1.5 hours to transport the tapes ) totally to have digital products produced ( the data volume of one Scan SAR to be processed is 1 G Bytes ), beginning from the start of receiving image data. it took 6 hours to completer a digital product of an image merged with a TM and a SAR image, or merged with images of different times. it took 10 hours ot produce a large frame photographic composite product. Thereby, near real time services was implemented for different levels of products. It was implemented for different levels of products. It was achieved not only because there was an existing commercialized operational RADARSET, but also because there was an entire set of ground operational system, beginning from data planning to data distribution . Earth observation is a kind of information industry by its nature. Its basic feature is : providing valuable information products to various departments of industries for daily use . where main factors, for the technical system to be qualified as an industry, are: " being operationalized ", of daily use, and the products are valuable " Operationalizaiton " is the basis, support, and it is of the nature of input, while the characteristics of daily use and the value produced by the system, are output, contribution, and reward . flood and waterlogging monitoring is one of the application of Earths observation. In particular time periods, it is required to use daily information, reflecting flood and waterlogging, that is to use valuable satellite images, while operational radar satellite technical system constitutes service system. This is also the fundamental reason, why the flood and waterlogging monitoring in 1998 was successful . 3. Development of Earth observation of data receiving and processing system in China which can be understood from flood and waterlogging monitoring since 90's A great number of flood and waterlogging monitoring since 90's, being part of applications of satellite Earth observation, were a good reference of operations capability of ground data receiving and processing system due to the critical requirements of high resolution and fast response (see table ). The task of flood and waterlogging monitoring I 1991 just relied on L5 TM as data source, which was mainly used for evaluation of disasters after events. Under restrictions of satellite orbits and weather conditions, the success at that time was a result of fortuitous coincidence. After 1993, our station has capability to receive and process data from satellites ERS-1/2 SAR and JERS-1 SAR. However, due to a variety or restrictions caused by design, operation agreement of cooperation with operation of the satellites, ground system capability, technical conditions, and financial support, there had been actual operational system. Therefore, for flood and waterlogging monitoring in 1994 and 1996 , the potentials of all weather SAR images were not fully explored.
The flood and waterlogging monitored in 1998 was a good example of successful dynamic monitoring a given area according to a plan in a period of less that 4 days for the first time. It is also a practical example of operational design and implementation of a plan from satellite to ground system. In respect of design of system configuration besides state-of-art technology was used. Radarsat ground system has tow subsystems of operation & management and network service inquiry in addition to traditional mode of receiving, pre-processing, post-processing, and photo-processing. Thus, receiving & processing, requirements of users, work management, and plan requests were brought into good combination with satellite work parameters, such that computerized automatic management in the entire process was implemented. Therefore, the problem of interfaces between various subsystems, and the problem of compatibility and connection between external interfaces of users and satellite management organization was resolved. In this way , there had been orderly operation of the system as a whole, and basic requirements of an operational system had been met. 4. it is to the National Government to plan as a whole and to perfect multi-satellite Earth observation data receiving an processing system. The purpose of authors of this paper to propose the integrated construction of multi-satellite Earth observation data receiving and processing system is to improve the operational capability and level of the gerund system in the whole Earth observation are. If there is not a ground receiving and processing system highly operationalized, requirements of various applications, such as flood and waterlogging monitoring. Etc. cannot be met,. Or cannot be met in a better way. The integrated construction of multi-satellite Earth observation data receiving and processing system covers tow kinds of substance: technology and management. 4.1 Goals of technical development of integrated construction. As a national ground system, its footprints should include all of this land and water territories at the least. Regarding kinds and quantities of satellite data eh station shall be able to receive and process also, generally speaking, all weather and all time data. the station should be able to revisit a given place 1Ê2 times in 24 hours' time . it should be able to receive and process data from satellite sensor with high; geometric and radiometric resolutions. Delivery of products, and the level, mode, and quality of user services should be up to international standards. Moreover, electronic delivery of products, urgent services, value added products, and information products, aiming to serve end users, should be provided. According to the above mentioned requirements, the goals of technical development are as follows.
The requirements of multi-satellite data receiving and processing, and requirements of being commercialized and operational, place in turn very critical requirements to communication of instructions for tasks between ground station systems and system of satellite mission management . in addition, reliable and powerful network of perfect services is required by data transfer among the subsystems, by the interactive communications between users and the ground station, by the fast delivery of data or information prods , and by the near real time services. The operation and management system is the commando of the entire receiving and processing; it is the interface between satellite mission planning and contacting user requests; it is responsible to coordinate plans of data transmission, data requirements , data allocation and coordination with organization of countries operating the satellites; it is responsible to plan and dispatch tasks of data receiving all network stations; it is responsible to do quality analysis of satellite data parameter extraction and quality test, and the definition and coordination of interfaces of tasks of all sub systems. Under the situation of multi-satellite data receiving an processing and commercialized satellite operation , the role of operation an management system will be more important and prominent within the entire ground receiving and processing operational system. Comparing with traditional ground system consisting of sequential receiving,. Archiving pre-processing , photo-processing and distribution, the configuration of new ground system, along with development of all related technologies and their infiltration to each other will develop in the direction of integrated technology. The computerized operation, computerized management system, and the network being operational, is the inexorable trend of development of integrated technology and commercialized satellite operation. 4.3 Mode of management of integrated construction As an important component of satellite Earth observation system, the integrated construction of ground receiving and processing system also has the issues of management mode of how to plan a whole, of integrated management, of coordination between different departments, of co-construction with users' participation, and of information sharing. According to the suggestion to perfect our country's Earth observation system and to develop information system and to develop information industry, according to the approach of Government support and co-construction with users, and according to the principle of who invests, who benefits, the management of China's Earth observation ground system can be divided into six layers: decision of leadership, user management, center for data operation and management, receiving networks, and users services. |