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.
Table
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.

• complete the construction of the network of three receiving stations to enable the civilian satellite remote sensing data acquisition will cover all our land and water territories, and some neighboring regions as well.
• Expand the existing ground data receiving and processing system, so that it can up to maintain to receive and process optical data from no less that 8 satellites, and SAR data from 4 satellites, so that the frequency index of dynamic observation can up to revisit a given place 1-2 times per day.
• Improve the capability to produce in depth products, and offer more kinds of value-added services.
• Speed up network construction, improve service level of ground station network system, and improve the capability of fast response.

4.2 New technical construction is to improve system operation- data transfer network system, and operation and management system.
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.