With the advancement of science and technology, humanity's pace of space exploration is accelerating. The demands of space missions are driving the upgrading and development of ground-based tracking and control systems, primarily reflected in: shorter construction cycles for tracking and control stations; more frequent updates, modifications, and additions to tracking and control equipment; and continuously expanding control capacity and links at tracking and control stations. A robust and efficient monitoring system for ground-based tracking and control systems can improve the working efficiency of tracking and control stations, increase the utilization rate of operational system equipment, shorten preparation time for tracking and control operations, and accurately and efficiently complete various tasks related to satellite operational tracking and control. This is of great significance for improving satellite control accuracy and extending satellite lifespan. The main tasks of the tracking and control station monitoring system within the tracking and control system are: ● Monitoring of ground-based tracking and control equipment ● Control and setting of ground-based tracking and control equipment ● Joint control between ground-based tracking and control equipment. Joint monitoring between tracking and control equipment is particularly useful for equipment debugging, system integration, and calibration. While tracking and control equipment only exchanges tracking and control data, it lacks a means of coordinating and cooperating on operating parameters and processes. The monitoring system, however, can control and monitor all equipment outside of operational operations. During these critical phases, the monitoring system plays a leading role, initiating and organizing various operational tasks, as well as monitoring and controlling the task progress. Existing centralized monitoring systems often employ a data acquisition card architecture, making system expansion difficult. A single card cannot accommodate a wide variety of device interfaces and suffers from data acquisition bottlenecks. In terms of software architecture, they typically focus on the current composition of the ground system, resulting in relatively fixed monitoring screens and operations. Once other models of equipment are replaced or device interfaces change, the source code needs to be modified to adapt, making maintenance inconvenient and affecting system stability and reliability. Therefore, we researched and developed a new monitoring system based on a reconfigurable architecture design. Centralized Monitoring System Existing monitoring systems are usually built together with ground equipment, generally adopting a centralized architecture. This consists of an industrial control computer and multiple data acquisition interface cards, working in conjunction with dedicated monitoring programs to form the monitoring system (see Figure 1). Figure 1. Composition Structure of a Centralized Monitoring System. In a centralized monitoring system, monitoring information from all measurement and control equipment is collected by one or more multi-channel data acquisition cards and sent to a processing computer. The data processing computer then processes the data according to the type of equipment and sends the results to the monitoring program for display or submits them to the user for processing. The centralized monitoring system has the following problems: ● All data acquisition and processing are handled by the data processing computer, placing high demands on the computer's processing power, especially its data acquisition capabilities. If the data processing volume is large or the real-time requirements are high, it can cause the computer to overload and crash, which is the biggest problem with existing centralized monitoring systems. ● Since centralized monitoring systems are mostly dedicated systems, data acquisition and software processing are combined. Once the system is built, the capacity and mode of the control equipment are basically determined, resulting in a closed architecture that is not easily expandable. ● The data acquisition interfaces are complex and concentrated, easily causing mutual interference. ● The wiring is complex and has a high failure rate. In a centralized monitoring system, the data acquisition interfaces are concentrated in one computer. The data interfaces of all measurement and control equipment distributed in different locations at the measurement and control station are connected to the data acquisition interface card. Various signals, such as digital and analog signals, are laid together, resulting in complex wiring. Design Philosophy of a Reconfigurable Monitoring System To adapt to new changes and complete design and debugging in the shortest possible time, the monitoring system supports the modification and addition of equipment within a certain range by adjusting the system's hardware configuration and software parameter settings, while overcoming the shortcomings of the existing system. The new system adopts a reconfigurable architecture design, employing distributed intelligent data interface units to convert the different physical data interfaces of all measurement and control equipment into a unified network interface. Data is then transmitted to the data processing computer via the network. Simultaneously, the monitoring system's control software adopts industrial control configuration design principles, abstracting the measurement and control equipment into different categories of control controls. These controls are then arranged and combined to form different channel control links, thus achieving the reconfigurable design of the entire system. The architecture of the reconfigurable monitoring system is shown in Figure 2. Figure 2: Composition Structure of a Reconfigurable Monitoring System. Specifically, the system adopts a distributed hardware topology and configurable controls. The distributed hardware topology uses several intelligent data interface units (DIUs) capable of exchanging information with multiple different data interface devices. The intelligent data interface unit can connect to measurement and control equipment with serial ports (including RS-232A, RS-422, RS-485), digital interfaces, and relay interfaces. It sends the acquired data to the data processing computer via a network interface and simultaneously sends control commands from the monitoring system to the measurement and control equipment. The software design incorporates the concept of configurable controls, abstracting different measurement and control equipment into different categories of device controls. A configuration database is established through interface configuration software, and the communication links and protocols of the measurement and control station hardware are configured. Graphical software is used to create system display graphs and parameter tables. Support for newly added measurement and control equipment is achieved by modifying the system and display configurations. In the reconfigurable monitoring system, various measurement and control devices, such as high-power amplifiers (HPA), frequency converters (CU), and linear amplifiers (LNA), connect to the intelligent data interface unit nearby or directly to the data processing computer via the network. Each intelligent data interface unit can manage 8 channels of measurement and control equipment with serial interfaces, 8 channels of measurement and control equipment with digital interfaces, and 4 channels of switching equipment with relay interfaces. Implementation of a Reconfigurable Monitoring System In a reconfigurable monitoring system, the key to achieving hardware reconfigurability is designing a Data Interface Unit (DIU) with intelligent management and control functions. This DIU can adapt to measurement and control equipment with different physical interfaces, manage and control the equipment locally, and convert all information from the measurement and control equipment into network interfaces for forwarding to the data processing computer. 1. Data Interface Unit (DIU) To ensure stable, reliable, and flexible system operation to adapt to different application needs, the mainstream industrial control product PC104 module is used for secondary development. ① Functions of the Data Interface Unit: ● Provides 8 full-duplex serial ports. The physical interfaces can be configured as RS-232C/RS-485/RS-422A according to actual system needs, flexibly adapting to the information interfaces of the controlled equipment. ● Provides 8 opto-isolated digital inputs and 8 relay output interfaces. ● Provides 1 10/100M adaptive Ethernet data interface (RJ-45). ● Automatically forwards information from the controlled equipment to the MCS operating computer via the network. ● Receives control information from the monitoring computer and automatically forwards it to the designated controlled equipment. ● The DIU's operating parameters, including communication rate and operating mode, can be configured via the monitoring computer. ● The MCS operating computer can query the DIU's operating status information. ② The hardware design of the data interface unit adopts a PC104 586 industrial control computer and interface modules adapted to the industrial control environment. CPU: 300MHz main frequency; 32MB DRAM memory; 16 interrupts; 2 RS-232C standard serial ports; 10M/100M BASE-T standard network interface; supports mouse/keyboard/floppy drive/IDE hard disk interface, and supports IDE Flash electronic disk. Communication card: Supports 8-channel RS-232C/RS-422A/RS-485 standard serial communication, each channel can be configured individually. Each channel supports a maximum communication rate of 115.2KB/s. Data acquisition card: Supports 8-channel opto-isolated DI and 8-channel relay output. Each input can support DC or AC input, and all inputs support SPDT mode with three states: common terminal, normally open, and normally closed, with a conversion rate of 5ms. ③ Embedded Software Design The software design of the data interface unit adopts embedded system design. We choose Linux as the development platform, and the tasks to be completed include: ● Appropriately tailoring Linux through the host machine. Due to the limited capacity of embedded systems, the large Linux distribution must be tailored to adapt to embedded applications. ● Implementing Linux drivers for the DOC2000 electronic disk. ● Designing drivers for the extended 8-channel serial communication card. ● Designing Linux system drivers for the digital I/O card. ● Designing data processing applications based on the functions implemented by the data interface unit. ● Burning a stable Linux image onto the DOC2000 electronic disk. After the data interface unit design is completed, it acts as an intelligent management device without input or output peripherals, managing and controlling its associated measurement and control equipment. 2 Configurable Software Design The monitoring software design adopts the configuration concept of industrial control systems, abstracting different measurement and control equipment into different categories of control device controls, constructing a system configuration database and a device control database. By modifying the database parameters, the software system can be flexibly configured. Figure 3 is a schematic diagram of the monitoring system software structure. Figure 3. Ground Station Monitoring System Software Structure ① Equipment Control Library: All measurement and control equipment is analyzed and categorized, abstracted into equipment controls with different display and control attributes, corresponding to the actual measurement and control equipment. Control of the physical measurement and control equipment can be achieved by operating these controls. Examples include frequency converter controls, switch matrix controls, and data acquisition interface units (see Figure 4). Since controls and the main monitoring system program can be developed separately, they have a certain degree of independence. Building an equipment control library increases the reusability and versatility of the entire ground monitoring software. After years of development and application, we have built a fairly large equipment control library, which can basically meet the monitoring needs of general ground station monitoring software. Figure 4. Using controls as the main display form in the system (example) ② System Configuration Database: To ensure the system's reconfigurability, a system configuration database is designed to store information such as the type, category, and interface form of the equipment controls in the current system, as well as the configuration of the system links, the IP addresses of multiple DIUs, and the configuration of their respective channel devices. When the composition of the measurement and control equipment in the measurement and control system changes or new equipment is added, the system configuration program can be used to modify the system configuration database or add necessary device controls, thus achieving a hardware-to-software reconfiguration. By separating the system framework and monitoring content through the configuration and running programs, and organically combining them through the configuration database, the system gains strong flexibility and scalability. ③ Graphical Interface Creation: The computer-based graphical monitoring interface is a user-friendly interface for controlling and monitoring the measurement and control station equipment. To accommodate the system's reconfigurable design, we specifically developed a drawing tool that allows for the creation of equipment information connection structures and control interfaces using a modular approach. Using this tool, graphical symbols of device controls are combined and connected onto one or more link diagrams (monitoring screens) reflecting the current measurement and control equipment link configuration. Then, by running the monitoring software and opening the pre-created link diagram, monitoring of the measurement and control station equipment can be achieved. For similar device controls, devices with the same function can have different access methods, monitoring interface protocols, control parameter forms and contents, and display formats—such as device icons, numerical parameters, color blocks, and analog graphics. Thus, they become different device controls, improving the software system's independence from devices. 3. System Construction Process First, the measurement and control equipment of the measurement and control station is analyzed, and functions such as system configuration and monitoring screen editing are completed, along with the framework design of the real-time monitoring program. After obtaining the monitoring interface control files of the measurement and control equipment, a configuration database is generated using the system configuration program, defining the device types, device connection relationships, device parameters, device control methods, and data processing methods in the system. The main monitoring screen is edited and designed using a drawing tool. During on-site installation, data interface units are installed according to the installation location and interface type of the measurement and control equipment, connecting the measurement and control equipment to the data processing computer through the data interface units. The communication parameters of each port of the data interface unit are set using the configuration program and downloaded to the data interface unit via the network. The physical measurement and control equipment is controlled through the device controls on the monitoring screen to verify the correctness of the system's hardware and software connections and settings. Conclusion We have successfully implemented this monitoring system with a reconfigurable architecture and applied it to the design and implementation of monitoring systems for multiple satellite operational tracking and control stations, including the Sino ground station in China and the Abuja ground station in Nigeria. Years of engineering practice and operation have proven the architecture to be highly successful.