Satellite-ground time synchronization system and method for satellite comprehensive test

Abstract

The invention discloses a satellite-ground time synchronization system and method for a satellite comprehensive test. The system comprises a navigation signal simulation source, time frequency equipment, ground special test equipment, a satellite-borne navigation receiver and a satellite-borne computer. According to the method, the uniform satellite-ground time reference is established, accurate and comparable timestamps with consistent sources are printed on all satellite telemetry data and ground test data, and the problem of information islands caused by disorder of the timestamps is solved. A ground navigation signal simulation source is used as a unique time source of satellite and ground special test equipment, a satellite-borne navigation receiver and ground time frequency equipment are used for resolving navigation radio frequency or low frequency signals of the navigation signal simulation source in parallel, and an inherent error accumulation chain in a cascade transmission synchronization mode is cut off. According to the ground time synchronization scheme of NMEA serial port second giving and second pulse frequency calibration, high-precision time synchronization can be realized only by receiving and analyzing standardized NMEA data and second pulse signals by ground time frequency equipment, and the hardware cost and the development difficulty of a software algorithm are reduced.

Description

Technical Field

[0001] This invention belongs to the field of satellite integrated testing technology, and relates to a system and method for achieving high-precision, automated time synchronization between the satellite and ground-based dedicated testing equipment during the satellite integrated testing phase. Background Technology

[0002] With the rapid development of aerospace technology, satellite functions are becoming increasingly complex, constellation networking has become an important development trend, and communication systems are also showing diversified characteristics. Against this backdrop, the scale and complexity of dedicated ground-based testing equipment have increased significantly.

[0003] Advanced communication systems place extremely high demands on time synchronization. Modern satellites, especially those employing low probability of intercept (PIO) and high anti-jamming communication systems such as time-division frequency hopping, rely heavily on high-precision time synchronization between the satellite and ground or between satellites for the establishment and maintenance of communication links. The generation and switching of frequency hopping patterns are directly controlled by the onboard time. During the overall satellite testing phase, even a millisecond-level deviation between the time of the ground-based testing equipment and the satellite time will prevent the ground from accurately tracking the frequency hopping sequence, ultimately making it difficult to establish and maintain a communication link. This prevents the advanced system from being fully validated during ground testing, significantly reducing the coverage and reliability of the tests and creating potential risks for on-orbit operation.

[0004] However, current integrated satellite testing systems still face a severe challenge in achieving time consistency. In existing integrated testing systems, the satellite's time reference typically comes from the onboard navigation receiver, while the time of dedicated ground testing equipment relies on its own independent local clock or operating system time, lacking a unified, high-precision synchronization mechanism. This fragmentation of time sources results in inaccurate timestamp alignment between onboard telemetry and data recorded by ground equipment. When a satellite malfunctions, it is necessary to troubleshoot massive amounts of data distributed across multiple devices. However, due to the inconsistent time references of each device, it is difficult to accurately locate faults and perform data correlation analysis based on the chaotic timestamps, significantly increasing the difficulty and time cost of troubleshooting.

[0005] Patent document CN111669218A discloses a ground verification platform and method for inter-satellite link signals. This method achieves synchronization by calculating the time deviation of inter-satellite link signals. However, the calculation of the time deviation depends on the comprehensive calculation of three parameters, resulting in high computational complexity. Furthermore, the accuracy of this method is easily affected by specific test cables and the orbital parameters of the satellite under test, and its low degree of automation leads to poor universality for different satellites and test scenarios.

[0006] Patent document CN102118847A discloses a method for time synchronization between a small satellite and its ground for ground-based whole-satellite testing. This method receives ground navigation simulation source signals through an onboard navigation receiver, and then transmits them step-by-step through the satellite's operational computer and control system (AOCC). Finally, the AOCC forwards the time signal to the ground dynamics simulation computer, forming a cascading synchronization path. The inherent drawback of this method is that the time signal undergoes multiple stages of transmission and processing, each introducing new delays and uncertainties, leading to a gradual accumulation of errors and making it difficult to guarantee the overall system synchronization accuracy. Furthermore, this method only synchronizes the ground simulation source and the dynamics simulation computer, failing to extend it to the entire ground testing system. Summary of the Invention

[0007] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a satellite-to-ground time synchronization system and method that is simple in principle, low in cost, highly automated and universally applicable. It can effectively reduce the cost of troubleshooting satellite integrated testing, meet the testing requirements of time-division frequency hopping communication system, and significantly improve test coverage and reliability.

[0008] The technical solution of this invention is: a satellite-to-ground time synchronization system for integrated satellite testing, comprising a navigation signal simulation source, a time and frequency device, a ground-based dedicated testing device, a satellite-borne navigation receiver, and a satellite-borne computer, wherein; Navigation signal simulation source: Generates a navigation radio frequency signal containing satellite orbit and time information, and sends it directly to the onboard navigation receiver via a radio frequency cable; generates a time reference signal containing NMEA data and 1PPS signal, and connects it to the input interface of the time and frequency equipment via a cable; the time reference signal is strictly aligned with the navigation radio frequency signal in time; Time and frequency equipment: Based on the time reference signal, it generates a ground time reference and sends it to a dedicated ground testing device; Ground-based dedicated testing equipment: performs specific satellite testing tasks according to the aforementioned ground time reference; Onboard navigation receiver: Installed on the satellite under test, it receives the navigation radio frequency signal, recovers the satellite's absolute time information and satellite's second pulse signal, and sends them to the onboard computer as the satellite's time reference; Onboard computer: Distributes the onboard time reference to each onboard terminal via the onboard data bus, enabling each onboard terminal to work collaboratively at a unified time.

[0009] Furthermore, the time-frequency device includes a receiving and processing unit, a time reconstruction unit, and an encoding and distribution unit, wherein: Receiving and processing unit: Receives time reference signal, extracts NMEA data and 1PPS signal, parses absolute date and time code information from NMEA data to achieve second-level time synchronization, and uses 1PPS signal to accurately lock the second time to achieve intra-second time synchronization; Time reconstruction unit: merges second-level time with time within seconds to synthesize a complete local absolute time; Encoding and Distribution Unit: Encodes the local absolute time into the standard IRIG-B time format and broadcasts it to all ground-based dedicated test equipment.

[0010] Preferably, the time and frequency device has multiple inputs and multiple outputs, supports the access of different types of time reference signals, and can provide a unified time for multiple ground-based dedicated test devices at the same time.

[0011] A satellite-to-ground time synchronization method for integrated satellite testing includes the following steps: Step 1: According to the test requirements, configure the orbital parameters and time information of the satellite under test in the navigation signal simulation source, start the navigation signal simulation source, and synchronously simulate and generate navigation radio frequency signals; at the same time, generate NMEA data and 1PPS signals that are synchronized with the navigation radio frequency signals. Step 2: The onboard navigation receiver receives and decodes the navigation radio frequency signal. After completing signal acquisition and tracking, it decodes the onboard absolute time information and the onboard 1PPS signal and outputs them to the onboard computer. Simultaneously, the ground time and frequency equipment receives the NMEA data and the 1PPS signal, decodes and recovers the ground absolute time, and distributes the time reference to each ground-dedicated test equipment in the form of IRIG-B code. Step 3: Send the satellite time synchronization command. The onboard computer receives the satellite's absolute time information and the satellite's 1PPS signal, and adjusts its own absolute time to match that of the onboard navigation receiver. Then, the onboard computer broadcasts and distributes the time and 1PPS signal to each terminal device on the satellite at fixed intervals through the satellite's internal data bus.

[0012] Preferably, the NMEA data is serial port time data conforming to the NMEA-0183 standard protocol.

[0013] The in-satellite data bus includes, but is not limited to, the 1553B bus, the CAN bus, and the SpaceWire bus.

[0014] The advantages of this invention compared to the prior art are: (1) By establishing a unified satellite-to-ground time reference, this invention provides all onboard telemetry data and ground test data with consistent and comparable timestamps. When satellite functions malfunction, the instructions sent by onboard telemetry and the data collected by ground equipment can be directly and accurately correlated and compared on a unified timeline, completely solving the "information silo" problem caused by chaotic timestamps. This makes the causal relationship between fault phenomena, onboard status and ground instructions clear at a glance, significantly reducing the troubleshooting costs and time cycle during the testing phase, and providing a strong guarantee for the smooth progress of the project. (2) This invention uses the ground navigation signal simulation source as the only time source for satellite and ground-specific test equipment. It uses the onboard navigation receiver and ground time and frequency equipment to solve the navigation radio frequency or low frequency signal of the navigation signal simulation source in parallel, which cuts off the inherent error accumulation chain in the "cascade transmission" synchronization method, fundamentally eliminates the systematic deviation caused by inconsistent time sources, and greatly simplifies the principle of satellite-ground time synchronization. (3) This invention proposes a ground time synchronization scheme of “NMEA serial port second transmission + 1PPS pulse frequency calibration”. The ground time and frequency equipment does not need to be configured with expensive radio frequency front-end and complex signal acquisition, tracking and calculation modules. It only needs to receive and parse standardized NMEA data stream and 1PPS signal to achieve high-precision time synchronization, which greatly reduces hardware cost and software algorithm development difficulty. (4) The system architecture of this invention does not depend on a specific satellite platform configuration or is not bound to a complex orbital dynamics model. Its core requirement is only that the satellite under test has a standard navigation signal receiving interface. This "platform independence" design concept enables the system to seamlessly adapt to comprehensive testing of various satellites of different models and orbits, demonstrating excellent versatility and flexibility. Whether for single-satellite testing or future constellation-based batch testing, the system of this invention can provide a unified and standardized time synchronization solution with strong lifecycle adaptability; (5) The high-precision and high-reliability satellite-to-ground time synchronization capability provided by the present invention provides key support for solving the ground verification problem of advanced anti-interference communication systems such as "time division frequency hopping", improves the test coverage of such technologies, and significantly reduces the risk of on-orbit operation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the time synchronization system of the present invention. Figure 2 This is a flowchart of the time synchronization method of the present invention. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings. The embodiments described in this section are intended to facilitate understanding of the present invention and do not constitute a limitation on the technical solutions.

[0017] like Figure 1 As shown, the present invention provides a satellite-to-ground time synchronization system for comprehensive satellite testing, comprising: a navigation signal simulation source, a time and frequency device, a ground-based dedicated testing device, a satellite-borne navigation receiver, and a satellite-borne computer.

[0018] The navigation signal simulation source is the time reference generation unit of the entire system, providing a unified time reference for both the onboard and ground systems. It possesses multi-system navigation signal simulation capabilities, generating navigation radio frequency (RF) signals conforming to the standards of specific satellite navigation systems (such as GPS and BeiDou) according to testing requirements. These signals contain precise satellite orbit and time information. Its RF output port is directly connected to the antenna interface of the onboard navigation receiver via an RF cable. Simultaneously, the navigation signal simulation source also outputs a low-frequency time reference signal that is strictly aligned with the navigation RF signal in time. This signal includes at least serial time data conforming to standards such as NMEA-0183 and a 1PPS (second pulse) signal aligned with the second edge of Coordinated Universal Time (UTC). The NMEA data output serial port and the 1PPS signal output port are connected to the corresponding input interfaces of the time and frequency equipment via cables.

[0019] The time and frequency equipment, serving as the center for establishing and distributing the ground time reference, is responsible for receiving time information output from the navigation signal analog source and providing a unified time reference for the entire ground testing system. It includes: a receiving and processing unit, a time reconstruction unit, and an encoding and distribution unit. The receiving and processing unit receives NMEA data and 1PPS signals from the navigation signal analog source, parses the absolute date and time code information from the NMEA data stream to achieve second-level time synchronization, and uses the 1PPS signal to precisely lock the second-level time, achieving high-precision synchronization within the second (nanosecond level). The time reconstruction unit fuses the second-level time and the within-second time to synthesize a complete and high-precision local absolute time. The encoding and distribution unit encodes the high-precision local absolute time into the standard IRIG-B time format and broadcasts it to all ground-specific testing equipment in the system through a dedicated interface, thereby establishing a unified ground time reference system.

[0020] Preferably, the time and frequency equipment has multi-channel input and output capabilities, supports the access of different types of time reference signals, and can provide unified time services for multiple ground-based dedicated test equipment at the same time.

[0021] Ground-based dedicated testing equipment is the terminal that performs specific testing tasks. It has a standard IRIG-B code interface and receives IRIG-B time codes distributed by time and frequency equipment to achieve time uniformity of the ground testing system, ensuring that all test command transmissions, data acquisitions and recordings have a unified, accurate and associative timestamp.

[0022] The onboard navigation receiver, as the onboard time reference unit, is installed on the satellite under test. Its function is to receive navigation radio frequency signals broadcast from the navigation signal analog source through radio frequency cables, perform acquisition, tracking and calculation processes, recover high-precision onboard absolute time information and onboard second pulse signals aligned with the UTC second edge from the navigation radio frequency signals, complete positioning and orbit determination, and provide the original time source for the satellite platform.

[0023] As the hub for the allocation and management of the onboard time reference, the onboard computer is responsible for receiving the onboard absolute time information and onboard second pulse signal output from the onboard navigation receiver. This information is used as the unified time reference for the entire satellite. The computer then distributes this information to the terminal devices of various subsystems on the satellite, such as the attitude and orbit control system, payload, and communication system, through the onboard data bus (such as the 1553B bus, CAN bus, or SpaceWire bus), ensuring that all units of the satellite work together under a unified time.

[0024] like Figure 2 As shown, the present invention also provides a satellite-to-ground time synchronization method for integrated satellite testing. Based on the above-described satellite-to-ground time synchronization system for integrated satellite testing, the steps are as follows: Step 1: According to the test requirements, configure the orbital parameters and time information of the satellite under test in the navigation signal simulation source, start the navigation signal simulation source, and synchronously simulate and generate navigation radio frequency signals; at the same time, generate a low-frequency NMEA data stream and second pulse signal that are synchronized with the navigation radio frequency signals. Step 2: The onboard navigation receiver receives and decodes the navigation radio frequency signal. After completing signal acquisition and tracking, it decodes the onboard absolute time information and onboard second pulse signal, and outputs them to the onboard computer. Step 3: Send the satellite time synchronization command. The onboard computer receives the satellite's absolute time information and the satellite's second pulse signal, and adjusts the onboard computer's own absolute time to be consistent with the onboard navigation receiver. Then, the onboard computer broadcasts and distributes the time and 1PPS signal to each terminal device on the satellite at fixed intervals through the satellite bus. Step four, synchronized with step two, the ground time and frequency equipment receives the NMEA data stream and second pulse signal, calculates and recovers the ground absolute time, and distributes the time reference to each ground-dedicated test equipment in the form of IRIG-B code.

[0025] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A satellite-ground time synchronization system for satellite integration test, characterized in that: The navigation signal simulation source, the time-frequency device, the ground special test device, the satellite navigation receiver and the satellite computer are included. The navigation signal simulation source generates navigation radio frequency signals containing satellite orbit and time information, and directly sends the signals to the satellite navigation receiver through radio frequency cable; the source generates time reference signals containing NMEA data and 1PPS signals, and connects the signals to the input interface of the time-frequency device through cable; the time reference signals are strictly aligned with the navigation radio frequency signals in time; The time-frequency device generates a ground time reference according to the time reference signals, and sends the reference to the ground special test device; The ground special test device performs specific satellite test tasks according to the ground time reference; The satellite navigation receiver installed on the satellite to be tested receives the navigation radio frequency signals, recovers the absolute time information on the satellite and the satellite 1PPS signal, and sends the signals to the satellite computer as a satellite time reference; The satellite computer distributes the satellite time reference to each satellite terminal through an intra-satellite data bus, so that each satellite terminal works cooperatively at a unified time.

2. The satellite-oriented integrated test time synchronization system according to claim 1, characterized in that: The time-frequency device includes a receiving and solving unit, a time reconstruction unit and a coding and distribution unit. The receiving and solving unit receives the time reference signals, extracts the NMEA data and 1PPS signals, parses the absolute date and time code information from the NMEA data, realizes the second-level time synchronization, and accurately locks the second time point by using the 1PPS signal to realize the second-level time synchronization; The time reconstruction unit fuses the second-level time and the second-level time to synthesize a complete local absolute time; The coding and distribution unit encodes the local absolute time into a standard IRIG-B time format, and broadcasts the time to all ground special test devices.

3. The satellite-oriented integrated test time synchronization system according to claim 1 or 2, characterized in that: The time-frequency device has multiple inputs and outputs, supports different types of time reference signal access, and can simultaneously provide unified time for multiple ground special test devices.

4. The satellite-oriented integrated test time synchronization system according to claim 1 or 2, characterized in that: The NMEA data is serial time data complying with the NMEA-0183 standard protocol.

5. The satellite-oriented integrated test time synchronization system according to claim 1 or 2, characterized in that: The navigation radio frequency signals comply with a specific satellite navigation system, including but not limited to the GPS system and the Beidou navigation system.

6. The satellite-oriented integrated test time synchronization system according to claim 1 or 2, characterized in that: The intra-satellite data bus includes but is not limited to the 1553B bus, the CAN bus and the SpaceWire bus.

7. A satellite-ground time synchronization method for satellite integrated testing, characterized in that: The method includes the following steps: Step one: according to the test requirements, configuring the satellite orbit parameters and time information of the satellite to be tested in the navigation signal simulation source, starting the navigation signal simulation source, and synchronously simulating the generation of navigation radio frequency signals; at the same time, generating NMEA data and 1PPS signals synchronized with the navigation radio frequency signals; Step two: the satellite navigation receiver receives and solves the navigation radio frequency signals, obtains the satellite absolute time information and the satellite 1PPS signal after completing signal acquisition and tracking, and outputs the signals to the satellite computer; synchronously, the ground time-frequency device receives the NMEA data and 1PPS signals, solves and recovers the ground absolute time, and distributes the time reference to each ground special test device in the form of IRIG-B code; In step three, the whole satellite time correction instruction is sent, the satellite computer receives the absolute time information and the 1PPS signal on the satellite, the absolute time of the satellite computer itself is adjusted to be consistent with the satellite navigation receiver, then the satellite computer broadcasts and distributes the time and the 1PPS signal to each terminal device on the satellite through the internal data bus of the satellite with a fixed period.

8. The method of claim 7, wherein the method further comprises: The ground time-frequency device receives the NMEA data and the 1PPS signal, solves and recovers the ground absolute time, specifically, the absolute date and time code information are parsed from the NMEA data, the second-level time synchronization is realized, the second time is accurately locked by using the 1PPS signal, and the time synchronization within a second is realized, then the second-level time and the time within a second are fused and processed to synthesize a complete ground absolute time.

9. The method of claim 7, wherein the method further comprises: The NMEA data is serial time data complying with the NMEA-0183 standard protocol.

10. The method of claim 7, wherein: The internal data bus of the satellite includes but is not limited to the 1553B bus, the CAN bus and the SpaceWire bus.

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