A high-orbit remote sensing satellite on-board time synchronization system and method

Abstract

The present invention relates to a time synchronization system and method on a high-orbit remote sensing satellite, and belongs to the technical field of on-board time systems for high-orbit satellites. The present invention proposes for the first time to use a high-orbit GNSS navigation receiving system in a high-orbit for satellite-ground time synchronization, which solves the problem that high-orbit satellites can only rely on ground measurement and control for time correction, and the time correction accuracy is not high and the operating cost is high. At the same time, the navigation receiving system is used to obtain the instantaneous characteristics of time error, and the long-term drift of the high-stability clock source and the high-stability clock is calibrated, which solves the problem of long-term indicator drift of the high-stability clock source and the high-stability clock, and ensures the accuracy of the on-board clock system. Then, a high-stability clock source is used to keep the precise time of the satellite, which solves the problem of low reliability of receiving GNSS navigation signals in high orbit.

Description

Technical Field

[0001] The present invention relates to a high-orbit remote sensing satellite on-board time synchronization system and method, belonging to the technical field of high-orbit satellite on-board time systems. Background Art

[0002] Geosynchronous orbit satellites generally use ground-based timekeeping and high-stability clocks on board to keep time. At the same time, they provide a solution for accurate platform time scale. This requires frequent time synchronization through the ground measurement and control station system and complex satellite-ground time alignment and correction measures. The satellite-ground time synchronization accuracy can be guaranteed to be 1 to 10 ms per day. If higher accuracy satellite-ground time synchronization accuracy is required, the ground measurement and control station needs to conduct one or several consecutive time calibrations every day or even a few hours. With the development and application of high-orbit remote sensing satellites, the requirements of payloads for satellite time accuracy are gradually increasing, and at the same time, users' demand for satellite autonomy is also gradually increasing. The existing methods of calibration through ground measurement and control station systems are difficult to adapt to the development requirements of high-precision and autonomous time synchronization of high-orbit remote sensing satellites. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and to propose a time synchronization system and method for a high-orbit remote sensing satellite. The system and method are a high-precision time synchronization system and method based on space-based autonomy, which can independently achieve microsecond or even nanosecond level satellite-ground time synchronization in orbit without relying on the calibration operation of the ground measurement and control station, reduce the satellite's dependence on the ground, and effectively improve the satellite's application flexibility and autonomous operation capability.

[0004] The technical solution of the present invention is:

[0005] An onboard time synchronization system for a high-orbit remote sensing satellite, the onboard time synchronization system comprising a high-orbit GNSS navigation receiving system, a highly stable clock source, a data management system and a bus terminal;

[0006] The bus terminals are divided into high-precision application requirement bus terminals and conventional precision application requirement bus terminals; the time accuracy of the high-precision application requirement bus terminals is in the μs order of magnitude; the time accuracy of the conventional precision application requirement bus terminals is in the ms order of magnitude;

[0007] The high-orbit GNSS navigation receiving system is used to receive navigation information from the navigation satellite constellation, and obtain the time information of the standard time according to the received navigation information as the basis for the satellite-to-ground time system calibration;

[0008] The high-orbit GNSS navigation receiving system converts the acquired time information of the standard time into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information;

[0009] The high-orbit GNSS navigation receiving system transmits the converted hardware pulse-per-second information to the high-stability clock source through a signal line;

[0010] The high-orbit GNSS navigation receiving system transmits the whole second time code corresponding to the converted hardware second pulse information to the high-stability clock source through the bus;

[0011] The highly stable clock source is used to receive the hardware pulse-per-second information and the whole-second time code transmitted by the high-orbit GNSS navigation receiving system, and use the received hardware pulse-per-second information and the whole-second time code to calibrate the internal clock to generate a time reference that can be used on the satellite;

[0012] The highly stable clock source converts the generated time reference used on the satellite into hardware second pulse information and whole second time code, the hardware second pulse information is transmitted to the high-precision application requirement bus terminal through the signal line, and the whole second time code is transmitted to the high-precision application requirement bus terminal through the bus, providing a time reference for the high-precision application requirement bus terminal;

[0013] The data management system sends the current time of the data management system to a high-stability clock source via a bus. The high-stability clock source calibrates the current time of the data management system using the time reference used on the generated satellite to generate a time correction time difference. The generated time correction time difference is transmitted to the data management system via the bus. The data management system completes time calibration based on the received time correction time difference, and sends the calibrated time to a bus terminal with conventional precision application requirements, thereby providing a time reference for the bus terminal with conventional precision application requirements.

[0014] Preferably, the high-precision application requires the time accuracy of the bus terminal to be 1 to 40 μs, and the conventional-precision application requires the time accuracy of the bus terminal to be 1 to 10 ms.

[0015] Preferably, the high-stability clock source also corrects the long-term clock drift of the high-stability clock based on the hardware pulse-per-second information received from the high-orbit GNSS navigation receiving system.

[0016] Preferably, the bus terminals with conventional precision application requirements are used to maintain the normal operation of the satellite, and receive the conventional precision time base broadcast by the data management system through the bus as the time base of these bus terminals, including thermal control subsystem, measurement and control subsystem, data transmission subsystem, etc.

[0017] Preferably, the bus terminal with high-precision application requirements participates in payload imaging applications and ensures imaging quality, including payload subsystems, control subsystems, and other subsystems with high time accuracy requirements.

[0018] Preferably, the method for the high-orbit GNSS navigation receiving system to obtain the time information of the standard time based on the received navigation information is: by configuring the high-orbit GNSS navigation system to receive the GNSS navigation signal transmitted from the opposite side of the earth, calculating the distance to the navigation satellite and the navigation message and other information, and obtaining the time information of the satellite at the current moment.

[0019] A method for onboard time synchronization of a high-orbit remote sensing satellite, the method comprising the steps of:

[0020] In the first step, the high-orbit GNSS navigation receiving system receives the navigation information of the navigation satellite constellation and obtains the time information of the standard time according to the received navigation information, which serves as the basis for the calibration of the satellite-ground time system.

[0021] In the second step, the high-orbit GNSS navigation receiving system converts the acquired time information of the standard time into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information, and transmits the converted hardware second pulse information to the high-stability clock source through the signal line. The high-orbit GNSS navigation receiving system transmits the whole second time code corresponding to the converted hardware second pulse information to the high-stability clock source through the bus;

[0022] In the third step, the high-stability clock source receives the hardware second pulse information and the whole second time code transmitted by the high-orbit GNSS navigation receiving system, and calibrates the clock inside the high-stability clock source according to the received hardware second pulse information and the whole second time code, generates a time reference that can be used on the satellite, and maintains the generated time reference used on the satellite; the high-stability clock source also uses its high-stability clock to provide a highly stable clock signal for the high-orbit GNSS navigation receiving system;

[0023] In the fourth step, the high-stability clock source converts the generated time reference used on the satellite into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information, and provides it to the bus terminal with high-precision application requirements that require high time accuracy;

[0024] Step 5: The high-stability clock source performs time calibration with the data management system through the bus. The data management system obtains the calibrated time information through the calibration of the high-stability clock source and maintains the time reference of conventional accuracy within the data management system.

[0025] Step 6: The data management system distributes the time information calibrated by the high-stability clock source to the bus terminals with conventional precision application requirements through broadcasting;

[0026] Step 7: The high-stability clock source maintains the generated time reference used on the satellite;

[0027] Step 8: The high-stability clock source uses the hardware pulse-per-second information of the high-orbit GNSS navigation receiving system to correct the long-term clock drift of the high-stability clock;

[0028] In the ninth step, the high-stability clock source provides the high-stability clock signal to the system on the satellite that needs to use the high-stability clock.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention proposes for the first time to use the GNSS navigation system in high orbit for satellite-ground time synchronization, solving the problem that high-orbit satellites can only rely on ground measurement and control for time calibration, and the calibration accuracy is low and the operating cost is high. At the same time, the real-time characteristics of the time error of the navigation receiving system are used to calibrate the long-term drift of the high-stability clock of the high-stability clock source, solving the problem of long-term indicator drift of the high-stability clock and ensuring the accuracy of the on-board clock system. The use of a high-stability clock to keep the precise time of the satellite solves the problem of low reliability of receiving GNSS navigation signals in high orbit.

[0031] (2) Compared with ordinary high-orbit remote sensing satellites, a high-orbit GNSS navigation receiving system has been added, which can be used for autonomous onboard time calibration. Compared with previous remote sensing satellites, the core equipment for timekeeping and timing has been transferred from the navigation receiving system to a high-stability clock source, which has improved the accuracy and reliability of the system. The use of the second pulse of the navigation receiving system to trace and calibrate the accuracy of the high-stability clock signal has been added, which solves the problem of errors caused by time offset after long-term operation in the process of autonomous timekeeping and timing.

[0032] (3) The on-board time synchronization system and method of the present invention is a design and solution with extremely low dependence on ground time synchronization and low constraints on the weak signal and low reliability of the high-orbit GNSS navigation receiving system. It reduces the time, personnel and economic costs of ground operation and control management, is highly reliable and accurate, and can operate autonomously, safely and stably. It meets the requirements of high-orbit remote sensing satellites for the accuracy of satellite-ground time synchronization and the accuracy of on-board time maintenance, and has great application value.

[0033] (4) The present invention aims at the autonomous requirements and characteristics of high-orbit remote sensing satellites for satellite-ground time synchronization accuracy and on-board time calibration, so that the satellite can autonomously complete satellite-ground time calibration during its in-orbit operation and maintain the accuracy within microseconds or even nanoseconds, and can be completely independent of ground measurement and control and time calibration for a long time. While meeting the time accuracy and autonomous requirements of high-orbit remote sensing satellites, this time synchronization system effectively reduces the cost of ground measurement and control and improves the usability and ease of use of satellites.

[0034] (5) The high-stability clock source of the present invention provides a high-stability clock signal to a system on a satellite that needs to use a high-stability clock, thereby ensuring the stability of its clock application and the consistency of the clock phase and improving the synchronization accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The figure is a schematic diagram of the composition of the onboard time synchronization system of the high-orbit remote sensing satellite of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0037] An onboard time synchronization system for a high-orbit remote sensing satellite, the onboard time synchronization system comprising a high-orbit GNSS navigation receiving system, a highly stable clock source, a data management system and a bus terminal;

[0038] The bus terminals are divided into high-precision application requirement bus terminals and conventional precision application requirement bus terminals; the time accuracy of the high-precision application requirement bus terminals is in the μs order of magnitude, preferably 1 to 40 μs, and the time accuracy of the conventional precision application requirement bus terminals is in the ms order of magnitude, preferably 1 to 10 ms;

[0039] The high-orbit GNSS navigation receiving system is used to receive navigation information from the navigation satellite constellation, and obtain the time information of the standard time according to the received navigation information as the basis for the satellite-ground time system calibration, that is, by configuring the high-orbit GNSS navigation system to receive the GNSS navigation signal transmitted from the opposite side of the earth, solving the distance to the navigation satellite and the navigation message and other information, and obtaining the time information of the satellite at the current time; the high-orbit GNSS navigation receiving system converts the obtained time information of the standard time into hardware second pulse information and the whole second time code corresponding to the second pulse information; the high-orbit GNSS navigation receiving system transmits the converted hardware second pulse information to the high-stability clock source through the signal line, and the high-orbit GNSS navigation receiving system transmits the whole second time code corresponding to the converted hardware second pulse information to the high-stability clock source through the bus (the commonly used bus is 1553B or CAN bus);

[0040] The high-stability clock source receives the hardware second pulse information and the whole second time code transmitted by the high-orbit GNSS navigation receiving system, and calibrates the time reference inside the high-stability clock source by using the received hardware second pulse information and the whole second time code through the internal timing module, generates a time reference that can be used on the satellite, and completes the timing operation; the high-stability clock of the high-stability clock source corrects the long-term clock drift (frequency difference compensation, phase compensation, etc.) of the high-stability clock according to the hardware second pulse information received from the high-orbit GNSS navigation receiving system by using the clock taming module, so as to ensure the long-term clock stability of the high-stability clock;

[0041] The highly stable clock source converts the generated time reference used on the satellite into hardware second pulse information and the whole second time code corresponding to the hardware second pulse, and transmits them to the high-precision application requirement bus terminal with high time accuracy requirements through the signal line and the bus, respectively, to provide time calibration for the high-precision application requirement bus terminal with high time accuracy requirements. The highly stable clock source is also used to perform time calibration on the data management system through the bus. First, the data management system sends the current time reference of the data management system to the highly stable clock source through the bus. The highly stable clock source uses the generated time reference used on the satellite to calibrate the time reference of the data management system, and transmits the calibration time difference to the data management system through the bus.

[0042] The high-stability clock source maintains the time reference generated for use on the satellite through the timekeeping module, and utilizes its own high-stability clock characteristics to maintain the accuracy of its own time information when the high-orbit GNSS navigation receiving system has no second pulse information and whole second time code for a long time.

[0043] The highly stable clock source outputs a stable clock signal to other satellite systems or devices that require a highly stable clock (including high-orbit GNSS navigation systems, data management systems, high-precision application requirement bus terminals, etc.).

[0044] The data management system communicates with the high-stability clock source through the bus to complete the time calibration action, and obtains the conventional precision time base for maintaining satellite operation through time calibration (the accuracy is generally 1 to 10ms). The calibration method is: the data management system transmits its own time code to the high-stability clock source, and the high-stability clock source compares the time code received from the data management system with the time base maintained in the high-stability clock source to obtain the time difference information, and then feeds the obtained time difference information back to the data management system. The data management system calibrates the time information inside the data management system according to the received time difference information, obtains the calibrated time information, and maintains the conventional precision time base inside the data management system. The data management system broadcasts the conventional precision time base obtained and maintained by itself to the conventional precision application requirement bus terminal through the bus (generally 1553B bus or CAN bus).

[0045] The normal accuracy application requires that the bus terminals receive the normal accuracy time base broadcast by the data management system through the bus as the time base of these bus terminals.

[0046] The high-precision application-required bus terminals receive hardware second pulse information and whole second time codes sent by a high-stability clock source through signal lines and buses, and obtain a high-precision time reference as the time reference for these bus terminals.

[0047] The bus terminal for conventional precision application requirements is generally a bus terminal for maintaining the basic operation of the satellite, including the satellite platform operation systems such as the thermal control subsystem, the measurement and control subsystem, and the data transmission subsystem;

[0048] The bus terminals with high-precision application requirements are generally involved in payload imaging applications and ensure imaging quality, including payload subsystems, control subsystems, other subsystems with high time accuracy requirements, and other satellite payload imaging-related systems. The bus terminals with high-precision application requirements use highly stable clock signals provided by highly stable clock sources;

[0049] The bus terminals all act as time users.

[0050] The device for receiving second pulses includes a high-stable clock source, a data management system, a high-precision application requirement bus terminal, etc. The signal using the second pulse is brought out to the surface of the device through a device connector, which facilitates the testing and correction of the delay accuracy of the received and used second pulses, increases its high-precision measurability, and ensures the accuracy and reliability of the high-precision time application.

[0051] A method for onboard time synchronization of a high-orbit remote sensing satellite, the method comprising the steps of:

[0052] In the first step, the high-orbit GNSS navigation receiving system receives navigation information from the navigation satellite constellation, and obtains the time information of the standard time according to the received navigation information as the basis for the satellite-ground time system calibration;

[0053] In the second step, the high-orbit GNSS navigation receiving system converts the acquired standard time information into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information, and transmits the converted hardware second pulse information to the high-stability clock source through the signal line. The high-orbit GNSS navigation receiving system transmits the whole second time code corresponding to the converted hardware second pulse information to the high-stability clock source through 1553B or CAN bus;

[0054] In the third step, the high-stability clock source receives the hardware second pulse information and the whole second time code transmitted by the high-orbit GNSS navigation receiving system, and calibrates the clock inside the high-stability clock source according to the received hardware second pulse information and the whole second time code, generates a time reference that can be used on the satellite, and maintains the timekeeping of the generated time reference used on the satellite; the high-stability clock source also uses its high-stability clock to provide a highly stable clock signal to the high-orbit GNSS navigation receiving system as the clock for its software and hardware operation.

[0055] In the fourth step, the highly stable clock source converts the generated time reference used on the satellite into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information, and provides it to the bus terminal with high-precision application requirements that require high time accuracy;

[0056] In the fifth step, the high-stability clock source is time-calibrated with the data management system through the bus. The data management system obtains calibrated time information through the calibration of the high-stability clock source. The time information can be used to maintain the operation and maintenance of the bus terminal of the conventional precision application requirement of the satellite platform;

[0057] Step 6: The data management system distributes the time information calibrated by the high-stability clock source to bus terminals with conventional precision application requirements in the form of broadcast;

[0058] In the seventh step, the high-stability clock source maintains the time reference generated for use on the satellite through the timekeeping module, and utilizes its own high-stability clock characteristics to maintain the accuracy of its own time when the high-orbit GNSS navigation receiving system has no second pulse information and whole second time code for a long time.

[0059] The bus terminal for conventional precision application requirements is generally a bus terminal for maintaining the basic operation of the satellite, including the satellite platform operation systems such as the thermal control subsystem, the measurement and control subsystem, and the data transmission subsystem;

[0060] The bus terminals with high-precision application requirements are generally systems involved in payload imaging applications and ensuring imaging, including payload subsystems, control subsystems, other subsystems with high time accuracy requirements, and other satellite payload imaging-related systems;

[0061] The high-precision application-required bus terminal, high-orbit GNSS navigation receiving system, and data management system use a high-stability clock signal provided by a high-stability clock source;

[0062] The bus terminals act as time users.

[0063] (1) Time Generation

[0064] The satellite time reference of the onboard time synchronization system of the high-orbit remote sensing satellite receives the GNSS navigation signal from the other side of the earth through the high-orbit GNSS navigation receiving system, measures and solves the current time, and converts the GNSS time into the time reference used by the satellite platform. The time accuracy can be guaranteed to be 1 to 50μs.

[0065] (2) Time traceability and calibration of high-stability clocks

[0066] The time base of the high-orbit remote sensing satellite's high-stability clock is aligned through the time base of the high-orbit GNSS. The alignment method uses high-precision hardware second pulse transmission, and the time accuracy can be guaranteed to be at the level of ±1μs or even ns. While the hardware second pulse is transmitted, the whole second time code of the high-orbit GNSS time base is transmitted to the high-stability clock source through the satellite platform's data bus. In this way, the high-precision satellite-to-ground time base is accurately transmitted to the high-stability clock source.

[0067] After receiving the hardware second pulse, the high-stability clock source uses the non-cumulative and irrelevant nature of the second pulse time accuracy to calibrate its timekeeping accuracy and high-stability clock accuracy, correct the accumulated time error caused by its long-term drift and the long-term drift deviation of the high-stability clock, thereby accurately correcting the satellite time reference and the high-stability clock source.

[0068] (3) Keeping time and maintaining high stability

[0069] High-orbit remote sensing satellites are equipped with highly stable clocks, generally hydrogen clocks, rubidium clocks or constant temperature crystal oscillators, to achieve the accuracy of satellite platform timekeeping. Taking rubidium clocks as an example, the 10MHz clock output has a long-term stability of ±1×10 -13 / day, the clock can keep time with a maximum time variation of 1μs per day. Since the navigation signal transmitted by the earth is weak and the reliability is poor, there may be irregular time interruptions. At this time, the high-stability time can be kept and maintained to reduce the constant transition dependence on the navigation receiving system.

[0070] (4) Satellite platform timing

[0071] There are some terminals with high-precision time application requirements on high-orbit remote sensing satellites, mainly payload subsystems (such as the optical payload subsystem of optical remote sensing satellites, the microwave payload subsystem of microwave remote sensing satellites) and control subsystems with high requirements for satellite attitude and orbit control accuracy. The time bases of these high-precision application-required bus terminals are aligned with the time base of a highly stable clock source. The alignment method uses highly accurate hardware second pulse transmission, and the time accuracy can be guaranteed to be ±1μs. At the same time as the hardware second pulse is transmitted, the whole second time code of the highly stable clock source reference is transmitted to the payload subsystem and the control subsystem through the satellite platform's data bus. In this way, the precise calibration of the time system of the satellite's high-precision application-required bus terminal is completed.

[0072] High-orbit remote sensing satellite platforms generally have some terminals with low sensitivity to time accuracy. These terminals are not related to the accuracy of payload applications and are mainly used to ensure the basic and reliable operation of satellite platforms, such as the measurement and control subsystem, thermal control subsystem, overall circuit subsystem, power subsystem, data transmission subsystem, digital computers in the data management system, remote units, etc. These bus terminals with conventional precision application requirements can meet the time accuracy requirements through the data management system time calibration. First, the data management system is timed through a high-stability clock source. The time calibration methods include forced time calibration and autonomous time calibration. Then, after the data management system is timed, the measurement and control subsystem, thermal control subsystem, overall circuit subsystem, power subsystem, data transmission subsystem, digital computers in the data management system, remote units, etc. are time-calibrated through the data bus.

[0073] (4) Satellite time system test interface

[0074] The timing accuracy of the onboard time system of high-orbit remote sensing satellites can be guaranteed to be 1μs or even ns level through hardware second pulses. When the bus terminals with high-precision application requirements, such as the payload subsystem and the control subsystem, receive the second pulses, after internal hardware and software processing, the second pulse accuracy of the final application has a certain delay. In order to confirm the exact value of the delay accuracy, the second pulses finally applied by the bus terminal with high-precision application requirements are led out to the test interface of the equipment through shunt and other measures, so as to directly measure the time delay accuracy from the second pulses output by the high-orbit GNSS navigation system to the second pulses finally applied by the bus terminal with high-precision application requirements.

[0075] Example

[0076] like Figure 1 As shown in the figure, a certain high-orbit microwave remote sensing satellite is equipped with a high-orbit GNSS navigation receiving system. The system automatically obtains the satellite's current time information by receiving the navigation radio frequency signals of the BDS constellation and GPS constellation transmitted from the opposite side of the earth through solution and processing, and completes the time synchronization with various ground systems through the BDS constellation and GPS constellation. The clock required for the operation and calculation of the high-orbit GNSS navigation receiving system is provided and guaranteed by the high-stability clock of the high-stability clock source configured on the satellite. This step completes the time unification between the satellite and the ground.

[0077] The high-orbit GNSS navigation receiving system converts the acquired standard time information into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information. The high-orbit GNSS navigation receiving system transmits the converted hardware second pulse information to the high-stability clock source through the signal line, and transmits the whole second time code corresponding to the converted hardware second pulse information to the high-stability clock source through the 1553B bus. The high-stability clock source receives the hardware second pulse information and whole second time code transmitted by the high-orbit GNSS navigation receiving system, and uses the received hardware second pulse information and whole second time code through the internal timing module to calibrate the time information inside the high-stability clock source, generate a time reference that can be used on the satellite, and complete the timing operation.

[0078] The high-stability clock source converts the generated time reference used on the satellite into hardware second pulse information and whole second time code, and transmits them to the high-precision application requirements bus terminal 1, bus terminal 2, ..., bus terminal n through signal lines and buses. Such terminals on the remote sensing satellite include the payload subsystem and the control subsystem, and provide time calibration for the payload subsystem and the control subsystem through hardware second pulse and whole second time code. The calibration accuracy can reach the μs level.

[0079] The high-stability clock source is also used to calibrate the time of the data management system through the bus. First, the data management system sends the current time base of the data management system to the high-stability clock source through the bus. The high-stability clock source uses the generated time base used on the satellite to calibrate the time base of the data management system and transmits the calibration time difference to the data management system through the bus. The data management system communicates with the high-stability clock source through the bus to complete the calibration action, and obtains the conventional precision time base for maintaining satellite operation (the accuracy is generally 1 to 10ms) through calibration.

[0080] The data management system broadcasts the conventional precision time base acquired and maintained by itself to bus terminal a, bus terminal b, and bus terminal m with conventional precision application requirements through the 1553B bus. Such terminals on the remote sensing satellite include the measurement and control subsystem, thermal control subsystem, data transmission subsystem, overall circuit subsystem, control subsystem, and remote units of the data management system, providing time calibration for these subsystems. The calibration accuracy can reach the ms level.

[0081] The high-stability clock source uses the timekeeping module to keep the generated time reference used on the satellite, and uses its own high-stability clock characteristics to maintain the accuracy of its own time when the high-orbit GNSS navigation receiving system has no second pulse information and full-second time code for a long time. Since the high-orbit GNN navigation receiving system receives navigation signals from the navigation constellation on the opposite side of the earth, these navigation signals are leaked from the side lobes of the navigation satellite, and the navigation receiving system may be unlocked for tens of minutes to several hours. At this time, the navigation receiving system cannot provide the high-stability clock source with a second pulse signal and the corresponding full-second time code. At this time, the high-stability clock source uses its own high-stability clock to extrapolate and maintain the time information it maintains.

[0082] The high-stability clock of the high-stability clock source uses the clock taming module to correct the long-term clock drift (frequency difference compensation, phase compensation, etc.) of the high-stability clock source according to the hardware second pulse information received from the high-orbit GNSS navigation receiving system, thereby ensuring the clock stability of the high-stability clock.

[0083] The high-stability clock source outputs a stable clock signal to other satellite systems or equipment that require a high-stability clock.

[0084] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A time synchronization system on a high-orbit remote sensing satellite, characterized in that: The onboard time synchronization system includes a high-orbit GNSS navigation receiving system, a highly stable clock source, a data management system and a bus terminal; The bus terminals are divided into high-precision application requirement bus terminals and conventional precision application requirement bus terminals; the time accuracy of the high-precision application requirement bus terminals is in the μs order of magnitude; the time accuracy of the conventional precision application requirement bus terminals is in the ms order of magnitude; The high-orbit GNSS navigation receiving system is used to receive navigation information from the navigation satellite constellation, and obtain the time information of the standard time according to the received navigation information as the basis for the satellite-to-ground time system calibration; The high-orbit GNSS navigation receiving system converts the acquired time information of the standard time into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information; The high-orbit GNSS navigation receiving system transmits the converted hardware pulse-per-second information to the high-stability clock source through a signal line; The high-orbit GNSS navigation receiving system transmits the whole second time code corresponding to the converted hardware second pulse information to the high-stability clock source through the bus; The highly stable clock source is used to receive the hardware pulse-per-second information and the whole-second time code transmitted by the high-orbit GNSS navigation receiving system, and use the received hardware pulse-per-second information and the whole-second time code to calibrate the internal clock to generate a time reference that can be used on the satellite; The highly stable clock source converts the generated time reference used on the satellite into hardware second pulse information and whole second time code, the hardware second pulse information is transmitted to the high-precision application requirement bus terminal through the signal line, and the whole second time code is transmitted to the high-precision application requirement bus terminal through the bus, providing a time reference for the high-precision application requirement bus terminal; The data management system sends the current time of the data management system to a high-stability clock source via a bus. The high-stability clock source calibrates the current time of the data management system using the time reference used on the generated satellite to generate a time correction time difference. The generated time correction time difference is transmitted to the data management system via the bus. The data management system completes time calibration based on the received time correction time difference, and sends the calibrated time to a bus terminal with conventional precision application requirements, thereby providing a time reference for the bus terminal with conventional precision application requirements.

2. The high-orbit remote sensing satellite onboard time synchronization system according to claim 1, characterized in that: The high-precision application requires the time accuracy of the bus terminal to be 1 to 40 μs, and the conventional-precision application requires the time accuracy of the bus terminal to be 1 to 10 ms.

3. The high-orbit remote sensing satellite onboard time synchronization system according to claim 1, characterized in that: The high-stability clock source also corrects the long-term clock drift of the high-stability clock according to the hardware pulse-per-second information received from the high-orbit GNSS navigation receiving system.

4. The high-orbit remote sensing satellite onboard time synchronization system according to claim 1, characterized in that: The bus terminals with conventional precision application requirements are used to maintain the normal operation of the satellite. The conventional precision time base broadcast by the data management system is received through the bus as the time base for these bus terminals, including the thermal control subsystem, the measurement and control subsystem, and the data transmission subsystem.

5. The high-orbit remote sensing satellite onboard time synchronization system according to claim 1, characterized in that: The bus terminal required for high-precision applications participates in payload imaging applications and ensures imaging quality, including a payload subsystem and a control subsystem.

6. The high-orbit remote sensing satellite onboard time synchronization system according to claim 1, characterized in that: The method for the high-orbit GNSS navigation receiving system to obtain the time information of the standard time according to the received navigation information is as follows: by configuring the high-orbit GNSS navigation system to receive the GNSS navigation signal transmitted from the opposite side of the earth, calculating the distance to the navigation satellite and the navigation message, and obtaining the time information of the satellite at the current moment.

7. A method for onboard time synchronization of a high-orbit remote sensing satellite, characterized in that The steps of the method include: In the first step, the high-orbit GNSS navigation receiving system receives the navigation information of the navigation satellite constellation and obtains the time information of the standard time according to the received navigation information as the basis for the calibration of the satellite-ground time system; In the second step, the high-orbit GNSS navigation receiving system converts the acquired time information of the standard time into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information, and transmits the converted hardware second pulse information to the high-stability clock source through the signal line. The high-orbit GNSS navigation receiving system transmits the whole second time code corresponding to the converted hardware second pulse information to the high-stability clock source through the bus; In the third step, the high-stability clock source receives the hardware second pulse information and the whole second time code transmitted by the high-orbit GNSS navigation receiving system, and calibrates the clock inside the high-stability clock source according to the received hardware second pulse information and the whole second time code, generates a time reference that can be used on the satellite, and maintains the generated time reference used on the satellite; the high-stability clock source also uses its high-stability clock to provide a highly stable clock signal for the high-orbit GNSS navigation receiving system; In the fourth step, the high-stability clock source converts the generated time reference used on the satellite into hardware second pulse information and the whole second time code corresponding to the hardware second pulse information, and provides it to the bus terminal with high-precision application requirements that require high time accuracy; Step 5: The high-stability clock source performs time calibration with the data management system through the bus. The data management system obtains the calibrated time information through the calibration of the high-stability clock source and maintains the time reference of conventional accuracy within the data management system. Step 6: The data management system distributes the time information calibrated by the high-stability clock source to the bus terminals with conventional precision application requirements through broadcasting; Step 7: The high-stability clock source maintains the generated time reference used on the satellite; Step 8: The high-stability clock source uses the hardware pulse-per-second information of the high-orbit GNSS navigation receiving system to correct the long-term clock drift of the high-stability clock; In the ninth step, the high-stability clock source provides the high-stability clock signal to the system on the satellite that needs to use the high-stability clock.

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