Method for switching main clock and standby clock of on-orbit navigation satellite
Technical Field
The invention relates to the technical field of satellite-borne atomic clocks, in particular to a method for switching master and slave clocks of an on-orbit navigation satellite.
Background
With the continuous development of the fields of satellite navigation positioning, satellite communication and the like, the requirement of the satellite effective load on the accuracy of time frequency is higher and higher. The satellite navigation system can provide high-precision and high-reliability positioning, navigation and time service for various users all day long in the world, and is concerned with national safety and national economic development. The precise time keeping technology is the technical basis for providing high-precision positioning, navigation and time service for the satellite navigation system. At present, a satellite navigation system is provided with a precise atomic clock, and keeps precise synchronization with atomic clocks of each monitoring station and a main control station all the time, so that precise navigation and time service are provided for users.
In order to ensure the stability and reliability of the operation of a navigation satellite system, a satellite-borne time-frequency processing system of the navigation satellite adopts a redundancy backup architecture design, two atomic clocks are powered on to work at the same time, one atomic clock is in a main working state, and the other atomic clock is in a hot backup working state. When the primary working atomic clock is abnormal or fails, the system can be automatically and stably switched to the hot backup atomic clock, so that the continuity of the navigation satellite frequency signal is ensured. In order to ensure that the time-frequency reference signal output by the system does not have large jitter and change before and after the master atomic clock and the standby atomic clock are switched, the system adopts a phase comparator to measure the phase difference of the master atomic clock and the standby atomic clock, and adjusts and controls the hot standby atomic clock signal to always follow the master atomic clock through a phase control word and a frequency control word according to the measured phase difference data, as shown in fig. 1.
The prior stable switching technology of the main clock and the standby clock can only realize a in the clock difference parameter 0 (phase difference), a 1 Smooth switching of (clock speed) does not enable a in the clock difference parameter 2 (frequency drift) and therefore optimal performance transfer of the primary and secondary clocks cannot be achieved. The clock error model of the on-orbit navigation satellite is delta t = a 0 +a 1 τ+a 2 τ 2 Where Δ t is the clock difference, τ is the time, a 0 Is a phase, a 1 Is a frequency, a 2 Is the frequency drift rate. The accuracy of the satellite Zhong Zhongcha parameter measurement and the long-term consistency thereof directly influence the satellite navigation positioning accuracy. At present, the methodIn order to ensure the stability and reliability of the operation of the navigation satellite system, the satellite-borne time-frequency processing system of the navigation satellite adopts a redundancy backup architecture design, two atomic clocks are powered on to work simultaneously, one atomic clock is in a main working state, the other atomic clock is in a hot backup working state, the main atomic clock and the standby atomic clock are in a tracking enabling state, and the clock difference parameter phase a of the hot backup atomic clock 0 prepare And frequency a 1 preparing Phase a with primary atomic clock 0 main And frequency a 1 main Keep consistent and hot backup atomic clock frequency drift rate a 2 prepare Frequency drift rate a with primary atomic clock 2 main Different. Therefore, when the primary atomic clock is abnormal or fails, the navigation satellite system is automatically switched to the hot backup atomic clock to operate, and only the phases a of the primary and backup clocks can be realized 0 And frequency a 1 Cannot realize the frequency drift rate a of the main and standby clocks 2 Is transmitted. Before and after the main and standby clocks are switched, the frequency drift rate a 2 Jump occurs and the optimal transfer of the performance of the satellite clock cannot be realized.
According to the clock error model, after the on-orbit navigation satellite is switched between the main clock and the standby clock, when the ground cannot timely inject new clock error parameters, the frequency drift rate a 2 The jump will cause the clock error prediction to increase as the square of the integral time, and has a great influence on long-term clock error prediction, for example, the clock error prediction error in 48 hours will reach dozens of nanoseconds, which seriously influences the time service precision of the navigation satellite and severely limits the autonomous navigation operation capability of the navigation satellite system. Therefore, a transfer technology for switching the optimal performance of the main clock and the standby clock of the on-orbit navigation satellite is urgently needed.
Disclosure of Invention
The invention aims to provide a method for switching between a master clock and a slave clock of an on-orbit navigation satellite, which aims to solve the problem that the frequency drift rate of the master clock and the slave clock cannot be transferred when the conventional navigation satellite system is automatically switched to a hot backup atomic clock.
In order to solve the technical problem, the invention provides a method for switching between a master clock and a slave clock of an in-orbit navigation satellite, which comprises the following steps:
firstly, the in-orbit navigation satellite adopts two atomic clocks to simultaneously work by electrifying, wherein one atomic clock is used as a main clock and is in a main working state, the other atomic clock is used as a hot standby clock and is in a hot standby working state;
combining with the satellite-ground bidirectional ranging observation data, calculating by using a satellite-ground bidirectional comparison method to obtain a plurality of main clock error parameters;
secondly, acquiring clock error parameters of the hot standby clock relative to a main clock through engineering telemetering data broadcast by the in-orbit navigation satellite;
thirdly, calculating to obtain a plurality of hot standby clock error parameters according to the main clock error parameters and the engineering telemetering data by adopting an on-satellite main/standby atomic clock phase comparison method;
in the following state of the main clock and the standby clock, the phase and the frequency of the hot standby clock and the phase and the frequency of the main clock are kept equal and synchronously change along with time, so that seamless switching can be realized;
after the in-orbit navigation satellite stably operates, the frequency drift rate of satellite clock error data is a constant, and the hot standby Zhong Zhongcha parameter is injected to the in-orbit navigation satellite for storage and standby;
and fifthly, when the on-orbit navigation satellite autonomously monitors that the main clock and the hot standby clock are switched, directly and autonomously calling the stored hot standby Zhong Zhongcha parameter to replace the main clock difference parameter as satellite clock difference data, compensating the switched satellite clock difference data, and correcting the frequency drift rate of the satellite clock difference data.
Optionally, in the method for switching between the main clock and the standby clock of the in-orbit navigation satellite, the downlink signal used for the satellite-to-ground two-way ranging is a satellite signal output after frequency reduction processing by a tuner, and the frequency of the satellite signal is 950MHZ to 2150MHZ.
Optionally, in the method for switching between a master clock and a slave clock of an in-orbit navigation satellite, combining the satellite-to-ground bidirectional ranging observation data, and obtaining a plurality of clock error parameters of the master clock by using a satellite-to-ground bidirectional comparison method includes:
the method comprises the steps that a ground operation and control system with a ground reference atomic clock as a reference transmits an uplink signal, an uplink ranging link is established with a satellite, the satellite uses a main clock of the satellite-borne atomic clock as a reference, meanwhile, the satellite transmits a downlink signal, a downlink ranging link is established with the ground operation and control system, the satellite measures uplink pseudo range values between satellites and the ground, and the ground operation and control system measures downlink pseudo range values between the satellites and the ground;
and the uplink pseudo range value is transmitted back to the ground operation and control system through telemetry, and the ground operation and control system calculates the clock error of the main clock relative to the ground reference atomic clock in the sampling period according to the downlink pseudo range value and the uplink pseudo range value.
Optionally, in the method for switching between the main clock and the standby clock of the in-orbit navigation satellite, the calculating by using a satellite-to-ground bidirectional comparison method to obtain a plurality of main clock difference parameters in combination with the satellite-to-ground bidirectional ranging observation data further includes:
the uplink pseudo range value between the satellite and the earth measured by the satellite is the sum of the microwave propagation delay between the satellite and the earth and the clock difference of the main clock relative to the ground reference atomic clock;
the ground operation and control system measures a downlink pseudo range value between the satellite and the ground as the difference between the microwave propagation time delay between the satellite and the ground and the clock difference of the main clock relative to the ground reference atomic clock;
and for the uplink pseudo range value measured in the same sampling period, the satellite-ground microwave propagation delay contained in the uplink pseudo range value is equal to the satellite-ground microwave propagation delay contained in the downlink pseudo range value.
Optionally, in the method for switching between the master clock and the slave clock of the in-orbit navigation satellite, obtaining the clock difference parameter of the hot slave clock relative to the master clock through the engineering telemetry data broadcast by the in-orbit navigation satellite includes:
and the satellite time-frequency processing system measures and records the clock difference of the hot standby clock relative to the main clock in real time.
Optionally, in the method for switching between the main clock and the standby clock of the in-orbit navigation satellite, the clock difference of the hot standby clock relative to the main clock, which is measured and recorded in real time by the satellite time-frequency processing system, is a difference between a phase of an output signal of the hot standby clock and a phase of an output signal of the main clock;
and measuring the phase difference between the output signal of the hot standby clock and the output signal of the main clock by using a phase discriminator of a satellite-borne time-frequency processing system, wherein the phase difference is the clock difference of the hot standby clock relative to the main clock.
Optionally, in the method for switching between master and slave clocks of an in-orbit navigation satellite, calculating a plurality of hot slave clock offset parameters according to the master clock offset parameter and the engineering telemetry data by using an on-satellite master and slave atomic clock ratio method includes:
and the clock difference of the standby clock relative to the main clock is transmitted back to the ground operation and control system through remote measurement, and the ground operation and control system obtains the clock difference of the standby clock relative to the ground reference atomic clock according to the clock difference of the main clock relative to the ground reference atomic clock and the clock difference of the standby clock relative to the main clock.
Optionally, in the method for switching between a master clock and a slave clock of an in-orbit navigation satellite, the uplink pseudorange value and the clock difference of the hot standby clock with respect to the master clock are both downloaded to the ground in real time through a satellite-to-ground measurement and control channel, and are collected to the ground operation and control system, so as to perform data processing, thereby obtaining the clock difference of the master clock with respect to a ground reference atomic clock and the clock difference of the hot standby clock with respect to a ground reference atomic clock.
According to the method for switching the main clock and the standby clock of the on-orbit navigation satellite, a plurality of hot standby clock difference parameters are obtained through calculation according to the main clock difference parameters and engineering telemetering data, the hot standby Zhong Zhongcha parameters are injected to the on-orbit navigation satellite for storage and standby, when the on-orbit navigation satellite autonomously monitors that the main clock and the hot standby clock are switched, the stored hot standby Zhong Zhongcha parameters are directly and autonomously called to replace the main clock difference parameters to serve as satellite clock difference data, the switched satellite clock difference data are compensated, the frequency drift rate of the satellite clock difference data is corrected, and optimal performance transfer during switching the main clock and the standby clock of the satellite is achieved. Therefore, the invention provides a transfer technology for the optimal performance of the switching between the main clock and the standby clock of the on-orbit navigation satellite, which can realize the optimal transfer of the phase, the frequency and the frequency drift rate when the main clock and the standby clock of the on-orbit are switched, improve the long-term clock error prediction precision by one order of magnitude and improve the autonomous navigation operation capability of the navigation satellite.
Drawings
FIG. 1 is a schematic diagram illustrating a conventional method for switching between master and slave clocks of an in-orbit navigation satellite;
FIG. 2 is a schematic diagram illustrating a clock difference change of a master/slave clock switching method of an existing in-orbit navigation satellite;
FIG. 3 is a schematic diagram illustrating a method for switching between master and slave clocks of an in-orbit navigation satellite according to an embodiment of the present invention;
shown in the figure: 10-a main clock; 20-hot standby clock; 30-a power supply; 40-a frequency synthesizer; 50-phase comparator; 60-a controller; 70-switch matrix.
Detailed Description
The method for switching between the main clock and the standby clock of the in-orbit navigation satellite provided by the invention is further described in detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
The core idea of the invention is to provide a method for switching between the main clock and the standby clock of the on-orbit navigation satellite, so as to solve the problem that the frequency drift rate of the main clock and the standby clock cannot be transferred when the conventional navigation satellite system is automatically switched to a hot backup atomic clock.
In order to realize the idea, the invention provides a method for switching between main clocks and standby clocks of an on-orbit navigation satellite, which comprises the following steps: firstly, the in-orbit navigation satellite adopts two atomic clocks to simultaneously work by electrifying, wherein one atomic clock is used as a main clock and is in a main working state, the other atomic clock is used as a hot standby clock and is in a hot standby working state; combining with the satellite-ground bidirectional ranging observation data, calculating by using a satellite-ground bidirectional comparison method to obtain a plurality of main clock error parameters; secondly, acquiring clock error parameters of the hot standby clock relative to the main clock through the engineering telemetering data broadcast by the in-orbit navigation satellite; thirdly, calculating to obtain a plurality of hot standby clock error parameters according to the main clock error parameters and the engineering telemetering data by adopting an on-satellite main-standby atomic clock phase comparison method; in the following state of the main clock and the standby clock, the phase and the frequency of the hot standby clock are equal to those of the main clock and synchronously change along with time, so that seamless switching can be realized; after the in-orbit navigation satellite stably operates, the frequency drift rate of satellite clock error data is a constant, and the hot standby Zhong Zhongcha parameter is injected to the in-orbit navigation satellite for storage and standby; and fifthly, when the on-orbit navigation satellite autonomously monitors that the main clock and the hot standby clock are switched, directly and autonomously calling the stored hot standby Zhong Zhongcha parameter to replace the main clock difference parameter as satellite clock difference data, compensating the switched satellite clock difference data, and correcting the frequency drift rate of the satellite clock difference data.
The clock error model of the on-orbit navigation satellite is delta t = a 0 +a 1 τ+a 2 τ 2 Where Δ t is the clock difference, τ is the time, a 0 Is a phase, a 1 Is a frequency, a 2 Is the frequency drift rate.
At present, in order to ensure the stability and reliability of the operation of a navigation satellite system, a satellite-borne time-frequency processing system of a navigation satellite adopts a redundant backup architecture design, as shown in fig. 1, a power supply 30 supplies power to the whole system, two atomic clocks are used for powering up and working at the same time, one atomic clock is in a main working state (a main clock/a main atomic clock 10) and the other atomic clock is in a hot backup working state (a hot backup clock/a hot backup atomic clock 20), the main clock and the standby clock are in a tracking enabling state, the phase and the frequency of the hot backup clock 20 and the main clock 10 keep following states (realized by a frequency synthesizer 40 and a controller 60, a phase comparator 50 is used for monitoring clock difference data between the main clock and the standby clock, the hot backup clock 20 is controlled to follow the main clock 10 jointly by the frequency synthesizer 40 and the controller 60 according to the clock difference data, the phase and the frequency parameters of the main clock and the standby clock are kept the same), and the output frequency of the system, namely the phase a of the standby clock, is realized by a switch matrix 70 0 prepare And frequency a 1 prepare Phase a of the main clock 0 main And frequency a 1 main Remain equal, but with a clock frequency drift rate a 2 prepare Frequency drift rate a of main clock 2 main Not equal. Therefore, when the main clock is abnormal or fails and the operation is automatically switched to the standby clock, only the phase a of the main clock and the standby clock can be realized 0 And frequency a 1 Cannot realize the frequency drift rate a of the main and standby clocks 2 Is transmitted. Due to the provision of the clockFrequency drift rate a 2 prepare Frequency drift rate a of main clock 2 main Unequal, frequency drift rate a after switching from master to slave 2 The jump occurs and the optimal transfer of the satellite clock performance cannot be achieved, as shown in figure 2 (at τ) 0 The clock is switched from the main clock to the standby clock), when the ground can not timely annotate new clock difference parameters, the clock difference parameter a used by the satellite 2 main And the actual clock difference parameter a after switching the standby clock 2 prepare The serious mismatch is that the long-term clock error prediction error increases squared with integration time.
To realize phase a when switching between on-track and off-track clocks 0 Frequency a 1 And a frequency drift rate a 2 After the navigation satellite atomic clock stably runs, the clock error parameter (a) of the standby clock relative to the main clock is obtained through the engineering telemetering data 'the phase difference between the standby clock and the main clock' broadcast under the in-orbit navigation satellite 0 prepare -a 0 main )、(a 1 prepare -a 1 main ) And (a) 2 prepare -a 2 main ). The main clock error parameter a can be calculated by combining L-band satellite-ground bidirectional distance measurement observation data and utilizing a satellite-ground bidirectional comparison method 0 main 、a 1 main And a 2 main Then, the phase difference parameter a of the spare clock can be calculated by adopting the on-satellite main/spare atomic clock phase comparison method 0 prepare 、a 1 preparing 、a 2 prepare . The phase a of the standby clock is in the following state 0 prepare And frequency a 1 prepare Phase a of the main clock 0 main And frequency a 1 main Keeping equal and synchronously changing along with time, seamless switching can be realized, and the frequency drift rate of the satellite atomic clock is basically a constant after stable operation, so that only the calculated Zhong Zhongcha parameter a is used 2 prepare And the data is injected to the satellite for storage and standby. When the satellite autonomously monitors the switching of the main clock and the standby clock, the stored parameter Zhong Zhongcha a is directly and autonomously called 2 prepare Replacing the clock error parameter a of the original main clock 2 main And compensating the switched satellite clock error data, correcting the frequency drift rate, and realizing the optimal performance transfer when the main and standby clocks of the satellite are switched.
< example one >
This embodiment provides a method for switching between master and slave clocks of an in-orbit navigation satellite, as shown in fig. 3The method for switching the main clock and the standby clock of the on-orbit navigation satellite comprises the following steps: firstly, the on-orbit navigation satellite adopts two atomic clocks to simultaneously power up for work, wherein one atomic clock is used as a main clock 10, the main clock 10 is in a main working state, the other atomic clock is used as a hot standby clock 20, and the hot standby clock 20 is in a hot standby working state; combining with the satellite-ground bidirectional distance measurement observation data, calculating by using a satellite-ground bidirectional comparison method to obtain a plurality of main clock error parameters a 0 main 、a 1 main And a 2 main (ii) a Secondly, acquiring clock error parameters (a) of the hot standby clock relative to the main clock through the engineering telemetering data broadcast by the in-orbit navigation satellite 0 prepare -a 0 main )、(a 1 prepare -a 1 main ) And (a) 2 prepare -a 2 main ) (ii) a Thirdly, calculating and obtaining a plurality of hot standby clock error parameters a according to the main clock error parameters and the engineering telemetering data by adopting an on-satellite main/standby atomic clock phase comparison method 0 prepare 、a 1 prepare And a 2 prepare (ii) a Fourthly, in the following state of the main clock and the standby clock, the phase and the frequency a of the hot standby clock 0 prepare And a 1 prepare Phase and frequency a of said main clock 0 main And a 1 main Keeping equal and changing synchronously with time, seamless switching can be realized; after the on-orbit navigation satellite stably operates, the frequency drift rate of the satellite clock error data is constant, and the hot standby Zhong Zhongcha parameter a is used 2 prepare The upper note is stored to the on-orbit navigation satellite for standby; step five, when the on-orbit navigation satellite autonomously monitors that the main clock and the hot standby clock are switched, the stored hot standby Zhong Zhongcha parameter a is directly and autonomously called 2 prepare Replacing said master clock difference parameter a 2 main And as satellite clock error data, compensating the switched satellite clock error data, and correcting the frequency drift rate of the satellite clock error data.
Specifically, in the method for switching between the main clock and the standby clock of the in-orbit navigation satellite, the downlink signal used for the satellite-to-ground two-way ranging is a satellite signal output after frequency reduction processing by a tuner, and the frequency of the satellite signal is 950MHZ to 2150MHZ. In the method for switching between the main clock and the standby clock of the in-orbit navigation satellite, combining the satellite-ground bidirectional ranging observation data, and obtaining a plurality of main clock difference parameters by utilizing a satellite-ground bidirectional comparison method comprises the following steps: the method comprises the steps that a ground operation and control system with a ground reference atomic clock as a reference transmits an uplink signal, an uplink ranging link is established with a satellite, the satellite uses a main clock of the satellite-borne atomic clock as a reference, meanwhile, the satellite transmits a downlink signal, a downlink ranging link is established with the ground operation and control system, the satellite measures uplink pseudo range values between satellites and the ground, and the ground operation and control system measures downlink pseudo range values between the satellites and the ground; and the uplink pseudo range value is transmitted back to the ground operation and control system through telemetry, and the ground operation and control system calculates the clock error of the main clock relative to the ground reference atomic clock in the sampling period according to the downlink pseudo range value and the uplink pseudo range value.
Further, in the method for switching between the main clock and the standby clock of the in-orbit navigation satellite, combining the satellite-ground bidirectional ranging observation data, and obtaining a plurality of main clock error parameters by using a satellite-ground bidirectional comparison method, the method further comprises the following steps: the uplink pseudo range value between the satellite and the earth measured by the satellite is the sum of the microwave propagation delay between the satellite and the earth and the clock difference of the main clock relative to the ground reference atomic clock; the ground operation and control system measures a downlink pseudo range value between the satellite and the ground as the difference between the microwave propagation time delay between the satellite and the ground and the clock difference of the main clock relative to the ground reference atomic clock; and for the uplink pseudo range value measured in the same sampling period, the satellite-ground microwave propagation delay contained in the uplink pseudo range value is equal to the satellite-ground microwave propagation delay contained in the downlink pseudo range value.
In addition, in the method for switching between the master clock and the slave clock of the in-orbit navigation satellite, acquiring clock error parameters of the hot slave clock relative to the master clock through engineering telemetry data broadcast by the in-orbit navigation satellite comprises the following steps: and the satellite time-frequency processing system measures and records the clock difference of the hot standby clock relative to the main clock in real time. In the method for switching the main clock and the standby clock of the in-orbit navigation satellite, the clock difference of the hot standby clock relative to the main clock, which is measured and recorded in real time by the satellite time-frequency processing system, is the difference between the phase of an output signal of the hot standby clock and the phase of an output signal of the main clock; and measuring the phase difference between the output signal of the hot standby clock and the output signal of the main clock by using a phase discriminator of a satellite-borne time-frequency processing system, wherein the phase difference is the clock difference of the hot standby clock relative to the main clock.
Specifically, in the method for switching between the main clock and the standby clock of the in-orbit navigation satellite, the calculating to obtain a plurality of hot standby clock error parameters according to the main clock error parameters and the engineering telemetering data by adopting an on-satellite main and standby atomic clock ratio method comprises the following steps: and the clock difference of the standby clock relative to the main clock is transmitted back to the ground operation and control system through remote measurement, and the ground operation and control system obtains the clock difference of the standby clock relative to the ground reference atomic clock according to the clock difference of the main clock relative to the ground reference atomic clock and the clock difference of the standby clock relative to the main clock. In the method for switching the primary and standby clocks of the in-orbit navigation satellite, the uplink pseudo range value and the clock difference of the hot standby clock relative to the primary clock are both downloaded to the ground in real time through a satellite-ground measurement and control channel and are collected to the ground operation and control system, and data processing is carried out to obtain the clock difference of the primary clock relative to the ground reference atomic clock and the clock difference of the hot standby clock relative to the ground reference atomic clock.
According to the method for switching the main clock and the standby clock of the on-orbit navigation satellite, a plurality of hot standby clock difference parameters are obtained through calculation according to the main clock difference parameters and engineering telemetering data, the hot standby Zhong Zhongcha parameters are injected to the on-orbit navigation satellite for storage and standby, when the on-orbit navigation satellite autonomously monitors that the main clock and the hot standby clock are switched, the stored hot standby Zhong Zhongcha parameters are directly and autonomously called to replace the main clock difference parameters to serve as satellite clock difference data, the switched satellite clock difference data are compensated, the frequency drift rate of the satellite clock difference data is corrected, and optimal performance transfer during switching the main clock and the standby clock of the satellite is achieved. Therefore, the invention provides a transfer technology for the optimal performance of the switching between the main clock and the standby clock of the on-orbit navigation satellite, which can realize the optimal transfer of the phase, the frequency and the frequency drift rate when the main clock and the standby clock of the on-orbit are switched, improve the long-term clock error prediction precision by one order of magnitude and improve the autonomous navigation operation capability of the navigation satellite.
In summary, the above embodiments describe in detail different configurations of the method for switching between the main and standby clocks of the in-orbit navigation satellite, and of course, the present invention includes but is not limited to the configurations listed in the above embodiments, and any content that is changed based on the configurations provided by the above embodiments belongs to the protection scope of the present invention. One skilled in the art can take the contents of the above embodiments to take a counter-measure.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.