Atomic Clock-Based Time-Frequency Consistency Control Method and System for Formed Satellites

Abstract

The present invention provides a time-frequency consistency control method and system for formation satellites based on atomic clocks, including: arranging a set of atomic clocks, navigation receivers, navigation antennas, and inter-satellite communication devices on two satellites respectively; the atomic clocks are used to provide clock sources, the navigation receivers receive navigation signals through the navigation antennas and perform acquisition and resolution, and the original measurement information including pseudorange and carrier phase demodulated is subjected to dual-satellite information interaction through the inter-satellite communication devices, and the received original measurement information of the other satellite is time-aligned with the original measurement information of the local satellite and then differential processing is performed to obtain relative measurement information; measuring the time difference between the formation satellites to perform time consistency control of the formation satellites; measuring the frequency difference between the formation satellites to perform frequency consistency control of the formation satellites. The present invention solves the problem of obtaining the time difference between two satellites through a navigation common-view satellite observation value resolution method, and realizes real-time measurement of the time reference deviation of on-orbit formation satellites.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace vehicles, and in particular, to a time-frequency consistency control method and system for formation satellites based on atomic clocks. Background Art

[0002] For dual-star formation SAR satellite interferometric imaging, it is required that the imaging data has high coherence. To achieve high coherence of the data, it is required that the time and frequency between satellites are synchronized, that is, the time and frequency are highly consistent, and the two satellites work in coordination.

[0003] In order to meet the time and frequency consistency requirements of dual-star formation, research and design on time-frequency consistency control systems and control methods have been carried out for dual-star formation satellites.

[0004] Patent document CN104298860A discloses a method for calculating the code and carrier phase deviation of a GEO satellite retransmitted signal. First, carrier large loop code pseudorange and carrier phase pseudorange equations are established, and then ionospheric parameters are solved using the observation results of dual-frequency code and carrier phase. The offsets of the code and carrier phase on C1 and C2 carriers are calculated respectively, and finally the real-time control quantities of the code and carrier phase on C1 and C2 carriers are obtained through filtering.

[0005] There are many time-frequency design schemes available for reference at home and abroad. However, the existing time-frequency consistency control schemes are only applicable to ground communication terminals and not to on-orbit satellites, or can only achieve the time-frequency consistency control of a single satellite with the navigation system time-frequency, or can only manually control the time-frequency of multiple satellites on the ground. The above schemes do not meet the current requirements for autonomous time-frequency consistency control of formation satellites. To solve the above problems, it is required that the designed time-frequency consistency control method has the functions of autonomous time-frequency measurement and synchronization for on-orbit formation satellites. Summary of the Invention

[0006] Aiming at the defects in the prior art, the purpose of the present invention is to provide a time-frequency consistency control method and system for formation satellites based on atomic clocks.

[0007] According to the time-frequency consistency control method for formation satellites based on atomic clocks provided by the present invention, it includes:

[0008] Arrange a set of atomic clock, navigation receiver, navigation antenna and inter-satellite communication equipment on each of the two satellites;

[0009] The atomic clock is used to provide a clock source. The navigation receiver receives navigation signals through the navigation antenna and performs acquisition and resolution, and performs dual-star information interaction on the original measurement information including pseudorange and carrier phase through the inter-satellite communication equipment. After aligning the received original measurement information of other satellites with the original measurement information of this satellite in time, differential processing is performed to obtain relative measurement information;

[0010] Measure the time difference of formation satellites and perform time consistency control for formation satellites;

[0011] Measure the frequency difference of formation satellites and perform frequency consistency control for formation satellites.

[0012] Preferably, a rubidium clock is selected as the atomic clock.

[0013] Preferably, the measurement of the time reference deviation between two satellites is obtained by solving based on the observed values of navigation common-view stars, and the expression is:

[0014] R A = ρ A + cδt r,A - cδt s + I A + B A + O A + ε A

[0015] R B = ρ B + cδt r,B - cδt s + I B + B B + O B + ε B

[0016] Among them, R A represents the GNSS pseudorange observation of satellite A; ρ A represents the geometric distance between satellite A and the GNSS satellite; c is the speed of light; δt r,A represents the receiver clock error correction of satellite A; δt s represents the satellite clock error correction; I A represents: the atmospheric delay error of satellite A; B A represents: the residual error after calibration of the receiver hardware delay of satellite A; O A represents: the GNSS satellite orbit error of satellite A; ε A represents: the receiver noise and multipath effect error of satellite A;

[0017] Take the difference between the above two observations, then there is:

[0018] ΔR AB = Δρ AB + c·Δδt r,AB + ΔI AB + ΔB AB + ΔO AB + Δε AB

[0019] Among them, ΔR AB represents the single difference of the GNSS pseudorange observation; Δρ ABRepresents the single difference of the geometric distance between the receiver and the GNSS satellite; Δδt r,AB Represents the single difference of the receiver clock error, that is, the time difference between two GNSS receivers; ΔI AB Represents the single difference of the atmospheric delay error; ΔB AB Represents the single difference of the residual error after calibration of the receiver hardware delay; ΔO AB Represents the single difference of the GNSS satellite orbit error; Δε AB Represents the single difference of the receiver noise and multipath effect error;

[0020] The relative clock difference between two satellite clocks is:

[0021]

[0022] Preferably, the two-satellite time consistency control adopts a one-way time difference compensation alignment control method, and the formation satellite time difference measurement exchanges the respective observed navigation measurement data through the inter-satellite link.

[0023] Preferably, measure the clock drift of the satellite and the navigation system, and convert the clock drift into a frequency difference;

[0024] After remotely measuring and calculating the frequency difference according to the satellite clock drift, adopt a one-way frequency correction compensation control method, and finely adjust the frequency by setting the frequency control word to finally achieve the two-satellite frequency consistency control.

[0025] According to the formation satellite time-frequency consistency control system based on atomic clocks provided by the present invention, it includes:

[0026] Arrange a set of atomic clocks, navigation receivers, navigation antennas and inter-satellite communication equipment on two satellites respectively;

[0027] The atomic clock is used to provide the clock source. The navigation receiver receives the navigation signal through the navigation antenna and performs acquisition and solution, and performs two-satellite information interaction on the original measurement information including pseudorange and carrier phase demodulated through the inter-satellite communication equipment. After aligning the received original measurement information of other satellites with the original measurement information of this satellite in time, perform differential processing to obtain relative measurement information;

[0028] Measure the time difference of the formation satellites and perform formation satellite time consistency control;

[0029] Measure the frequency difference of the formation satellites and perform formation satellite frequency consistency control.

[0030] Preferably, the atomic clock selects a rubidium clock.

[0031] Preferably, the two-satellite time reference deviation measurement is obtained by solving based on the navigation common view star observation value, and the expression is:

[0032] R A =ρA +cδt r,A -cδt s +I A +B A +O A +ε A

[0033] R B = ρ B +cδt r,B -cδt s +I B +B B +O B +ε B

[0034] Wherein, R A represents the pseudo-range observation of satellite A of GNSS; ρ A represents the geometric distance between satellite A and the GNSS satellite; c is the speed of light; δt r,A represents the receiver clock error correction of satellite A; δt s represents the satellite clock error correction; I A represents: the atmospheric delay error of satellite A; B A represents: the residual error after calibration of the receiver hardware delay of satellite A; O A represents: the GNSS satellite orbit error of satellite A; ε A represents: the receiver noise and multipath effect error of satellite A;

[0035] >Taking the difference between the above two observations, we have:

[0036] ΔR AB = Δρ AB +c·Δδt r,AB +ΔI AB +ΔB AB +ΔO AB +Δε AB

[0037] Wherein, ΔR AB represents the single difference of the GNSS pseudo-range observation; Δρ AB represents the single difference of the geometric distance between the receiver and the GNSS satellite; Δδt r,AB represents the single difference of the receiver clock error, that is, the time difference between two GNSS receivers; ΔI AB represents the single difference of the atmospheric delay error; ΔB AB represents the single difference of the residual error after calibration of the receiver hardware delay; ΔO AB represents the single difference of the GNSS satellite orbit error; Δε AB represents the single difference of the receiver noise and multipath effect error;

[0038] The relative clock error between the two satellite clocks is:

[0039]

[0040] Preferably, the dual-satellite time consistency control adopts a one-way time difference compensation alignment control method, and the time difference measurement of the formation satellites exchanges the respective observed navigation measurement data through the inter-satellite link.

[0041] Preferably, measure the clock drift of the measurement satellite and the navigation system, and convert the clock drift into a frequency difference;

[0042] After remotely measuring and calculating the frequency difference according to the satellite clock drift, adopt a one-way frequency correction compensation control method, and finely adjust the frequency by setting the frequency control word to finally achieve the dual-satellite frequency consistency control.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) Divide according to the functions in the entire in-orbit satellite system, and conduct system design on the formation dual-satellite time-frequency consistency control system;

[0045] (2) By using a rubidium clock as the time-frequency atomic clock, the problem of poor stability of the traditional crystal oscillator is solved, and the formation satellites are enabled to have high-precision and high-stability time-frequency characteristics;

[0046] (3) By using the navigation common-view satellite observation value solution method, the problem of obtaining the dual-satellite time difference is solved, and the real-time measurement of the time reference deviation of the in-orbit formation satellites is realized;

[0047] (4) By using the one-way time difference compensation alignment control method based on real-time dual-satellite time difference measurement, the problem of on-orbit time synchronization of dual satellites is solved, and the formation time consistency control is realized;

[0048] (5) By measuring the clock drift of the satellite and the navigation system, and then converting the clock drift into a frequency difference, the acquisition of the frequency difference of the formation dual satellites is realized;

[0049] (6) After remotely measuring and calculating the frequency difference according to the satellite clock drift, adopt a one-way frequency correction compensation control method, and finely adjust the frequency by setting the frequency control word to finally achieve the dual-satellite frequency consistency control;

[0050] (7) Through the inter-satellite communication link, the navigation measurement data observed by each satellite are exchanged in real time and the real-time time difference measurement is carried out based on the real-time observation data. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects and advantages of the present invention will become more apparent:

[0052] Figure 1 It is a schematic diagram of the composition of a time and frequency consistency control system based on double - star formation in the present invention;

[0053] Figure 2 It is a schematic diagram of time difference measurement for double - star formation involved in the present invention;

[0054] Figure 3 It is a schematic diagram of time consistency control for double - star formation involved in the present invention;

[0055] Figure 4 It is a schematic diagram of frequency difference measurement for double - star formation involved in the present invention;

[0056] Figure 5 It is a schematic diagram of frequency consistency control for double - star formation involved in the present invention. Specific embodiments

[0057] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all fall within the protection scope of the present invention.

[0058] Embodiment 1

[0059] As Figure 1 shown, the present invention provides a time - frequency consistency control system for formation satellites based on atomic clocks, including rubidium clocks, navigation receivers, navigation receiving antennas, and inter - satellite communication devices, and each satellite in the formation that requires time - frequency consistency control needs to be equipped with the same above - mentioned devices.

[0060] Specifically, a rubidium clock is selected as the atomic clock, and its high - precision and high - stability characteristics are used as the time - frequency source for the entire satellite.

[0061] The respective navigation observation values of the two stars are mutually transmitted and exchanged through the inter - satellite communication link.

[0062] As Figure 2 shown, for the time difference measurement scheme of the formation double - star system, it is realized by using the common - view GNSS navigation satellites. The specific implementation method is as follows: The navigation receiver on each star receives the navigation signal received by the navigation antenna, and by synchronously observing the same navigation star, the relative clock deviation between the two user clocks is measured to achieve the purpose of high - precision time comparison.

[0063] R A = ρ A + cδt r,A - cδt s + I A + B A + O A + εA

[0064] R B = ρ B + cδt r,B - cδt s + I B + B B + O B + ε B

[0065] Taking the difference between the above two observables, we have:

[0066] ΔR AB = Δρ AB + c·Δδt r,AB + ΔI AB + ΔB AB + ΔO AB + Δε AB

[0067] The meanings of the symbols in the above formula are as follows:

[0068] ΔR AB represents the single difference of the GNSS pseudorange observable; Δρ AB represents the single difference of the geometric distance between the receiver and the GNSS satellite; Δδt r,AB represents the single difference of the receiver clock error, that is, the time difference between two GNSS receivers; ΔI AB represents the single difference of the atmospheric delay error; ΔB AB represents the single difference of the residual error after calibration of the receiver hardware delay; ΔO AB represents the single difference of the GNSS satellite orbit error; Δε AB represents the single difference of the receiver noise and multipath effect error.

[0069] Therefore, the relative clock difference between the two satellite clocks is:

[0070]

[0071] As Figure 3 shown, based on the measured time difference between the two satellites, the satellite with the earlier time can correct the local time according to the relative time difference value to align the time of this satellite with the satellite with the later time, and finally achieve the time consistency control of the two satellites.

[0072] As Figure 4 shown, the navigation receiver on each satellite receives the navigation signal received by the navigation antenna, measures the frequency difference between the local clock of the receiver and the clock of the navigation satellite system, and transmits it downlink in the form of a clock drift parameter through telemetry. After the ground receives the respective clock drift parameters transmitted downlink by the two satellites, the frequency difference between the two satellites is obtained by comparison and calculation.

[0073] As Figure 5As shown, the ground determines one satellite as the frequency reference satellite according to the obtained double - star frequency difference, compensates and calculates the frequency value of the other satellite according to the frequency difference, and uploads the corrected value as the new frequency control word to the satellite to achieve the control of double - star frequency consistency.

[0074] Embodiment 2

[0075] The present invention also provides a time - frequency consistency control system for formation satellites based on atomic clocks. The time - frequency consistency control system for formation satellites based on atomic clocks can be realized by executing the process steps of the time - frequency consistency control method for formation satellites based on atomic clocks. That is, those skilled in the art can understand the time - frequency consistency control method for formation satellites based on atomic clocks as the preferred implementation manner of the time - frequency consistency control system for formation satellites based on atomic clocks.

[0076] According to the time - frequency consistency control system for formation satellites based on atomic clocks provided by the present invention, it includes:

[0077] Arrange a set of atomic clocks, navigation receivers, navigation antennas and inter - satellite communication devices on two satellites respectively;

[0078] The atomic clock is used to provide a clock source. The navigation receiver receives navigation signals through the navigation antenna and performs acquisition and solution. The original measurement information including pseudorange and carrier phase demodulated is used for double - star information interaction through the inter - satellite communication device. After aligning the received original measurement information of the other satellite with the original measurement information of this satellite in time, differential processing is performed to obtain relative measurement information;

[0079] Measure the time difference of formation satellites and perform time consistency control of formation satellites;

[0080] Measure the frequency difference of formation satellites and perform frequency consistency control of formation satellites.

[0081] The atomic clock selects a rubidium clock.

[0082] The measurement of the double - star time - reference deviation is obtained by solving based on the navigation common - view star observation value, and the expression is:

[0083] R A =ρ A +cδt r,A -cδt s +I A +B A +O A +ε A

[0084] R B =ρ B +cδt r,B -cδt s +I B +BB +O B +ε B

[0085] Among them, R A represents the pseudo-range observation of Satellite A of GNSS; ρ A represents the geometric distance between Satellite A and the GNSS satellite; c is the speed of light; δt r,A represents the receiver clock error correction of Satellite A; δt s represents the satellite clock error correction; I A represents: the atmospheric delay error of Satellite A; B A represents: the residual error after calibration of the receiver hardware delay of Satellite A; O A represents: the GNSS satellite orbit error of Satellite A; ε A represents: the receiver noise and multipath effect error of Satellite A;

[0086] Taking the difference between the above two observations, we have:

[0087] ΔR AB =Δρ AB +c·Δδt r,AB +ΔI AB +ΔB AB +ΔO AB +Δε AB

[0088] Among them, ΔR AB represents the single difference of the GNSS pseudo-range observation; Δρ AB represents the single difference of the geometric distance between the receiver and the GNSS satellite; Δδt r,AB represents the single difference of the receiver clock error, that is, the time difference between two GNSS receivers; ΔI AB represents the single difference of the atmospheric delay error; ΔB AB represents the single difference of the residual error after calibration of the receiver hardware delay; ΔO AB represents the single difference of the GNSS satellite orbit error; Δε AB represents the single difference of the receiver noise and multipath effect error;

[0089] The relative clock difference between the two satellite clocks is:

[0090]

[0091] The time consistency control of the two satellites adopts the one-way time difference compensation alignment control method, and the time difference measurement of the formation satellites exchanges the respective observed navigation measurement data through the inter-satellite link.

[0092] Measure the clock drift of the satellite and the navigation system, and convert the clock drift into a frequency difference;

[0093] After remotely measuring and calculating the frequency difference according to the satellite clock drift, a unidirectional frequency correction and compensation control method is adopted. The frequency is finely adjusted by setting the frequency control word, and finally the frequency consistency control of the two satellites is achieved.

[0094] Those skilled in the art know that in addition to implementing the systems, devices, and their respective modules provided by the present invention in the form of pure computer-readable program codes, the method steps can be logically programmed to enable the systems, devices, and their respective modules provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, etc. Therefore, the systems, devices, and their respective modules provided by the present invention can be regarded as a kind of hardware component, and the modules included therein for implementing various programs can also be regarded as the structures within the hardware component; the modules for implementing various functions can also be regarded as either software programs for implementing the methods or the structures within the hardware component.

[0095] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A time-frequency consistency control method for formation satellites based on atomic clocks, characterized in that, including: arranging a set of atomic clock, navigation receiver, navigation antenna and inter-satellite communication equipment on each of the two satellites respectively; the atomic clock is used to provide a clock source, the navigation receiver receives navigation signals through the navigation antenna and performs acquisition and resolution, and exchanges the original measurement information including pseudorange and carrier phase obtained by demodulation through the inter-satellite communication equipment for dual-satellite information interaction. After aligning the received original measurement information of the other satellite with the original measurement information of this satellite in time, differential processing is carried out to obtain relative measurement information; measuring the time difference of the formation satellites and performing time consistency control of the formation satellites; measuring the frequency difference of the formation satellites and performing frequency consistency control of the formation satellites; selecting a rubidium clock as the atomic clock; the measurement of the dual-satellite time reference deviation is obtained by resolving based on the navigation common-view star observation value, and the expression is: Among them, represents the pseudo-range observation of satellite A's GNSS; represents the geometric distance between satellite A and the GNSS satellite; is the speed of light; represents the receiver clock error correction of satellite A; represents the satellite clock error correction; represents the atmospheric delay error of satellite A; represents the residual error after calibration of the receiver hardware delay of satellite A; represents the GNSS satellite orbit error of satellite A; represents the receiver noise and multipath effect error of satellite A; represents the pseudo-range observation of satellite B's GNSS; represents the geometric distance between satellite B and the GNSS satellite; is the speed of light; represents the receiver clock error correction of satellite B; represents the satellite clock error correction; represents the atmospheric delay error of satellite B; represents the residual error after calibration of the receiver hardware delay of satellite B; represents the GNSS satellite orbit error of satellite B; represents the receiver noise and multipath effect error of satellite B; taking the difference between the above two observation quantities, then there is: Among them, represents the single difference of GNSS pseudorange observations; represents the single difference of the geometric distance between the receiver and the GNSS satellite; represents the single difference of the receiver clock error, that is, the time difference between two GNSS receivers; represents the single difference of the atmospheric delay error; represents the single difference of the residual error after calibration of the receiver hardware delay; represents the single difference of the GNSS satellite orbit error; represents the single difference of the receiver noise and multipath effect error; the relative clock difference between the two satellite clocks is: 。 2. The time-frequency consistency control method for formation satellites based on atomic clocks according to claim 1, wherein, the dual-satellite time consistency control adopts a one-way time difference compensation alignment control method, and the time difference measurement of the formation satellites exchanges the respective observed navigation measurement data through the inter-satellite link.

3. The time-frequency consistency control method for formation satellites based on atomic clocks according to claim 1, characterized in that, measuring the clock drift of the satellite and the navigation system, and converting the clock drift into a frequency difference; after remotely measuring and calculating the frequency difference according to the satellite clock drift, adopting a one-way frequency correction compensation control method, and finely adjusting the frequency by setting a frequency control word, finally realizing the dual-satellite frequency consistency control.

4. A time-frequency consistency control system for formation satellites based on atomic clocks, characterized in that, including: arranging a set of atomic clock, navigation receiver, navigation antenna and inter-satellite communication equipment on each of the two satellites respectively; the atomic clock is used to provide a clock source, the navigation receiver receives navigation signals through the navigation antenna and performs acquisition and resolution, and exchanges the original measurement information including pseudorange and carrier phase obtained by demodulation through the inter-satellite communication equipment for dual-satellite information interaction. After aligning the received original measurement information of the other satellite with the original measurement information of this satellite in time, differential processing is carried out to obtain relative measurement information; measuring the time difference of the formation satellites and performing time consistency control of the formation satellites; measuring the frequency difference of the formation satellites and performing frequency consistency control of the formation satellites; selecting a rubidium clock as the atomic clock; the measurement of the dual-satellite time reference deviation is obtained by resolving based on the navigation common-view star observation value, and the expression is: Among them, represents the GNSS pseudorange observation of satellite A; represents the geometric distance between satellite A and the GNSS satellite; is the speed of light; represents the receiver clock error correction of satellite A; represents the satellite clock error correction; represents the atmospheric delay error of satellite A; represents the residual error after calibration of the receiver hardware delay of satellite A; represents the GNSS satellite orbit error of satellite A; represents the receiver noise and multipath effect error of satellite A; represents the GNSS pseudorange observation of satellite B; represents the geometric distance between satellite B and the GNSS satellite; is the speed of light; represents the receiver clock error correction of satellite B; represents the satellite clock error correction; represents the atmospheric delay error of satellite B; represents the residual error after calibration of the receiver hardware delay of satellite B; represents the GNSS satellite orbit error of satellite B; represents the receiver noise and multipath effect error of satellite B; taking the difference between the above two observation quantities, then there is: Among them, represents the single difference of GNSS pseudorange observables; represents the single difference of the geometric distance between the receiver and the GNSS satellite; represents the single difference of the receiver clock error, that is, the time difference between two GNSS receivers; represents the single difference of the atmospheric delay error; represents the single difference of the residual error after calibration of the receiver hardware delay; represents the single difference of the GNSS satellite orbit error; represents the single difference of the receiver noise and multipath effect error; the relative clock difference between the two satellite clocks is: 。 5. The time-frequency consistency control system for formation satellites based on atomic clocks according to claim 4, characterized in that the dual-satellite time consistency control adopts a one-way time difference compensation alignment control method, and the time difference measurement of the formation satellites exchanges the respective observed navigation measurement data through the inter-satellite link.

6. The time-frequency consistency control system for formation satellites based on atomic clocks according to claim 4, characterized in that measuring the clock drift of the satellite and the navigation system, and converting the clock drift into a frequency difference; after remotely measuring and calculating the frequency difference according to the satellite clock drift, adopting a one-way frequency correction compensation control method, and finely adjusting the frequency by setting a frequency control word, finally realizing the dual-satellite frequency consistency control.

Images