CN115664489A - Inter-satellite time synchronization method, system, electronic equipment and computer storage medium - Google Patents
Inter-satellite time synchronization method, system, electronic equipment and computer storage medium Download PDFInfo
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Abstract
The invention relates to an inter-satellite time synchronization method, an inter-satellite time synchronization system, electronic equipment and a computer storage medium, which relate to the technical field of time synchronization, and the method comprises the following steps: acquiring original pseudo-range data of a satellite-borne receiver; determining a set inter-satellite clock error by using a satellite common view method according to the original pseudo range data; determining the geometric distance of the two stars by a bidirectional one-way method according to the signal sending time and the signal receiving time; determining clock error between the two stars according to the geometric distance of the two stars by utilizing a bidirectional carrier phase time comparison principle; determining a system difference by utilizing a least square method according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference; filtering according to the clock error between the double stars and the system error to determine double-star carrier phase clock error data; and the double-star carrier phase clock difference data is used for time synchronization between the planet. The invention can give consideration to both algorithm difficulty and time synchronization precision.
Description
Technical Field
The present invention relates to the field of time synchronization technologies, and in particular, to a method, a system, an electronic device, and a computer storage medium for inter-satellite time synchronization.
Background
The K-band microwave precise ranging system (KBR) is adopted by the precision ranging system for measuring the satellite-to-satellite distance of the Chinese gravitational field satellite and the distance change rate, the precision of the measurement of the satellite-to-satellite distance is superior to 10 microns, the precision of the measurement of the distance change rate can reach 1 micron/second, the change of the satellite distance caused by the anomaly of the gravitational field on the earth surface can be sufficiently measured, and the KBR is the most core payload and represents the highest level of the current international inter-satellite microwave ranging; in addition, the gravity satellite is also provided with a dual-frequency GNSS receiver for determining the satellite orbit and providing time synchronization service, and the orbit precision is better than 5 cm/direction.
Compared with a pseudo code ranging method, the KBR carrier phase ranging method has high ranging accuracy, but has certain defects. The carrier phase ranging method can obtain a high-precision ranging value without depending on pseudo code ranging, and can perform ranging by transmitting only a microwave ranging signal without transmitting a pseudo code ranging signal. When the measured distance is much larger than the wavelength of the transmitted carrier, carrier phase integer ambiguity problems arise because the carrier is a sine wave without any sign. In addition, when the carrier phase measurement is used, the carrier phase needs to be tracked and synchronized for a long time, so that if the satellite equipment fails, the carrier phase measurement is interrupted and cannot be continued.
Theoretically, the ranging precision of the KBR is required to reach the micron level, and the measurement time scale synchronization precision of two gravity satellites is required to reach the 200ps level. The GNSS receiver carried by the gravity satellite can obtain pseudo-range measurement information, and the time synchronization precision of the GNSS satellite common-view method can only reach nanosecond level. In order to obtain high-precision time synchronization precision, carrier phase information of the KBR is required, but when high-precision time difference calculation is carried out by utilizing the KBR carrier phase, cycle slip detection and ambiguity calculation must be carried out, the difficulty of the algorithm is increased suddenly, and the precision is low because the GNSS satellite is used for carrying out time synchronization in a common view mode, and a high-precision time synchronization result cannot be obtained.
Disclosure of Invention
The invention aims to provide an inter-satellite time synchronization method, an inter-satellite time synchronization system, electronic equipment and a computer storage medium, which can give consideration to both algorithm difficulty and time synchronization precision.
In order to achieve the purpose, the invention provides the following scheme:
an inter-satellite time synchronization method, comprising:
acquiring original pseudo range data of a satellite-borne receiver;
determining and setting inter-satellite clock error by using a satellite common-view method according to the original pseudo-range data;
determining the geometric distance of the two stars by a bidirectional one-way method according to the signal sending time and the signal receiving time; the geometric distance of the double stars is the distance with errors between the double stars; the signal transmission time comprises a signal transmission time from a first gravity satellite and a signal transmission time from a second gravity satellite; the signal receiving time comprises the receiving time when the signal reaches the first gravity satellite and the receiving time when the signal reaches the second gravity satellite;
determining clock difference between the two stars according to the geometric distance of the two stars by utilizing a bidirectional carrier phase time comparison principle;
determining a system difference by using a least square method according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference;
filtering according to the clock difference between the double stars and the system difference to determine double-star carrier phase clock difference data; and the double-satellite carrier phase clock difference data is used for time synchronization between the satellites.
Optionally, the determining, by using a satellite common view method according to the original pseudorange data, a set inter-satellite clock bias specifically includes:
performing pseudo-range gross error elimination and error elimination on the original pseudo-range data to obtain the pseudo-range data after elimination;
acquiring the time difference between the time of two gravity satellites and the clock of the GNSS satellite in the pseudo-range data after the elimination;
and differencing the time differences at the same time point to obtain the set inter-satellite clock difference.
Optionally, the determining a geometric distance between two satellites by using a bidirectional one-way method according to the signal sending time and the signal receiving time specifically includes:
determining a one-way measurement distance from a first gravity satellite to a second gravity satellite according to a receiving time when the signal reaches the second gravity satellite and a transmitting time when the signal starts from the first gravity satellite;
determining a one-way measurement distance from the second gravity satellite to the first gravity satellite according to a receiving time of the signal to the first gravity satellite and a transmitting time of the signal from the second gravity satellite;
determining a two-star geometric distance from the one-way measured distance from the first gravity satellite to the second gravity satellite and the one-way measured distance from the second gravity satellite to the first gravity satellite.
Optionally, the determining a clock offset between two stars according to the geometric distance between two stars and using a bidirectional carrier phase time comparison principle specifically includes:
respectively determining the geometric distance time delay from the first gravity satellite to the second gravity position and the geometric distance time delay from the second gravity satellite to the first gravity satellite according to the double-satellite geometric distance;
determining a space propagation delay according to the geometric distance delay from the first gravity satellite to the second gravity position and the geometric distance delay from the second gravity satellite to the first gravity satellite;
and calculating the clock difference between the two satellites according to the space propagation delay.
Optionally, the determining a system difference according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference by using a least square method specifically includes:
performing Lagrange interpolation according to the set inter-satellite clock difference and the double-inter-satellite clock difference to obtain a carrier phase clock difference result;
carrying out forward and backward epoch difference according to the carrier phase clock difference result to obtain a difference result;
determining cycle slip according to the difference result and a set threshold value;
and determining a system difference by utilizing minimum second multiplication according to the time scale segment of the cycle slip, the set inter-satellite clock difference and the double-satellite inter-satellite clock difference.
Optionally, the filtering according to the clock difference between the two satellites and the system difference to determine the clock difference data of the two-satellite carrier phases specifically includes:
subtracting the system difference from the clock difference between the double stars to obtain a double-star coherent clock difference;
and performing Kalman filtering or von-randak filtering on the double-satellite coherent clock error to obtain double-satellite carrier phase clock error data.
The invention also provides an inter-satellite time synchronization system, comprising:
the acquisition module is used for acquiring original pseudo-range data of the satellite-borne receiver;
the set inter-satellite clock difference determining module is used for determining the set inter-satellite clock difference by using a satellite common-view method according to the original pseudo-range data;
the double-star geometric distance determining module is used for determining the double-star geometric distance by utilizing a bidirectional one-way method according to the signal sending time and the signal receiving time; the geometric distance of the double stars is the distance with errors between the double stars; the signal transmission time comprises a transmission time when a signal starts from a first gravity satellite and a transmission time when the signal starts from a second gravity satellite; the signal receiving time comprises the receiving time when the signal reaches the first gravity satellite and the receiving time when the signal reaches the second gravity satellite;
the bidirectional carrier phase time comparison module is used for determining clock error between the two satellites according to the geometric distance of the two satellites by utilizing a bidirectional carrier phase time comparison principle;
the least square module is used for determining a system difference by utilizing minimum multiplication according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference;
the filtering module is used for carrying out filtering according to the clock difference between the double satellites and the system difference to determine double satellite carrier phase clock difference data; and the double-satellite carrier phase clock difference data is used for time synchronization between the satellites.
Optionally, the setting inter-satellite clock difference determining module specifically includes:
the error elimination unit is used for carrying out pseudo-range gross error elimination and error elimination on the original pseudo-range data to obtain the eliminated pseudo-range data;
the acquisition unit is used for acquiring the time difference between the time of two gravity satellites and the clock of the GNSS satellite in the pseudo-range data after the elimination;
and the difference making unit is used for making a difference between the time differences at the same time point to obtain a set inter-satellite clock difference.
The present invention also provides an electronic device comprising:
one or more processors;
a storage device having one or more programs stored thereon;
the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method as in any above.
The invention also provides a computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements a method as set forth in any one of the above.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
determining and setting inter-satellite clock error by using a satellite common-view method according to the original pseudo-range data; determining the geometric distance of the two stars by a bidirectional one-way method according to the signal sending time and the signal receiving time; the geometric distance of the double stars is a distance with errors between the double stars; the signal transmission time comprises a transmission time when a signal starts from a first gravity satellite and a transmission time when the signal starts from a second gravity satellite; the signal receiving time comprises the receiving time when the signal reaches the first gravity satellite and the receiving time when the signal reaches the second gravity satellite; determining clock error between the two satellites by utilizing a bidirectional carrier phase time comparison principle according to the geometric distance between the two satellites; determining a system difference by using a least square method according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference; filtering according to the clock difference between the double satellites and the system difference to determine double satellite carrier phase clock difference data; and the double-satellite carrier phase clock difference data is used for time synchronization between the satellites. The invention utilizes the satellite common-view method and the bidirectional carrier phase time comparison principle, not only can realize high-precision inter-satellite time synchronization, but also can avoid resolving cycle slip and integer ambiguity of the carrier phase, and achieves double-satellite real-time synchronization with simple algorithm and high precision.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a satellite-borne microwave distance measuring system of a Chinese gravity satellite;
FIG. 2 is a schematic diagram of satellite common view time comparison;
FIG. 3 is a schematic diagram of an inter-satellite time synchronization method according to the present invention;
FIG. 4 is a processing flow chart of a satellite common view method for acquiring double-satellite time difference data;
FIG. 5 is a flow chart of a process for acquiring two-satellite time difference data by an inter-satellite bidirectional carrier phase time synchronization method;
FIG. 6 is a schematic diagram of the time difference of the AB stars obtained by the satellite co-view calculation;
FIG. 7 is a schematic diagram of the time difference of AB stars calculated by KBR carrier phase inter-satellite bidirectional method;
FIG. 8 is a schematic diagram of the time difference (system difference exists) of the AB star calculated by the satellite common view method and the KBR carrier phase inter-satellite bidirectional method;
fig. 9 is a schematic diagram of the time difference (system difference removed) of the AB satellite calculated by the satellite common view method and the KBR carrier phase inter-satellite bidirectional method;
FIG. 10 is a time difference residual error result graph of AB stars obtained by KBR carrier phase inter-satellite bidirectional method;
fig. 11 is a flowchart of the inter-satellite time synchronization method provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide an inter-satellite time synchronization method, an inter-satellite time synchronization system, electronic equipment and a computer storage medium, which can take account of both algorithm difficulty and time synchronization precision.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 3 and fig. 11, the inter-satellite time synchronization method provided in the present invention includes:
step 101: and acquiring raw pseudo range data of the satellite-borne receiver.
Step 102: and determining the set inter-satellite clock error by using a satellite common-view method according to the original pseudo-range data.
performing pseudo-range gross error elimination and error elimination on the original pseudo-range data to obtain the pseudo-range data after elimination; acquiring the time difference between the time of two gravity satellites and the clock of the GNSS satellite in the pseudo-range data after the elimination; and differencing the time differences at the same time point to obtain the set inter-satellite clock difference.
As shown in fig. 4 and fig. 2, the specific steps of calculating the time difference between two gravity satellites by the satellite common view method include:
1.1: pseudo range data of two satellites and navigation messages are collected through a satellite-borne GNSS receiver installed on a gravity satellite.
1.2: and reading raw pseudo range data acquired by the two satellite-borne receivers.
1.3: and removing pseudorange gross error by adopting a 3-time sigma principle.
1.4: and calculating the position of the GNSS navigation satellite by adopting the broadcast ephemeris.
1.5: and eliminating ionosphere errors by adopting ionosphere elimination combination.
1.6: eliminating relativistic effect and earth rotation error.
1.7: and obtaining the time difference between the time of the two gravity satellites and the clock of the GNSS satellite.
1.8: finding out the same time point to make difference, obtaining clock difference data of two stars based on pseudo range, namely setting clock difference between stars.
The satellite common view principle is that a satellite common view receiver is mounted on two gravity satellites, and if the same navigation satellite I is observed at the same time, the time difference between a navigation satellite clock and a gravity satellite A clock and the time difference between the navigation satellite clock and a gravity satellite B clock can be obtained. The first gravity satellite of the invention is a gravity satellite A, and the second gravity satellite is a gravity satellite B.
Δt AI ＝(t I -t A )
Δt BI ＝(t I -t B )
The two equations are differenced to obtain the time difference between the satellite clock of the gravity satellite a and the satellite clock of the gravity satellite B as shown in fig. 6,
Δt AI -Δt BI ＝t B -t A
in the above formula: Δ t AI For the time difference, Δ t, between the navigation satellite I and the gravity satellite A BI Time difference, t, between navigation satellite I and gravity satellite B I Is satellite clock time, t A The satellite clock time, t, of gravity satellite A B The satellite clock time of gravity satellite B.
Step 103: determining the geometric distance of the two satellites by a bidirectional one-way method according to the signal sending time and the signal receiving time; the geometric distance of the double stars is the distance with errors between the double stars; the signal transmission time comprises a transmission time when a signal starts from a first gravity satellite and a transmission time when the signal starts from a second gravity satellite; the signal receiving time comprises a receiving time when the signal reaches the first gravity satellite and a receiving time when the signal reaches the second gravity satellite.
determining a one-way measurement distance from a first gravity satellite to a second gravity satellite according to a receiving time when the signal reaches the second gravity satellite and a transmitting time when the signal starts from the first gravity satellite; determining a one-way measurement distance from a second gravity satellite to the first gravity satellite according to a receiving time when the signal reaches the first gravity satellite and a transmitting time when the signal starts from the second gravity satellite; determining a two-star geometric distance from the one-way measured distance from the first gravity satellite to the second gravity satellite and the one-way measured distance from the second gravity satellite to the first gravity satellite.
Obtaining the distance with errors between two stars by a bidirectional one-way method, which comprises the following steps:
2.1: the one-way measured distance from satellite a to satellite B is:
in the formula, t r Indicating the time of reception of the signal arriving at satellite B,
indicating a distance deviation caused by a clock deviation; t is t t Indicating that the signal begins at the transmission time of satellite a,
which represents the distance deviation due to the clock deviation, and R represents the measured distance between two satellites without clock deviation. And the measured distance between two satellites without clock deviation is the actual geometric distance of the double stars.
2.2: the one-way measured distance from satellite B to satellite a is:
in the formula, t r Indicating the reception time of the signal arriving at satellite a,
indicating a distance deviation caused by a clock deviation; t is t t Indicating that the signal starts at the transmission time of satellite B,
which represents the distance deviation due to clock deviation, and R represents the measured distance between two satellites without clock deviation.
2.3: the one-way distance of two satellites is combined to obtain a two-way one-way distance which is as follows:
the slow drift deviation of the clock (clock deviation which can be approximately regarded as constant in the propagation time) can be counteracted in the measuring distance of 'two-way one-way', and the influence of the medium-long term instability of the crystal oscillator on the distance measurement precision is reduced.
2.4: because the carrier phase is used for ranging, the measured pseudorange distance is the product of the carrier phase cycle and the carrier wavelength, and the geometric distance of the double satellites, namely the actual geometric distance of the double satellites, is as follows:
wherein σ Acircle Is the phase cycle number, sigma, of the A-satellite carrier Bcircle Is the phase cycle number of the B satellite carrier, lambda wavelength Is the carrier phase wavelength.
The KBR two-way one-way distance measurement principle is as follows:
as shown in fig. 1, the chinese gravity satellite drives and generates a K/Ka band microwave signal, i.e., a local reference oscillator signal of each satellite, with a satellite-borne ultra stable crystal oscillator (USO) as a reference. Meanwhile, each satellite transmits and receives K/Ka wave band signals to a remote satellite through a microwave antenna, and an inter-satellite microwave measurement link is established. Each satellite converts the received K/Ka microwave signal into an electronic signal, then heterodyne interference is carried out on the electronic signal and a local reference oscillator signal to generate a differential signal, original data with the sampling rate of 10Hz is extracted and output through a processing unit, and a sampling clock signal is generated by a local USO.
The USO has frequency instability, and key frequency instability noise of the K/Ka microwave is caused by a frequency doubling process. Microwave phase signal for recording time t
Wherein
Is the nominal phase, delta phi i And (t) is phase noise caused by carrier frequency instability of K/Ka, the index i = A, and B marks A and B stars of the Chinese gravity satellite. At the same time, USO instability will introduce non-uniformity to the sampling time of the data. At a nominal time t, the clock label of the ith satellite is recorded as t i ＝t+Δt i ， Δt i Is the deviation of the time stamp from the nominal time. At time t, the microwave phase signal received by the i satellite from the j satellite can be recorded as:
in the formula
Represents the jth satellite
The microwave signal is sent out at any time,
representing the time of flight (TOF) of the microwave from the j satellite to the i satellite,
representing the phase deviation of the microwave signal as it passes through the ionosphere,
including instrumental, multipath microwave reflections and neutral atmospheric drift,
representing system noise, including electronic noise, etc.
The i star local reference phase signal and the received microwave phase signal from the j star obtain a differential phase measurement signal of the i star through beat frequency
The unit of formula (3) is cycle, wherein
Is an integer period ambiguity. Carrier instability phase noise delta phi i And (t) dividing the noise into long-time correlated noise and high-frequency random noise. Since the phase noise generated by the local USO of each satellite is transferred to the two-satellite KBR differential phase data, combining the two-satellite KBR differential phase data at the same time after the time tag is accurately calibrated suppresses phase errors associated with times greater than the microwave propagation time. Thus, the two-way one-way phase measurement value Θ (t) obtained by combining the two-star KBR differential phase measurement value data is
Wherein the reference phase and the phase noise can be linearly expanded as follows
The two-way one-way phase measurement value of the double star of the gravity satellite in China at the nominal time t can be obtained by the following formula (4):
the first term in the above equation is the nominal measurement phase, the second term represents the carrier frequency instability phase noise, and the third term is from the phase measurement noise caused by the time tag error, and the error after the time calibration through the GNSS network is much smaller than the contribution of the second term, which can be ignored. The fourth term is the coupling term of frequency noise and time tag error, and can be ignored. Meanwhile, for Chinese gravity satellite
And
the difference is only about 0.05 mus, much less than the microwave time of flight tau 1ms, thus making
The first term of the equation can be approximated as
Wherein Δ Θ TOF (t) for time-of-flight correction, converting the formula into a bidirectional one-way microwave with an off-star spacing:
wherein the first term represents the instantaneous satellite spacing at time t, the second term represents the time-of-flight correction, and the third term represents the satellite spacing noise caused by the residual high-frequency carrier frequency noise, and the period of the satellite spacing noise is less than the time-of-flight tau. Recording K/Ka frequency band bidirectional one-way microwave with offset star spacing of R K /R Ka 。
Step 104: and determining clock error between the two stars according to the geometric distance of the two stars by utilizing a bidirectional carrier phase time comparison principle.
respectively determining the geometric distance time delay from the first gravity satellite to the second gravity position and the geometric distance time delay from the second gravity satellite to the first gravity satellite according to the double-satellite geometric distance; determining a space propagation delay according to the geometric distance delay from the first gravity satellite to the second gravity position and the geometric distance delay from the second gravity satellite to the first gravity satellite; and calculating the clock error between the two stars according to the space propagation delay.
As shown in fig. 5, the steps of calculating the inter-satellite time difference of the two stars according to the bidirectional carrier phase-time comparison principle are as follows:
3.1: and reading the measured carrier phase measurement distance from the A star to the B star and from the B star to the A star.
3.2: and eliminating relativistic errors and multipath effect errors.
3.3: and phase center errors of the A-star and B-star antennas, delay errors of the A-star and B-star devices, and transmission and reception delay errors of the A-star and B-star antennas are eliminated.
3.4: calculating the geometric distance delay from the satellite A to the satellite B
3.5: calculating the geometric distance time delay from the satellite B to the satellite A
In the formula, X A (t r )(X B (t r ) Represents the position of satellite a (B) at the time of reception; x A (t e )(X B (t e ))(X B (t r ) Represents the position of satellite a (B) at the time of transmission; v A (V B ) Is the velocity of movement of satellite a (B) assuming constant satellite velocity during signal propagation. c is the speed of light in vacuum.
The spatial propagation delay from satellite a to satellite B and from satellite B to satellite a is calculated.
The inter-satellite clock bias of the satellite AB with system bias and ambiguity is calculated.
The bidirectional time comparison principle of the inter-satellite carrier phase is as follows:
carrier phase observations, i.e., methods for determining pseudoranges by measuring the phase change of a carrier signal in the propagation path. The frequency of the transmitted carrier ranging signal is very high, and the phase has very high resolution, so that a high-precision ranging value can be obtained by calculating the phase difference of the carrier in the carrier phase ranging process. The random error of the pseudo-range change rate measured by the carrier phase is only in the centimeter magnitude. The initial phases of the receiver oscillators of the two ranging terminals are equal, and the clocks are also synchronous, so that the difference between the measured carrier phase of the sender at the time t1 and the measured carrier phase of the receiver copied at the time t2 is multiplied by the carrier wavelength to obtain the geometric distance between the two satellite terminals in the two-way ranging and time synchronization, the measured value contains various errors, and the measured value is not the true geometric distance between the two satellites and is the pseudo-range containing errors.
The gravity satellites A and B send radio ranging signals at the same time, the distance between the two satellites is measured respectively, and statistics is carried out by using carrier phase cycles. Because the signal propagation paths are basically consistent, the difference between the two distances can eliminate related terms in the observed quantity, so that the relative clock difference of the clocks of the two gravity satellites is obtained, and the time synchronization between the two satellites is realized.
After epoch planning, the gravity satellites A and B receive radio ranging signals sent by the other side at the same time, and the transmission time delay TIC (A) and TIC (B) between the two satellites are measured respectively.
The time delay from satellite a to satellite B signal transmission is:
TIC(B)＝cl(B)-cl(A)+t AT +t AB +t BR
the time delay from satellite B to satellite a signal transmission is:
TIC(A)＝cl(A)-cl(B)+t BT +t BA +t AR
wherein: cl represents the clock difference relative to the system time; t is t AT ，t BT Respectively representing the equipment transmission time delay of the satellite A and the satellite B; t is t AR ，t BR Respectively representing the equipment receiving time delay of the satellite A and the satellite B; t is t AB ，t BA Representing the spatial transmission delay from satellite a to satellite B and satellite B to satellite a, respectively.
Step 105: and determining the system difference by using a least square method according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference.
performing Lagrange interpolation according to the set inter-satellite clock difference and the double-inter-satellite clock difference to obtain a carrier phase clock difference result; carrying out forward and backward epoch difference according to the carrier phase clock difference result to obtain a difference result; determining cycle slip according to the difference result and a set threshold value; and determining a system difference by using a least square method according to the time scale segment of the cycle slip, the set inter-satellite clock difference and the double-inter-satellite clock difference.
The method for obtaining the system difference of the two clock differences in a segmented mode by adopting the least square method specifically comprises the following steps:
4.1 Lagrange interpolation is carried out on the inter-satellite clock difference calculated by the KBR carrier phase according to the time standard of the inter-satellite clock difference calculated by the satellite common view method, and new carrier phase clock difference result data is generated.
4.2 carrying out forward and backward epoch difference on the clock difference calculated by the KBR carrier phase, comparing the difference result with a threshold value, and if the difference result is greater than the threshold value, determining that cycle slip occurs. And finding out the specific epoch of the cycle slip of the clock difference between KBR carrier phases in a segmented manner, and if the specific epoch is smaller than a threshold value, determining that the data is normal, and no cycle slip occurs, and not recording.
And 4.3, performing a least square method on the inter-satellite clock difference calculated by the KBR carrier phase and the inter-satellite clock difference calculated by the satellite common-view method according to the time scale segments of the cycle slip to obtain a system difference.
The algorithm idea of the least square method is as follows: for a given set of data (x) i ,y i ) (i =0, 1.. Eta., m), is required to be in the function class
Find a function y = s * (x) So that the sum of squares of errors
And is minimal.
Here, the
Step 106: filtering according to the clock error between the double satellites and the system error to determine double satellite carrier phase clock error data; and the double-satellite carrier phase clock difference data is used for time synchronization between the satellites.
deducting the system difference from the clock difference between the two satellites to obtain a two-satellite coherent clock difference; and performing Kalman filtering or von-randak filtering on the double-satellite coherent clock error to obtain double-satellite carrier phase clock error data.
Clock error deducting and removing system error based on KBR carrier phase calculation to obtain clock error of two-star coherence; filtering random noise of the clock error in a two-star coherent manner by adopting a Kalman filtering method or a von-rank filtering method; and obtaining double-satellite-carrier phase high-precision clock difference data.
The method is based on GNSS data and KBR data, and achieves the consideration of algorithm difficulty and time synchronization precision. The method provided by the invention realizes double-satellite high-precision time synchronization by using GNSS observation data and KBR inter-satellite range information, realizes double-satellite time difference calculation by respectively using a GNSS satellite common-view method and a KBR carrier phase inter-satellite bidirectional time synchronization method, does not need cycle slip detection and ambiguity calculation, and is simple and easy to understand because a KBR carrier phase inter-satellite time synchronization algorithm is the same as a pseudo-range inter-satellite time synchronization algorithm. Because cycle slip detection and ambiguity resolution are not carried out, the clock difference of KBR carrier phase inter-satellite bidirectional time synchronization calculation contains system difference, the clock difference of GNSS satellite common view and the clock difference of carrier phase inter-satellite bidirectional time synchronization calculation are calculated in a segmented mode through a least square method to obtain the system difference, and finally the clock difference of pure carrier phase can be obtained after the system difference is eliminated in a segmented mode through the clock difference of KBR carrier phase calculation.
According to the method, the GNSS observation data is utilized to obtain the double-satellite time difference through a satellite common-view method, the KBR carrier phase inter-satellite bidirectional time difference resolving result is assisted, the defect that a simple carrier phase resolving algorithm is complex is overcome, and therefore the high-precision double-satellite time synchronization result is obtained. The inter-satellite clock correction obtained by the satellite common-view method is a basis, and clock correction data are coherent; the clock error calculated through the KBR carrier phase has high precision but is discontinuous; and taking the inter-satellite clock difference obtained by the satellite common-view method as a reference, obtaining the system difference of the clock difference calculated by the KBR carrier phase and the satellite common-view clock difference by a least square method in a segmentation manner, and deducting the system difference to obtain the inter-satellite clock difference of the high-precision pure KBR carrier phase. And eliminating random noise for the clock error of the construction scheme of the KBR carrier phase calculation.
As shown in fig. 7, after the time difference of AB stars calculated bidirectionally between phases of KBR carrier phases is locally amplified, it can be clearly seen that the clock difference jumps because the ambiguity is not eliminated. As can be seen from fig. 8, the AB star clock difference calculated by the KBR carrier phase has ambiguity, and a step jump occurs; as can be seen from fig. 9, the AB satellite time difference calculated by the KBR carrier phase is smoother and less fluctuating. FIG. 10: the invention discloses an AB star clock difference residual error result, a carrier phase clock difference result and a filtered residual error which are calculated by a KBR carrier phase inter-satellite bidirectional method.
The statistical result of the time difference of the AB stars calculated bidirectionally between the satellite common-view method and the KBR carrier phase satellites is shown in the table 1, and the accuracy of the satellite common-view method is about 5ns as can be seen from the table 1.
Table 1 simulated maneuver protocol MA maneuver parameter settings
The invention also provides an inter-satellite time synchronization system, comprising:
and the acquisition module is used for acquiring the original pseudo range data of the satellite-borne receiver.
And the set inter-satellite clock difference determining module is used for determining the set inter-satellite clock difference by using a satellite common-view method according to the original pseudo-range data.
The double-star geometric distance determining module is used for determining the double-star geometric distance by utilizing a bidirectional one-way method according to the signal sending time and the signal receiving time; the geometric distance of the double stars is the distance with errors between the double stars; the signal transmission time comprises a transmission time when a signal starts from a first gravity satellite and a transmission time when the signal starts from a second gravity satellite; the signal receiving time comprises the receiving time when the signal reaches the first gravity satellite and the receiving time when the signal reaches the second gravity satellite.
And the bidirectional carrier phase time comparison module is used for determining clock error between the two satellites by utilizing a bidirectional carrier phase time comparison principle according to the geometric distance between the two satellites.
And the least square module is used for determining the system difference by utilizing minimum two-multiplication according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference.
The filtering module is used for filtering according to the clock difference between the double satellites and the system difference to determine double satellite carrier phase clock difference data; and the double-star carrier phase clock difference data is used for time synchronization between the planet.
In practical application, the set inter-satellite clock difference determining module specifically includes:
and the error elimination unit is used for carrying out pseudorange gross error elimination and error elimination on the original pseudorange data to obtain the pseudorange data after being eliminated.
And the acquisition unit is used for acquiring the time difference between the time of two gravity satellites in the pseudo-range data after the elimination and the clock of the GNSS satellite.
And the difference making unit is used for making a difference between the time differences at the same time point to obtain a set inter-satellite clock difference.
The present invention also provides an electronic device comprising:
one or more processors.
A storage device having one or more programs stored thereon.
The one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method as in any above.
The invention also provides a computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements a method as set forth in any one of the above.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the foregoing, the description is not to be taken in a limiting sense.
Claims (10)
1. An inter-satellite time synchronization method, comprising:
acquiring original pseudo-range data of a satellite-borne receiver;
determining and setting inter-satellite clock error by using a satellite common-view method according to the original pseudo-range data;
determining the geometric distance of the two stars by a bidirectional one-way method according to the signal sending time and the signal receiving time; the geometric distance of the double stars is the distance with errors between the double stars; the signal transmission time comprises a transmission time when a signal starts from a first gravity satellite and a transmission time when the signal starts from a second gravity satellite; the signal receiving time comprises the receiving time when the signal reaches the first gravity satellite and the receiving time when the signal reaches the second gravity satellite;
determining clock difference between the two satellites by utilizing a bidirectional carrier phase time comparison principle according to the geometric distance between the two satellites;
determining a system difference by utilizing a least square method according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference;
filtering according to the clock difference between the double satellites and the system difference to determine double satellite carrier phase clock difference data; and the double-satellite carrier phase clock difference data is used for time synchronization between the satellites.
2. The method according to claim 1, wherein the determining a set inter-satellite clock bias using a satellite common view method based on the raw pseudorange data specifically comprises:
performing pseudo-range gross error elimination and error elimination on the original pseudo-range data to obtain the pseudo-range data after elimination;
acquiring the time difference between the time of two gravity satellites and the clock of the GNSS satellite in the pseudo-range data after the elimination;
and differencing the time differences at the same time point to obtain the set inter-satellite clock difference.
3. The inter-satellite time synchronization method according to claim 1, wherein determining a two-satellite geometric distance by using a bidirectional one-way method according to the signal transmission time and the signal reception time specifically comprises:
determining a one-way measurement distance from a first gravity satellite to a second gravity satellite according to a receiving time when the signal reaches the second gravity satellite and a transmitting time when the signal starts from the first gravity satellite;
determining a one-way measurement distance from a second gravity satellite to the first gravity satellite according to a receiving time when the signal reaches the first gravity satellite and a transmitting time when the signal starts from the second gravity satellite;
determining a two-star geometric distance from the one-way measured distance of the first gravity satellite to the second gravity satellite and the one-way measured distance of the second gravity satellite to the first gravity satellite.
4. The inter-satellite time synchronization method according to claim 1, wherein determining a two-satellite inter-satellite clock bias by using a bidirectional carrier phase time contrast principle according to the two-satellite geometric distance specifically comprises:
respectively determining the geometric distance time delay from the first gravity satellite to the second gravity position and the geometric distance time delay from the second gravity satellite to the first gravity satellite according to the double-satellite geometric distance;
determining a space propagation delay according to the geometric distance delay from the first gravity satellite to the second gravity position and the geometric distance delay from the second gravity satellite to the first gravity satellite;
and calculating the clock error between the two stars according to the space propagation delay.
5. The method according to claim 1, wherein the determining a system difference by using a least square method according to the set inter-satellite clock difference and the dual-satellite inter-satellite clock difference specifically includes:
performing Lagrange interpolation according to the set inter-satellite clock difference and the double-inter-satellite clock difference to obtain a carrier phase clock difference result;
carrying out forward and backward epoch difference according to the carrier phase clock difference result to obtain a difference result;
determining cycle slip according to the difference result and a set threshold value;
and determining a system difference by using a least square method according to the time scale segment of the cycle slip, the set inter-satellite clock difference and the double-satellite inter-satellite clock difference.
6. The inter-satellite time synchronization method according to claim 1, wherein the filtering according to the dual-satellite inter-satellite clock difference and the system difference to determine dual-satellite carrier phase clock difference data specifically includes:
subtracting the system difference from the clock difference between the double stars to obtain a double-star coherent clock difference;
and performing Kalman filtering or von drak filtering on the double-satellite coherent clock error to obtain double-satellite carrier phase clock error data.
7. An inter-satellite time synchronization system, comprising:
the acquisition module is used for acquiring original pseudo range data of the satellite-borne receiver;
the set inter-satellite clock difference determining module is used for determining the set inter-satellite clock difference by using a satellite common-view method according to the original pseudo-range data;
the double-star geometric distance determining module is used for determining the double-star geometric distance by utilizing a bidirectional one-way method according to the signal sending time and the signal receiving time; the geometric distance of the double stars is the distance with errors between the double stars; the signal transmission time comprises a transmission time when a signal starts from a first gravity satellite and a transmission time when the signal starts from a second gravity satellite; the signal receiving time comprises the receiving time when the signal reaches the first gravity satellite and the receiving time when the signal reaches the second gravity satellite;
the bidirectional carrier phase time comparison module is used for determining clock error between the two stars by utilizing a bidirectional carrier phase time comparison principle according to the geometric distance between the two stars;
the least square module is used for determining a system difference by using a least square method according to the set inter-satellite clock difference and the double-satellite inter-satellite clock difference;
the filtering module is used for carrying out filtering according to the clock error between the double stars and the system error to determine double-star carrier phase clock error data; and the double-star carrier phase clock difference data is used for time synchronization between the planet.
8. The system according to claim 7, wherein the set inter-satellite clock difference determining module specifically includes:
the error elimination unit is used for carrying out pseudo-range gross error elimination and error elimination on the original pseudo-range data to obtain the eliminated pseudo-range data;
the acquisition unit is used for acquiring the time difference between the time of two gravity satellites in the removed pseudo-range data and a GNSS satellite clock;
and the difference making unit is used for making a difference between the time differences at the same time point to obtain the set inter-satellite clock difference.
9. An electronic device, comprising:
one or more processors;
a storage device having one or more programs stored thereon;
the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method of any of claims 1-6.
10. A computer storage medium, having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the method of any one of claims 1 to 6.
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