CN117388881A - Method and system for tracing satellite-borne atomic clock of low-orbit satellite to UTC (k) - Google Patents
Method and system for tracing satellite-borne atomic clock of low-orbit satellite to UTC (k) Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
- G01S19/256—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to timing, e.g. time of week, code phase, timing offset
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- G—PHYSICS
- G04—HOROLOGY
- G04F—TIME-INTERVAL MEASURING
- G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
- G04F5/14—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks
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- G—PHYSICS
- G04—HOROLOGY
- G04R—RADIO-CONTROLLED TIME-PIECES
- G04R20/00—Setting the time according to the time information carried or implied by the radio signal
- G04R20/02—Setting the time according to the time information carried or implied by the radio signal the radio signal being sent by a satellite, e.g. GPS
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Abstract
The invention relates to a method and a system for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k), and belongs to the technical field of satellites. The system comprises a satellite-borne atomic clock, a GNSS receiving module, a satellite clock control module and a satellite-borne data processing module; the method comprises the steps that a GNSS receiving module of a low-orbit satellite obtains precise coordinates of a GNSS navigation satellite, precise clock differences relative to UTC (k), broadcast ephemeris, code pseudo-range and carrier phase observation values from a plurality of ground GNSS observation stations and the GNSS navigation satellite; the satellite-borne data processing module of the low-orbit satellite adopts the data to calculate the clock difference between the local time Ts and UTC (k); the satellite clock control module of the low orbit satellite controls the satellite-borne atomic clock according to the calculated clock difference, so that the tracking from the satellite-borne atomic clock to UTC (k) is realized. The invention can realize reliable tracing from the high-precision low-orbit satellite to UTC (k).
Description
Technical Field
The invention belongs to the technical field of satellites, and particularly relates to a method and a system for tracing a satellite-borne atomic clock of a low-orbit satellite to a high-precision frequency source UTC (k) (ground reference of navigation system time).
Background
Currently, low-orbit satellites are used as expansion, enhancement and supplement of four large satellite navigation systems including an American global positioning system, a Russian Galileo navigation system, an European Galileo navigation system and a China Beidou navigation system, and low-orbit satellite navigation, positioning and time service enhancement services are one of important development trends of navigation systems. The large-scale low-orbit satellite constellation can provide high-precision positioning, navigation and time service for users. To ensure accuracy and reliability of the service, the satellite-borne clock of the low-orbit satellite needs to trace to a high-accuracy frequency source to provide high-accuracy coordinate and clock error data. The low-orbit satellite is in a high-speed motion state, the visual time is short, and the tracing technology of the satellite-borne clock of the low-orbit satellite is one of the difficulties of low-orbit satellite application.
Disclosure of Invention
The technical problems to be solved by the invention are as follows:
the invention provides a method and a system for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k) based on a precise single-point positioning technology (PPP, precisePointPositioning) in order to realize tracing of the low-orbit satellite to a high-precision frequency source, which are one of the key problems to be solved by the application of the low-orbit satellite because the difficulty in acquiring space-time reference becomes one of the important development trends of a navigation system.
In order to solve the technical problems, the invention adopts the following technical scheme:
the method for tracing the satellite-borne atomic clock of the low-orbit satellite to UTC (k) is characterized by comprising the following steps:
s1: the low orbit satellite acquires precise ephemeris of the GNSS navigation satellite from a plurality of ground GNSS observers, wherein the precise ephemeris comprises precise orbit coordinates of the GNSS navigation satellite and precise clock difference relative to reference time UTC (k); acquiring broadcast ephemeris and observation data of a GNSS navigation satellite through a GNSS receiving module, wherein the observation data comprises code pseudo-range and carrier phase observation values;
s2: calculating the clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the low-orbit satellite according to the precise orbit coordinates of the GNSS navigation satellite, the precise clock difference relative to the reference time UTC (k), the broadcast ephemeris, the code pseudo-range and the carrier phase observation value;
s3: and controlling the satellite-borne atomic clock according to the clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the low-orbit satellite, adjusting the output signal frequency of the satellite-borne atomic clock, synchronizing the output satellite standard time Ts with UTC (k), and realizing the tracing from the satellite-borne atomic clock to UTC (k).
The invention further adopts the technical scheme that: s1 comprises the following steps:
s101, a plurality of ground GNSS observation stations observe GNSS navigation satellites, and calculate precise orbit coordinates of the GNSS navigation satellites and precise clock differences relative to reference time UTC (k);
s102, a plurality of ground GNSS observation stations send precise orbit coordinates of GNSS navigation satellites and precise clock differences relative to reference time UTC (k) to low-orbit satellites;
s103, at the same time of the step 101, a satellite-borne GNSS receiving module of the low-orbit satellite receives broadcast ephemeris, code pseudo-range and carrier phase observation values of the GNSS navigation satellite;
s104, the satellite-borne data processing module of the low-orbit satellite receives the broadcast ephemeris, the code pseudo-range and the carrier phase observation value of the GNSS navigation satellite, the precise orbit coordinates of the GNSS navigation satellite and the precise clock difference relative to the reference time UTC (k).
The invention further adopts the technical scheme that: the data interval of the precise orbit coordinate is 15 minutes, and the data of the precise clock difference is 30 seconds.
The invention further adopts the technical scheme that: s2 comprises the following steps:
s201, preprocessing precise orbit coordinate data and precise clock difference data of GNSS navigation satellites; the preprocessing comprises error term processing and interpolation processing;
s202, calculating various error correction items in a propagation path of observation data from a GNSS navigation satellite to a GNSS receiving module of a low-orbit satellite;
s203, taking the code pseudo-range observation value, broadcast ephemeris and various error correction terms into a code pseudo-range observation equation, and estimating the clock difference of the low orbit satellite at the initial moment relative to the reference time UTC (k) through a pseudo-range single-point positioning method, wherein the estimated result is used as an initial value of subsequent Kalman filtering calculation; substituting the code pseudo-range and the precise ephemeris into a code pseudo-range observation equation, substituting the carrier phase observation value and the precise ephemeris into a carrier phase observation equation, and carrying out parameter estimation of a precise single-point positioning technology by adopting a Kalman filtering mode through the simultaneous code pseudo-range observation equation and the carrier phase observation equation; and carrying out residual error detection on the estimated parameters to obtain clock difference Ts-UTC (k).
The invention further adopts the technical scheme that: the interpolation processing includes: the precise orbit coordinate data of the GNSS navigation satellite adopts high-order Lagrange interpolation, and the precise clock difference data adopts linear interpolation.
The invention further adopts the technical scheme that: s3 comprises the following steps:
s301, a satellite clock control module of a low-orbit satellite predicts the acquired clock difference Ts-UTC (k);
s302, a star clock control module of the low-orbit satellite generates frequency steering quantity according to a clock difference forecast value;
s303, a satellite clock control module of the low-orbit satellite receives an original signal of a satellite-borne atomic clock;
s304, a satellite clock control module of the low-orbit satellite controls the satellite-borne atomic clock according to the frequency control quantity, so as to trace the source of UTC (k) and output satellite standard time Ts.
The system for tracing the satellite-borne atomic clock of the low-orbit satellite to UTC (k) is characterized by comprising a satellite-borne atomic clock, a GNSS receiving module, a satellite clock control module and a satellite-borne data processing module;
the satellite-borne atomic clock outputs 10MHz signals to a satellite clock control module and a satellite-borne data processing module respectively, the signals are amplified and split through the satellite clock control module, one path of the signals are input to a GNSS receiving module to serve as a reference source, and the other path of the signals are input to the satellite-borne data processing module to be used for comparison calculation;
the satellite clock control module adjusts the frequency and the phase of a time-frequency signal output by the satellite-borne atomic clock according to clock difference data and outputs the adjusted time-frequency signal;
the GNSS receiving module receives broadcast ephemeris and observation data of the GNSS navigation satellite through an antenna and inputs the broadcast ephemeris and the observation data into the satellite-borne data processing module; simultaneously receiving the precise ephemeris transmitted by the GNSS observation station and inputting the precise ephemeris into the satellite-borne data processing module;
the satellite-borne data processing module calculates and obtains clock difference Ts-UTC (k) of a local frequency source and a reference frequency source according to the input broadcast ephemeris, observation data and precise ephemeris; and calculating a star clock control quantity according to the calculated clock difference Ts-UTC (k), a signal input by the star-borne atomic clock and a time-frequency signal adjusted by the star clock control module, and inputting the calculated star clock control quantity to the star clock control module to realize the tracing of the star clock to the UTC (k).
The invention further adopts the technical scheme that: a top-up communication link is also included for data communication between the terrestrial GNSS observation station and the low-orbit satellite.
The invention has the beneficial effects that:
according to the method and the system for tracing the satellite-borne atomic clock of the low-orbit satellite to UTC (k), the ground station uploads the precise orbit coordinates of the GNSS navigation satellite and the precise clock difference data taking UTC (k) as a reference to the low-orbit satellite, so that the clock difference data of the satellite-borne atomic clock of the low-orbit satellite and UTC (k) can be directly calculated on the low-orbit satellite, and reliable tracing of the high-precision low-orbit satellite to UTC (k) is realized. Has the following advantages:
1) The invention is based on GNSSPPP technology, and can realize subnanosecond time tracing;
2) The tracing method provided by the invention can realize high-precision tracing from the low-orbit satellite to UTC (k) by only once GNSSPPP calculation, and has the advantages of simpler flow and easiness in realization;
3) The tracing method and the tracing system provided by the invention depend on the ground GNSS observation station and the existing facilities of the low-orbit satellite, and the cost for realizing the tracing method is low.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
Fig. 1 is a flowchart of a method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k).
Fig. 2 is a detailed diagram of a method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k).
Fig. 3 is a diagram of a traceability system from a satellite-borne atomic clock of a low-orbit satellite to UTC (k).
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The embodiment of the invention provides a method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k), which is shown in figure 1 and specifically comprises the following steps:
step S1, describing the method steps of obtaining the observation data and broadcast ephemeris of each large satellite navigation system satellite by the low orbit satellite through observation, and obtaining the precise ephemeris (precise orbit coordinates and precise clock difference) from the ground station, wherein the precise ephemeris is relative to the broadcast ephemeris; the method comprises the following steps: the GNSS receiving module of the low orbit satellite observes and receives multi-frequency observation data and broadcast ephemeris of the United states Global satellite navigation system, the Russian Georr navigation system, the European Union Galileo navigation system and the China Beidou navigation system, wherein the observation data comprises code pseudo-range and carrier phase observation values; meanwhile, the low-orbit satellite also receives the precise orbit coordinates and the precise clock error uploaded by the ground station; all the data are integrated by the satellite-borne data processing module and are ready for the next processing;
step S2, describes the method steps of calculating the clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the low-orbit satellite by the GNSSPPP method, specifically: the satellite-borne data processing module of the low-orbit satellite interpolates and fills the precise ephemeris according to the observation data, calculates a plurality of error correction terms, substitutes the error correction terms into a code pseudo-range and a carrier phase observation equation, carries out parameter estimation in a Kalman filtering mode, and obtains clock errors Ts-UTC (k) of local time and reference time UTC (k) of the low-orbit satellite after residual error inspection;
step S3, the satellite-borne data processing module adopts the clock difference T obtained by calculation S The method comprises the steps that UTC (k) data and comparison results of original signals output by a satellite-borne atomic clock and time-frequency signals regulated by a satellite clock control system are input to a satellite clock control module, the satellite clock control module performs forecast processing on the comparison results and generates control mount, and the satellite-borne atomic clock of a low-orbit satellite is regulated and controlled to realize tracing from the satellite-borne atomic clock to UTC (k);
in step S1, method steps are described in which the low-orbit satellite obtains the observation data, broadcast ephemeris of each large satellite navigation system satellite by observation, and precise orbit coordinates and precise clock difference from the ground station.
As shown in fig. 2, in one embodiment of the present invention, the method specifically includes the following sub-steps:
s101, a plurality of ground GNSS observers observe GNSS navigation satellites, and calculate precise orbit coordinates of the GNSS navigation satellites and precise clock differences relative to reference time UTC (k).
Specifically, the precise orbit coordinate data interval of the satellite should be 15 minutes group, the precise clock difference data should be 30 seconds group, and the precise ephemeris includes the data of GPS, grosvenor, galileo and Beidou four-system navigation satellite;
s102, a ground GNSS observation station transmits precise orbit coordinates of a GNSS navigation satellite and precise clock difference relative to reference time UTC (k) to a low-orbit satellite through an uplink communication link;
s103, at the same time of the step S101, a GNSS receiving module of the low orbit satellite receives broadcast ephemeris of the observable GNSS navigation satellite and generates code pseudo-range and carrier phase observation values;
s104, a satellite-borne data processing module of the low-orbit satellite receives the code pseudo-range and the carrier phase observation value, the broadcast ephemeris of the GNSS navigation satellite, the precise orbit coordinates of the GNSS navigation satellite and the precise clock difference relative to the reference time UTC (k), and prepares for the next processing;
in step S1, the low-orbit satellites obtain the code pseudo-range and carrier phase observation values of the GNSS navigation satellites, the broadcast ephemeris of the GNSS navigation satellites, the precise orbit coordinates of the GNSS navigation satellites and the precise clock difference with respect to the reference time UTC (k) from the ground station and the GNSS receiving module, respectively, and are used as raw data for calculation processing in the subsequent steps.
In step S2, the method steps of obtaining the clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the low-orbit satellite by performing the precise single-point positioning technique processing on all the data acquired in step S1 are described.
As shown in fig. 2, in one embodiment of the present invention, the method specifically includes the following sub-steps:
s201, a satellite-borne data processing module of a low-orbit satellite preprocesses received original data;
the specific preprocessing method comprises the steps of firstly removing coarse error values of original data, and then carrying out interpolation processing on precise orbit coordinates and precise clock differences of GNSS navigation satellites according to data intervals of observation data, wherein the precise orbit coordinates of the GNSS navigation satellites are interpolated by using high-order Lagrange, and the precise clock differences are interpolated by using linearity;
finally, cycle slip detection and clock slip detection can be performed, and common cycle slip detection methods include MW (Melbourne-Wubbena) combination and GF (geometryfree) combination cycle slip detection. The MW combination method is obtained by subtracting the narrow lane combination of the pseudo-range observation values from the wide lane combination of the phase observation values of the same epoch, and is suitable for cycle slip detection of the real-time observation values. The GF combination utilizes the difference value of the observed value of the previous epoch and the current epoch combination to detect cycle slip, and can detect cycle slip which cannot be detected by the MW combination when the cycle slip occurs simultaneously. For clock jump, real-time compensation processing can be performed by adopting an inter-epoch difference method;
s202, a satellite-borne data processing module of a low-orbit satellite calculates various error correction items in a propagation path of an observation signal from a GNSS navigation satellite to a GNSS receiving module of the low-orbit satellite; each error correction term comprises ionospheric delay correction, hardware delay correction, antenna phase center correction and relativistic effect correction.
The propagation path of the observation signal from the GNSS navigation satellite to the GNSS receiving module of the low orbit satellite contains a plurality of error sources. The ionosphere is distributed from 50 km up to about 1000 km from the ground, and the orbit heights of some low-orbit satellites are within this range, and signals are affected by the ionosphere. The refractive index of a signal in the ionosphere is related to the signal frequency, and the ionosphere delay is inversely related to the square of the signal frequency. By adopting the double-frequency observation value, the time delay of the low-order ionosphere can be eliminated well. In addition, the signal transmission process also comprises the time delay of hardware equipment of the low-orbit satellite and the GNSS navigation satellite, the error caused by the antenna phase winding effect and the error caused by the difference between the physical reference point of the signal and the antenna phase center, and corresponding correction item information is generally obtained through equipment calibration and corresponding antenna data files. Meanwhile, the low-orbit satellite is in a high-speed motion state, and the influence of relativistic effects on the satellite-borne atomic clocks of the low-orbit satellite, the satellite-borne atomic clocks of the GNSS navigation satellite and the signal transmission process is required to be considered;
s203, performing parameter estimation by a satellite-borne data processing module of the low-orbit satellite, and calculating clock difference Ts-UTC (k) of local time and reference time UTC (k) of the low-orbit satellite;
the GNSS receiving module data, broadcast ephemeris, precise ephemeris and various error correction terms of the low-orbit satellite obtained in the steps S201 and S202 form a code pseudo-range observation equation and a carrier phase observation equation. Wherein, the double-frequency code pseudo-range observation equation can be expressed as formula (1):
(1)
where i represents the GNSS navigation satellite number, j represents the observed value frequency band number,represents the speed of light>Representing observed code pseudorange values,/->Representing the physical distance between the GNSS navigation satellite coordinates and the receiving coordinates, and (2)>And->Represents the GNSS receiving module reference time, the GNSS navigation satellite time and the clock difference of the satellite navigation system reference time respectively, < >>Representing GNSS receiving module and GNSS navigation satellite hardware time delay, < ->Representing the error correction terms described in step S202,code pseudorange observation noise representative of a GNSS receiving module.
The carrier phase observation equation can be expressed as formula (2):
(2)
in the method, in the process of the invention,representing carrier phase observations,/>Representing carrier wavelength, < >>Is obtained from carrier phase observation files in the original carrier observations of surrounding units, +.>Representing integer ambiguity, +.>Representing frequency dependent GNSS receiving module and GNSS navigation satellite hardware delay +.>Representing carrier observation noise.
Firstly, the code pseudo-range observation value, satellite coordinates of broadcast ephemeris and clock difference information are brought into a code pseudo-range observation equation, the coordinates of a low orbit satellite at the initial moment and the clock difference of a GNSS receiving module relative to reference time UTC (k) are estimated through a pseudo-range single-point positioning method, and the estimated result is used as an initial value of subsequent Kalman filtering calculation. And substituting the code pseudo-range and carrier phase observation value, the precise satellite coordinates and the clock error into the code pseudo-range observation equation and the carrier phase observation equation, and estimating PPP parameters by adopting a Kalman filtering mode. Taking the above mathematical model, the formulas (1) and (2) as examples. N satellites are observed at a certain moment, and 4n observation equations can be established by adopting double-frequency code pseudo-range and carrier phase observation data. The error equation is represented by equation (3):
(3)
where n is the number of GNSS navigation satellites, m is the parameter to be estimated, where m=2n+4,for the residual vector of the observed value,is a coefficient matrix->Is a state vector +.>Is the difference between the observed value and the calculated value. The parameters to be estimated of the state vector include the coordinate vector of the low-orbit satellite +.>Local clock error->(i.e., clock difference between local time of low-orbit satellite and reference time UTC (k)), double-frequency ambiguity +.>And->The state vector may be represented by equation (4):
(4)
in the method, in the process of the invention,、/>and->Coordinate vector for low-orbit satellite>Three-dimensional coordinates of>、/>Representing the dual-frequency ambiguity of the nth GNSS navigation satellite.
From the combination of the formulas (1) (2), the coefficient matrix can be expressed as formula (5):
(5)
in the method, in the process of the invention,、/>、/>the directions cosine and +.f of the connection line from the 1 st GNSS navigation satellite to the low orbit satellite are respectively shown>、/>、The directional cosine of the nth GNSS navigation satellite to low orbit satellite link, respectively. The corresponding system noise variance matrix is shown in formula (6):
(6)
where Q is the system noise matrix,covariance matrix of three-dimensional coordinates of low-orbit satellite,>covariance matrix for clock difference, +.>And->Is the covariance matrix of the dual-frequency ambiguity.
The kalman filter process can be expressed as formula (7):
(7)
in the method, in the process of the invention,and->For the updated state matrix and the system noise variance matrix, R is the variance matrix of the observed noise, which can be determined according to the satellite altitude angle or the signal-to-noise ratio random model, I is the identity matrix, and I is->Is the transpose of matrix H. After parameter estimation, residual error inspection is carried out on the calculated result, and the inspected low rail is passedThe clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the satellite is the output result of this step.
S204, the satellite-borne data processing module of the low-orbit satellite stores the clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the low-orbit satellite obtained by the GNSSPPP data processing calculation and sends the clock difference Ts-UTC (k) to the satellite clock control module of the low-orbit satellite for further processing.
In the step, the low-orbit satellite directly obtains the clock difference of the local time and the reference time UTC (k) of the low-orbit satellite through one GNSSPPP data processing process, and the data is used for further controlling the satellite-mounted atomic clock so as to realize the tracing from the satellite-mounted atomic clock of the low-orbit satellite to the UTC (k).
In step S3, the method steps of the satellite clock control module of the low-orbit satellite for realizing the tracing from the low-orbit satellite to UTC (k) by adopting the calculated clock difference data to control the satellite-borne atomic clock data signal of the low-orbit satellite are described.
As shown in fig. 2, in one embodiment of the present invention, the method specifically includes the following sub-steps:
s301, a satellite clock control module of a low-orbit satellite obtains clock difference TS-UTC (k) of satellite-borne atomic clock time and reference time through the step S2, wherein the clock difference TS-UTC (k) is post-processing data and needs to be subjected to forecasting processing;
s302, a star clock control module of the low-orbit satellite generates frequency control driving quantity of an atomic clock according to a clock difference forecast value;
s303, a satellite clock control module of the low-orbit satellite receives an original signal from a satellite-borne atomic clock;
s304, a satellite clock control module of the low-orbit satellite controls the driving quantity according to the frequency, carries out frequency modulation processing on the satellite-borne atomic clock, synchronizes the satellite-borne atomic clock to UTC (k), realizes tracing of the satellite-borne atomic clock to UTC (k), and outputs satellite standard time Ts.
In the step, the tracing from the satellite-borne atomic clock of the low-orbit satellite to UTC (k) is realized according to the data obtained in the step S2.
In summary, the present embodiment provides a method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k), which specifically includes that the low-orbit satellite obtains precise coordinates of a GNSS navigation satellite, precise clock differences relative to UTC (k), broadcast ephemeris, code pseudoranges and carrier phase observations from a plurality of terrestrial GNSS observers and GNSS navigation satellites; the satellite-borne data processing module of the low-orbit satellite adopts the data to calculate the clock difference between the local time Ts and UTC (k); the satellite clock control module of the low orbit satellite controls the satellite-borne atomic clock according to the calculated clock difference, so that the tracking from the satellite-borne atomic clock to UTC (k) is realized.
The embodiment of the invention also provides a system for tracing the satellite-borne atomic clock of the low-orbit satellite to UTC (k).
As shown in fig. 3, the system comprises a satellite-borne atomic clock, a GNSS receiving module, a satellite clock control module, a satellite-borne data processing module and a uploading communication link; wherein,
the satellite-borne atomic clock outputs 10MHz signals to a satellite clock control module and a satellite-borne data processing module respectively, the signals are amplified and split through the satellite clock control module, one path of the signals are input to a GNSS receiving module to serve as a reference source, and the other path of the signals are input to the satellite-borne data processing module to be used for comparison calculation;
the star clock control module adjusts the frequency and the phase of a time-frequency signal output by the star-borne atomic clock according to clock difference data and stably outputs the adjusted time-frequency signal;
the GNSS receiving module is used for receiving the time-frequency signals output by the satellite clock control module of the low-orbit satellites as a local frequency reference and can receive broadcast ephemeris and observation data of all GNSS navigation satellites; simultaneously receiving the precise ephemeris transmitted by the GNSS observatory;
the satellite-borne data processing module is used for analyzing broadcast ephemeris and observation data generated by the GNSS receiving module and precise ephemeris uploaded by the ground station, processing the original data to obtain and output deviation data of low-orbit satellite time and UTC (k);
and a top-up communication link through which the ground GNSS observatory transmits precise orbit coordinates of the GNSS navigation satellite and clock difference data relative to UTC (k) to the low-orbit satellite.
In summary, the tracing system from the satellite-borne atomic clock of the low-orbit satellite to the UTC (k) provided in the embodiment of the present application may receive various navigation information such as broadcast ephemeris and precise ephemeris of various GNSS navigation satellites, generate corresponding observation data, calculate clock differences between the satellite-borne atomic clock and the UTC (k) using the above raw data, and control the satellite-borne atomic clock using the clock difference data, thereby implementing tracing from the satellite-borne atomic clock of the low-orbit satellite to the UTC (k).
While the invention has been described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various changes and substitutions of equivalents may be made without departing from the spirit and scope of the invention.
Claims (8)
1. The method for tracing the satellite-borne atomic clock of the low-orbit satellite to UTC (k) is characterized by comprising the following steps:
s1: the low orbit satellite acquires precise ephemeris of the GNSS navigation satellite from a plurality of ground GNSS observers, wherein the precise ephemeris comprises precise orbit coordinates of the GNSS navigation satellite and precise clock difference relative to reference time UTC (k); acquiring broadcast ephemeris and observation data of a GNSS navigation satellite through a GNSS receiving module, wherein the observation data comprises code pseudo-range and carrier phase observation values;
s2: calculating the clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the low-orbit satellite according to the precise orbit coordinates of the GNSS navigation satellite, the precise clock difference relative to the reference time UTC (k), the broadcast ephemeris, the code pseudo-range and the carrier phase observation value;
s3: and controlling the satellite-borne atomic clock according to the clock difference Ts-UTC (k) of the local time and the reference time UTC (k) of the low-orbit satellite, adjusting the output signal frequency of the satellite-borne atomic clock, synchronizing the output satellite standard time Ts with UTC (k), and realizing the tracing from the satellite-borne atomic clock to UTC (k).
2. The method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k) according to claim 1, wherein S1 comprises the steps of:
s101, a plurality of ground GNSS observation stations observe GNSS navigation satellites, and calculate precise orbit coordinates of the GNSS navigation satellites and precise clock differences relative to reference time UTC (k);
s102, a plurality of ground GNSS observation stations send precise orbit coordinates of GNSS navigation satellites and precise clock differences relative to reference time UTC (k) to low-orbit satellites;
s103, at the same time of the step 101, a satellite-borne GNSS receiving module of the low-orbit satellite receives broadcast ephemeris, code pseudo-range and carrier phase observation values of the GNSS navigation satellite;
s104, the satellite-borne data processing module of the low-orbit satellite receives the broadcast ephemeris, the code pseudo-range and the carrier phase observation value of the GNSS navigation satellite, the precise orbit coordinates of the GNSS navigation satellite and the precise clock difference relative to the reference time UTC (k).
3. The method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k) according to claim 2, wherein the data interval of the precise orbit coordinates is a group of 15 minutes, and the data of the precise clock difference is a group of 30 seconds.
4. The method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k) according to claim 1, wherein S2 comprises the steps of:
s201, preprocessing precise orbit coordinate data and precise clock difference data of GNSS navigation satellites; the preprocessing comprises error term processing and interpolation processing;
s202, calculating various error correction items in a propagation path of observation data from a GNSS navigation satellite to a GNSS receiving module of a low-orbit satellite;
s203, taking the code pseudo-range observation value, broadcast ephemeris and various error correction terms into a code pseudo-range observation equation, and estimating the clock difference of the low orbit satellite at the initial moment relative to the reference time UTC (k) through a pseudo-range single-point positioning method, wherein the estimated result is used as an initial value of subsequent Kalman filtering calculation; substituting the code pseudo-range and the precise ephemeris into a code pseudo-range observation equation, substituting the carrier phase observation value and the precise ephemeris into a carrier phase observation equation, and carrying out parameter estimation of a precise single-point positioning technology by adopting a Kalman filtering mode through the simultaneous code pseudo-range observation equation and the carrier phase observation equation; and carrying out residual error detection on the estimated parameters to obtain clock difference Ts-UTC (k).
5. The method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k) according to claim 4, wherein the interpolation process comprises: the precise orbit coordinate data of the GNSS navigation satellite adopts high-order Lagrange interpolation, and the precise clock difference data adopts linear interpolation.
6. The method for tracing a satellite-borne atomic clock of a low-orbit satellite to UTC (k) according to claim 1, wherein S3 comprises the steps of:
s301, a satellite clock control module of a low-orbit satellite predicts the acquired clock difference Ts-UTC (k);
s302, a star clock control module of the low-orbit satellite generates frequency steering quantity according to a clock difference forecast value;
s303, a satellite clock control module of the low-orbit satellite receives an original signal of a satellite-borne atomic clock;
s304, a satellite clock control module of the low-orbit satellite controls the satellite-borne atomic clock according to the frequency control quantity, so as to trace the source of UTC (k) and output satellite standard time Ts.
7. The system for tracing the satellite-borne atomic clock of the low-orbit satellite to UTC (k) is characterized by comprising a satellite-borne atomic clock, a GNSS receiving module, a satellite clock control module and a satellite-borne data processing module;
the satellite-borne atomic clock outputs 10MHz signals to a satellite clock control module and a satellite-borne data processing module respectively, the signals are amplified and split through the satellite clock control module, one path of the signals are input to a GNSS receiving module to serve as a reference source, and the other path of the signals are input to the satellite-borne data processing module to be used for comparison calculation;
the satellite clock control module adjusts the frequency and the phase of a time-frequency signal output by the satellite-borne atomic clock according to clock difference data and outputs the adjusted time-frequency signal;
the GNSS receiving module receives broadcast ephemeris and observation data of the GNSS navigation satellite through an antenna and inputs the broadcast ephemeris and the observation data into the satellite-borne data processing module; simultaneously receiving the precise ephemeris transmitted by the GNSS observation station and inputting the precise ephemeris into the satellite-borne data processing module;
the satellite-borne data processing module calculates and obtains clock difference Ts-UTC (k) of a local frequency source and a reference frequency source according to the input broadcast ephemeris, observation data and precise ephemeris; and calculating a star clock control quantity according to the calculated clock difference Ts-UTC (k), a signal input by the star-borne atomic clock and a time-frequency signal adjusted by the star clock control module, and inputting the calculated star clock control quantity to the star clock control module to realize the tracing of the star clock to the UTC (k).
8. The system for tracing a satellite borne atomic clock of a low earth orbit satellite to UTC (k) according to claim 7, further comprising an up-link communication link for data communication between a terrestrial GNSS observation station and the low earth orbit satellite.
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