Spacecraft and ground time synchronization method

Abstract

The invention discloses a spacecraft and ground time synchronization method, which comprises the following steps of: measuring a device-ground time sampling difference value at a multi-gear telemetering code rate, and carrying out pre-processing operation including time pre-correction, frame length normalization and code rate normalization on measurement data, so as to reduce calculation errors, standardize a data processing flow and adapt to the measurement data under different frame lengths; the method solves the problem of period ambiguity in a conventional time synchronization method, can be suitable for a spacecraft development stage and an on-orbit task stage, and has the advantages that the design of a single-machine hardware interface of a spacecraft is simplified, the measurement process is simplified, the configuration of test equipment is simplified, and the like.

Description

Technical Field

[0001] This invention relates to the field of spacecraft time maintenance technology, and in particular to a method for synchronizing spacecraft time with the ground. Background Technology

[0002] In spacecraft on-orbit missions, especially deep space exploration missions, accurate synchronization between spacecraft time and ground time is crucial. During one-way time synchronization between spacecraft and ground, the spacecraft-to-ground telemetry delay must be measured in advance. Existing methods for measuring spacecraft-to-ground telemetry delay have the following problems and shortcomings: 1. The measurement results contain ambiguity that is an integer multiple of the telemetry frame period. The reasonable range of the measurement results must be known a priori in order to effectively resolve the ambiguity, which increases the uncertainty of the measurement.

[0003] 2. Due to limitations of the test interface, the measurement process can only be carried out during the single-unit development stage of the digital tube, and cannot be carried out during the overall AIT stage or the on-orbit mission stage, which is not conducive to data retesting and updating.

[0004] 3. A dedicated hardware interface needs to be designed for the measurement process on the single-unit data management system, and a dedicated ground equipment needs to be configured, which increases the system resource overhead.

[0005] In summary, there is an urgent need to establish a spacecraft-to-ground telemetry delay measurement and spacecraft-to-ground time synchronization method without periodic ambiguity, which can be applied to the spacecraft development stage and the on-orbit mission stage. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for synchronizing spacecraft and ground time. This method solves the periodic ambiguity problem in traditional time synchronization methods, covers both the spacecraft development stage and the on-orbit mission stage, and has advantages such as simplifying the design of single-machine hardware interfaces for spacecraft, simplifying the measurement process and the configuration of testing equipment.

[0007] The technical solution of this invention is: to provide a method for synchronizing spacecraft and ground time, comprising: Preparation phase: Z1. Specify the measurement rate for each bit range. Telemetry frame length at various bitrates And the telemetry frame delay coefficient corresponding to each telemetry frame length. ; , For the number of gears; Z2, at various bitrate levels The following records the on-device time sampling values ​​corresponding to the same telemetry frame. Ground time sample value The time sampling difference between the device and the ground was calculated. ; Z3, to Pre-calibration processing is performed using telemetry frame length. and telemetry framing delay coefficient Processing results during pre-calibration Perform normalized frame length processing to obtain the processing result. For each bit rate Normalization is performed to obtain the normalized coefficients. ; Z4. Utilize the processing results and normalization coefficient By linear fitting, the fitted value of the device-to-ground telemetry delay at the highest code rate was obtained. Fitted values ​​of the instrument-ground clock difference during the preparation phase ; Z5, through fitted values and fitted values calculate Fitted values ; for fitted values Perform a rationality check. If the check passes, proceed to the time calibration stage. If the check fails, return to step Z2. School period: S1, at the highest bit rate Measurement and calculator - ground time sampling difference Thus, the time difference between the device and the ground during the time synchronization phase can be calculated. ; S2, Using the time synchronization phase's clock difference between the device and the ground. Generate centralized time synchronization instructions, upload them to the spacecraft, and complete the time synchronization between the spacecraft and the ground.

[0008] Furthermore, in step Z2, for The pre-calibration process is performed as follows:

[0009] In the formula, This is the pre-calibration time constant.

[0010] Furthermore, in step Z2, the pre-calibration processing result is... Normalization of frame length is performed, specifically as follows:

[0011] .

[0012] Furthermore, in step Z2, the bit rate of each bit is... Normalization is performed, specifically as follows: .

[0013] Furthermore, in step Z4, the linear fitting is a univariate linear fitting, and the fitting formula is:

[0014]

[0015]

[0016]

[0017] In the formula, and The calculation formula is:

[0018] .

[0019] Furthermore, in step Z5, the fitted values ​​are... and fitted values calculate Fitted values The specific method is as follows: .

[0020] Furthermore, in step Z5, the fitted values ​​are... The reasonableness test is conducted in the following ways:

[0021] In the formula, This represents the upper limit of the measurement data error for each code rate; if the above inequality holds true, the test is passed; otherwise, the test is failed.

[0022] A computer program product is provided, which, when executed by a processor, implements the steps of the method described above.

[0023] A computer-readable storage medium is provided, wherein a computer program therein, when executed by a processor, implements the steps of the method as described above.

[0024] It also relates to the application of the aforementioned spacecraft-to-ground time synchronization method for synchronizing spacecraft with ground time using a variable code rate telemetry system.

[0025] The advantages of this invention compared to the prior art are: (1) This invention innovatively proposes a method for achieving time synchronization between spacecraft and the ground by joint measurement under multiple code rates. The spacecraft-ground time sampling difference is measured under multiple telemetry code rates, and the spacecraft-ground telemetry delay is obtained by fitting the time sampling data through linear regression, which solves the periodic ambiguity problem in previous time synchronization methods.

[0026] (2) Before performing linear regression calculation, this invention proposes a preprocessing method for measurement data, including time calibration, normalized frame length and normalized code rate, which reduces calculation error, standardizes data processing flow and adapts to measurement data under different frame lengths.

[0027] (3) The present invention also has the advantages of simplifying the design of single-machine hardware interface of spacecraft, simplifying the measurement process and test equipment configuration, and the time synchronization error is less than 1ms, which is applicable to the spacecraft development stage and on-orbit mission stage. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0029] To better understand the technical solution of the present invention, the specific embodiments of the present invention are described below.

[0030] like Figure 1 As shown, the spacecraft-to-ground time synchronization method proposed in this invention consists of two stages: a preparation stage and a time synchronization stage.

[0031] Steps one through five are performed during the preparation phase: Step 1: Telemetry code rate planning Specify the code rate for each measurement range. R i , i =1, …, n Telemetry frame length at various bitrates FL i , i =1,…, n ; and the telemetry frame delay coefficient corresponding to each telemetry frame length. a i , i =1, …, n .

[0032] Step 2: Measurement device-to-ground time sampling difference At each bit rate R i The following records the on-device time sampling values ​​corresponding to the same telemetry frame. t i s Ground time sample value ti g Calculator - Ground Time Sampling Difference t i :

[0033] Step 3: Data Preprocessing (a) During pre-calibration The purpose of pre-calibration is to control rounding errors in subsequent calculations. It involves rounding to a value close to the nearest integer. t i constant t 0, for t i The following processing is performed to obtain :

[0034] (b) Normalized frame length If the telemetry frame length is different at different code rates, it is necessary to... Normalized frame length processing is performed to obtain The purpose is to standardize the form of the equation system. The normalization frame length processing procedure is as follows:

[0035]

[0036] (c) Normalized code rate Code rate R i Normalization is performed to obtain the normalized coefficients. k i :

[0037] Step 4: Linear Regression The device-to-ground telemetry delay at the highest code rate is obtained using a univariate linear regression method based on the following system of linear equations. D Fitted value of 1 and the clock difference between the instrument and the ground during the preparation phase Fitted values .

[0038]

[0039] The fitting formula is:

[0040]

[0041]

[0042]

[0043] Step 5: Verification of the reasonableness of measurement data The purpose of measurement data rationality verification is to determine whether there are unreasonable data with large deviations in the measured data, and to reduce the impact of unreasonable data on the measurement results.

[0044] (a) According to D 1 and Calculation of fitted values Fitted values:

[0045] (b) Verification of the reasonableness of measurement data calculate The sum of squares of the differences between the measured and fitted values, and the upper limit of the error Δ between the measured data and the predicted data at each bit rate. t i By comparing the sum of squares, we obtain the criterion for verifying the reasonableness of the measurement data:

[0046] If the above inequality holds true, the test passes and the process can proceed to the next step; otherwise, the test fails, and the test is checked and measured again. t i .

[0047] Steps six and seven are conducted during school hours: Step Six: Measurement of Instrument-Ground Clock Difference A. At the highest bitrate R 1. Measurement and calculator - Ground time sampling difference t :

[0048] B. Calculate the time difference between the instrument and the ground during the time synchronization phase. t :

[0049] Step 7: Centralized Time Calibration Using the time synchronization phase of the instrument-ground clock difference t A centralized time synchronization command is generated and transmitted to the spacecraft via a remote control channel to synchronize the spacecraft's time with the ground.

[0050] Below is a specific embodiment of the method of the present invention: Step 1: Telemetry code rate planning Two measurement code rates are planned: R 1 = 16384bps and R2=4096bps. The parameters such as telemetry frame length and telemetry framing delay coefficient under the two code rates are shown in Table 1.

[0051] Step 2: Measurement device-to-ground time sampling difference During the preparation phase, the device-to-ground time sampling difference was measured at two code rates as follows: t 1 = 167735121.254s and t 2 = 167735120.931s.

[0052] Step 3: Data Preprocessing Based on the measured time difference between the device and the ground, the pre-calibration time constant is taken. t 0 = 167735120.000s, the processed value after pre-calibration. t 1 ’ =1.254s and t 2 ’ =0.931s. The processed values ​​after normalizing the frame length are respectively t 1 ” =1.254s and t 2 ” =10.431s. (Regarding...) R 1. R The coefficients after normalization of the code rate are: k 1=1 and k 2 = 4.

[0053] Step 4: Linear Regression Solve the system of linear equations:

[0054] The fitting formula is obtained as follows:

[0055]

[0056] Substitute data t 1 ” , t 2 ” , k 1. k 2. Calculation results D The fitted value for 1 is 3.059s. the The fitted value is -1.805s.

[0057] Step 5: Verification of the reasonableness of measurement data calculate t 1 ” and t 2 ”The fitted values ​​were 1.254s and 10.431s, respectively, meaning the fitted values ​​were equal to the measured values. Substituting the measured and fitted values ​​into the reasonableness test criterion, we get:

[0058] The measurement data passed the reasonableness test.

[0059] Step Six: Measurement of Instrument-Ground Clock Difference During my school years, in terms of code rate R 1=16384bps measurement device-to-ground time sampling difference t ,use D 1 Fitting Value Calculator - Ground Clock Difference t .

[0060] Step 7: Centralized Time Calibration The time difference between the clock and the ground is obtained by measuring the time synchronization phase. t A centralized time synchronization command is generated and transmitted to the spacecraft via a remote control channel to synchronize the spacecraft's time with the ground.

[0061] Table 1 Examples of Instrument-to-Ground Telemetry Delay Measurement and Data Processing

[0062] It is understood that this invention has been described through embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific circumstances without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this invention.

[0063] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method of time synchronizing a spacecraft with the ground, the method comprising: include: Preparation phase: Z1, each bin code rate used for explicit measurement , telemetry frame length under each bin code rate , and telemetry group framing delay coefficient corresponding to each telemetry frame length ; , bin number Z2, at various bitrate levels The following records the on-device time sampling values ​​corresponding to the same telemetry frame. Ground time sample value The time sampling difference between the device and the ground was calculated. ; Z3, to Pre-calibration processing is performed using telemetry frame length. and telemetry framing delay coefficient Processing results during pre-calibration Perform normalized frame length processing to obtain the processing result. ; For each bit rate Normalization is performed to obtain the normalized coefficients. ; Z4. Utilize the processing results and normalization coefficient By linear fitting, the fitted value of the device-to-ground telemetry delay at the highest code rate was obtained. Fitted values ​​of the instrument-ground clock difference during the preparation phase ; Z5, through fitted values and fitted values calculate Fitted values ; for fitted values Perform a rationality check. If the check passes, proceed to the time calibration stage. If the check fails, return to step Z2. School period: S1, at the highest bit rate Measurement and calculator - ground time sampling difference Thus, the time difference between the device and the ground during the time synchronization phase can be calculated. ; S2, Using the time synchronization phase's clock difference between the device and the ground. Generate centralized time synchronization instructions, upload them to the spacecraft, and complete the time synchronization between the spacecraft and the ground.

2. The spacecraft-ground time synchronization method according to claim 1, characterized in that: In step Z2, for The pre-calibration process is performed as follows: In the formula, This is the pre-calibration time constant.

3. The spacecraft-ground time synchronization method according to claim 1, characterized in that: In step Z2, the pre-calibration time processing result is... Normalization of frame length is performed, specifically as follows: 。 4. The spacecraft-ground time synchronization method according to claim 1, characterized in that: In step Z2, the bit rate of each bit is... Normalization is performed, specifically as follows: 。 5. The spacecraft-ground time synchronization method according to claim 1, characterized in that: In step Z4, the linear fitting is a univariate linear fitting, and the fitting formula is: In the formula, and The calculation formula is: 。 6. The spacecraft-ground time synchronization method according to claim 5, characterized in that: In step Z5, the fitted values ​​are used... and fitted values calculate Fitted values The specific method is as follows: 。 7. The spacecraft-ground time synchronization method according to claim 1, characterized in that: In step Z5, the fitted values The reasonableness test is conducted in the following ways: In the formula, This represents the upper limit of measurement data error for each code rate. If the above inequality holds true, the test is passed; otherwise, the test is failed.

8. A computer program product, characterized in that: When the computer program product is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 7.

9. A computer-readable storage medium, characterized in that: When the computer program within the medium is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 7.

10. The spacecraft-to-ground time synchronization method according to any one of claims 1 to 7 is used to synchronize the spacecraft with ground time using a variable code rate telemetry system.

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