Beidou satellite orbit determination method, system, medium and equipment

Abstract

The invention discloses a Beidou satellite orbit determination method and system, a medium and equipment, and relates to the technical field of satellite geodetic survey, and the method comprises the steps: obtaining inter-satellite link distance measurement observation value data, and carrying out the preprocessing; according to the preprocessed observation value data, obtaining a clock-correction-free combined observation quantity and a clock-correction-free combined observation quantity at the same moment, and establishing a clock-correction-free combined observation model and a geometric-correction-free combined observation model; after the inter-satellite link observation residual error is fitted, a time domain is converted into a frequency domain through Fourier transform, and a periodic signal of the frequency domain is detected; establishing a link observation model, introducing a star-star pair deviation of an inter-satellite link, and adding a cosine term and a sine term of an orbital period parameter to obtain an improved link observation model; converting the refined link observation equation in the observation time period into a normal equation form, superposing all normal equations, and processing through a least square method to obtain to-be-estimated orbit parameters; and performing orbit fitting on the to-be-estimated orbit parameters to obtain orbit parameters, and further confirming a Beidou satellite orbit determination result.

Description

Technical Field

[0001] The present invention relates to the field of satellite geodetic technology, and in particular to a Beidou satellite orbit determination method, system, medium and equipment. Background Art

[0002] BDS-3 can provide global positioning, navigation and timing services. As one of the key technologies of BDS-3, the intersatellite link adopts a time division multiple access system. According to the predetermined routing table, each satellite takes turns to build links with other visible satellites or ground anchor stations. Each time the link is established, each pair of satellites completes two-way ranging in a short time (3s). Using the two-way observation values ​​after epoch reduction, the clock-free observation and the geometry-free observation can be decoupled to determine the satellite orbit and clock error. At present, the main error terms considered for orbit determination using BDS-3 intersatellite link (ISL) observations are the satellite antenna phase center, tropospheric delay, relativistic effect and hardware delay assumed to be constant. With the increasing number of BDS-3 intersatellite link observations and the refinement of its geometric observation model, many studies have found that the post-test fitting residuals of the intersatellite link satellites have obvious constant deviations and non-zero mean and non-normal distribution characteristics of the periodic terms, and the existing ranging data model does not effectively deal with the systematic errors of the intersatellite link, thereby limiting the precision of BDS-3 intersatellite link precise orbit determination. Therefore, it is necessary to accurately model and correct the various system errors of the BDS-3 satellite inter-satellite link observation values, so as to improve the inter-satellite link data processing model, effectively play the BDS-3 inter-satellite link function, and improve the comprehensive service performance of my country's Beidou system.

[0003] If the observation errors in the BDS-3 intersatellite link precise orbit determination process are fully considered, the residuals after verification of precise orbit determination should satisfy the characteristics of zero mean normal distribution. However, in the existing BDS-3 precise orbit determination process based on intersatellite link observation data, there are systematic errors in constants and periodic terms in the post-verification fitting residuals, which makes the residual distribution deviate from the normal distribution characteristics, thereby reducing the accuracy of the final BDS-3 intersatellite link precise orbit determination. The existing intersatellite link observation model uses the sum of the satellite's intersatellite link signal transmission and reception delays as parameter estimation, which makes it difficult to correct the ranging error characteristics of the intersatellite link satellite-satellite pair, and thus cannot separate the characteristics of the systematic deviation and periodic error of the intersatellite link satellite pair, which has an adverse impact on the BDS-3 intersatellite link precise orbit determination. Summary of the invention

[0004] In order to overcome the shortcomings of the existing intersatellite link observation model in the above-mentioned prior art that takes the sum of the satellite's intersatellite link signal transmission and reception delays as parameter estimation, it is difficult to correct the ranging error characteristics of the intersatellite link satellite-satellite pair, and further cannot separate the characteristics of the systematic deviation and periodic error of the intersatellite link satellite pair, which has an adverse effect on the intersatellite link precise orbit determination of BDS-3, the main purpose of the present invention is to provide a Beidou satellite orbit determination method, system, medium and equipment.

[0005] To achieve the above object, the present invention adopts the following technical scheme, a Beidou satellite orbit determination method, comprising the following steps:

[0006] Acquire intersatellite link ranging observation value data, extract intersatellite link ranging observation residuals, fit the intersatellite link observation residuals, and obtain the periodic term signal in the observation residual sequence;

[0007] Based on the periodic term signal, an intersatellite link observation model is established, the satellite-satellite pair deviation of the intersatellite link is introduced, and the cosine term and sine term with orbital period parameters are added to obtain an improved intersatellite link observation model.

[0008] The intersatellite link observation model within the observation period is converted into the normal equation form, and all normal equations are superimposed and processed by the least square method to obtain the orbital parameters to be estimated;

[0009] The orbital parameters to be estimated are obtained through orbit fitting, and then the orbit determination results of Beidou satellite are confirmed.

[0010] The method of obtaining inter-satellite link ranging observation value data and extracting inter-satellite link ranging observation residuals comprises the following steps:

[0011] Acquire intersatellite link ranging observation data and preprocess it to obtain preprocessed observation data;

[0012] According to the preprocessed observation data, a two-way one-way pseudorange observation in the Ka band is obtained, the two-way one-way pseudorange observation is epoch-normalized, the two-way pseudorange observation at the same time is added and subtracted, the clock-free combined observation and the geometry-free combined observation are obtained at the same time, and a clock-free combined observation model and a geometry-free combined observation model are established;

[0013] According to the clock-error-free combined observation model and the geometry-free combined observation model, a predicted value is obtained, and the inter-satellite link ranging observation value is compared with the predicted value to obtain an inter-satellite link observation residual.

[0014] The preprocessing of the intersatellite link ranging observation value data adopts a residual method, including the following steps:

[0015] Obtain intersatellite link ranging observation data, use the residual method to eliminate the gross errors of ranging observations, and obtain preliminary processed observation data;

[0016] The gross error threshold of the broadcast ephemeris satellite orbit and clock error is initially set to 10m, and in the iterative process of intersatellite link orbit determination and clock error estimation, the gross error threshold is gradually reduced to perform residual editing, so that the residual root mean square value is less than 3 times the mean error to obtain the observed value.

[0017] The step of fitting the intersatellite link observation residuals to obtain the periodic term signal in the observation residual sequence includes fitting the intersatellite link observation residuals, converting the time domain into the frequency domain through Fourier transform, detecting the periodic signal in the observation residual sequence, and obtaining the periodic term signal in the observation residual sequence.

[0018] The observation equation of the clock-free combined observation is:

[0019]

[0020] Among them, ρ BA (t 0 ) and ρ BA (t 0 ) is the naturalized epoch t 0 The bidirectional intersatellite link observation value at time, and t 0 The position vectors of satellites A and B at time, is the transmission delay of satellite A signal, is the reception delay of satellite A signal, is the transmission delay of satellite B signal, is the B satellite signal reception delay, and are half of the sum of the transmission and reception delays of the intersatellite link satellite A and B equipment respectively; Δρ AB and Δρ BA They are the other geometric error correction items related to the two-way link, including antenna phase center, yaw attitude error and relativistic response.

[0021] The observation equation of the non-geometric combination observation is:

[0022]

[0023] Where c is the speed of light in vacuum, which is 299792458 m / s, dt B (t 0 ) and dt A (t 0 ) is t 0 The satellite clock error at time.

[0024] The observation equation of the improved link observation model is:

[0025]

[0026] Where D AB is the hardware transmit / receive delay of the intersatellite link satellite pair, and Ts is the orbital period parameter.

[0027] A Beidou satellite orbit determination method system, comprising:

[0028] A data acquisition processing module is used to acquire inter-satellite link ranging observation data, extract inter-satellite link ranging observation residuals, fit the inter-satellite link observation residuals, and obtain a periodic term signal in the observation residual sequence;

[0029] The optimization and improvement module is used to establish an intersatellite link observation model based on the periodic term signal, introduce the satellite-to-satellite pair deviation of the intersatellite link, add the cosine term and sine term with the orbital period parameter, and obtain the improved intersatellite link observation model;

[0030] The satellite orbit determination module is used to convert the intersatellite link observation model within the observation period into the normal equation form, superimpose all the normal equations, and obtain the estimated orbital parameters through the least squares method; the estimated orbital parameters are obtained through orbit fitting, and then the Beidou satellite orbit determination results are confirmed.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. By introducing the satellite-to-satellite pair deviation of the inter-satellite link and analyzing the error frequency domain characteristics based on Fourier transform, the relevant parameters of the added satellite orbit period are determined to effectively absorb the systematic deviation in the inter-satellite link observation.

[0033] 2. By adding the orbital period T s The cosine and sine terms of the parameters are used to establish an improved inter-satellite link observation model. The satellite precise orbit determination based on this observation model effectively reduces the magnitude of the observation residuals and weakens the periodic errors in the residual time series, thereby significantly improving the orbit accuracy of the BDS-3 satellite. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0035] Figure 1 It is a schematic diagram of the process structure of the present invention;

[0036] FIG2( a ) is a schematic diagram of a post-fitting residual time series before adopting the improved intersatellite link observation model of the present invention;

[0037] FIG2( b ) is a schematic diagram of a post-fitting residual time series after adopting the improved intersatellite link observation model of the present invention;

[0038] FIG3( a ) is a schematic diagram of residual error after POD fitting before using the improved intersatellite link observation model in the present invention;

[0039] FIG3( b ) is a schematic diagram of the residual error after POD fitting using the improved intersatellite link observation model of the present invention. DETAILED DESCRIPTION

[0040] In the existing BDS-3 precise orbit determination process based on intersatellite link observation data, there are systematic errors in constants and periodic terms in the post-validation fitting residuals, which makes the residual distribution deviate from the normal distribution characteristics, thereby reducing the accuracy of the final BDS-3 intersatellite link precise orbit determination. The existing intersatellite link observation model uses the sum of the satellite's intersatellite link signal transmission and reception delays as parameter estimation, which makes it difficult to correct the ranging error characteristics of the intersatellite link satellite-satellite pair, and thus cannot separate the characteristics of the systematic deviation and periodic error of the intersatellite link satellite pair, which has an adverse impact on the BDS-3 intersatellite link precise orbit determination.

[0041] In order to overcome the disadvantages that the existing intersatellite link observation model in the above-mentioned prior art uses the sum of the satellite's intersatellite link signal transmission and reception delays as parameter estimation, it is difficult to correct the ranging error characteristics of the intersatellite link satellite-satellite pair, and thus cannot separate the characteristics of the systematic deviation and periodic error of the intersatellite link satellite pair, which has an adverse effect on the intersatellite link precise orbit determination of BDS-3, the main purpose of the present invention is to provide a Beidou satellite orbit determination method, which specifically includes the following steps:

[0042] Acquire intersatellite link ranging observation value data, extract intersatellite link ranging observation residuals, fit the intersatellite link observation residuals, and obtain the periodic term signal in the observation residual sequence;

[0043] Based on the periodic term signal, an intersatellite link observation model is established, the satellite-satellite pair deviation of the intersatellite link is introduced, and the cosine term and sine term with orbital period parameters are added to obtain an improved intersatellite link observation model.

[0044] The intersatellite link observation model within the observation period is converted into the normal equation form, and all normal equations are superimposed and processed by the least square method to obtain the orbital parameters to be estimated;

[0045] The orbital parameters to be estimated are obtained through orbit fitting, and then the orbit determination results of Beidou satellite are confirmed.

[0046] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0047] Example:

[0048] 1. Preprocessing of intersatellite link ranging observation data. This patent uses the residual method to eliminate the gross errors of ranging observations, and uses the broadcast ephemeris satellite orbit and clock error to set the gross error threshold to 10m. Then, during the iterative process of intersatellite link orbit determination and clock error estimation, the threshold is gradually reduced to perform residual editing, thereby obtaining a cleaner observation value.

[0049] 2. Establish a clock-free combined observation model for satellite orbit determination. Taking satellites A and B as an example, after establishing a link through reasonable routing planning, they receive measurement signals from each other at different times, form two-way one-way pseudo-range observations in the Ka band, and perform epoch normalization on the two-way observations. The two-way pseudo-range observations at the same time are added to eliminate the satellite orbits to form clock-free combined observations at the same time. The observation equation can be expressed as:

[0050]

[0051] Among them, ρ AB (t 0 ) and ρ BA (t 0 ) is the naturalized epoch t 0 The bidirectional intersatellite link observation value at time, and t 0 The position vectors of satellites A and B at time, is the transmission delay of satellite A signal, is the reception delay of satellite A signal, is the transmission delay of satellite B signal, is the B satellite signal reception delay, and are half of the sum of the transmission and reception delays of the intersatellite link satellite A and B equipment respectively; Δρ AB and Δρ BA They are the other geometric error correction items related to the two-way link, including antenna phase center, yaw attitude error and relativistic response.

[0052] 3. Establish a geometry-free combined observation model for noise analysis. Similar to step 2, subtract the two-way pseudo-range observations at the same time to eliminate the satellite orbit to form a geometry-free combined observation. Its observation equation can be expressed as:

[0053]

[0054] Where c is the speed of light in vacuum (299792458 m / s), dt B (t0 ) and dt A (t 0 ) is t 0 The satellite clock error at the time, the other parameters are the same as those in the above text and have the same meanings. The clock error-free combined observation model and the geometry-free combined observation model are used to obtain the predicted value, and the intersatellite link ranging observation value is compared with the predicted value to obtain the intersatellite link observation residual.

[0055] 4. Fitting residual periodic term signal detection: After fitting the intersatellite link observation residual generated in step (3), the time domain is converted into the frequency domain through Fourier transform to detect its periodic signal.

[0056] 5. Establish a refined link observation model. Considering that the hardware delays of different satellite intersatellite link pairs are not necessarily equal and there are periodic signals, the satellite-to-satellite pair deviation of the intersatellite link is introduced, and the cosine and sine terms with orbital period Ts parameters are added to reduce the periodic term error in the intersatellite link observation. The observation equation can be expressed as:

[0057]

[0058] Where D AB is the hardware transmit / receive delay of the intersatellite link satellite pair, Ts is the orbital period parameter, and the remaining parameters are the same as those mentioned above and have the same meanings.

[0059] 6. Parameter estimation. This patent uses the least square method of superimposed normal equations to solve all parameters to be estimated, that is, the refined link observation equations within the observation period are converted into normal equation form and all normal equations are superimposed, and then all parameters to be estimated such as orbit and delay are solved by the least square method.

[0060] 7. Generate BDS-3 orbital. The orbital parameters obtained in step (6) are used to obtain the final BDS-3 orbital through orbital fitting.

[0061] 8. Observation value fitting residual distribution verification: The final fitting residual of the improved model using this patent is verified by periodic terms and residual distribution to check whether there is a significant improvement effect.

[0062] 9. Track accuracy verification. Use satellite laser ranging data to perform external accuracy verification on the BDS-3 satellite track produced by this patent, and compare and analyze with existing products to verify whether the track product of this patent has higher accuracy.

[0063] 9. Production of high-precision BDS-3 track products. Under the conditions of meeting steps (8) and (9) at the same time, produce BDS-3 track products with higher precision.

[0064] Example

[0065] Based on the specific content of a Beidou satellite orbit determination method, in this embodiment, an improved observation model is used to solve the BDS-3 satellite orbit and verify its orbit accuracy for the BDS-3 intersatellite link data for one month from January 192 to January 212, 2020.

[0066] 1. Changes in post-test fitting residuals. For details, see Figure 2 (a) before and after the improved inter-satellite link observation model is adopted, and Figure 2 (b) after the improved inter-satellite link observation model is adopted.

[0067] Using the improved intersatellite link observation model proposed in the present application, the intersatellite link residuals can be reduced in the time series Figures 2(a), (b) after fitting and Figures 3(a), (b) of the POD fitting residual schematic diagrams before and after using the improved intersatellite link observation model, where the post-test fitting residuals are corrected to a zero-mean normal distribution, which is significantly reduced by 45% compared with the commonly used observation model.

[0068] 2. BDS-3 orbit accuracy improvement, see Table 1.

[0069] Table 1 Laser ranging track verification results (unit: cm)

[0070]

[0071] Combined with the L-band observation data of the ground GNSS tracking network, two orbit determination strategies were used with and without the improved intersatellite link observation model of this patent. The orbit verification results using satellite laser ranging data are shown in Table 1, indicating that the performance of the BeiDou-3 MEO satellite has been improved. The performance of the satellites manufactured by CAST (C20 / C21) and SECM (C29 / C30) is different, resulting in slightly different improvements. Statistical results show that the average improvement of the four BeiDou-3 satellites can reach nearly 20%.

[0072] It should be noted that, in the present invention, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0073] The above embodiments are merely examples of the present invention and do not limit the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A Beidou satellite orbit determination method, characterized in that: The following steps are involved: Acquire intersatellite link ranging observation value data, extract intersatellite link ranging observation residuals, fit the intersatellite link observation residuals, and obtain the periodic term signal in the observation residual sequence; Based on the periodic term signal, an intersatellite link observation model is established, the satellite-satellite pair deviation of the intersatellite link is introduced, and the cosine term and sine term with orbital period parameters are added to obtain an improved intersatellite link observation model. The intersatellite link observation model within the observation period is converted into the normal equation form, and all normal equations are superimposed and processed by the least square method to obtain the orbital parameters to be estimated; The orbital parameters to be estimated are obtained through orbit fitting, and then the orbit determination results of Beidou satellite are confirmed.

2. The Beidou satellite orbit determination method according to claim 1, wherein: The method of obtaining inter-satellite link ranging observation value data and extracting inter-satellite link ranging observation residuals comprises the following steps: Acquire intersatellite link ranging observation data and preprocess it to obtain preprocessed observation data; According to the preprocessed observation data, a two-way one-way pseudorange observation in the Ka band is obtained, the two-way one-way pseudorange observation is epoch-normalized, the two-way pseudorange observation at the same time is added and subtracted, the clock-free combined observation and the geometry-free combined observation are obtained at the same time, and a clock-free combined observation model and a geometry-free combined observation model are established; According to the clock-error-free combined observation model and the geometry-free combined observation model, a predicted value is obtained, and the inter-satellite link ranging observation value is compared with the predicted value to obtain an inter-satellite link observation residual.

3. The Beidou satellite orbit determination method according to claim 2, characterized in that: The preprocessing of the intersatellite link ranging observation value data adopts a residual method, including the following steps: Obtain intersatellite link ranging observation data, use the residual method to eliminate the gross errors of ranging observations, and obtain preliminary processed observation data; The gross error threshold of the broadcast ephemeris satellite orbit and clock error is initially set to 10m, and in the iterative process of intersatellite link orbit determination and clock error estimation, the gross error threshold is gradually reduced to perform residual editing, so that the residual root mean square value is less than 3 times the mean error to obtain the observed value.

4. The Beidou satellite orbit determination method according to claim 1, characterized in that: The step of fitting the intersatellite link observation residuals to obtain the periodic term signal in the observation residual sequence includes fitting the intersatellite link observation residuals, converting the time domain into the frequency domain through Fourier transform, detecting the periodic signal in the observation residual sequence, and obtaining the periodic term signal in the observation residual sequence.

5. The Beidou satellite orbit determination method according to claim 2, characterized in that: The observation equation of the clock-free combined observation is: Among them, ρ AB (t0) and ρ BA (t0) is the bidirectional intersatellite link observation value at the normalized epoch t0, and is the position vector of satellites A and B at time t0, is the transmission delay of satellite A signal, is the reception delay of satellite A signal, is the transmission delay of satellite B signal, is the reception delay of satellite B signal, and are half of the sum of the transmission and reception delays of the intersatellite link satellite A and B equipment respectively; Δρ AB and Δρ BA They are the other geometric error correction items related to the two-way link, including antenna phase center, yaw attitude error and relativistic response.

6. The Beidou satellite orbit determination method according to claim 5, characterized in that: The observation equation of the non-geometric combination observation is: Where c is the speed of light in vacuum, dt B (t0) and dt A (t0) is the satellite clock error at time t0.

7. The Beidou satellite orbit determination method according to claim 6, characterized in that: The observation equation of the improved link observation model is: Among them, D AB is the hardware transmission and reception delay of the satellite pair of the intersatellite link, T s is the orbital period parameter.

8. A Beidou satellite orbit determination method system, characterized in that: include: A data acquisition processing module is used to acquire inter-satellite link ranging observation data, extract inter-satellite link ranging observation residuals, fit the inter-satellite link observation residuals, and obtain a periodic term signal in the observation residual sequence; The optimization and improvement module is used to establish an intersatellite link observation model based on the periodic term signal, introduce the satellite-to-satellite pair deviation of the intersatellite link, add the cosine term and sine term with the orbital period parameter, and obtain the improved intersatellite link observation model; The satellite orbit determination module is used to convert the intersatellite link observation model within the observation period into the normal equation form, and superimpose all the normal equations, and obtain the orbit parameters to be estimated through the least squares method; The orbital parameters to be estimated are obtained through orbit fitting, and then the orbit determination results of Beidou satellite are confirmed.

9. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

10. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in any one of claims 1 to 7 is implemented.

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