Hybrid ambiguity fixed real-time orbit determination method and device based on inter-satellite ranging

Abstract

The invention discloses a hybrid ambiguity fixed real-time orbit determination method and device based on inter-satellite distance measurement, and belongs to the technical field of satellite navigation and precise orbit determination. According to the method, satellite-borne GNSS observation data and inter-satellite ranging data are fused, a joint filtering model is constructed, state estimation is performed by using extended Kalman filtering, inter-satellite ranging constraints are introduced to enhance ambiguity covariance, a covariance structure is adjusted through a dynamic weighting factor, and the whole-cycle ambiguity fixing success rate is improved. And an LAMBDA algorithm is adopted to realize quick fixation of the ambiguity, and back substitution is carried out to re-estimate the orbit state. The method effectively solves the problems that a traditional PPP-AR method is slow in ambiguity fixation and poor in stability in a low-orbit high-dynamic environment, real-time orbit determination with faster convergence, higher precision and higher robustness is achieved, and the method is suitable for low-orbit constellation formation control, remote sensing, navigation enhancement and other applications.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation and precise orbit determination technology, specifically relating to a hybrid ambiguity fixed real-time orbit determination method and device based on inter-satellite ranging. Background Technology

[0002] Real-time precise orbit determination (RT-POD) for low-Earth orbit (LEO) satellites is a core technology supporting critical missions such as high-precision remote sensing, constellation networking, and space time synchronization. Currently, the mainstream methods in this field rely on carrier phase and pseudorange observation data acquired by onboard GNSS receivers, combined with real-time precise ephemeris and clock bias products, and employ precise point positioning (PPP) algorithms to estimate the orbit and clock bias of LEO satellites, aiming to achieve centimeter-level orbit determination accuracy. To further improve the stability and convergence speed of the solution, ambiguity-fixed precise point positioning (PPP-AR) technology has been introduced, which improves estimation performance by fixing the integer ambiguity of the carrier phase. However, existing PPP-AR methods have significant limitations: firstly, ambiguity fixing heavily relies on long observation times to construct stable ambiguity covariance, resulting in long initialization times; secondly, this method is extremely sensitive to error sources such as observation geometry, ionospheric delay, and multipath effects. Under conditions of high-dynamic operation of LEO satellites and frequent signal obstruction and switching, the fixation failure rate is high, seriously affecting the real-time performance and continuity of orbit determination.

[0003] Furthermore, most existing orbit determination technologies rely solely on a single GNSS observation source, making them susceptible to ionospheric disturbances, signal interruptions, and multipath interference in complex space environments. This results in significant fluctuations in orbit accuracy and insufficient robustness, making it difficult to meet the demands for consistently high-precision orbit determination. Although inter-satellite links (such as laser and microwave ranging systems) are becoming increasingly prevalent in low-Earth orbit constellations, providing centimeter-level or even millimeter-level independent ranging data and introducing high-precision geometric constraints for orbit determination, existing methods have not fully utilized inter-satellite ranging data to assist in ambiguity resolution and have failed to effectively integrate multi-source observation information to improve overall orbit determination performance.

[0004] Therefore, there is an urgent need to develop a new orbit determination method that can integrate inter-satellite ranging and GNSS observation to enhance ambiguity fixation capabilities, improve convergence speed and positioning accuracy, and ensure the stable, continuous, and high-precision orbit determination requirements of low-Earth orbit satellites in complex mission environments. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a real-time orbit determination method and apparatus based on inter-satellite ranging with hybrid ambiguity fixation. The aim is to enhance ambiguity covariance constraints, improve the success rate of ambiguity fixation, and enhance the accuracy, convergence speed, and robustness of orbit calculation, thereby meeting the needs of complex orbit control and high-precision formation applications.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A hybrid ambiguity-based real-time orbit determination method based on inter-satellite ranging, the method comprising:

[0008] Step 1: Synchronously acquire onboard GNSS multi-frequency carrier phase and pseudorange observation data and inter-satellite ranging observations between low-orbit satellites, construct an ionospheric-free combined observation data and perform time alignment processing;

[0009] Step 2: Establish a state vector containing satellite position, velocity, receiver clock error, and integer ambiguity, and construct a GNSS ionospheric-free combined observation model and an inter-satellite ranging observation model;

[0010] Step 3: Construct the ambiguity indirect covariance based on the error characteristics of the inter-satellite ranging observation model, and dynamically weight and fuse it with the GNSS ambiguity covariance to generate a hybrid ambiguity covariance matrix;

[0011] Step 4: Based on the hybrid ambiguity covariance matrix, the LAMBDA algorithm is used to fix the integer ambiguity. Combined with the GNSS ionospheric-free combined observation model, the orbital state of the low-orbit satellite is re-estimated and verified, and the real-time orbital results are output.

[0012] On the other hand, the present invention provides a hybrid ambiguity fixed real-time orbit determination device based on inter-satellite ranging, comprising:

[0013] The acquisition module is used to synchronously acquire onboard GNSS multi-frequency carrier phase and pseudorange observation data and inter-satellite ranging observations between low-orbit satellites, construct ionospheric-free combined observations and perform time alignment processing;

[0014] The module is used to establish a state vector containing satellite position, velocity, receiver clock error and integer ambiguity, and to build a GNSS ionospheric-free combined observation model and an inter-satellite ranging observation model.

[0015] The fusion module is used to construct an indirect ambiguity covariance based on the error characteristics of the inter-satellite ranging observation model, and dynamically weight and fuse it with the GNSS ambiguity covariance to generate a hybrid ambiguity covariance matrix.

[0016] The output module is used to fix integer ambiguities based on the hybrid ambiguity covariance matrix using the LAMBDA algorithm, and to re-estimate and verify the orbital state of the low-orbit satellite using the GNSS ionospheric-free combined observation model, and output the real-time orbital results.

[0017] Thirdly, the present invention provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned method for fixed real-time orbit determination based on inter-satellite ranging with hybrid ambiguity.

[0018] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned method for real-time orbit determination based on inter-satellite ranging with hybrid ambiguity.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention significantly improves the performance of real-time orbit determination for low-Earth orbit (LEO) satellites by fusing inter-satellite ranging and GNSS observation data. Firstly, the introduction of inter-satellite ranging constraints effectively enhances the ambiguity covariance structure, greatly improving the success rate and speed of integer ambiguity fixation, reducing the convergence time from over 10 minutes in the traditional PPP-AR method to less than 3 minutes. Secondly, the joint filtering model fully utilizes the high precision and strong geometric constraints of inter-satellite ranging, reducing the orbit positioning error from the order of 10 centimeters to approximately 5 centimeters, significantly improving orbit determination accuracy. Thirdly, the multi-source fusion mechanism enhances the system's tolerance to anomalies such as GNSS signal interruptions and ionospheric disturbances, ensuring the continuity and robustness of orbit determination in highly dynamic and multi-interference environments. This invention is applicable to tasks such as LEO constellation formation flight, remote sensing, and real-time navigation enhancement, and has promising engineering application prospects. Attached Figure Description

[0021] Figure 1 This is a flowchart of a real-time orbit determination method based on inter-satellite ranging with hybrid ambiguity fixed according to the present invention.

[0022] Figure 2a The orbit determination accuracy curve for existing technical methods;

[0023] Figure 2b This is the orbit determination accuracy curve based on the method of this invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, this invention proposes a hybrid ambiguity-fixed real-time orbit determination method based on inter-satellite ranging enhancement. It fuses onboard GNSS and inter-satellite ranging (ISL) observation information to construct a joint filtering model. Through covariance enhancement and dynamic weighting, it improves the success rate of ambiguity fixation and the accuracy of orbit calculation. The overall process consists of the following four steps:

[0026] Step 1: Synchronous Acquisition and Preprocessing of Multi-Source Observation Data; Synchronously acquire onboard GNSS multi-frequency carrier phase and pseudorange observation data, as well as inter-satellite ranging observations between low-orbit satellites, construct an ionospheric-free combined observation set, and perform time alignment processing; including:

[0027] (1) Acquiring multi-frequency carrier phase data from a spaceborne GNSS receiver and pseudo-distance Observational data, among which Indicates GNSS frequency points, such as L1 / L2 or B1 / B2;

[0028] (2) Constructing an ionosphere-free composite observation:

[0029] ,

[0030] ,

[0031] in, This indicates the GNSS frequency point. The subscripts 1 and 2 are used to distinguish different frequency points, such as L1 / L2 or B1 / B2. and These represent carrier and pseudorange observations without ionospheric combinations, respectively.

[0032] (3) Synchronously collect inter-satellite ranging observations , where i and j are low-orbit satellites with different numbers;

[0033] (4) Perform time alignment of GNSS and ISL data, unify the time scale (such as BDST), and standardize different data formats to ensure that they are synchronized and usable when entering the filtering model.

[0034] Step 2: State Vector Modeling and Observation Model Construction; Establish state vectors containing satellite position, velocity, receiver clock bias, and integer ambiguity; construct GNSS ionospheric-free combined observation model and inter-satellite ranging observation model; including:

[0035] (1) Construct an extended Kalman filter (EKF) system, with the state vector defined as follows:

[0036] ,

[0037] in:

[0038] The position of low-Earth orbit satellite i;

[0039] : The speed of low-Earth orbit satellite i;

[0040] : Clock bias of onboard receiver;

[0041] : Integer ambiguity vector associated with GNSS observations.

[0042] (2) Construct a GNSS observation model (ionospheric-free combination), using linear combinations of GNSS carrier phase and pseudorange observations of different frequencies to eliminate the influence of the first-order term of ionospheric delay, and form carrier phase and pseudorange observations without ionospheric combination:

[0043] ,

[0044] ,

[0045] in:

[0046] GNSS satellite-Low Earth Orbit satellite i-on-board receiver geometric distance;

[0047] GNSS satellite clock bias;

[0048] , : These represent carrier noise and pseudorange observation noise, respectively;

[0049] GNSS carrier wavelength;

[0050] : Integer ambiguity vector associated with GNSS observations.

[0051] (3) Construct an inter-satellite ranging observation model ρ, and establish an observation equation based on the geometric distance between two low-orbit satellites and the inter-satellite clock difference, wherein the geometric distance is the Euclidean distance between the current positions of the two satellites;

[0052] ,

[0053] in:

[0054] : The Euclidean distance between low-orbit satellites i and j;

[0055] Inter-satellite clock difference between low-Earth orbit satellites i and j;

[0056] Inter-satellite ranging error term.

[0057] Step 3: Ambiguity Covariance Enhancement and Fusion Modeling; Based on the error characteristics of the inter-satellite ranging observation model, construct the ambiguity indirect covariance, and fuse it with the GNSS ambiguity covariance to generate a hybrid ambiguity covariance matrix; including:

[0058] This invention introduces inter-satellite ranging constraints to enhance ambiguity covariance, constructs a hybrid ambiguity covariance matrix, and improves the fixation success rate.

[0059] ,

[0060] in:

[0061] Ambiguity variance estimation under traditional GNSS observations;

[0062] : Indirect covariance of ambiguity constructed from the propagation of inter-satellite ranging errors;

[0063] ∈[0,1]: Dynamic weighting factor, adjusted in real time based on inter-satellite ranging accuracy and residual consistency, can be defined as:

[0064] ,

[0065] in:

[0066] : Standard deviation (estimated value) of inter-satellite ranging error;

[0067] Standard deviation (estimated value) of GNSS observation error.

[0068] Step 4: Ambiguity Fixation and Orbit State Estimation; Based on the aforementioned hybrid ambiguity covariance matrix, the LAMBDA algorithm is used to fix integer ambiguities. Combined with the aforementioned GNSS ionospheric-free combined observation model, the orbit state of the low-Earth orbit satellite is re-estimated and verified, outputting real-time orbit results. This includes:

[0069] (1) Using the above-mentioned mixed covariance to construct the integer ambiguity fixed condition, the LAMBDA (Least-squares AM Biguity Decorrelation Adjustment) algorithm is used to solve for the optimal integer ambiguity vector. ;

[0070] (2) Substitute the optimal integer ambiguity back into the spaceborne GNSS observation equations to obtain the orbital state vector of the low-Earth orbit satellite. , and Perform a re-estimation and run a residual consistency test;

[0071] (3) If the test passes, output the trajectory estimation result and covariance for use by the attitude control system, formation control or payload mission, to ensure real-time acquisition of trajectory information with centimeter-level accuracy. If the test fails, retain the floating-point solution.

[0072] Figure 2a and Figure 2b The accuracy results of real-time orbit determination based on conventional algorithms and the method of this invention are shown in the figure. It can be seen that the three-dimensional real-time orbit determination accuracy of conventional algorithms is about 11.0 cm, while the three-dimensional real-time orbit determination accuracy of this invention is about 5.5 cm, which effectively improves the orbit determination accuracy.

[0073] On the other hand, the present invention provides a hybrid ambiguity fixed real-time orbit determination device based on inter-satellite ranging, which includes modules capable of implementing the steps of the aforementioned method, specifically including:

[0074] The acquisition module is used to synchronously acquire onboard GNSS multi-frequency carrier phase and pseudorange observation data and inter-satellite ranging observations between low-orbit satellites, construct ionospheric-free combined observations and perform time alignment processing;

[0075] The module is used to establish a state vector containing satellite position, velocity, receiver clock error and integer ambiguity, and to build a GNSS ionospheric-free combined observation model and an inter-satellite ranging observation model.

[0076] The fusion module is used to construct an indirect ambiguity covariance based on the error characteristics of the inter-satellite ranging observation model, and dynamically weight and fuse it with the GNSS ambiguity covariance to generate a hybrid ambiguity covariance matrix.

[0077] The output module is used to fix integer ambiguities based on the hybrid ambiguity covariance matrix using the LAMBDA algorithm, and to re-estimate and verify the orbital state of the low-orbit satellite using the GNSS ionospheric-free combined observation model, and output the real-time orbital results.

[0078] Thirdly, the present invention provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned method for fixed real-time orbit determination based on inter-satellite ranging with hybrid ambiguity.

[0079] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned method for real-time orbit determination based on inter-satellite ranging with hybrid ambiguity.

[0080] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hybrid ambiguity fixed real-time orbit determination method based on inter-satellite ranging, characterized in that, The method includes: Step 1: Synchronously acquire onboard GNSS multi-frequency carrier phase and pseudorange observation data and inter-satellite ranging observations between low-orbit satellites, construct an ionospheric-free combined observation data and perform time alignment processing; Step 2: Establish a state vector containing satellite position, velocity, receiver clock error, and integer ambiguity, and construct a GNSS ionospheric-free combined observation model and an inter-satellite ranging observation model; Step 3: Construct the ambiguity indirect covariance based on the error characteristics of the inter-satellite ranging observation model, and dynamically weight and fuse it with the GNSS ambiguity covariance to generate a hybrid ambiguity covariance matrix; Step 4: Based on the hybrid ambiguity covariance matrix, fix the integer ambiguity, and combine the GNSS ionospheric-free combined observation model to re-estimate and verify the orbital state of the low-orbit satellite, and output the real-time orbital results.

2. The real-time orbit determination method based on inter-satellite ranging with hybrid ambiguity as described in claim 1, characterized in that, In step 1, the time alignment process specifically involves unifying the GNSS multi-frequency carrier phase and pseudorange observation data with the inter-satellite ranging data into the BDST or GPST time scale system.

3. The real-time orbit determination method based on inter-satellite ranging with hybrid ambiguity as described in claim 1, characterized in that, In step 2, constructing the GNSS ionospheric-free combined observation model includes: linearly combining GNSS carrier phase and pseudorange observations of different frequencies to eliminate the influence of the first-order term of ionospheric delay, forming ionospheric-free combined carrier phase and pseudorange observations; constructing the inter-satellite ranging observation model includes: establishing observation equations based on the geometric distance between two low-orbit satellites and the inter-satellite clock difference, wherein the geometric distance is the Euclidean distance between the current positions of the two satellites.

4. The real-time orbit determination method based on inter-satellite ranging with hybrid ambiguity as described in claim 1, characterized in that, In step 3, the mixed ambiguity covariance matrix is ​​a weighted sum of the GNSS ambiguity covariance and the ambiguity indirect covariance.

5. The real-time orbit determination method based on inter-satellite ranging with hybrid ambiguity as described in claim 4, characterized in that, The weighted sum is achieved by applying a dynamic weighting factor to the indirect covariance of the ambiguity, which is adjusted in real time according to the ratio of the standard deviation of the inter-satellite ranging observation error to the standard deviation of the GNSS observation error.

6. The real-time orbit determination method based on inter-satellite ranging with hybrid ambiguity as described in claim 1, characterized in that, In step 4, the optimal integer ambiguity vector is searched and determined using the LAMBDA algorithm based on the mixed ambiguity covariance matrix; the optimal integer ambiguity vector is then substituted back into the GNSS ionospheric-free combined observation equation as a known value. Based on the back-substitution of the observation equations, the position, velocity, and receiver clock error parameters of the low-orbit satellites are re-estimated.

7. The real-time orbit determination method based on inter-satellite ranging with hybrid ambiguity as described in claim 6, characterized in that, Step 4 further includes re-estimating the orbital state of the low-orbit satellite and performing a residual consistency check. If the check passes, the final real-time orbit determination result is output. If the solution fails, either keep the floating-point solution or use the fixed solution from the previous epoch.

8. A hybrid ambiguity fixed real-time orbit determination device based on inter-satellite ranging, characterized in that, include: The acquisition module is used to synchronously acquire onboard GNSS multi-frequency carrier phase and pseudorange observation data and inter-satellite ranging observations between low-orbit satellites, construct ionospheric-free combined observations and perform time alignment processing; The module is used to establish a state vector containing satellite position, velocity, receiver clock error and integer ambiguity, and to build a GNSS ionospheric-free combined observation model and an inter-satellite ranging observation model. The fusion module is used to construct an indirect ambiguity covariance based on the error characteristics of the inter-satellite ranging observation model, and dynamically weight and fuse it with the GNSS ambiguity covariance to generate a hybrid ambiguity covariance matrix. The output module is used to fix integer ambiguities based on the hybrid ambiguity covariance matrix using the LAMBDA algorithm, and to re-estimate and verify the orbital state of the low-orbit satellite using the GNSS ionospheric-free combined observation model, and output the real-time orbital results.

9. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When one or more programs are executed by the one or more processors, the one or more processors implement the hybrid ambiguity fixed real-time orbit determination method based on inter-satellite ranging as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, It stores executable instructions that, when executed by a processor, enable the processor to implement the hybrid ambiguity fixed real-time orbit determination method based on inter-satellite ranging as described in any one of claims 1-7.

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