A method for calibrating the transmission delay of downlink navigation signals from low-orbit satellites

Abstract

The present invention relates to a method for calibrating the transmission delay of a downlink navigation signal of a low-orbit satellite, comprising: using a low-orbit satellite onboard receiver to perform post-orbit determination of the low-orbit satellite on the observation data of n GPS satellites and the GPS data of an IGS analysis center, and obtaining the orbit parameters of the low-orbit satellite and the clock error sequence of the low-orbit satellite onboard receiver within a fixed time period; using a ground monitoring station receiver to perform post-point positioning on the observation data of n GPS satellites and the GPS data of the IGS analysis center within the same time period as the first step, and obtaining the coordinates and clock error sequence of the ground monitoring station receiver; selecting the time when the ground monitoring station is visible to the low-orbit satellite within the same time period as the first step, calculating the user equivalent distance error of the ground monitoring station to the low-orbit satellite, and obtaining the user equivalent distance error sequence of the ground monitoring station to the low-orbit satellite; and calculating the average value of the user equivalent distance error sequence. Accurate calibration of the transmission delay of the downlink navigation signal of the low-orbit satellite is achieved.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation technology, and in particular to a method for calibrating the transmission delay of a downlink navigation signal from a low-orbit satellite. Background Art

[0002] Establishing a low-orbit satellite constellation and using low-orbit satellites to broadcast navigation signals to enhance the Global Navigation Satellite System (GNSS) and achieve low-orbit navigation enhancement is an effective way to overcome the inherent fragility and limitations of GNSS. As navigation satellites, low-orbit satellites broadcast navigation signals to the ground, with the advantages of high ground reception signal strength and fast geometric changes. They can complement the medium- and high-orbit GNSS constellations and play a significant role in enhancing the accuracy, integrity, continuity and availability of GNSS. They have become a hot topic in the current satellite navigation field. The basic principle of low-orbit satellites providing navigation services is to carry GNSS onboard receivers on low-orbit satellites, receive signals from medium- and high-orbit navigation satellites, and accurately determine orbits through the "one-step method" or "two-step method" to accurately calculate the orbit of each low-orbit satellite and the onboard receiver clock error relative to the satellite navigation system. The orbit and clock error of the low-orbit satellite itself will be compiled into a message and broadcast to users. However, due to various delays within the low-orbit satellite, there will inevitably be a systematic difference between the time when the low-orbit satellite broadcasts the downlink navigation signal and the satellite navigation system time, which is referred to as the low-orbit satellite downlink navigation signal transmission delay. If the low-orbit satellite downlink navigation signal transmission delay is unknown, users will not be able to use low-orbit satellites and GNSS navigation satellites for joint positioning. Therefore, accurate calibration of the downlink navigation signal transmission delay of each low-orbit satellite is a prerequisite for achieving high-precision low-orbit navigation enhancement services. Summary of the invention

[0003] In order to overcome the defects existing in the above-mentioned prior art, the purpose of the present invention is to provide a method for calibrating the transmission delay of a low-orbit satellite downlink navigation signal, so as to achieve accurate calibration of the transmission delay of a low-orbit satellite downlink navigation signal.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0005] The present invention provides a method for calibrating the transmission delay of a low-orbit satellite downlink navigation signal, comprising:

[0006] Step 1: Use the low-orbit satellite onboard receiver to perform post-orbit determination of the low-orbit satellite based on the observation data of n GPS satellites and the GPS data of the IGS analysis center, and obtain the low-orbit satellite orbit parameters and the clock error sequence of the low-orbit satellite onboard receiver within a fixed time period;

[0007] Step 2: using the ground monitoring station receiver to perform post-positioning on the observation data of the n GPS satellites and the GPS data of the IGS analysis center within the same time period as step 1, to obtain the coordinates and clock difference sequence of the ground monitoring station receiver;

[0008] Step 3: Select a time when the ground monitoring station is visible to the low-orbit satellite within the same time period as step 1, calculate the user equivalent distance error of the ground monitoring station to the low-orbit satellite, and obtain a user equivalent distance error sequence of the ground monitoring station to the low-orbit satellite;

[0009] Step 4: Calculate the average value of the user equivalent distance error sequence, which is the calibration value of the low-orbit satellite downlink navigation signal transmission delay.

[0010] According to one aspect of the present invention, step 1 comprises:

[0011] Step 11, obtaining pseudo-range observation data and carrier phase observation data of the n GPS satellites by the onboard receiver of the low-orbit satellite within a fixed time period;

[0012] Step 12, obtaining GPS data in the same time period as step 11 from the IGS analysis center;

[0013] Step 13: Use the pseudorange observation data and the carrier phase observation data to form a dual-frequency pseudorange ionosphere-free combination and a dual-frequency carrier phase ionosphere-free combination, respectively. The obtained dual-frequency pseudorange ionosphere-free combination observation values ​​and dual-frequency carrier phase ionosphere-free combination observation values ​​are respectively:

[0014]

[0015] Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudo-range observation values ​​of GPS satellites at L1 and L2 frequencies, respectively. 1 , L 2 are the carrier phase observation values ​​of GPS satellite at L1 and L2 frequencies respectively;

[0016] Step 14: using the GPS data as a time-space reference, using the dual-frequency pseudorange ionosphere-free combined observation value and the dual-frequency carrier phase ionosphere-free combined observation value as observation quantities, and performing post-hoc orbit determination of the low-orbit satellite using the orbit determination observation equation, wherein the orbit determination observation equation is:

[0017] Y=H(X,t)+ε

[0018] Wherein, Y is the observation value of the low-orbit satellite onboard receiver at time t, H is the observation function of the low-orbit satellite onboard receiver at time t, X is the orbit parameter to be estimated including the low-orbit satellite orbit parameter, the low-orbit satellite onboard receiver clock error parameter, ambiguity parameter and atmospheric parameter, and ε is the observation error;

[0019] Step 15: Linearize the orbit determination observation equations at all epochs within the fixed time period, estimate the orbit determination parameters using the least squares batch processing method, and obtain the low-orbit satellite orbit parameters and the clock error sequence of the low-orbit satellite onboard receiver.

[0020] According to one aspect of the present invention, step 2 comprises:

[0021] Step 21, obtaining pseudorange observation data and carrier phase observation data of the n GPS satellites by the ground monitoring station receiver in the same time period as in step 1;

[0022] Step 22, obtaining GPS data in the same time period as step 21 from the IGS analysis center;

[0023] Step 23: Use the pseudorange observation data and the carrier phase observation data to form a dual-frequency pseudorange ionosphere-free combination and a dual-frequency carrier phase ionosphere-free combination, respectively. The obtained dual-frequency pseudorange ionosphere-free combination observation values ​​and dual-frequency carrier phase ionosphere-free combination observation values ​​are respectively:

[0024]

[0025] Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudo-range observation values ​​of GPS satellites at L1 and L2 frequencies, respectively. 1 , L 2 are the carrier phase observation values ​​of GPS satellite at L1 and L2 frequencies respectively;

[0026] Step 24: using the GPS data as a time-space reference, using the dual-frequency pseudorange ionosphere-free combined observation value and the dual-frequency carrier phase ionosphere-free combined observation value as observation quantities, and using a single-point positioning function model to perform post-point positioning on all visible GPS satellites in the same observation epoch to obtain the coordinates and clock difference sequence of the ground monitoring station receiver. The single-point positioning function model is:

[0027] y=Gx

[0028] Among them, y is the residual of pseudorange and carrier phase observation, G is the design matrix formed according to the GPS satellite position, the approximate coordinates of the ground monitoring station receiver, and the tropospheric wet delay mapping function, and x is the parameter to be estimated including the coordinates and clock error of the ground monitoring station receiver, the tropospheric delay parameters, and the ambiguity parameters.

[0029] According to one aspect of the present invention, the GPS data includes GPS satellite orbit data and GPS satellite clock error data.

[0030] According to one aspect of the present invention, the number n of GPS satellites in step 1 is a positive integer greater than 30.

[0031] According to one aspect of the present invention, step 3 comprises:

[0032] Step 31: acquiring pseudorange observation data of the ground monitoring station receiver on the low-orbit satellite during the visible time of the ground monitoring station on the low-orbit satellite in the same time period as in step 1;

[0033] Step 32: Use the pseudorange observation data to form a dual-frequency pseudorange ionosphere-free combination, and obtain the dual-frequency pseudorange ionosphere-free combination observation value as follows:

[0034]

[0035] Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudorange observation values ​​of GPS satellites at L1 and L2 frequencies respectively;

[0036] Step 33: Utilize the orbital parameters of the low-orbit satellite and the coordinates of the ground monitoring station receiver to obtain the geometric distance between the low-orbit satellite and the ground monitoring station receiver; calculate the user equivalent distance error of each observation epoch within the visible time of the low-orbit satellite by the ground monitoring station based on the geometric distance, the clock error of the onboard receiver of the low-orbit satellite, the clock error of the ground monitoring station receiver and the system error, and obtain a user equivalent distance error sequence.

[0037] According to one aspect of the present invention, the user equivalent distance error of the ground monitoring station for each observation epoch during the visible time of the low-orbit satellite is:

[0038]

[0039] Wherein, P(t) is the dual-frequency ionospheric-free combined pseudorange observation value of the ground monitoring station receiver to the low-orbit satellite at epoch time t, t light The transmission of downlink navigation signals from low-orbit satellites takes time. is the low-orbit satellite position at the time of signal transmission obtained by interpolating the low-orbit satellite orbital parameters in step 1, is the receiver coordinates of the ground monitoring station in step 2, δClk LEO is the low-orbit satellite receiver clock error at the time of signal transmission obtained by interpolation calculation of the low-orbit satellite receiver clock error sequence in step 1, δClk REC is the ground monitoring station receiver clock error at epoch time t calculated in step 2, δErr sys It is the system error including tropospheric delay, antenna phase center deviation and solid tide influence calculated by the model. UERE(t) is the user equivalent distance error of the ground monitoring station to the low-orbit satellite at epoch time t.

[0040] According to one aspect of the present invention, the step 4 calculates the average value of the user equivalent distance error sequence of all epochs within the visible time of the ground monitoring station to the low-orbit satellite, which is:

[0041]

[0042] Among them, UERE(t i ) is the observation epoch t i is the user equivalent distance error of the ground monitoring station to the low-orbit satellite at the moment, and k is the total number of observation epochs of the ground monitoring station to the low-orbit satellite during the visible time period of the low-orbit satellite.

[0043] According to one aspect of the present invention, the fixed time period is one day.

[0044] According to one aspect of the present invention, the number of the low-orbit satellite onboard receiver and the number of the ground monitoring station receiver are both one.

[0045] Beneficial effects:

[0046] According to the solution of the present invention, a method for calibrating the transmission delay of the low-orbit satellite downlink navigation signal is proposed from the perspective of post-data processing, that is, the low-orbit satellite orbit and the clock error of the low-orbit satellite onboard receiver, as well as the coordinates and clock error of the ground monitoring station receiver are fixed, and the user equivalent distance error calculation method is used to calculate the transmission delay of the low-orbit satellite downlink navigation signal, so as to realize the precise in-orbit calibration of the transmission delay of the low-orbit satellite downlink navigation signal. This ensures that users can use low-orbit satellites and GPS satellites for joint positioning, providing guarantee for the realization of low-orbit navigation enhancement services.

[0047] In addition, the ground equipment for implementing the method of the present invention is simple, and does not require a large-scale ground monitoring station network. It only relies on a ground monitoring station receiver that can receive the downlink navigation signal of the low-orbit satellite. The required data is easy to obtain, and the process is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A flowchart schematically showing a method for calibrating the transmission delay of a downlink navigation signal from a low-orbit satellite according to an embodiment of the present invention;

[0049] Figure 2 A flowchart schematically showing step 1 of a method for calibrating a transmission delay of a downlink navigation signal from a low-orbit satellite according to an embodiment of the present invention;

[0050] Figure 3 A flowchart schematically showing step 2 of a method for calibrating a transmission delay of a downlink navigation signal from a low-orbit satellite according to an embodiment of the present invention;

[0051] Figure 4 The flowchart of step 3 in the method for calibrating the transmission delay of a downlink navigation signal from a low-orbit satellite according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0053] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not therefore limited to the following embodiments.

[0054] like Figure 1 As shown, a method for calibrating the transmission delay of a low-orbit satellite downlink navigation signal in this embodiment mainly includes the following steps:

[0055] Step 1: Use a low-orbit satellite onboard receiver to perform post-orbit determination of low-orbit satellites based on the observation data of n GPS satellites and the GPS data of the IGS analysis center, and obtain the low-orbit satellite orbit parameters of one day arc and the clock error sequence of the low-orbit satellite onboard receiver. Here n is a positive integer greater than 30.

[0056] Step 2: Select any ground monitoring station that can receive the downlink navigation signal from the low-orbit satellite. At the same time as the post-orbit determination period of the low-orbit satellite in step 1, use the ground monitoring station receiver to perform post-point positioning on the observation data of n GPS satellites and the GPS data of the IGS analysis center to obtain the coordinates and clock difference sequence of the ground monitoring station receiver.

[0057] Step 3: In the same time period as steps 1 and 2, select the time when the ground monitoring station is visible to the low-orbit satellite, calculate the user equivalent distance error of the ground monitoring station to the low-orbit satellite, and obtain the user equivalent distance error sequence of the ground monitoring station to the low-orbit satellite.

[0058] Step 4: Calculate the average value of the above user equivalent distance error sequence, which is the calibration value of the low-orbit satellite downlink navigation signal transmission delay.

[0059] Among them, Figure 2 As shown, the above step 1, using a low-orbit satellite onboard receiver to perform post-orbit determination of low-orbit satellites based on the observation data of n GPS satellites and the GPS data of the IGS analysis center, specifically includes the following steps:

[0060] Step 11, using a low-orbit satellite onboard receiver to observe pseudo-range data and carrier phase observation data of n GPS satellites within 1 day;

[0061] Step 12, obtain GPS data from the IGS analysis center within the same day as step 11;

[0062] Step 13: Use pseudorange observation data and carrier phase observation data to form a dual-frequency pseudorange ionosphere-free combination and a dual-frequency carrier phase ionosphere-free combination, respectively. The obtained dual-frequency pseudorange ionosphere-free combination observation values ​​and dual-frequency carrier phase ionosphere-free combination observation values ​​are:

[0063]

[0064] Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudo-range observation values ​​of GPS satellites at L1 and L2 frequencies, respectively. 1 , L 2 are the carrier phase observation values ​​of GPS satellite at L1 and L2 frequencies respectively;

[0065] Step 14: Using the GPS data obtained in step 12 as the time and space reference, using the dual-frequency pseudorange ionosphere-free combined observation value and the dual-frequency carrier phase ionosphere-free combined observation value as the observation quantity, and using the orbit determination observation equation to perform post-orbit determination of the low-orbit satellite. The orbit determination observation equation is:

[0066] Y=H(X,t)+ε

[0067] Where Y is the observation value of the LEO satellite onboard receiver at time t, H is the observation function of the LEO satellite onboard receiver at time t, X is the orbit parameter to be estimated including the LEO satellite orbit parameter, the LEO satellite onboard receiver clock error parameter, ambiguity parameter and atmospheric parameter, and ε is the observation error;

[0068] Step 15: Linearize the orbit determination observation equations at all epochs within one day, estimate the orbit determination parameters using the least squares batch processing method, and obtain the low-orbit satellite orbit parameters and the clock error sequence of the low-orbit satellite onboard receiver.

[0069] Among them, Figure 3 As shown, the process of performing post-positioning of the observation data of n GPS satellites and the GPS data of the IGS analysis center using the ground monitoring station receiver in step 2 specifically includes the following steps:

[0070] Step 21, select any one ground monitoring station that can receive the downlink navigation signal of the low-orbit satellite, and obtain the pseudo-range observation data and carrier phase observation data of the ground monitoring station receiver on n GPS satellites. The observation time is the same as the time of post-orbit determination of the low-orbit satellite in step 1.

[0071] Step 22, obtaining GPS data from the IGS analysis center within the same day as step 21;

[0072] Step 23: Use pseudorange observation data and carrier phase observation data to form a dual-frequency pseudorange ionosphere-free combination and a dual-frequency carrier phase ionosphere-free combination, respectively. The obtained dual-frequency pseudorange ionosphere-free combination observation values ​​and dual-frequency carrier phase ionosphere-free combination observation values ​​are respectively:

[0073]

[0074] Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudo-range observation values ​​of GPS satellites at L1 and L2 frequencies, respectively. 1 , L 2 They are the carrier phase observation values ​​of GPS satellite at L1 and L2 frequencies respectively.

[0075] Step 24: Using GPS data as the time and space reference, dual-frequency pseudorange ionosphere-free combined observations and dual-frequency carrier phase ionosphere-free combined observations as observation quantities, and using the single-point positioning function model to perform post-point positioning on all visible GPS satellites in the same observation epoch, and obtain the coordinates and clock difference sequence of the ground monitoring station receiver. The single-point positioning function model is:

[0076] y=Gx

[0077] Among them, y is the residual of pseudorange and carrier phase observation, G is the design matrix formed according to the GPS satellite position, the approximate coordinates of the ground monitoring station receiver, and the tropospheric wet delay mapping function, and x is the parameter to be estimated including the coordinates and clock error of the ground monitoring station receiver, the tropospheric delay parameters, and the ambiguity parameters.

[0078] The above-mentioned GPS data includes GPS satellite orbit data and GPS satellite clock error data.

[0079] Among them, Figure 4 As shown, the process of calculating the user equivalent distance error of the ground monitoring station to the low-orbit satellite in the above step 3 specifically includes the following steps:

[0080] Step 31, during the visible time of the ground monitoring station to the low-orbit satellite in the same time period as step 1 and step 2, obtaining pseudo-range observation data of the ground monitoring station receiver to the low-orbit satellite;

[0081] Step 32: Use pseudorange observation data to form a dual-frequency pseudorange ionosphere-free combination, and obtain the dual-frequency pseudorange ionosphere-free combination observation value as follows:

[0082]

[0083] Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudorange observation values ​​of GPS satellites at L1 and L2 frequencies respectively;

[0084] Step 33: Use the orbital parameters of the low-orbit satellite and the coordinates of the ground monitoring station receiver to obtain the geometric distance between the low-orbit satellite and the ground monitoring station receiver. According to the geometric distance, the clock error of the low-orbit satellite onboard receiver, the clock error of the ground monitoring station receiver and the system error, calculate the user equivalent distance error of the ground monitoring station for each observation epoch within the visible time of the low-orbit satellite to obtain the user equivalent distance error sequence.

[0085] Among them, the user equivalent distance error of the ground monitoring station in step 33 for each observation epoch within the visible time of the low-orbit satellite is:

[0086]

[0087] Where P(t) is the dual-frequency ionospheric-free combined pseudorange observation value of the ground monitoring station receiver to the low-orbit satellite at epoch time t, t light The transmission of downlink navigation signals from low-orbit satellites takes time. is the low-orbit satellite position at the time of signal transmission obtained by interpolation of the low-orbit satellite orbital parameters in step 1, is the receiver coordinates of the ground monitoring station in step 2, δClk LEO is the low-orbit satellite receiver clock error at the time of signal transmission obtained by interpolation of the low-orbit satellite receiver clock error sequence in step 1, δClk REC is the ground monitoring station receiver clock error at epoch time t calculated in step 2, δErr sys is the systematic error including tropospheric delay, antenna phase center deviation and solid tide influence calculated by the model. UERE(t) is the user equivalent range error of the ground monitoring station to the low-orbit satellite at epoch time t.

[0088] The average value of the user equivalent distance error sequence of all epochs in the visible time of the ground monitoring station to the low-orbit satellite in step 4 above is:

[0089]

[0090] Among them, UERE(t i ) is the observation epoch t i The user equivalent distance error of the ground monitoring station to the low-orbit satellite at the moment, k is the total number of observation epochs of the ground monitoring station to the low-orbit satellite during the visible period of the low-orbit satellite. The average value is the calibration value of the transmission delay of the low-orbit satellite downlink navigation signal.

[0091] The transmission delay of the low-orbit satellite downlink navigation signal calculated in this embodiment actually also includes the reception delay of the ground monitoring station receiver for the low-orbit satellite downlink navigation signal. However, when the user uses the low-orbit satellite and the GPS satellite for joint positioning, an additional system difference parameter between the low-orbit satellite and the GPS satellite will be estimated. This system difference parameter will absorb the reception delay of the ground monitoring station receiver for the low-orbit satellite downlink navigation signal. Therefore, the reception delay of the ground monitoring station receiver for the low-orbit satellite downlink navigation signal included in the transmission delay of the low-orbit satellite downlink navigation signal will not affect the low-orbit navigation enhancement service.

[0092] The serial numbers of the above-mentioned steps involved in the method of the present invention do not mean the order of execution of the method. The execution order of each step should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation mode of the present invention.

[0093] The above is only one embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calibrating the transmission delay of a low-orbit satellite downlink navigation signal. include: Step 1: Use the low-orbit satellite onboard receiver to perform post-orbit determination of the low-orbit satellite based on the observation data of n GPS satellites and the GPS data of the IGS analysis center, and obtain the low-orbit satellite orbit parameters and the clock error sequence of the low-orbit satellite onboard receiver within a fixed time period; Step 2: using the ground monitoring station receiver to perform post-positioning on the observation data of the n GPS satellites and the GPS data of the IGS analysis center within the same time period as step 1, to obtain the coordinates and clock difference sequence of the ground monitoring station receiver; Step 3: Select a time when the ground monitoring station is visible to the low-orbit satellite within the same time period as step 1, calculate the user equivalent distance error of the ground monitoring station to the low-orbit satellite, and obtain a user equivalent distance error sequence of the ground monitoring station to the low-orbit satellite; Step 4: Calculate the average value of the user equivalent distance error sequence, which is the calibration value of the low-orbit satellite downlink navigation signal transmission delay.

2. The method according to claim 1, It is characterized in that The step 1 comprises: Step 11, obtaining pseudo-range observation data and carrier phase observation data of the n GPS satellites by the onboard receiver of the low-orbit satellite within a fixed time period; Step 12, obtaining GPS data in the same time period as step 11 from the IGS analysis center; Step 13: Use the pseudorange observation data and the carrier phase observation data to form a dual-frequency pseudorange ionosphere-free combination and a dual-frequency carrier phase ionosphere-free combination, respectively. The obtained dual-frequency pseudorange ionosphere-free combination observation values ​​and dual-frequency carrier phase ionosphere-free combination observation values ​​are respectively: Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudo-range observation values ​​of GPS satellites at L1 and L2 frequencies, respectively. 1 , L 2 are the carrier phase observation values ​​of GPS satellite at L1 and L2 frequencies respectively; Step 14: using the GPS data as a time-space reference, using the dual-frequency pseudorange ionosphere-free combined observation value and the dual-frequency carrier phase ionosphere-free combined observation value as observation quantities, and performing post-hoc orbit determination of the low-orbit satellite using the orbit determination observation equation, wherein the orbit determination observation equation is: Y=H(X,t)+ε Wherein, Y is the observation value of the low-orbit satellite onboard receiver at time t, H is the observation function of the low-orbit satellite onboard receiver at time t, X is the orbit parameter to be estimated including the low-orbit satellite orbit parameter, the low-orbit satellite onboard receiver clock error parameter, ambiguity parameter and atmospheric parameter, and ε is the observation error; Step 15: Linearize the orbit determination observation equations at all epochs within the fixed time period, estimate the orbit determination parameters using the least squares batch processing method, and obtain the low-orbit satellite orbit parameters and the clock error sequence of the low-orbit satellite onboard receiver.

3. The method according to claim 1, It is characterized in that The step 2 comprises: Step 21, obtaining pseudorange observation data and carrier phase observation data of the n GPS satellites by the ground monitoring station receiver in the same time period as in step 1; Step 22, obtaining GPS data in the same time period as step 21 from the IGS analysis center; Step 23: Use the pseudorange observation data and the carrier phase observation data to form a dual-frequency pseudorange ionosphere-free combination and a dual-frequency carrier phase ionosphere-free combination, respectively. The obtained dual-frequency pseudorange ionosphere-free combination observation values ​​and dual-frequency carrier phase ionosphere-free combination observation values ​​are respectively: Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudo-range observation values ​​of GPS satellites at L1 and L2 frequencies, respectively. 1 , L 2 are the carrier phase observation values ​​of GPS satellite at L1 and L2 frequencies respectively; Step 24: using the GPS data as a time-space reference, using the dual-frequency pseudorange ionosphere-free combined observation value and the dual-frequency carrier phase ionosphere-free combined observation value as observation quantities, and using a single-point positioning function model to perform post-point positioning on all visible GPS satellites in the same observation epoch to obtain the coordinates and clock difference sequence of the ground monitoring station receiver. The single-point positioning function model is: y=Gx Among them, y is the residual of pseudorange and carrier phase observation, G is the design matrix formed according to the GPS satellite position, the approximate coordinates of the ground monitoring station receiver, and the tropospheric wet delay mapping function, and x is the parameter to be estimated including the coordinates and clock error of the ground monitoring station receiver, the tropospheric delay parameters, and the ambiguity parameters.

4. The method according to any one of claims 1 to 3, It is characterized in that The GPS data includes GPS satellite orbit data and GPS satellite clock error data.

5. The method according to any one of claims 1 to 3, It is characterized in that The number n of GPS satellites in step 1 is a positive integer greater than 30.

6. The method according to claim 1, It is characterized in that The step 3 comprises: Step 31: acquiring pseudorange observation data of the ground monitoring station receiver on the low-orbit satellite during the visible time of the ground monitoring station on the low-orbit satellite in the same time period as in step 1; Step 32: Use the pseudorange observation data to form a dual-frequency pseudorange ionosphere-free combination, and obtain the dual-frequency pseudorange ionosphere-free combination observation value as follows: Among them, f 1 、f 2 are the frequencies of GPS satellites at L1 and L2, respectively. 1 , P 2 are the pseudorange observation values ​​of GPS satellites at L1 and L2 frequencies respectively; Step 33: Utilize the orbital parameters of the low-orbit satellite and the coordinates of the ground monitoring station receiver to obtain the geometric distance between the low-orbit satellite and the ground monitoring station receiver; calculate the user equivalent distance error of each observation epoch within the visible time of the low-orbit satellite by the ground monitoring station based on the geometric distance, the clock error of the onboard receiver of the low-orbit satellite, the clock error of the ground monitoring station receiver and the system error, and obtain a user equivalent distance error sequence.

7. The method according to claim 6, It is characterized in that The user equivalent distance error of the ground monitoring station for each observation epoch during the visible time of the low-orbit satellite is: Wherein, P(t) is the dual-frequency ionospheric-free combined pseudorange observation value of the ground monitoring station receiver to the low-orbit satellite at epoch time t, t light It takes time to transmit downlink navigation signals from low-orbit satellites. is the low-orbit satellite position at the time of signal transmission obtained by interpolating the low-orbit satellite orbital parameters in step 1, is the receiver coordinates of the ground monitoring station in step 2, δClk LEO is the low-orbit satellite receiver clock error at the time of signal transmission obtained by interpolation calculation of the low-orbit satellite receiver clock error sequence in step 1, δClk REC is the ground monitoring station receiver clock error at epoch time t calculated in step 2, δErr sys It is the system error including tropospheric delay, antenna phase center deviation and solid tide influence calculated by the model. UERE(t) is the user equivalent distance error of the ground monitoring station to the low-orbit satellite at epoch time t.

8. The method according to claim 7, It is characterized in that The step 4 calculates the average value of the user equivalent distance error sequence of all epochs within the visible time of the ground monitoring station to the low-orbit satellite, which is: Where UERE(ti) is the observation epoch t i is the user equivalent distance error of the ground monitoring station to the low-orbit satellite at the moment, and k is the total number of observation epochs of the ground monitoring station to the low-orbit satellite during the visible time period of the low-orbit satellite.

9. The method according to any one of claims 1 to 3 and 6, It is characterized in that The fixed time period is one day.

10. The method according to claim 1, It is characterized in that The number of the low-orbit satellite onboard receiver and the number of the ground monitoring station receiver are both 1.

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