CN118091718A - A method to improve UT1 solution accuracy through downlink navigation signals from low-orbit satellites - Google Patents

Abstract

The present invention discloses a method for improving the accuracy of UT1 solution through downlink navigation signals from low-orbit satellites, by pre-processing the pseudo-range observations and carrier phase observations corresponding to the GNSS satellites and low-orbit satellites respectively; then performing inter-station and inter-satellite double difference processing to obtain the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and low-orbit satellites respectively; solving the global network solution product according to the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and low-orbit satellites respectively, and obtaining UT1-UTC from the global network solution product, and then obtaining UT1 from UT1-UTC. The present invention combines GNSS satellites and low-orbit satellites in the process of solving UT1, so that the global network solution product solved by the present invention has higher accuracy, thereby improving the solution accuracy of UT1.

Description

A method to improve UT1 solution accuracy by downlinking navigation signals from low-orbit satellites

Technical Field

The invention belongs to the field of communication, navigation and remote sensing, and in particular relates to a method for improving UT1 solution accuracy by downlinking navigation signals from low-orbit satellites.

Background technique

The precise determination of the Earth's rotation parameters is an important prerequisite for the conversion between the celestial reference system and the terrestrial reference system, and plays an indispensable role in aerospace measurement and control, deep space exploration, precision timing, satellite navigation and other fields. The Earth's rotation parameters mainly include polar motion parameters 、/> , and UT1 (Universal Time) - UTC (Coordinated Universal Time), where UT1-UTC represents the difference between Universal Time and Coordinated Universal Time. There are many ways to measure the Earth's rotation parameters. The most common ones are Very Long Baseline Interfere (VLBI), Satellite Laser Ranging (SLR), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) and Global Navigation Satellite System (GNSS). Among them, the Earth's rotation parameter measurement technology based on GNSS observation has unique advantages and can provide stable and routine Earth's rotation parameter products. This is mainly due to the relatively low cost of GNSS ground stations, the wide distribution of ground stations, continuous observations, and the increasing number of satellites in each GNSS system. The solution of UT1 is often carried out simultaneously with the GNSS satellite orbit determination and a series of other parameter solutions. It is one of the fixed output products of major GNSS analysis centers around the world, including my country's international GNSS Monitoring & Assessment System (iGMAS) when performing GNSS global network solutions.

However, since GNSS satellites are medium- and high-orbit satellites, their flight speed is limited, and the geometric changes of the ground stations on the earth are slow, which leads to low calculation accuracy of GNSS global network products. Correspondingly, the calculation accuracy of UT1-UTC is also relatively low.

Summary of the invention

In order to solve the above problems existing in the prior art, the present invention provides a method for improving the UT1 solution accuracy by downlinking navigation signals from low-orbit satellites.

The technical problem to be solved by the present invention is achieved through the following technical solutions:

The present invention provides a method for improving UT1 solution accuracy by downlinking navigation signals from low-orbit satellites, the method comprising:

Perform data preprocessing on the pseudo-range observations and carrier phase observations corresponding to the GNSS satellites and low-orbit satellites;

The pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellites and low-orbit satellites after data preprocessing are subjected to inter-station and inter-satellite double difference processing respectively, so as to obtain double-difference pseudo-range observation values and double-difference carrier phase observation values corresponding to the GNSS satellites and low-orbit satellites respectively;

A global network solution product is calculated according to the double-difference pseudo-range observation values and the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, and UT1-UTC is obtained from the global network solution product, and UT1 is obtained from the UT1-UTC; the global network solution product includes multiple global network solution parameters, and the multiple global network solution parameters include the UT1-UTC.

Optionally, calculating a global network solution product according to double-difference pseudorange observation values and double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, and obtaining UT1-UTC from the global network solution product, including:

In the case of unfixed ambiguity, the global network solution product is calculated based on the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and low-orbit satellites respectively;

Using the global network solution product without fixed ambiguity as the initial value, the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite is fixed to obtain the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite;

Substituting the integer ambiguities of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, so as to update the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite;

The global network solution product under the condition of fixed ambiguity is recalculated according to the double-difference pseudo-range observation values corresponding to the GNSS satellite and the low-orbit satellite and the updated double-difference carrier phase observation values, and UT1-UTC is obtained from the global network solution product solved this time.

Optionally, data preprocessing is performed on the pseudorange observation values and carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, including:

The ionosphere-free combined single-point positioning method is used to preprocess the pseudorange observations corresponding to the GNSS satellites and the low-orbit satellites, and the inter-station single-difference processing method is used to preprocess the carrier phase observations corresponding to the GNSS satellites and the low-orbit satellites.

Optionally, inter-station and inter-satellite double difference processing is performed on the pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively after data preprocessing to obtain double-difference pseudo-range observation values and double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively, including:

For each GNSS satellite, obtain the first inter-station single difference of the pseudorange observation values of the GNSS satellite to different ground stations;

For every two GNSS satellites, the difference between the first inter-station single differences of the two GNSS satellites for the same ground station group is obtained as the double-difference pseudo-range observation values corresponding to the two GNSS satellites;

For each GNSS satellite, obtain the second inter-station single difference of the carrier phase observation values of the GNSS satellite to different ground stations;

For every two GNSS satellites, obtain the difference between the second inter-station single differences of the two GNSS satellites for the same ground station group as the double-difference carrier phase observation values corresponding to the two GNSS satellites;

For each low-orbit satellite, obtain the third-station single difference of the pseudo-range observation values of the low-orbit satellite to different ground stations;

For every two low-orbit satellites, obtain the difference between the third stations of the two low-orbit satellites for the same ground station group as the double-difference pseudo-range observation values corresponding to the two low-orbit satellites;

For each low-orbit satellite, obtain the fourth inter-station single difference of the carrier phase observation values of the low-orbit satellite to different ground stations;

For every two low-orbit satellites, the difference between the fourth inter-station single differences of the two low-orbit satellites for the same ground station group is obtained as the double-difference carrier phase observation values corresponding to the two low-orbit satellites.

Optionally, the global network solution product specifically includes: ground station coordinates, tropospheric parameters, GNSS satellite orbits, low-orbit satellite orbits, GNSS satellite clock errors, low-orbit satellite clock errors and the UT1-UTC.

The present invention provides a method for improving UT1 solution accuracy through downlink navigation signals from low-orbit satellites. The method comprises the following steps: performing data preprocessing on pseudo-range observation values and carrier phase observation values corresponding to GNSS satellites and low-orbit satellites respectively; performing inter-station and inter-satellite double difference processing on pseudo-range observation values and carrier phase observation values corresponding to GNSS satellites and low-orbit satellites respectively after data preprocessing, so as to obtain double-difference pseudo-range observation values and double-difference carrier phase observation values corresponding to GNSS satellites and low-orbit satellites respectively; solving global network solution products according to double-difference pseudo-range observation values and double-difference carrier phase observation values corresponding to GNSS satellites and low-orbit satellites respectively, obtaining UT1-UTC from the global network solution products, and obtaining UT1 from UT1-UTC; the global network solution products include multiple global network solution parameters, and the multiple global network solution parameters include UT1-UTC.

Compared with the prior art, the present invention significantly increases the number of satellites by combining GNSS satellites and low-orbit satellites to work together in the UT1-UTC solution process, and utilizes the characteristics of GNSS satellites that can cover the earth over a large area and provide continuous observation values, and the characteristics of low-orbit satellites and ground stations that have rapid relative geometric changes and can provide more observation values. The global network solution product calculated by the present invention is more accurate, so a more accurate UT1-UTC can be obtained from the global network solution product, and a more accurate UT1 can be obtained from UT1-UTC, thereby improving the solution accuracy of UT1.

The present invention will be further described in detail below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a flow chart of a method for improving UT1 solution accuracy by downlinking navigation signals from low-orbit satellites provided in an embodiment of the present invention;

FIG2 is a flow chart of another method for improving UT1 solution accuracy through downlink navigation signals from low-orbit satellites provided in an embodiment of the present invention.

Detailed ways

The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

The precise measurement of UT1-UTC changes is an important prerequisite for realizing the conversion between the celestial reference system and the terrestrial reference system. The difference between UT1 and UTC is caused by factors such as the instability of the earth's rotation speed and perturbation factors. UT1 stands for Universal Time, which is the time determined according to the earth's rotation period. It can accurately reflect the angular position of the earth in space and is the time scale used by the astronomical community. UTC stands for Coordinated Universal Time, which is a time measurement system that is as close to the universal time as possible in terms of time. Therefore, the accuracy of UT1-UTC changes is obtained by exploring the solution accuracy of UT1. In order to solve the problem of low solution accuracy of UT1, an embodiment of the present invention provides a method for improving the solution accuracy of UT1 by downlinking navigation signals from low-orbit satellites.

A method for improving UT1 solution accuracy by downlinking navigation signals from low-orbit satellites provided by an embodiment of the present invention will be described in detail below. Referring to FIG. 1 , FIG. 1 is a flow chart of a method for improving UT1 solution accuracy by downlinking navigation signals from low-orbit satellites provided by an embodiment of the present invention, and the steps are as follows:

Step S101, performing data preprocessing on pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively.

In the embodiment of the present invention, the GNSS satellite is a medium or high orbit satellite. Because of its long orbit period, it can cover a large area of the earth, so that the ground station has better tracking and communication capabilities. The satellite orbit of the low-orbit satellite is low, and the relative geometry changes with the ground station are fast. And because of the large number of low-orbit satellites, it can provide more observation values.

A pseudorange observation value refers to the distance calculated by the propagation time from the pseudorange signal transmitted by the satellite to the ground station. The measured distance contains errors, that is, the distance represented by the observation value is not the true distance. Therefore, the observation value is a pseudorange observation value.

In the embodiment of the present invention, for a GNSS satellite, the pseudorange observation value of the GNSS satellite is determined by the propagation time of the GNSS satellite pseudorange signal sent by the GNSS satellite to the ground station. For a low-orbit satellite, the pseudorange observation value of the low-orbit satellite is determined by the propagation time of the low-orbit satellite downlink pseudorange signal sent by the low-orbit satellite to the ground station.

The carrier phase observation value is the measured value of the phase difference between the carrier signal transmitted by the satellite and the local oscillator signal of the ground station receiver after the ground station locks the satellite.

In the embodiment of the present invention, for a GNSS satellite, its carrier phase observation value is the measurement value of the phase difference between the carrier signal sent by the GNSS satellite and the local oscillator signal of the ground station receiver after the ground station receiver locks the GNSS satellite. For a low-orbit satellite, its carrier phase observation value is the measurement value of the phase difference between the carrier signal sent by the low-orbit satellite and the local oscillator signal of the ground station after the ground station receiver locks the low-orbit satellite.

Data preprocessing is performed on the pseudorange observations and carrier phase observations corresponding to the GNSS satellites and low-orbit satellites, including:

The ionosphere-free combined single-point positioning method is used to preprocess the pseudorange observations corresponding to the GNSS satellite and the low-orbit satellite, and the inter-station single-difference processing method is used to preprocess the carrier phase observations corresponding to the GNSS satellite and the low-orbit satellite.

In the embodiment of the present invention, the ionospheric-free combination technology refers to a linear combination technology that uses dual-frequency observation to eliminate the first-order ionospheric delay, which can greatly reduce the impact of ionospheric delay on the propagation of signals from GNSS satellites and low-orbit satellites. Single-point positioning is a basic positioning method, which refers to a method of determining the position of a ground station based on satellite broadcast ephemeris and pseudo-range observations of the ground station, and is used for approximate navigation positioning.

In an embodiment of the present invention, the step of performing data preprocessing on pseudorange observation values corresponding to the GNSS satellite and the low-orbit satellite respectively by using the ionosphere-free combined single-point positioning method comprises:

(1) Using the GNSS satellite broadcast ephemeris, GNSS satellite pseudorange signals and ground station prior coordinates, the ionosphere-free combined single-point positioning method is used to preprocess the GNSS pseudorange observations.

Among them, GNSS satellite broadcast ephemeris is determined and provided by the ground control part of the global positioning system. It is a data format in which the satellite navigation system broadcasts relevant information of GNSS satellites to ground stations via radio signals so that users can accurately locate and navigate. GNSS satellite broadcast ephemeris includes GNSS satellite number, GNSS satellite root number, GNSS satellite clock error and other GNSS satellite related information.

(2) Using the initial orbit of the low-orbit satellite, the downlink pseudo-range signal of the low-orbit satellite and the prior coordinates of the ground station, the ionosphere-free combined single-point positioning method is used to preprocess the downlink pseudo-range observation of the low-orbit satellite.

Among them, the initial low-orbit satellite orbit refers to the low-orbit satellite orbit with slightly lower accuracy that is initially used in the calculation.

In the embodiment of the present invention, the ionosphere-free combined single-point positioning method is used to perform data preprocessing on the pseudo-range observation values corresponding to the GNSS satellite and the low-orbit satellite, and the gross errors of the pseudo-range observations can be eliminated by calculating the residuals.

In an embodiment of the present invention, using an inter-station single difference processing method to perform data preprocessing on carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite includes:

The carrier phase observations corresponding to the GNSS satellites and low-orbit satellites are processed by inter-station single difference. Inter-station single difference refers to the difference of the observations of the same satellite by two ground stations at a single moment. Inter-station single difference can eliminate satellite clock errors and significantly reduce delay errors in the ionosphere and troposphere.

After the inter-station single difference processing, the carrier phase observations corresponding to the GNSS satellites and LEO satellites are preprocessed using the prior GNSS satellite orbits, the prior LEO satellite orbits and the prior ground station coordinates, and cycle slip detection is carried out to eliminate wild values and unreasonable values in the carrier phase observations corresponding to the GNSS satellites and LEO satellites.

In an embodiment of the present invention, data preprocessing is performed on the pseudorange observation values and carrier phase observation values corresponding to the GNSS satellites and the low-orbit satellites respectively, so that observations of poor quality can be eliminated, providing a more stable and reliable data basis for subsequent data processing.

Step S102, performing inter-station and inter-satellite double difference processing on the pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing, to obtain double-difference pseudo-range observation values and double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite.

In the embodiment of the present invention, the inter-station single difference refers to the difference between the observation values of two ground stations on the same satellite, and the observation value refers to the pseudorange observation value or the carrier phase observation value. After observing two satellites at two different ground stations, two inter-station single differences are formed, and the process of combining the two inter-station single differences is called inter-station and inter-satellite double differences.

The pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing are subjected to inter-station and inter-satellite double difference processing respectively, and the double difference pseudo-range observation values and double difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite are obtained, including:

For each GNSS satellite, the first inter-station single difference of the pseudorange observation values of the GNSS satellite for different ground stations is calculated; for every two GNSS satellites, the difference between the first inter-station single differences of the two GNSS satellites for the same ground station group is calculated as the double-difference pseudorange observation values corresponding to the two GNSS satellites.

For each GNSS satellite, the second inter-station single difference of the carrier phase observation values of the GNSS satellite for different ground stations is calculated; for every two GNSS satellites, the difference between the second inter-station single differences of the two GNSS satellites for the same ground station group is calculated as the double-difference carrier phase observation values corresponding to the two GNSS satellites.

For each low-orbit satellite, the third-station single difference of the pseudo-range observation values of the low-orbit satellite for different ground stations is calculated; for every two low-orbit satellites, the difference between the third-station single differences of the two low-orbit satellites for the same ground station group is calculated as the double-difference pseudo-range observation values corresponding to the two low-orbit satellites.

For each low-orbit satellite, the fourth inter-station single difference of the carrier phase observation values of the low-orbit satellite for different ground stations is calculated; for every two low-orbit satellites, the difference between the fourth inter-station single differences of the two low-orbit satellites for the same ground station group is calculated as the double-difference carrier phase observation value corresponding to the two low-orbit satellites.

In an embodiment of the present invention, by performing inter-station and inter-satellite double difference processing on the pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellites and low-orbit satellites after data preprocessing, errors such as satellite clock error, ground clock error, satellite hardware delay, and receiver hardware delay can be eliminated.

Step S103, calculating the global network solution product according to the double-difference pseudo-range observation values and double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, and obtaining UT1-UTC from the global network solution product, and obtaining UT1 from UT1-UTC.

Specifically, the global network solution product includes multiple global network solution parameters, including ground station coordinates, tropospheric parameters, GNSS satellite orbits, low-orbit satellite orbits, GNSS satellite clock errors, low-orbit satellite clock errors, and UT1-UTC. Therefore, UT1-UTC can be obtained from the global network solution product, and UT1 can be obtained from UT1-UTC.

The ground station coordinates refer to the coordinates of the reference point of the ground station in the earth-fixed coordinate system.

Tropospheric parameters refer to zenith tropospheric parameters.

Satellite orbit refers to the coordinates of the satellite in the Earth-fixed coordinate system.

Satellite clock error refers to the difference between the atomic clock on the satellite and the reference time scale (such as GPST). Correspondingly, the GNSS satellite clock error is the difference between the atomic clock on the GNSS satellite and the reference time scale; the low-orbit satellite clock error is the difference between the atomic clock on the low-orbit satellite and the reference time scale.

In the embodiment of the present invention, according to the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and the low-orbit satellites, the initial values calculated according to various models are substituted in the solution process, and then the global network solution products are gradually solved according to the least squares method. Among them, various models include the earth gravity field model, the Saastamoinen tropospheric model, the relativistic effect model and other models.

The specific solution process can be found in the prior art.

From the solved global network solution product, UT1-UTC can be obtained, and UT1 can be obtained from UT1-UTC.

Compared with the prior art, the embodiment of the present invention significantly increases the number of satellites by combining GNSS satellites and low-orbit satellites to work together in the UT1-UTC solution process. GNSS satellites can cover a large area of the earth and provide continuous observation values. The relative geometry of low-orbit satellites and ground stations changes rapidly, and more observation values can be provided. As a result, the global network solution product calculated by the embodiment of the present invention has higher accuracy. Therefore, a more accurate UT1-UTC can be obtained from the global network solution product, and a more accurate UT1 can be obtained from UT1-UTC, thereby improving the solution accuracy of UT1.

In an embodiment of the present invention, the specific steps of calculating the global network solution product according to the double-difference pseudo-range observation values and the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, and obtaining UT1-UTC from the global network solution product include:

Step 1: Under the condition of not fixing the ambiguity, the global network solution product is solved according to the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and the low-orbit satellites.

In the embodiment of the present invention, the ambiguity is the integer ambiguity. The integer ambiguity refers to the integer cycle number of the carrier phase measured from the satellite to the ground station, which is an unknown quantity. The unfixed ambiguity can be understood as a floating point ambiguity. Specifically, the floating point ambiguity is that the integer ambiguity of the carrier phase is not fixed to an integer, but is replaced by a floating point estimate.

In the case of unfixed ambiguity, according to the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and the low-orbit satellites, the initial values calculated according to various models are substituted into the solution process, and the difference between the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and the low-orbit satellites and the initial values calculated by various models is calculated. The initial global network solution product can be obtained by gradually solving according to the least squares method. Compared with the prior art that only uses the relevant data of GNSS satellites to solve the global network solution product, since the double-difference pseudo-range observations and double-difference carrier phase observations of low-orbit satellites have been introduced, the accuracy of various parameters in the initial global network solution product obtained at this time has been improved compared with the accuracy of various parameters in the global network solution product under the condition of unfixed ambiguity in the prior art, but in order to further improve the accuracy, the following operations can be performed.

Step 2: Using the global network solution product without fixed ambiguity as the initial value, perform integer ambiguity fixing processing on the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, and obtain the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite.

In the embodiment of the present invention, the global network solution product under the condition of unfixed ambiguity is used as the initial value to perform integer ambiguity fixing processing. The process of integer ambiguity fixing processing is to map the floating point ambiguity to the integer domain. The specific operation mode of integer ambiguity fixing processing can be implemented by Kalman algorithm or LAMBDA algorithm (an iterative algorithm for solving function optimization problems), etc. For details, please refer to the prior art, which is not limited here.

In the embodiment of the present invention, the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite is obtained, that is, the fixed solution of the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite is obtained. The fixed solution indicates that the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite has been solved, which is the most accurate solution type of the integer ambiguity.

Step 3: Substitute the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, so as to update the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite.

In an embodiment of the present invention, since the integer ambiguity has been resolved, the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite can be substituted into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, and the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite can be updated to more correct values.

Step 4: Recalculate the global network solution product under the fixed ambiguity condition according to the double-difference pseudo-range observation values corresponding to the GNSS satellite and the low-orbit satellite and the updated double-difference carrier phase observation values, and obtain UT1-UTC from the global network solution product solved this time.

In the embodiment of the present invention, since the integer ambiguity has been substituted into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, the global network solution product under the condition of fixed ambiguity can be recalculated according to the double-difference pseudo-range observation values corresponding to the GNSS satellite and the low-orbit satellite and the double-difference carrier phase observation values substituted into the integer ambiguity, thereby obtaining a global network solution product under the condition of fixed ambiguity with higher accuracy of various parameters. Then, UT1-UTC is obtained from the global network solution product with higher accuracy of various parameters, thereby improving the accuracy of UT1-UTC solution.

In the embodiment of the present invention, the global network solution product under the condition of non-fixed ambiguity is used to solve the integer ambiguity. Since the fixed solution of the integer ambiguity is the most accurate solution type of the integer ambiguity, the accuracy of various parameters of the global network solution product under the condition of fixed ambiguity calculated based on the solved integer ambiguity is further improved. Therefore, a higher accuracy UT1-UTC can be obtained according to the global network solution product under the condition of fixed ambiguity.

It is understandable that the accuracy of various parameters in the global network solution product under the condition of unfixed ambiguity is lower than the accuracy of various parameters in the global network solution product under the condition of fixed ambiguity.

In order to further illustrate how to improve the UT1 solution accuracy through the downlink navigation signal of the low-orbit satellite, an embodiment of the present invention provides another method for improving the UT1 solution accuracy through the downlink navigation signal of the low-orbit satellite, referring to FIG. 2, FIG. 2 is a flow chart of another method for improving the UT1 solution accuracy through the downlink navigation signal of the low-orbit satellite provided by an embodiment of the present invention, and the steps are as follows:

Step S201, performing data preprocessing on the pseudo-range observation values corresponding to the GNSS satellite and the low-orbit satellite.

The specific data preprocessing process is as described in step S101 and will not be repeated here.

Step S202: GNSS satellite carrier phase preprocessing and low-orbit satellite carrier phase preprocessing.

Specifically, the inter-station single-difference processing method is used to preprocess the carrier phase observation values corresponding to GNSS satellites and low-orbit satellites respectively, which can eliminate satellite clock errors and significantly reduce delay errors in the ionosphere and troposphere.

Step S203, floating point ambiguity global network solution.

In the embodiment of the present invention, the floating point ambiguity can be understood as unfixed ambiguity, that is, the global network solution product is solved without fixing the ambiguity.

First, it is necessary to perform inter-station and inter-satellite double-difference processing on the pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively to eliminate errors such as satellite clock error, ground clock error, satellite hardware delay, and receiver hardware delay, and obtain the double-difference pseudo-range observation values and double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively.

The meaning of the inter-station and inter-satellite double differences has been described above and will not be repeated here.

After obtaining the double-difference pseudo-range observations and double-difference carrier phase observations corresponding to the GNSS satellites and low-orbit satellites respectively, the global network solution products are solved according to the obtained double-difference pseudo-range observations and double-difference carrier phase observations without fixing the ambiguity, and the preliminary global network solution products are obtained to complete the floating-point ambiguity global network solution.

Step S204, the GNSS satellite integer ambiguity is fixed and the low-orbit satellite integer ambiguity is fixed.

In an embodiment of the present invention, integer ambiguity fixing processing is performed on the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively according to the preliminary global network solution product obtained in step S203, so that the integer ambiguity of the double-difference carrier phase observation value corresponding to the GNSS satellite and the integer ambiguity of the double-difference carrier phase observation value corresponding to the low-orbit satellite can be obtained.

Step S205, fix the ambiguity global network solution.

After obtaining the integer ambiguity of the double-difference carrier phase observation value corresponding to the GNSS satellite and the integer ambiguity of the double-difference carrier phase observation value corresponding to the low-orbit satellite, they are substituted into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively to update the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite respectively.

In order to further improve the accuracy of various parameters in the global network solution products, the global network solution products under fixed ambiguity conditions can be recalculated according to the double-difference pseudo-range observations corresponding to the GNSS satellites and the low-orbit satellites and the updated double-difference carrier phase observations, so as to obtain the global network solution products under fixed ambiguity conditions, and then the more accurate UT1-UTC can be obtained according to the global network solution products under fixed ambiguity conditions, and then the more accurate UT1 can be obtained from UT1-UTC.

In an embodiment of the present invention, the downlink navigation signal of the low-orbit satellite and the signal of the GNSS satellite are integrated into the UT1 solution process, so that the number of observation values is greatly increased. The GNSS satellite can cover the earth over a large area and provide the characteristics of continuous observation values. The relative geometric changes between the low-orbit satellite and the ground station are fast, and more observation values can be provided. Therefore, the calculated global network solution product has higher accuracy. Therefore, a more accurate UT1-UTC can be obtained from the global network solution product, and a more accurate UT1 can be obtained from UT1-UTC, thereby improving the UT1 solution accuracy.

It should be noted that the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. On the contrary, they are merely examples of methods consistent with some aspects of the present invention.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art can understand and implement other changes to the disclosed embodiments by viewing the drawings and the disclosed content. In the description of the present invention, the term "comprising" does not exclude other components or steps, "one" or "an" does not exclude multiple situations, and "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims (5)

1. A method for improving UT1 resolution via low-orbit satellite downlink navigation signals, the method comprising:

performing data preprocessing on pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellites and the low-orbit satellites respectively;

Respectively carrying out inter-station inter-satellite double-difference processing on the pseudo-range observed value and the carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing to obtain a double-difference pseudo-range observed value and a double-difference carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite;

According to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which correspond to the GNSS satellite and the low-orbit satellite respectively, calculating a global network solution product, acquiring UT1-UTC from the global network solution product, and acquiring UT1 from the UT 1-UTC; the global solution product includes a plurality of global solution parameters including the UT1-UTC.

2. The method of claim 1, wherein resolving a global solution product from the double-differential pseudorange observations and the double-differential carrier-phase observations corresponding to each of the GNSS satellites and the low-orbit satellites, and obtaining UT1-UTC from the global solution product, comprises:

Under the condition of no fixed ambiguity, calculating a global network solution product according to the double-difference pseudo-range observed value and the double-difference carrier phase observed value which correspond to the GNSS satellite and the low-orbit satellite respectively;

taking a global solution product under the condition of unfixed ambiguity as an initial value, and performing integer ambiguity fixing processing on the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively to obtain the integer ambiguity of the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively;

Substituting the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite so as to update the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite;

And re-calculating a global network solution product under the condition of fixed ambiguity according to the double-difference pseudo-range observation value corresponding to the GNSS satellite and the low-orbit satellite and the updated double-difference carrier phase observation value, and acquiring UT1-UTC from the calculated global network solution product.

3. The method of claim 1, wherein the data preprocessing of the pseudorange observations and the carrier phase observations for each of the GNSS satellites and the low-orbit satellites comprises:

and carrying out data preprocessing on pseudo-range observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an ionosphere-free combined single-point positioning method, and carrying out data preprocessing on carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an inter-station single-difference processing method.

4. The method of claim 1, wherein performing inter-station inter-satellite double difference processing on the pseudo-range observed values and the carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites after the data preprocessing respectively to obtain double-difference pseudo-range observed values and double-difference carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites respectively, comprises:

For each GNSS satellite, obtaining a first inter-station single difference of pseudo-range observation values of the GNSS satellite on different ground stations;

For each two GNSS satellites, calculating the difference of single differences between the two GNSS satellites for the first stations of the same ground station group, and taking the difference as a double-difference pseudo-range observation value corresponding to the two GNSS satellites;

For each GNSS satellite, obtaining a second inter-station single difference of carrier phase observed values of the GNSS satellite on different ground stations;

for every two GNSS satellites, calculating the difference of single differences between the two GNSS satellites and the second stations of the same ground station group, and taking the difference as a double-difference carrier phase observation value corresponding to the two GNSS satellites;

for each low-orbit satellite, calculating a third inter-station single difference of pseudo-range observation values of the low-orbit satellite to different ground stations;

For each two low-orbit satellites, calculating the difference of single differences between the two low-orbit satellites and a third station of the same ground station group, and taking the difference as a double-difference pseudo-range observation value corresponding to the two low-orbit satellites;

for each low-orbit satellite, obtaining a fourth inter-station single difference of carrier phase observed values of the low-orbit satellite for different ground stations;

For each two low-orbit satellites, the difference of single differences between the two low-orbit satellites and a fourth station of the same ground station group is obtained and is used as a double-difference carrier phase observation value corresponding to the two low-orbit satellites.

5. The method according to claim 1, characterized in that said global solution product comprises in particular: ground station coordinates, tropospheric parameters, GNSS satellite orbits, low-orbit satellite orbits, GNSS satellite clock biases, low-orbit satellite clock biases, and the UT1-UTC.