CN114814891A - Integrity monitoring method of satellite navigation system - Google Patents
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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- G—PHYSICS
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Abstract
The invention relates to the technical field of satellite navigation systems, and provides a method for monitoring the integrity of a satellite navigation system, wherein the satellite navigation system executes the following actions: receiving bidirectional measurement data of an inter-satellite link, correcting errors, and performing reduction on bidirectional observation data of the inter-satellite link by using a forecast orbit and a forecast clock error parameter to determine a first inter-satellite geometric distance and a first relative clock error; calculating a second inter-satellite geometric distance and a second relative clock error according to the satellite navigation message; respectively subtracting the second inter-satellite geometric distance and the second relative clock difference from the first inter-satellite geometric distance and the first relative clock difference to determine a geometric distance residual error and a relative clock difference residual error; receiving pseudo-range data and phase data of a satellite downlink navigation signal from a ground monitoring station, correcting errors, and calculating a navigation satellite equivalent distance error by using a satellite navigation message; and judging the intact state of the satellite load according to the geometric distance residual error, the relative clock error residual error and the navigation satellite equivalent distance error.
Description
Technical Field
The present invention relates generally to the field of satellite navigation systems. In particular, the invention relates to a method for integrity monitoring of a satellite navigation system.
Background
The integrity of a satellite navigation system, which requires that the satellite navigation system can monitor the in-orbit operation state of a satellite in real time and inform a user of an imperfect identification the first time after a satellite failure affecting the navigation service, is one of its important service attributes. In the current satellite navigation system, a GPS system and a Galileo system both design a completeness parameter system with strict logic and a service mechanism. With the benefit of being able to arrange a ground monitoring station and a data transmission link globally, the GPS system and the Galileo system can monitor the health of the satellites globally in real time and inform users of abnormal situations.
The Beidou satellite navigation system is a satellite navigation system independently constructed in China. Its construction follows the development strategy of "three-step walking". In 2003, the construction of the Beidou I system with independent positioning of constrained elevation is completed, and the first-step development planning is completed. In 2012, Beidou II completes system construction and provides navigation positioning time service for Asia-Pacific region. In 2020, the Beidou third system completes networking and formally provides service to the global scope.
However, the satellite integrity monitoring method of the GPS system and the Galileo system using the global distribution monitoring station is not suitable for the beidou satellite navigation system. This is because the beidou satellite navigation system does not realize the construction of global distribution ground stations, and the design of beidou satellites is significantly different from GPS satellites and Galileo satellites, and the on-satellite load of beidou satellites is more complicated, and faces more integrity monitoring objects.
The Beidou No. two system designs a complete satellite state real-time monitoring and abnormal alarming method, and is continued to the Beidou No. three system, and the satellite load state is judged in real time by monitoring satellite clock error of satellite-ground bidirectional time synchronization real-time measurement and satellite user equivalent distance error calculated by a monitoring receiver. If the clock error of the satellite is abnormal and the equivalent distance error of the user is normal, the satellite uplink spread spectrum receiver can be positioned to be abnormal; if the satellite clock error is abnormal and the user equivalent distance error is abnormal, the satellite-borne atomic clock can be positioned as a satellite fault; if the satellite clock error is normal and the user equivalent distance error is abnormal, the satellite downlink navigation signal can be positioned to be abnormal in transmission.
However, since the Beidou satellite navigation system can only distribute stations in a region, when the Beidou satellite runs out, the satellite-ground bidirectional time synchronization result and the monitoring result of the equivalent distance error of the monitoring receiver user are not effective any more. In addition, different from the Beidou second satellite, the Beidou third satellite carries inter-satellite link load, and the original method cannot meet the integrity monitoring requirement of the inter-satellite link load.
Therefore, according to the engineering practice of the Beidou third satellite navigation system, a Beidou third satellite overseas arc segment integrity monitoring and abnormity warning method is required.
Scientists in the german space navigation bureau (DLR) have proposed using inter-satellite link measurements to achieve satellite integrity status monitoring and anomaly alerts. However, the method can only identify satellite faults, the reliability of the inter-satellite link load is believed, the possible fault conditions are ignored, the satellite fault load cannot be judged and identified, and false alarms and false alarm failures are easily generated.
At present, the Beidou satellite III is designed and an on-satellite autonomous integrity monitoring method is realized. However, the method can only realize the small-circle monitoring of the satellite faults, and cannot identify all the satellite faults. And the on-orbit operation of the prior Beidou third satellite shows that the satellite autonomous integrity monitoring load also has the problems of poor reliability, more false alarms and the like.
Disclosure of Invention
To at least partially solve the above problems in the prior art, the present invention provides an integrity monitoring method for a satellite navigation system, wherein the following actions are performed by the satellite navigation system:
receiving bidirectional measurement data of an inter-satellite link, correcting errors, and performing reduction on bidirectional observation data of the inter-satellite link by using a forecast orbit and a forecast clock error parameter to determine a first inter-satellite geometric distance and a first relative clock error;
calculating a second inter-satellite geometric distance and a second relative clock error according to the satellite navigation message;
respectively subtracting the second inter-satellite geometric distance and the second relative clock difference from the first inter-satellite geometric distance and the first relative clock difference to determine a geometric distance residual error and a relative clock difference residual error;
receiving pseudo-range data and phase data of a satellite downlink navigation signal from a ground monitoring station, correcting errors, and calculating a navigation satellite equivalent distance error by using a satellite navigation message; and
and judging the intact state of the satellite load according to the geometric distance residual error, the relative clock error residual error and the navigation satellite equivalent distance error.
In one embodiment of the invention, it is provided that the determination of the first inter-satellite geometric distance and the first relative clock offset comprises the following steps:
at a first time t 1 And a second time t 2 Receiving bidirectional measurement data of an inter-satellite link and deducting errors to construct an observation equation, which is expressed as the following formula:
where ρ is AB (t 1 ) Indicating that the second satellite is at t 1 The time of day is received from a pseudorange measurement, p, from a first satellite BA (t 2 ) Indicating a first satellite at t 2 A pseudorange measurement is received from a second satellite at a time,
indicating the three-dimensional position of the first satellite and the second satellite, clk A 、clk B Respectively representing the satellite clock error of the first satellite and the second satellite, c representing the speed of light, Δ t 1 And Δ t 2 When the line of light is represented, the line of light,
and
respectively representing the transmit delay and the receive delay of the first satellite,
and
respectively representing the transmission delay and the reception delay of the second satellite,
and
respectively representing first error correction terms;
the first time t 1 And a second time t 2 The bidirectional measurement data of the inter-satellite link is reduced to the target time t 0 Expressed as the following formula:
where d ρ AB And d ρ BA Respectively representing the satellite distance difference and the satellite clock difference between the observation epoch and the target epoch, and calculating by using the forecast orbit and the forecast clock difference parameters, wherein the parameters are represented as follows:
determining a first inter-satellite geometric distance, wherein p AB (t 0 ) Andρ BA (t 0 ) Adding to eliminate satellite clock error information, represented by the following equation:
determining a first relative clock difference, wherein p AB (t 0 ) And ρ BA (t 0 ) Differencing to eliminate satellite orbit information is expressed as:
in one embodiment of the invention it is provided that the first error correction term comprises satellite antenna phase centre error, relativistic effects error, tropospheric delay error, station eccentricity error and tidal effects error.
In one embodiment of the invention, it is provided that the calculated geometric distance residual is expressed as:
wherein,
representing the geometric range residuals of the first satellite and the second satellite,
and
respectively representing the positions of the second satellite and the first satellite calculated by using the satellite navigation messages; and
the calculated relative clock error residual is expressed as:
wherein,
a calculated residual, clk, representing the relative clock difference of the first satellite and the second satellite B (t 0 ) And clk A (t 0 ) Respectively, the clock offsets of the second satellite and the first satellite calculated using the satellite navigation messages.
In one embodiment of the invention, the pseudo range data P and the phase data of the satellite downlink navigation signals of the ground monitoring station are provided
Represented by the formula:
wherein, λ represents the wavelength corresponding to the phase data,
and
representing satellite and receiver position vectors, c the speed of light, at, respectively rcvclk And Δ t satclk Respectively representing receiver clock error and satellite clock error, Δ D phs Representing satellite antenna phase centre deviation, Δ D rel Representing the delay, Δ D, due to relativistic effects trop Representing tropospheric delay, Δ D Ion Indicating ionospheric delay, Δ D ecc Indicating the correction of the eccentricity of the survey station, Δ D gtide Indicating station tidal correction, Δ D plm Indicating the range deviation caused by the displacement of the station, N indicating the phase data ambiguity, ε c And ε P Multipath and noise representing pseudo range and phase respectively; and
the navigation satellite equivalent range error UERE is expressed as:
where PC represents the ionosphere-free combination of pseudorange data.
In one embodiment of the invention, a geometric distance residual error threshold value, a relative clock error residual error threshold value and a navigation satellite equivalent distance error threshold value are provided, and the geometric distance residual error, the relative clock error residual error and the navigation satellite equivalent distance error of all ground monitoring stations to the first satellite of the first satellite relative to all other satellites in the satellite navigation system are calculated.
In one embodiment of the invention, when the geometric distance residual error of the first satellite relative to all other satellites in the satellite navigation system exceeds the geometric distance residual error threshold value and the navigation satellite equivalent distance error of all ground monitoring stations to the first satellite exceeds the navigation satellite equivalent distance error threshold value, the description precision of the broadcast ephemeris of the first satellite to the satellite orbital motion is judged to be reduced; and/or
When the geometric distance residual or the relative clock error residual of the first satellite relative to all other satellites in the satellite navigation system exceeds the geometric distance residual threshold or the relative clock error residual threshold, and the navigation satellite equivalent distance error of all the ground monitoring stations to the first satellite does not exceed the navigation satellite equivalent distance error threshold, judging that the inter-satellite link measurement of the first satellite is abnormal; and/or
When the relative clock error residual of the first satellite relative to all other satellites in the satellite navigation system exceeds the relative clock error residual threshold and the navigation satellite equivalent distance error of all the ground monitoring stations to the first satellite exceeds the navigation satellite equivalent distance error threshold, judging that the satellite-borne atomic clock of the first satellite is abnormal; and/or
And when the relative clock error residual and the geometric distance residual of the first satellite relative to all other satellites in the satellite navigation system do not exceed the relative clock error residual threshold and the geometric distance residual threshold, and the navigation satellite equivalent distance error of all the ground monitoring stations to the first satellite exceeds the navigation satellite equivalent distance error threshold, judging that the downlink navigation load of the first satellite is abnormal.
In one embodiment of the invention, it is provided that an alarm is issued when an abnormality in the satellite load is determined.
The invention has at least the following beneficial effects: the invention utilizes the inter-satellite link measurement as one of the means for monitoring the satellite health, comprehensively utilizes the inter-satellite link measurement and the pseudo-range phase measurement of a monitoring receiver to realize the real-time judgment of the satellite load fault, and can carry out the method for accurately positioning the satellite fault load. The method can be applied to the outer arc section of the Beidou navigation system, fully considers the requirement of monitoring the integrity of the satellite load of the Beidou third navigation satellite, and can realize the monitoring of various satellite loads including a downlink navigation signal generator, an inter-satellite link load, a satellite-borne atomic clock and the like.
Drawings
To further clarify the advantages and features that may be present in various embodiments of the present invention, a more particular description of various embodiments of the invention will be rendered by reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings, the same or corresponding parts will be denoted by the same or similar reference numerals for clarity.
Fig. 1 is a flow chart illustrating an integrity monitoring method of a satellite navigation system according to an embodiment of the invention.
Detailed Description
It should be noted that the components in the figures may be exaggerated and not necessarily to scale for illustrative purposes. In the figures, identical or functionally identical components are provided with the same reference symbols.
In the present invention, "disposed on …", "disposed over …" and "disposed over …" do not exclude the presence of an intermediate therebetween, unless specifically indicated otherwise. Further, "disposed on or above …" merely indicates the relative positional relationship between two components, and may also be converted to "disposed below or below …" and vice versa in certain cases, such as after reversing the product direction.
In the present invention, the embodiments are only intended to illustrate the aspects of the present invention, and should not be construed as limiting.
In the present invention, the terms "a" and "an" do not exclude the presence of a plurality of elements, unless otherwise specified.
It is further noted herein that in embodiments of the present invention, only a portion of the components or assemblies may be shown for clarity and simplicity, but those of ordinary skill in the art will appreciate that, given the teachings of the present invention, required components or assemblies may be added as needed in a particular scenario. Furthermore, features from different embodiments of the invention may be combined with each other, unless otherwise indicated. For example, a feature of the second embodiment may be substituted for a corresponding or functionally equivalent or similar feature of the first embodiment, and the resulting embodiments are likewise within the scope of the disclosure or recitation of the present application.
It is also noted herein that, within the scope of the present invention, the terms "same", "equal", and the like do not mean that the two values are absolutely equal, but allow some reasonable error, that is, the terms also encompass "substantially the same", "substantially equal". By analogy, in the present invention, the terms "perpendicular", "parallel" and the like in the directions of the tables also cover the meanings of "substantially perpendicular", "substantially parallel".
The numbering of the steps of the methods of the present invention does not limit the order in which the method steps are performed. Unless specifically stated, the method steps may be performed in a different order.
The invention is further elucidated with reference to the drawings in conjunction with the detailed description.
Aiming at the problem that the existing Beidou navigation satellite lacks an effective integrity monitoring means in an overseas arc section, the invention provides an integrity monitoring method which can integrate inter-satellite link measurement and data observed by a ground monitoring station and is used for the Beidou satellite in the overseas arc section.
Fig. 1 is a flow chart illustrating a method for integrity monitoring of a satellite navigation system according to an embodiment of the invention. As shown in fig. 1, the method may include receiving inter-satellite link bidirectional measurement data and correcting errors, and normalizing inter-satellite link bidirectional observation data using the forecasted orbit and forecasted clock error parameters to determine a first inter-satellite geometric distance and a first relative clock error; calculating a second inter-satellite geometric distance and a second relative clock error according to the satellite navigation message; respectively subtracting the second inter-satellite geometric distance and the second relative clock difference from the first inter-satellite geometric distance and the first relative clock difference to determine a geometric distance residual error and a relative clock difference residual error; receiving pseudo-range data and phase data of a satellite downlink navigation signal from a ground monitoring station, correcting errors, and calculating a navigation satellite equivalent distance error by using a satellite navigation message; and judging the intact state of the satellite load according to the geometric distance residual error, the relative clock error residual error and the navigation satellite equivalent distance error.
Specifically, one embodiment of the present invention may include the following steps:
step 100: the satellite navigation system receives the bidirectional measurement data of the inter-satellite link of the full constellation in real time, deducts errors such as a satellite antenna phase center, equipment time delay, relativistic delay and the like, and reduces the bidirectional observation data of the inter-satellite link by using the forecast orbit and clock error parameters to obtain the geometric distance and the relative clock error between the satellites.
Step 200: and calculating the geometric distance between the satellites and the theoretical value of the relative clock error by the satellite navigation system according to the satellite broadcast ephemeris and the clock error parameters contained in the navigation messages broadcast by the satellites. And respectively subtracting the geometric distance between the satellites and the relative clock error theoretical value from the geometric distance between the satellites and the relative clock error obtained in the step one to obtain a geometric distance residual error and a relative clock error residual error.
Step 300: the satellite navigation system receives pseudo-Range phase data of a satellite downlink navigation signal of a ground monitoring station obtained in a public or other mode in real time, deducts relativistic delay, troposphere delay, ionosphere delay and receiver antenna phase center Error, and calculates a navigation satellite Equivalent distance Error (UERE) by using broadcast ephemeris, clock Error and group delay parameters contained in a Beidou satellite navigation message.
Step 400: and judging the real-time health status of the satellite load by the satellite navigation system according to the UERE, the relative geometric distance residual error and the relative clock error residual error of the ground monitoring receiver, and immediately giving an alarm when the satellite load is abnormal.
The following steps may be included in step 100:
step 101: suppose the second satellite is at t 1 Receiving pseudorange measurements ρ from a first satellite at a time AB (t 1 ) The first satellite is at t 2 Receiving pseudorange measurements ρ from a second satellite at a time BA (t 2 ) The observation equation can be expressed as:
wherein,
indicating the three-dimensional position of the first satellite and the second satellite, clk A 、clk B Respectively representing the satellite clock error of the first satellite and the second satellite, c representing the speed of light, Δ t 1 And Δ t 2 When the line of light is represented, the line of light,
and
respectively representing a first satelliteThe transmission delay and the reception delay of the antenna,
and
respectively representing the transmission delay and the reception delay of the second satellite,
and
respectively, error correction terms that can be accurately modeled in one-way ranging. The error correction term may include satellite antenna phase center and relativistic effects, etc. For earth observations, the error correction terms may also include errors such as tropospheric delay, station eccentricity, tidal effects, etc., where the error correction terms can all be accurately modeled.
Step 102: with t 1 And t 2 Representing different moments that differ by no more than 3 s.
The addition of the two-way pseudo ranges at the same time can eliminate satellite clock difference and only include satellite distance for satellite orbit determination; and the subtraction of the simultaneous bidirectional pseudoranges may eliminate the satellite orbit and include only the satellite clock error for clock error determination. It is thus possible to reduce the two-way observations at different times to the same time, assuming that t is assumed 1 And t 2 The measured range value needs to be reduced to the target time t 0 The reduction formula can be expressed as:
where d ρ AB And d ρ BA Respectively representing the satellite distance difference and the satellite clock difference between an observation epoch and a target epochAnd d ρ AB And d ρ BA May be represented by the following formula:
where d ρ AB And d ρ BA Calculations can be made from the satellite predicted orbit and predicted clock error parameters.
Step 103: ρ in step 102 AB (t 0 ) And ρ BA (t 0 ) The method cannot be directly used for measuring the satellite orbit and the clock error and needs further operation.
Will rho AB (t 0 ) And ρ BA (t 0 ) The addition can eliminate satellite clock error information, only contains constraint on satellite orbit parameters, and can be directly used for precise orbit determination processing, and is represented as the following formula:
will rho AB (t 0 ) And ρ BA (t 0 ) The satellite orbit information can be eliminated by differencing, and the satellite clock difference can be directly used for clock difference measurement only and is represented as the following formula:
the following steps may be included in step 200:
step 201: calculating the satellite position by using a broadcast ephemeris transmitted by a satellite navigation signal, and subtracting the calculated geometric distance of the inter-satellite link to obtain the geometric distance residual error of the inter-satellite link of two satellites, wherein the geometric distance residual error is expressed as the following formula:
wherein,
a computed residual representing the geometric distance of the first satellite and the second satellite,
and
respectively, represent the satellite positions computed using broadcast ephemeris.
Step 202: calculating the satellite position by using the broadcast clock error parameter issued by the satellite navigation signal, and subtracting the relative clock error reduced by the inter-satellite link to obtain the relative clock error residual error of the inter-satellite link of two satellites, which is expressed as the following formula:
wherein,
a calculated residual, clk, representing the relative clock difference of the first satellite and the second satellite B (t 0 ) And clk A (t 0 ) Respectively, represent the satellite clock bias calculated using broadcast ephemeris.
The following steps may be included in step 300:
step 301: pseudorange phase data is an important data source for calculating the equivalent range error (UERE) of a navigation satellite. The measurement model in which the pseudorange data P and the phase data are represented by the following equation:
wherein, λ represents the wavelength corresponding to the phase data,
and
representing satellite and receiver position vectors, c the speed of light, at, respectively rcvclk And Δ t satclk Representing receiver clock error and satellite clock error, Δ D, respectively phs Representing satellite antenna phase centre deviation, Δ D rel Representing the delay, Δ D, due to relativistic effects trop Representing tropospheric delay, Δ D Ion Indicating ionospheric delay, Δ D ecc Indicating the correction of the eccentricity of the survey station, Δ D gtide Indicating station tidal correction, Δ D plm Indicating the range deviation caused by the displacement of the station, N indicating the phase data ambiguity, ε c And ε P Multipath and noise representing pseudorange and phase, respectively.
Step 302: the equivalent range error (UERE) of the navigation satellite is comprehensively influenced by satellite orbit error, clock error, medium delay correction error of a space segment and multipath and thermal noise at a receiver end on pseudo-range measurement. For a specific space constellation of the navigation satellite, the smaller the UERE is, the higher the positioning time service precision of the user is. The calculation formula of UERE can be expressed as follows:
where PC represents the ionosphere-free combination of pseudorange data.
If Δ t satclk The precision of the satellite clock error measured in real time by adopting satellite-ground bidirectional time-frequency transmission can be better than 0.5ns, and epsilon represents the noise and the multipath effect at the receiver end. To avoid the influence of pseudo-range multipath, the ue re estimation may use pseudo-range observation values after one-way smoothing of phase data.
The following steps may be included in step 400:
step 401: judging that the description precision of the satellite orbital motion by the broadcast ephemeris of the satellite is reduced when the following conditions occur:
the inter-satellite link geometric distance residual error of a certain satellite to all other satellites calculated according to step 201 at a certain moment
The set threshold is exceeded and the UERE for that satellite for all monitoring stations calculated per step 302 exceeds the set threshold.
Step 402: judging the inter-satellite link measurement abnormality of the satellite when one of the following conditions occurs:
the inter-satellite link geometric distance residual error of a certain satellite to all other satellites calculated according to step 201 at a certain moment
Exceeding a set threshold value, and the UERE of the satellite by all monitoring stations calculated according to the step 302 does not exceed the set threshold value; or
The inter-satellite link relative clock difference residual error of a certain satellite to all other satellites calculated according to step 201 at a certain moment
The set threshold is exceeded and the UERE for that satellite for all monitoring stations calculated per step 302 does not exceed the set threshold.
Step 403: judging the satellite-borne atomic clock of the satellite to be abnormal when the following conditions occur:
the inter-satellite link relative clock difference residual error of a certain satellite to all other satellites calculated according to step 201 at a certain moment
The set threshold is exceeded and the UERE for that satellite for all monitoring stations calculated per step 302 exceeds the set threshold.
Step 404: judging that the downlink navigation load of the satellite is abnormal when the following conditions occur:
a satellite calculated at a time according to step 201 is paired with all other satellitesInter-satellite link relative clock error residual error of satellite
If the set threshold is not exceeded, the inter-satellite link geometric distance residual error of a certain satellite to all other satellites calculated in step 201 is calculated
The set threshold is not exceeded and the UERE for that satellite for all monitoring stations calculated per step 302 exceeds the set threshold.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various combinations, modifications, and changes can be made thereto without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention disclosed herein should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
Claims (8)
1. A method for integrity monitoring of a satellite navigation system, comprising the acts of:
receiving bidirectional measurement data of an inter-satellite link, correcting errors, and performing reduction on bidirectional observation data of the inter-satellite link by using a forecast orbit and a forecast clock error parameter to determine a first inter-satellite geometric distance and a first relative clock error;
calculating a second inter-satellite geometric distance and a second relative clock error according to the satellite navigation message;
respectively subtracting the second inter-satellite geometric distance and the second relative clock difference from the first inter-satellite geometric distance and the first relative clock difference to determine a geometric distance residual error and a relative clock difference residual error;
receiving pseudo-range data and phase data of a satellite downlink navigation signal from a ground monitoring station, correcting errors, and calculating a navigation satellite equivalent distance error by using a satellite navigation message; and
and judging the intact state of the satellite load according to the geometric distance residual error, the relative clock error residual error and the navigation satellite equivalent distance error.
2. The method of integrity monitoring for a satellite navigation system of claim 1, wherein determining the first inter-satellite geometric distance and the first relative clock offset comprises the steps of:
at a first time t 1 And a second time t 2 Receiving bidirectional measurement data of an inter-satellite link and deducting errors to construct an observation equation, which is expressed as the following formula:
where ρ is AB (t 1 ) Indicating that the second satellite is at t 1 The time of day is received from a pseudorange measurement, p, from a first satellite BA (t 2 ) Indicating a first satellite at t 2 A pseudorange measurement is received from a second satellite at a time,
indicating the three-dimensional position of the first satellite and the second satellite, clk A 、clk B Respectively representing the satellite clock error of the first satellite and the second satellite, c representing the speed of light, Δ t 1 And Δ t 2 When the line of light is represented, the line of light,
and
respectively representing the transmit delay and the receive delay of the first satellite,
and
respectively representing the transmission delay and the reception delay of the second satellite,
and
respectively representing first error correction terms;
the first time t 1 And a second time t 2 The bidirectional measurement data of the inter-satellite link is reduced to the target time t 0 Expressed as the following formula:
where d ρ AB And d ρ BA Respectively representing the satellite distance difference and the satellite clock difference between the observation epoch and the target epoch, and calculating by using the forecast orbit and the forecast clock difference parameters, wherein the parameters are represented as follows:
determining a first inter-satellite geometric distance, wherein p AB (t 0 ) And ρ BA (t 0 ) Adding to eliminate satellite clock error information, represented by the following equation:
determining a first relative clock difference, wherein p AB (t 0 ) And ρ BA (t 0 ) Differencing to eliminate satellite orbit information is expressed as:
3. the method of integrity monitoring for a satellite navigation system according to claim 2, wherein the first error correction term comprises satellite antenna phase center error, relativistic effects error, tropospheric delay error, station eccentricity error and tidal effects error.
4. The method of integrity monitoring for a satellite navigation system of claim 2, wherein the computed geometric distance residual is represented by the following equation:
wherein,
representing the geometric range residuals of the first satellite and the second satellite,
and
respectively representCalculating the positions of the second satellite and the first satellite by using the satellite navigation message; and
the calculated relative clock error residual is expressed as:
wherein,
a calculated residual, clk, representing the relative clock difference of the first satellite and the second satellite B (t 0 ) And clk A (t 0 ) Respectively, the clock offsets of the second satellite and the first satellite calculated using the satellite navigation messages.
5. Method for integrity monitoring of a satellite navigation system according to claim 4, characterized in that the pseudo-range data P and the phase data of the satellite downlink navigation signals from the ground monitoring station are used
Expressed as the following formula:
wherein, λ represents the wavelength corresponding to the phase data,
and
representing satellite and receiver position vectors, c the speed of light, at, respectively rcvclk And Δ t satclk Respectively representing receiver clock error and satellite clock error, Δ D phs Representing satellite antenna phase centre deviation, Δ D rel Representing the delay, Δ D, due to relativistic effects trop Representing the troposphereRetardation, Δ D Ion Indicating ionospheric delay, Δ D ecc Indicating the correction of the eccentricity of the survey station, Δ D gtide Indicating station tidal correction, Δ D plm Indicating the range deviation caused by the displacement of the station, N indicating the phase data ambiguity, ε c And ε P Multipath and noise representing pseudo range and phase respectively; and
the navigation satellite equivalent range error UERE is expressed as:
where PC represents the ionosphere-free combination of pseudorange data.
6. The method of integrity monitoring of a satellite navigation system of claim 5, wherein a geometric distance residual threshold, a relative clock error residual threshold, and a navigation satellite equivalent distance error threshold are provided, and wherein the geometric distance residual, the relative clock error residual, and the navigation satellite equivalent distance error of the first satellite from all ground monitoring stations are calculated for the first satellite relative to all other satellites in the satellite navigation system.
7. The method for integrity monitoring of a satellite navigation system according to claim 6, wherein when the geometric distance residual of the first satellite relative to all other satellites in the satellite navigation system exceeds the geometric distance residual threshold, and the navigation satellite equivalent distance error of all ground monitoring stations to the first satellite exceeds the navigation satellite equivalent distance error threshold, it is determined that the description accuracy of the broadcast ephemeris of the first satellite to the satellite orbital motion is degraded; and/or
When the geometric distance residual errors or relative clock error residual errors of the first satellite relative to all other satellites in the satellite navigation system exceed the geometric distance residual error threshold value or the relative clock error residual error threshold value and the navigation satellite equivalent distance errors of all the ground monitoring stations relative to the first satellite do not exceed the navigation satellite equivalent distance error threshold value, judging that the inter-satellite link measurement of the first satellite is abnormal; and/or
When the relative clock error residual of the first satellite relative to all other satellites in the satellite navigation system exceeds the relative clock error residual threshold and the navigation satellite equivalent distance error of all the ground monitoring stations to the first satellite exceeds the navigation satellite equivalent distance error threshold, judging that the satellite-borne atomic clock of the first satellite is abnormal; and/or
And when the relative clock error residual and the geometric distance residual of the first satellite relative to all other satellites in the satellite navigation system do not exceed the relative clock error residual threshold and the geometric distance residual threshold, and the navigation satellite equivalent distance error of all the ground monitoring stations to the first satellite exceeds the navigation satellite equivalent distance error threshold, judging that the downlink navigation load of the first satellite is abnormal.
8. The method of claim 1, wherein an alarm is issued when the satellite load is determined to be abnormal.
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