CN113885055A - Satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system and method - Google Patents
Satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system and method Download PDFInfo
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- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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Abstract
The invention provides a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system and a method thereof, wherein the system comprises: an error correction unit configured to perform error correction on the orbital pseudorange observed quantities of different ground monitoring station receivers of the Beidou system according to satellite clock errors, wherein: the satellite clock error is derived from satellite-to-ground time synchronization based on a radio two-way method; and a multi-satellite orbit determination unit configured to perform multi-satellite precise orbit determination using the orbit determination pseudo-range observation amount corrected by the error correction unit.
Description
Technical Field
The invention relates to the technical field of navigation satellites, in particular to a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system and method.
Background
The regional satellite navigation system in China adopts a mixed constellation consisting of GEO/IGSO/MEO satellites, and realizes the monitoring of the satellites by depending on domestic regional monitoring stations. Compared with the GPS and Galileo navigation systems, the hybrid constellation has the particularity that the current orbit determination technology adopted by the navigation satellite is a pseudo-range orbit determination method under the multi-satellite and multi-station support condition.
In the pseudorange orbit determination method, a local satellite navigation system in China mainly adopts an L-waveband pseudorange navigation system. The navigation system firstly needs to deduct the influence of satellite clock error and station-finding clock error from pseudo-range data, and then can carry out pseudo-range orbit determination. The pseudorange orbit determination adopts a multi-satellite orbit determination method at present, and simultaneously solves a satellite orbit, a satellite clock error and a survey station clock error. The GEO satellite is an important component in a space constellation, but the geostationary property of the GEO satellite causes the ranging error in the ground monitoring network to be amplified to the orbit determination result of the GEO satellite, which causes the correlation between the satellite orbit and the clock error parameter to be increased, thereby causing the orbit accuracy of the GEO satellite to be obviously worse than that of the IGSO satellite and the MEO satellite. If only depending on the monitoring stations in the domestic area to carry out orbit determination, the correlation between the satellite orbit and the clock error parameter is strong because the net type is poor. Therefore, the method has certain limitation when being applied to precise orbit determination of the navigation satellite in the regional navigation system.
Disclosure of Invention
The invention aims to provide a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system and a method, which aim to solve the problem that the conventional multi-satellite orbit determination has certain limitation when being applied to the precise orbit determination of a navigation satellite in a regional navigation system.
In order to solve the technical problem, the invention provides a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system and a method thereof, wherein the method comprises the following steps:
an error correction unit configured to perform error correction on the orbital pseudorange observations of receivers of different ground monitoring stations of a Beidou system according to a satellite clock difference determined by satellite-to-ground time synchronization based on a radio two-way method; and
and the multi-satellite orbit determination unit is configured to perform multi-satellite precise orbit determination by using the orbit determination pseudo range observed quantity corrected by the error correction unit.
Optionally, in the satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system, the orbit determination pseudorange observation error correction model is as follows:
ρ(tk)＝R(tk-δtk-τ,tk-δtk)+cδtk-cδts+ΔDtrop+ΔDion+ΔDrel+ΔDant+ΔDtide+ΔDsys+ε
where ρ is the measured pseudorange, tsIs the clock face of the satellite, tkIs the clock face of the receiver, c is the speed of light, relative to the satellite clock and the receiver station clockThe clock difference of the standard time is delta taus、δτkτ is the propagation time corresponding to the true geometric distance of the signal from the satellite to the receiver, R (t)k-δtk-τ,tk-δtk) For the geometric distance between the satellite position and the receiver, Δ DtropFor tropospheric delay error, Δ DionIs ionospheric delay error, Δ DrelFor generalized relativistic error, Δ DantIs the deviation of the antenna phase center, Δ DtideIs the earth tidal error, Δ DsysThe time frequency system difference between the independent time synchronization system and the monitoring receiver is shown, and epsilon is an accidental error.
Optionally, in the satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system, correction of troposphere delay errors is completed in orbit determination calculation by using meteorological observation data actually measured by a tracking station, correction of troposphere delay errors is performed on pseudo-range phase observation data by using a Saastamoinen-Neil model, and computation of troposphere delay errors is completed by inputting temperature, air pressure and humidity in the Saastamoinen-Neil model;
under the condition of dual-frequency observation, the ionosphere delay error is corrected by adopting dual-frequency deionization layer combination, and under the condition of single-frequency observation only, the ionosphere delay amount of the puncture point corresponding to each monitoring station and the satellite is calculated by adopting a global precise ionosphere delay model provided by the European orbit determination center and utilizing a global ionosphere delay map.
Optionally, in the satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system, the generalized relativistic error is calculated by using the following formula:
Δτ＝2·R·V/C2
r, V are the position and velocity vectors of the satellite, respectively, and C is the speed of light;
the earth tidal error is calculated using the following formula:
wherein GM is the gravitational constant of the earth; GM (GM)jTo attract the tide the gravitational constant of celestial bodyWhen j is 2, it is moon, and when j is 3, it is sun;
r,Rjthe earth center positions of the survey station and the tide inducing celestial body respectively,
is a corresponding unit vector, h2Is a Love number,/2Is the Shida number;
and correcting the clock error, wherein the correction comprises the correction of the satellite clock error and the station measuring clock error, and the station measuring clock error is derived from the station measuring clock error calculated by multi-satellite orbit determination.
Optionally, in the satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system, the design of the beidou navigation system adopts a satellite-to-ground radio bidirectional time comparison method to synchronize the time of the navigation satellite and the time of the master control station, and includes:
the satellite S and the ground k station respectively generate and broadcast pseudo code ranging signals under the control of a local clock, and the ground k station generates and broadcasts pseudo code ranging signals when the ground station is in a clock face T corresponding to local 1ppsk(t0) Observing time to obtain downlink pseudo range
The pseudo range contains a negative satellite clock error, and the satellite S has clock face time T corresponding to local 1ppsS(t1) Observing time to obtain uplink pseudo range
The pseudo range contains a positive satellite clock error;
meanwhile, the satellite sends the uplink pseudo-range observation value of the satellite to a ground station k through a communication link, the ground station k obtains the clock error of the satellite relative to the ground station k by using the difference between the locally measured downlink pseudo-range and the received uplink pseudo-range, and therefore the time comparison between the satellite and the ground is completed, and the time comparison result between the satellite and the ground is the satellite clock error.
Optionally, in the satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system,
according to the clock error of the measuring station, the clock error of the measuring station is derived from the clock error of the measuring station which is calculated by multi-satellite orbit determination, and the multi-satellite orbit determination adopts a plurality of measuring stations to perform integrated orbit determination on the observed quantities of a plurality of satellites to obtain high-precision orbit information, dynamic information and measurement information;
the monitoring receiver carries out pseudo-range observation to obtain phase data with higher precision;
and performing orbit determination on the multi-satellite orbit determination integrated pseudo range and phase data, estimating satellite clock errors and station clock errors, and determining the precise orbit of the mixed constellation by adopting a batch processing least square method in the orbit determination.
Optionally, in the satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system, when the clock difference is modeled by a simple polynomial according to the random variation rule of the variation of the clock differences of the satellite and the receiver among the epochs, the polynomial fitting residual error of the clock difference is absorbed by the parameters of the orbit part, and the modeling and estimation are performed on the clock differences of the single-epoch satellite and the receiver in the multi-satellite orbit determination calculation;
resolving clock errors of a satellite and a receiver according to a single epoch, and precisely determining orbit and estimating clock error parameters;
the multi-satellite orbit determination adopts a clock error reduction algorithm, clock error parameters are reduced by epochs, and satellite state parameters and phase ambiguity are reserved so as to reduce the size of a normal equation, reduce storage space and accelerate solving speed.
Optionally, in the satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system, the performing multi-satellite precise orbit determination by the multi-satellite orbit determination unit using the orbit determination pseudorange observed quantity corrected by the error correction unit includes:
reading orbit determination parameters, wherein the orbit determination parameters comprise an orbit determination arc length, an orbit determination station and a data frequency reduction frequency;
reading the distance observed quantity of the monitoring station corrected by the error correction unit;
and resolving the orbit parameters by using the read orbit determination parameters and the distance observed quantity.
Optionally, in the satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system, performing orbit parameter solution by using the read orbit determination parameters and the distance observation quantity includes:
determining a dynamic model and an observation model to carry out a dynamic orbit determination method; wherein the kinetic model is:
wherein
Is the position vector and velocity vector of the satellite, mu ═ GMeThe gravity constant, epsilon, is related to physical parameters such as radiation pressure coefficient, etc., t is any time, t0 is an initial time,
are the initial position vector and the initial velocity vector of the satellite,
the gravity acceleration and the perturbation acceleration of the central body are the sum of the gravity acceleration and the perturbation acceleration;
the observation model is as follows:
Y＝G(X,ρ,t)+v
wherein Y is pseudo-range observed quantity, X is orbit parameter and kinetic parameter, and rho is kinematic parameter;
and performing parameter estimation by adopting a traditional batch processing method based on a least square method.
The invention also provides a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination method, which comprises the following steps:
the error correction unit performs error correction on the orbit determination pseudo-range observed quantities of different ground monitoring station receivers of the Beidou system according to the satellite clock error, wherein:
the satellite clock error is derived from satellite-to-ground time synchronization based on a radio two-way method; and
and the multi-satellite orbit determination unit performs multi-satellite precise orbit determination by using the orbit determination pseudo-range observed quantity corrected by the error correction unit.
In the satellite-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system and method provided by the invention, the satellite clock difference is derived from satellite-ground time synchronization based on a radio bidirectional method, namely the satellite clock difference source is the satellite clock difference synchronously calculated by satellite-ground time, and because the satellite clock difference synchronously calculated by satellite-ground time is not influenced by orbit errors, error correction is carried out on the observed quantities of the orbit determination pseudo ranges of different ground monitoring station receivers of the Beidou system according to the satellite clock difference, so that the correlation between orbit parameters to be estimated and clock difference parameters during precise orbit determination is reduced, and the orbit determination precision of the Beidou satellite, especially a GEO satellite, is improved.
The invention provides a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination method, which is a high-precision, high-stability and independent orbit determination method, and has the advantages that compared with a pseudo-range orbit determination method: the satellite clock error source is satellite clock error of satellite-ground time synchronous calculation, and the satellite clock error of satellite-ground time synchronous calculation is not influenced by orbit errors, so that the correlation between orbit parameters to be estimated and clock error parameters in precise orbit determination is reduced, and the orbit determination precision of the Beidou satellite, particularly the GEO satellite, is improved. The method effectively improves the orbit determination precision of the navigation satellite in the Beidou regional satellite navigation system, and improves the availability of the regional satellite navigation system.
Drawings
FIG. 1 is a schematic flow chart of a method for determining a multi-satellite orbit of a navigation satellite with satellite-to-ground two-way clock error constraint according to an embodiment of the present invention;
fig. 2 is a schematic diagram of UERE accuracy for predicting a 24-hour arc segment in a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination method according to an embodiment of the present invention.
Detailed Description
The invention is further elucidated with reference to the drawings in conjunction with the 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 otherwise specified. 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 of execution of the steps of the methods. Unless specifically stated, the method steps may be performed in a different order.
The present invention provides a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system and method, which are described in further detail below with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
The invention aims to provide a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system and a method, which aim to solve the problem that the conventional multi-satellite orbit determination has certain limitation when being applied to the precise orbit determination of a navigation satellite in a regional navigation system.
The invention also aims to provide a satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination method, which can perform multi-satellite precise orbit determination by using pseudo range data and satellite clock difference data provided by a satellite-to-ground time synchronization method, thereby improving the orbit determination precision.
In order to achieve the purpose, the invention provides a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system and a method thereof, wherein the method comprises the following steps: an error correction unit configured to perform error correction on the orbital pseudorange observed quantities of different ground monitoring station receivers of the Beidou system according to satellite clock errors, wherein: the satellite clock error is derived from satellite-to-ground time synchronization based on a radio two-way method; and a multi-satellite orbit determination unit configured to perform multi-satellite precise orbit determination using the orbit determination pseudo-range observation amount corrected by the error correction unit.
Specifically, the invention discloses a satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination method, which comprises the following steps: s1: error correction is carried out on the orbit determination pseudo-range observed quantities of different station finding receivers, and satellite clock error is derived from satellite-ground time synchronization based on a radio two-way method; s2: and performing multi-satellite precise orbit determination by using the pseudo-range observed quantity corrected by the S1. The invention reduces the correlation between the satellite orbit and the clock error parameter caused by poor network type of the regional monitoring station, simultaneously reduces the correlation between the GEO satellite orbit and the clock error parameter caused by the geostationary property of the GEO, and improves the orbit determination precision. Based on the experimental analysis of a navigation satellite in a Beidou regional satellite navigation system, the sight direction precision of orbit prediction 24h of satellite-ground bidirectional clock error constraint multi-satellite orbit determination is superior to 1.2m, and the user equivalent distance error precision is superior to 2 m.
The embodiment provides a satellite-to-ground bidirectional clock error constrained multi-satellite orbit determination method for a navigation satellite, wherein the multi-satellite orbit determination is realized by integrally determining the observed quantities of a plurality of satellites by adopting a plurality of observation stations, so that high-precision orbit information, dynamic information and measurement information are obtained. The monitoring receiver not only can carry out pseudo range observation, but also can obtain phase data with higher precision. The multi-satellite orbit determination can be carried out by integrating pseudo range and phase data, and high-precision satellite clock error and station-finding clock error can be obtained by single epoch estimation of satellite clock error and station-finding clock error, and the precise orbit determination of a mixed constellation is carried out by adopting a batch processing least square method in the orbit determination.
The flow of the multi-satellite orbit determination method for the satellite-to-ground bidirectional clock error constraint of the embodiment is shown in fig. 1, and includes: s1: error correction is carried out on pseudo-range observed quantities received by a receiver of a ground monitoring station of the Beidou system, and satellite clock error is derived from satellite-ground time synchronization based on a radio two-way method; the principle of monitoring station receiver pseudorandom code ranging is to measure the propagation time τ' of the signal from the satellite to the receiver by correlating the local code of the receiver with the pseudorandom code of the satellite signal. If T represents the unified Beidou, T is setsIs the clock face of satellite s, tkThe clock differences of the satellite clock and the receiver clock relative to the standard T are delta tau when the clock of the receiver k is the clock face of the receiver ks、δτkIt is defined as:
satellite s at satellite clock tsTime of day signal transmission (corresponding to time T of big Dipper)s) At the receiver clock tkTime of day (corresponding to T)kTime of day) arrives at the receiver k, the observed quantity τ' is measured by the pseudo-random code, then
τ′＝tk-ts
＝(Tk+δtk)-(Ts+δts)＝(Tk-Ts)+(δtk-δts)
＝τ+δtk-δts (2)
Multiplying both sides by the speed of light c:
ρ＝cτ′＝cτ+cδtk-cδts＝R(Ts,Tk)+cδtk-cδts (3)
due to tsCannot be observed, so the above equation is written as t at the receiver clockkIs a standard observation equation:
ρ(tk)＝R(tk-δtk-τ,tk-δtk)+cδtk-cδts (4)
where ρ is the measured pseudorange, R (t)k-δtk-τ,tk-δtk) Is the geometric distance between the satellite position and the receiver, i.e. the true distance. Tropospheric delay deltad taking into account previous analysistropAnd ionospheric delay deltadionAnd generalized relativity Δ DrelAntenna phase center deviation delta DantInfluence of Earth Tide Δ DtideTime-frequency system difference delta D between independent time synchronization system and monitoring receiversysAnd if the accidental error epsilon and the like have influences on the tau, correcting the above formula to obtain a pseudo-range non-differential observation model:
when the error correction is carried out on the orbit determination pseudo range observed quantity of each survey station receiver, firstly, each tracking station carries out antenna phase center correction, namely, antenna phase center deviation is deducted, secondly, relativistic effect and earth tide error are deducted from pseudo range data, thirdly, troposphere error is required to be propagated and deducted from L-band pseudo range data, ionosphere delay error is also required to be deducted from non-ionosphere combined observed quantity, and finally, satellite clock error and receiver survey station clock error are required to be deducted;
for the correction of the antenna phase center, the precise calibration can be carried out in the factory process of the measuring equipment, and the calibration result is provided for a user to use, so that the error can be corrected by using the parameters provided by a manufacturer.
For troposphere delay errors, meteorological observation data measured by a tracking station are utilized to complete the correction of the errors in orbit determination calculation, and pseudorange phase observation data are subjected to error correction by adopting a Saastamoinen-Neil model. In the model, the tropospheric delay error calculation can be completed by inputting the temperature, the air pressure and the humidity.
For ionospheric delay errors, under the condition of dual-frequency observation, dual-frequency ionospheric elimination combination is adopted
Wherein f is1、f2Frequencies of two frequency points, L, respectively1、L2Pseudo-range observations at two frequency points, respectively, by LCThe combination can eliminate the influence of ionospheric errors to correct the ionospheric errors, and the ionospheric delay amount of the puncture points corresponding to each monitoring station and the satellite is calculated by using a global ionospheric delay diagram by adopting a global precise ionospheric delay model provided by a European orbit determination Center (CODE) under the condition of only single-frequency observation.
For generalized relativistic errors, the following formula can be used for calculation:
Δτ＝2·R·V/C2 (6)
where R, V are the position and velocity vectors of the satellite, respectively, and C is the speed of light.
For earth tidal errors, the following formula can be used for calculation:
wherein GM is the gravitational constant of the earth; GM (GM)jThe gravity constant of the celestial body (i.e. moon when j is 2 and sun when j is 3) is induced by the tide, R, RjThe earth center positions of the survey station and the tide inducing celestial body respectively,
is a corresponding unit vector, h2Is a Love number,/2Is the Shida number.
And correcting the clock error, wherein the clock error comprises the correction of satellite clock error and station-finding clock error, the satellite clock error is derived from the satellite-ground time synchronization based on a radio bidirectional method, and the station-finding clock error is derived from the station-finding clock error of multi-satellite orbit determination calculation.
The satellite clock error in the pseudo-range correction is derived from satellite-to-ground time synchronization based on a radio two-way method, and the Beidou navigation system is designed to realize the time synchronization of a navigation satellite and a master control station by adopting a satellite-to-ground radio two-way time comparison method. The basic principle is as follows: the satellite S and the ground k station respectively generate and broadcast pseudo code ranging signals under the control of a local clock, and the ground k station generates and broadcasts pseudo code ranging signals when the ground station is in a clock face T corresponding to local 1ppsk(t0) Observing time to obtain downlink pseudo range
(the pseudo range contains a negative satellite clock error), and the satellite S has a clock face time T corresponding to local 1ppsS(t1) Observing time to obtain uplink pseudo range
(the pseudorange contains a positive satellite clock bias). Meanwhile, the satellite sends the uplink pseudo-range observation value of the satellite to a ground station k through a communication link, the ground station k obtains the clock error of the satellite relative to the ground station k by using the difference between the locally measured downlink pseudo-range and the received uplink pseudo-range, so that the time comparison between the satellite and the ground is completed, and the time comparison result between the satellite and the ground is the satellite clock error.
The clock error of the measuring station is derived from the clock error of the measuring station calculated by multi-satellite orbit determination. And the multi-satellite orbit determination is that a plurality of observation stations are adopted to perform integrated orbit determination on the observed quantities of a plurality of satellites to obtain high-precision orbit information, dynamics information and measurement information.
The monitoring receiver not only can carry out pseudo range observation, but also can obtain phase data with higher precision. The multi-satellite orbit determination can be carried out by integrating pseudo range and phase data, the estimation of satellite clock error and survey station clock error is realized, and the precise orbit determination of a mixed constellation is carried out by adopting a batch processing least square method in the orbit determination.
Because the variation of the clock error of the satellite and the receiver among the epochs is in a random variation rule, if the clock error is subjected to simple polynomial modeling, the clock error polynomial fitting residual error is absorbed by partial parameters of the orbit, thereby influencing the precision orbit determination precision. Therefore, single epoch satellite and receiver clock differences are modeled and estimated in the multi-satellite orbit determination solution.
Since single epoch needs to resolve satellite and receiver clock differences, precise orbit determination needs to estimate a large number of clock difference parameters. In order to improve the processing efficiency, the multi-satellite orbit determination adopts a clock error reduction algorithm, clock error parameters are reduced by epochs, and only global parameters such as satellite state parameters, phase ambiguity and the like are reserved, so that the size of a normal equation is reduced, the storage space is reduced, and the solving speed is accelerated.
Let the observation error equation be:
y＝HX+ε (8)
wherein y is observed quantity, H is coefficient matrix, X is orbit determination solution parameter, namely parameter to be estimated, epsilon is observation noise, according to the principle of least square, the parameter to be estimated is estimated as follows:
X＝(HTH)-1HTy (9)
wherein: the parameter to be estimated is
Is m0A global parameter, which is a function of the global parameter,
is the ith (i is 1,2, … N) observation epoch miAnd the clock difference parameters to be estimated comprise satellite and receiver clock differences.
The normal equation is (H)T·H)·X＝HTY, component form:
the second equation of the system can be:
the first epoch clock error parameter can be eliminated by substituting the equation set into the first equation
Finishing to obtain:
according to the method, the clock error is eliminated from epoch to epoch, a large number of clock error parameters are eliminated, and the normal equation only keeps the parameters of the satellite state, the phase ambiguity and the like.
The method can obtain the precise orbit result of multi-satellite orbit determination and the resolving result of the satellite clock error and the measuring station clock error.
S2 of the method for determining multiple satellites in a satellite-to-ground bidirectional clock difference-constrained navigation satellite according to the present embodiment includes: and performing orbit determination by using the pseudo-range observed quantity corrected by the S1. The method comprises the following specific steps:
s2.1, reading the orbit determination parameters; reading various parameters used in orbit determination according to orbit determination requirements, wherein the parameters comprise an arc length of orbit determination, a station for orbit determination and data frequency reduction frequency, and providing effective information for generating orbit determination observed quantity; s2.2, reading pseudo-range observed quantity preprocessed by the S1 to form orbit determination observed quantity; and S2.3, orbit determination and calculation. The dynamic orbit determination method firstly determines a dynamic model and an observation model, and the solving process of the dynamic model is as follows:
the motion of the satellite in space is described by the following ordinary differential equation initial value problem:
wherein
Is the position vector and velocity vector of the satellite, mu ═ GMeThe gravity constant, epsilon, is related to physical parameters such as radiation pressure coefficient, etc., t is any time, t0 is an initial time,
are the initial position vector and the initial velocity vector of the satellite,
is the sum of gravitational acceleration and perturbation acceleration of the central body. The perturbation acceleration is provided by perturbation force, the perturbation force is small relative to the gravity of the earth center, and is specifically divided into two types, namely conservative force perturbation and non-conservative force perturbation, wherein the conservative force perturbation comprises N-body perturbation, earth spherical perturbation, tide perturbation (solid tide perturbation and sea tide perturbation), the non-conservative force perturbation comprises atmospheric resistance perturbation, direct solar radiation pressure perturbation, earth albedo radiation pressure perturbation and satellite body radiation perturbation, and for a GEO satellite, an atmospheric resistance perturbation item can be ignored. The earth gravitational field adopts a model of 10 multiplied by 10 order JGM-3, the planet calendar adopts JPL DE403 parameters, the nutation model adopts an IAU80 model, the sunlight pressure and earth reflection radiation pressure model adopts a simple Box-Wing model, and the solid tide adopts an IERS96 model. The integral calculation of the formula (12) can be performed from the initial epoch t0The position/velocity vector at a given time is estimated. The solution of equation (12) is in the form of a kinetic model, whose functional model can be written in the form:
X＝F(X0,σ,t) (13)
wherein X0Is a reference epoch t0The time of day state quantity, i.e. the position velocity vector of the satellite, is in the form:
sigma is a dynamic parameter and mainly comprises a solar radiation pressure parameter, namely a satellite surface reflection coefficient.
The solution process of the observation model is as follows:
the geometric distance in the pseudo-range data after data preprocessing is defined as follows:
where Y is the pseudorange observation,
and
respectively the position vectors of the satellite and the survey station in the geocentric inertial system at the time t,
and
the position vectors of the satellite and the station in the earth's fixed system at time t can be converted by coordinate rotation. Substituting the expression (13) into the expression (14) to obtain a corrected observation equation, wherein X in the expression (13) is equal to the expression (10)
Or
The resulting functional model can be written as follows:
Y＝G(X,ρ,t)+v (15)
wherein Y is a pseudo-range observed quantity, and X is an orbit parameter and a kinetic parameter. ρ is a kinematic parameter, which mainly refers to a common system error of each station.
The orbit determination solution further comprises parameter estimation, and the parameter estimation adopts a traditional batch processing method based on a least square method. The kinetic parameters and kinematic parameters contained in the kinetic model (13) and observation model (15) are uncertain, so the estimated parameters should include kinetic parameters (solar light pressure parameters, etc.) and kinematic parameters (common system error of each station) in addition to the position velocity of the initial epoch. (13) And (15) the non-linear equation, which needs to be linearized first:
Y＝G(X,ρ,t)＝G(F(X0,σ,t),ρ,t)+v (16)
build new state quantities as follows
Then
(16) The formula is as follows:
Y＝G(F(X0,t))+v (19)
wherein X0Namely, the initial value is needed for dynamic orbit determination, and the initial value of the state quantity is set as
Is represented by the formula (19)
The process is developed as follows:
wherein
Order to
Referred to as the observation matrix, is,
referred to as the state transition matrix,
the higher order terms of equation (18) are omitted, the final form being:
y＝HΦx0+v (21)
according to the least square method, x0The optimal estimate of (c) is:
wherein R is-1Is, is set as an identity matrix if there is no such information,
and
the state quantities and the prior values of the weight inverse matrix are respectively set to be 0 if no information exists. The corrected state quantities were found to be:
And carrying out orbit determination tests by utilizing the measurement data of the Beidou regional monitoring network, wherein Sat01 is a GEO satellite, Sat08 and Sat10 are IGSO satellites, Sat11 is an MEO satellite, and the orbit determination precision of each satellite is shown in table 1.
TABLE 1 laser evaluation accuracy of Beidou satellite constraint satellite clock error orbit determination
| Satellite | Orbit determination residual error | SLR estimation exogenous symbol apparent direction accuracy |
| Sat01 | 0.871 | 0.470 |
| Sat08 | 0.655 | 0.185 |
| Sat10 | 0.584 | 0.307 |
| Sat11 | 0.818 | 0.368 |
As can be seen from the data in Table 1, the orbit apparent direction accuracy of the multi-satellite orbit determination of the satellite-ground bidirectional clock difference constrained navigation satellite is better than 0.5m, and the orbit determination accuracy is more stable.
The positioning accuracy of the user depends on both the range error and the observation geometry due to navigation. The UERE reflects the user equivalent ranging error, so the UERE precision is another external coincidence means for estimating the track precision, and the UERE is defined as: the pseudorange data deducts various error correction terms to obtain the distance observed quantity from the satellite to the observation station, and then the distance observed quantity is differed with the theoretical distance from the satellite to the observation station (the theoretical distance from the observation station to the satellite can be calculated by the precise orbit obtained by short-short arc orbit determination and the known coordinates of the observation station), and the difference value is the UERE value. Table 2 shows UERE accuracy statistics of Sat01, Sat02, Sat03, Sat04 and Sat05 satellites in multi-satellite orbit determination forecast for 24 hours of satellite-to-satellite two-way clock error constrained navigation satellites, and Sat01, Sat02, Sat03, Sat04 and Sat05 are GEO satellites.
TABLE 2 GEO satellite orbit determination precision statistical table (Unit: m)
| Satellite | UERE(RMS) |
| Sat01 | 0.55 |
| Sat02 | 0.53 |
| Sat03 | 0.52 |
| Sat04 | 0.84 |
| Sat05 | 1.15 |
From the results in table 2, it can be seen that the accuracy of the invention in predicting a 24-hour ue re is better than 1.2 m. Fig. 2 shows ue re accuracy maps for 24 hours of Sat01, Sat02, Sat03, Sat04, and Sat05 satellite predictions, where red and green represent ue re calculated using conventional multi-satellite orbit prediction orbits and fixed satellite clock error orbit prediction modes, respectively.
From fig. 2, it can be seen that when the orbit determination method of satellite-ground bidirectional clock error constraint provided by the invention is adopted to perform multi-satellite precise orbit determination, the accuracy of UERE (unified equipment error rate) forecasting for 24 hours is better than 2m on the whole. Wherein the linear variation trend of the UERE is caused by periodic errors of the orbit, the orbit period of the GEO satellite is 1 day, and the UERE has a periodic oscillation every day. The green curve has a period fluctuation significantly smaller than that of the red curve. After the clock error of the satellite is fixed, the UERE of the GEO satellite is obviously reduced, and the orbit precision is improved.
Based on the tests, the following conclusion can be drawn that the sight direction precision of orbit prediction 24h of satellite-to-ground two-way clock error constraint multi-satellite orbit determination is better than 1.2m, the orbit determination precision is stable, the UERE precision of the GEO satellite is integrally better than 2m, the orbit determination precision of a navigation satellite, particularly the GEO satellite, in the Beidou regional satellite navigation system is effectively improved, and the service precision of the regional satellite navigation system is improved.
In summary, the above embodiments have described in detail different configurations of the satellite-to-satellite bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system and method, but it is understood that the present invention includes, but is not limited to, the configurations listed in the above embodiments, and any modifications made on the configurations provided in the above embodiments are within the scope of the present invention. One skilled in the art can take the contents of the above embodiments to take a counter-measure.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (10)
1. A satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination system is characterized by comprising:
an error correction unit configured to perform error correction on the orbital pseudorange observations of receivers of different ground monitoring stations of a Beidou system according to a satellite clock difference determined by satellite-to-ground time synchronization based on a radio two-way method; and
and the multi-satellite orbit determination unit is configured to perform multi-satellite precise orbit determination by using the orbit determination pseudo range observed quantity corrected by the error correction unit.
2. The satellite-to-ground two-way clock-difference constrained navigation satellite multi-satellite orbiting system of claim 1 wherein said orbiting pseudorange observation error correction is performed by the following equation:
ρ(tk)＝R(tk-δtk-τ,tk-δtk)+cδtk-cδts+ΔDtrop+ΔDion+ΔDrel+ΔDant+ΔDtide+ΔDsys+ε
where ρ is the measured pseudorange, tsIs the clock face of the satellite, tkThe clock face of the receiver, c is the speed of light, and the clock differences of the satellite clock and the receiver station clock relative to the standard time are delta taus、δτkτ is the propagation time corresponding to the true geometric distance of the signal from the satellite to the receiver, R (t)k-δtk-τ,tk-δtk) For the geometric distance between the satellite position and the receiver, Δ DtropFor tropospheric delay error, Δ DionIs ionospheric delay error, Δ DrelFor generalized relativistic error, Δ DantIs the deviation of the antenna phase center, Δ DtideIs the earth tidal error, Δ DsysThe time frequency system difference between the independent time synchronization system and the monitoring receiver is shown, and epsilon is an accidental error.
3. The satellite-to-ground bi-directional clock-difference constrained navigation satellite multi-satellite orbital determination system of claim 2,
correcting troposphere delay errors in orbit determination calculation by utilizing meteorological observation data measured by a tracking station, correcting troposphere delay errors by adopting a Saastamoinen-Neil model for pseudo-range phase observation data, and inputting temperature, air pressure and humidity in the Saastamoinen-Neil model to finish computation of the troposphere delay errors;
under the condition of dual-frequency observation, the ionosphere delay error is corrected by adopting dual-frequency deionization layer combination, and under the condition of single-frequency observation only, the ionosphere delay amount of the puncture point corresponding to each monitoring station and the satellite is calculated by adopting a global precise ionosphere delay model provided by the European orbit determination center and utilizing a global ionosphere delay map.
4. The satellite-to-ground bi-directional clock-difference constrained navigation satellite multi-satellite orbital determination system of claim 2,
the generalized relativistic error is calculated using the following formula:
Δτ＝2·R·V/C2
r, V are the position and velocity vectors of the satellite, respectively, and C is the speed of light;
the earth tidal error is calculated using the following formula:
wherein GM is the gravitational constant of the earth; GM (GM)jThe gravity constant of the celestial body for inducing the tide, wherein when j is 2, the moon is shown, and when j is 3, the sun is shown;
r,Rjthe earth center positions of the survey station and the tide inducing celestial body respectively,
is a corresponding unit vector, h2Is a Love number,/2Is the Shida number;
and correcting the clock error, wherein the correction comprises the correction of the satellite clock error and the station measuring clock error, and the station measuring clock error is derived from the station measuring clock error calculated by multi-satellite orbit determination.
5. The satellite-to-ground two-way clock error constrained navigation satellite multi-satellite orbit determination system of claim 4, wherein the Beidou navigation system is designed to adopt a satellite-to-ground radio two-way time comparison method for time synchronization of the navigation satellite and the master control station, and comprises:
the satellite S and the ground k station respectively generate and broadcast pseudo code ranging signals under the control of a local clock, and the ground k station generates and broadcasts pseudo code ranging signals when the ground station is in a clock face T corresponding to local 1ppsk(t0) Observing time to obtain downlink pseudo range
The pseudo range contains a negative satellite clock error, and the satellite S has clock face time T corresponding to local 1ppsS(t1) Observing time to obtain uplink pseudo range
The pseudo range contains a positive satellite clock error;
meanwhile, the satellite sends the uplink pseudo-range observation value of the satellite to a ground station k through a communication link, the ground station k obtains the clock error of the satellite relative to the ground station k by using the difference between the locally measured downlink pseudo-range and the received uplink pseudo-range, and therefore the time comparison between the satellite and the ground is completed, and the time comparison result between the satellite and the ground is the satellite clock error.
6. The satellite-to-ground bi-directional clock-difference constrained navigation satellite multi-satellite orbital determination system of claim 4,
according to the clock error of the measuring station, the clock error of the measuring station is derived from the clock error of the measuring station which is calculated by multi-satellite orbit determination, and the multi-satellite orbit determination adopts a plurality of measuring stations to perform integrated orbit determination on the observed quantities of a plurality of satellites to obtain high-precision orbit information, dynamic information and measurement information;
the monitoring receiver carries out pseudo-range observation to obtain phase data with higher precision;
and performing orbit determination on the multi-satellite orbit determination integrated pseudo range and phase data, estimating satellite clock errors and station clock errors, and determining the precise orbit of the mixed constellation by adopting a batch processing least square method in the orbit determination.
7. The satellite-to-ground bidirectional clock difference constrained navigation satellite multi-satellite orbit determination system of claim 1, wherein according to the random variation rule of the variation of the clock differences of the satellite and the receiver among the epochs, when the clock differences are modeled by a simple polynomial, the polynomial fitting residual errors of the clock differences are absorbed by the parameters of the orbit part, and the modeling and estimation are carried out on the clock differences of the satellite and the receiver of a single epoch in the multi-satellite orbit determination solution;
resolving clock errors of a satellite and a receiver according to a single epoch, and precisely determining orbit and estimating clock error parameters;
the multi-satellite orbit determination adopts a clock error reduction algorithm, clock error parameters are reduced by epochs, and satellite state parameters and phase ambiguity are reserved so as to reduce the size of a normal equation, reduce storage space and accelerate solving speed.
8. The system of claim 1, wherein the multi-satellite precise orbit determination using the pseudo range observed quantity after the error correction unit comprises:
reading orbit determination parameters, wherein the orbit determination parameters comprise an orbit determination arc length, an orbit determination station and a data frequency reduction frequency;
reading the distance observed quantity of the monitoring station corrected by the error correction unit;
and resolving the orbit parameters by using the read orbit determination parameters and the distance observed quantity.
9. The satellite-to-ground two-way clock-error-constrained navigation satellite multi-satellite orbit determination system of claim 8, wherein the orbit parameter solution using the read orbit determination parameters and the distance observations comprises:
determining a dynamic model and an observation model to carry out a dynamic orbit determination method; wherein the kinetic model is:
wherein
Is the position vector and velocity vector of the satellite, mu ═ GMeThe gravity constant, epsilon, is related to physical parameters such as radiation pressure coefficient, etc., t is any time, t0 is an initial time,
are the initial position vector and the initial velocity vector of the satellite,
the gravity acceleration and the perturbation acceleration of the central body are the sum of the gravity acceleration and the perturbation acceleration;
the observation model is as follows:
Y＝G(X,ρ,t)+v
wherein Y is pseudo-range observed quantity, X is orbit parameter and kinetic parameter, and rho is kinematic parameter;
and performing parameter estimation by adopting a traditional batch processing method based on a least square method.
10. A satellite-to-ground bidirectional clock error constrained navigation satellite multi-satellite orbit determination method is characterized by comprising the following steps:
error correction is carried out on the orbit determination pseudo range observed quantities of receivers of different ground monitoring stations of the Beidou system by an error correction unit according to satellite clock error, wherein the satellite clock error is determined through satellite-ground time synchronization based on a radio bidirectional method; and
and the multi-satellite orbit determination unit performs multi-satellite precise orbit determination by using the orbit determination pseudo-range observed quantity corrected by the error correction unit.
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