CN111398994B

CN111398994B - Method and device for positioning and time service of medium-orbit communication satellite

Info

Publication number: CN111398994B
Application number: CN202010341338.9A
Authority: CN
Inventors: 陈曦; 王晓伟; 冯佳傲; 魏齐辉; 詹亚锋
Original assignee: Shanghai Qingshen Technology Development Co ltd; Tsinghua University
Current assignee: Shanghai Qingshen Technology Development Co ltd; Tsinghua University
Priority date: 2020-04-26
Filing date: 2020-04-26
Publication date: 2020-10-30
Anticipated expiration: 2040-04-26
Also published as: CN111398994A

Abstract

The invention provides a method and a device for positioning and time service of a medium-orbit communication satellite, which relate to the technical field of communication and comprise the steps of obtaining target observation quantity of a target medium-orbit communication satellite to be positioned and time service at a historical epoch moment, wherein the target observation quantity comprises at least one of the following components: a navigation observation, a first observation, a second observation, and a third observation; calculating estimated navigation state quantities of the first clock difference and the target medium orbit communication satellite at the current epoch moment based on the target observed quantity; and calibrating parameters in the estimated navigation state quantity based on the connection relation between the target medium-orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity, and finally determining the target navigation state quantity of the target medium-orbit communication satellite at the current epoch moment. In the positioning time service process, the navigation observation quantity, the first observation quantity, the second observation quantity and the third observation quantity are combined, and the technical problem that the space-time reference of the medium-orbit communication satellite in the prior art is difficult to obtain is effectively solved.

Description

Method and device for positioning and time service of medium-orbit communication satellite

Technical Field

The invention relates to the technical field of communication, in particular to a method and a device for positioning and time service of an intermediate orbit communication satellite.

Background

The spatio-temporal references (position, velocity and time) are an important basis for each satellite in a satellite communication constellation to communicate with terrestrial users. The low earth orbit communication satellite receives the navigation satellite signal to the sky, can obtain position, speed and time information reliably. For a medium orbit communication satellite with an orbit height of 2 kilometers, the satellite-borne navigation receiver antenna can only be installed on the ground by itself to receive the main lobe which is not shielded by the earth and the side lobe signal transmitted by the global navigation satellite so as to obtain the space-time reference information, but in view of the fact that the navigation receiver installed on the ground is not only weak in received navigation signal, but also may be interfered and deceived from the ground, the output of the satellite-borne navigation receiver is abnormal or even unavailable, and in sum, the space-time reference of the medium orbit communication satellite in the prior art is difficult to obtain.

Disclosure of Invention

The invention aims to provide a method and a device for positioning and time service of a medium-orbit communication satellite, so as to solve the technical problem that the space-time reference of the medium-orbit communication satellite is difficult to obtain in the prior art.

In a first aspect, an embodiment of the present invention provides a method for positioning and time service by an intermediate orbit communication satellite, including: the method comprises the steps of obtaining a target observation quantity of a target medium orbit communication satellite to be positioned and timed at a historical epoch moment, wherein the target observation quantity comprises at least one of the following: a navigation observation, a first observation, a second observation, and a third observation; the first observation represents an observation between the target medium orbit communication satellite and a medium orbit communication satellite adjacent to the target medium orbit communication satellite, the second observation represents an observation between the target medium orbit communication satellite and a ground gateway station, and the third observation represents an observation between the target medium orbit communication satellite and a target Beidou satellite visible to the target medium orbit communication satellite; calculating a first clock error and an estimated navigation state quantity of the target middle-orbit communication satellite at the current epoch moment based on the target observed quantity, wherein the first clock error represents the clock error between the target middle-orbit communication satellite and a navigation satellite constellation, and the estimated navigation state quantity comprises at least one of the following: estimating a position vector, a speed vector and time; the satellites in the navigation satellite constellation can provide navigation signals for communication satellites; calibrating parameters in the estimated navigation state quantity based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity; and determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration.

In a second aspect, an embodiment of the present invention provides an intermediate orbit communication satellite positioning and time service apparatus, including: the acquisition module is used for acquiring a target observation quantity of a target medium orbit communication satellite to be positioned and timed at a historical epoch moment, wherein the target observation quantity comprises at least one of the following: a navigation observation, a first observation, a second observation, and a third observation; a calculating module, configured to calculate, based on the target observation, a first clock difference and an estimated navigation state quantity of the target medium orbit communication satellite at a current epoch time, where the first clock difference represents a clock difference between the target medium orbit communication satellite and a navigation satellite constellation, and the estimated navigation state quantity includes at least one of: estimating a position vector, a speed vector and time; the satellites in the navigation satellite constellation can provide navigation signals for communication satellites; the calibration module is used for calibrating parameters in the estimated navigation state quantity based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity; and the determining module is used for determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration.

The invention provides a middle orbit communication satellite positioning and time service method, which comprises the following steps: the method comprises the steps of obtaining a target observed quantity of a target medium orbit communication satellite to be positioned and timed at a historical epoch moment, wherein the target observed quantity comprises at least one of the following: a navigation observation, a first observation, a second observation, and a third observation; the first observation quantity represents the observation quantity between a target medium orbit communication satellite and a medium orbit communication satellite adjacent to the target medium orbit communication satellite, the second observation quantity represents the observation quantity between the target medium orbit communication satellite and a ground gateway station, and the third observation quantity represents the observation quantity between the target medium orbit communication satellite and a target Beidou satellite visible to the target medium orbit communication satellite; calculating a first clock error and an estimated navigation state quantity of the target middle orbit communication satellite at the current epoch moment based on the target observed quantity, wherein the first clock error represents the clock error between the target middle orbit communication satellite and a navigation satellite constellation, and the estimated navigation state quantity comprises at least one of the following: estimating a position vector, a speed vector and time; satellites in the navigation satellite constellation can provide navigation signals for communication satellites; calibrating parameters in the estimated navigation state quantity based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock difference and the target observed quantity; and determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration.

According to the method for positioning and time service of the medium-orbit communication satellite, in the process of positioning and time service of the target medium-orbit communication satellite, the navigation observation quantity obtained by the satellite-borne navigation receiver, the first observation quantity between the target medium-orbit communication satellite and the adjacent medium-orbit communication satellite, the second observation quantity between the target medium-orbit communication satellite and the ground gateway station and the third observation quantity between the target medium-orbit communication satellite and the target Beidou satellite visible to the target medium-orbit communication satellite are combined, high-precision positioning and time service of the medium-orbit communication satellite is realized, the high-precision time-space reference can be still obtained when the medium-orbit communication satellite is unavailable in navigation signals or invisible in the ground, and the technical problem that the difficulty in obtaining the time-space reference of the medium-orbit communication satellite in the prior art is high is effectively solved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a flowchart of a method for positioning and time service by an intermediate orbit communication satellite according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of various measurement means of a medium orbit communication satellite according to an embodiment of the present invention;

fig. 3 is a flowchart illustrating calibration of estimated time based on a connection relationship between a target medium orbit communication satellite and a ground gateway station, a first clock offset, a first observed quantity, a second observed quantity, and a third observed quantity according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a satellite internal pulse-per-second generation mechanism according to an embodiment of the present invention;

FIG. 5 is a functional block diagram of a middle orbit communication satellite positioning and timing device according to an embodiment of the present invention;

fig. 6 is a schematic diagram of an electronic device according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Some embodiments of the invention are described in detail below with reference to the accompanying drawings. The embodiments described below and the features of the embodiments can be combined with each other without conflict.

Example one

In the prior art, a medium-orbit communication satellite with an orbit height of 2 kilometers can obtain space-time reference (position, speed and time) information only by receiving a main lobe which is not shielded by the earth and a side lobe signal which are transmitted by a global navigation satellite, but because the distance between the medium-orbit communication satellite and a navigation satellite constellation is relatively long, a satellite-borne navigation receiver on the medium-orbit communication satellite receives a relatively weak navigation signal and is easily interfered by the ground, the output of the satellite-borne navigation receiver is abnormal or even unavailable, and the difficulty in obtaining the space-time reference of the medium-orbit communication satellite is relatively high.

Fig. 1 provides a flowchart of a method for positioning and time service by an intermediate orbit communication satellite, and as shown in fig. 1, the method specifically includes the following steps:

and step S12, acquiring the target observed quantity of the target medium orbit communication satellite to be positioned and timed at the historical epoch moment.

Before positioning and time service are performed on a target medium orbit communication satellite, firstly, a target observation quantity of the target medium orbit communication satellite at a historical epoch time needs to be acquired, and if a current epoch time is k, a target observation quantity from a 1 st epoch time to a k th epoch time needs to be acquired, wherein the target observation quantity includes at least one of the following: a navigation observation, a first observation, a second observation, and a third observation. The navigation observation quantity is an observation quantity from a navigation satellite constellation obtained by a target medium-orbit communication satellite through a satellite-borne navigation receiver, the satellite in the navigation satellite constellation can provide a navigation signal for the communication satellite, the first observation quantity represents an observation quantity between the target medium-orbit communication satellite and a medium-orbit communication satellite adjacent to the target medium-orbit communication satellite, the second observation quantity represents an observation quantity between the target medium-orbit communication satellite and a ground gateway station, and the third observation quantity represents an observation quantity between the target medium-orbit communication satellite and a target Beidou satellite visible to the target medium-orbit communication satellite. That is to say, as shown in fig. 2, in order to obtain a fused space-time reference, in the process of positioning and timing an intermediate orbit communication satellite, while using a satellite-borne navigation receiver, the present invention further introduces a first observed quantity between the intermediate orbit communication satellites (obtained through an inter-satellite link), a second observed quantity between the intermediate orbit communication satellite and a ground gateway station (obtained through a feeder link), and a ranging and timing service of the beidou core network (not shown in fig. 2).

The third observed quantity is obtained through a distance measurement and time service of a Beidou core network, specifically, a Beidou satellite navigation system inter-satellite link in the Beidou satellite navigation system core network can also be connected with a non-Beidou satellite, so that distance measurement and time service between the Beidou satellite and the non-Beidou satellite are provided for the non-Beidou satellite, a load capable of receiving a Beidou inter-satellite link signal is installed on a medium orbit communication satellite, and an inter-satellite link can be established with a specific Beidou satellite under the ground unified control, so that distance measurement information and Beidou space-time reference information between the satellite and a link building satellite are obtained.

And step S14, calculating the first clock error and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the target observed quantity.

Wherein, the first clock error represents the clock error between the target medium orbit communication satellite and the navigation satellite constellation, and the estimated navigation state quantity comprises at least one of the following: estimating a position vector, a speed vector and time; the satellites in the navigation satellite constellation are capable of providing navigation signals to communication satellites.

In an embodiment of the invention, the target observation comprises at least one of: the method comprises the following steps of (1) Navigation observed quantity, first observed quantity, second observed quantity and third observed quantity, wherein a Navigation signal provided by a Global Navigation Satellite System (GNSS) is measured from the whole second, namely the measurement frequency of the Navigation observed quantity is 1 time per second; inter-satellite measurements between communication satellites may be up to 10 times per second, i.e., the measurement frequency of the first observation is 10 times per second; the feeder link of each communication satellite is visible once every 24 hours, i.e. the measurement frequency of the second observation is 1 time every 24 hours; the Beidou ranging time service is about once in 5 minutes, namely, the measurement frequency of the third observation is 1 time every 5 minutes.

As can be seen from the above description, due to inconsistency of the measurement means and the measurement frequencies of the respective observations, when the positioning time service is performed on the medium orbit communication satellite, the navigation observations, the first observation, the second observation and the third observation are not all available at the same time, and the available target observations are used in the actual calculation. After the target observed quantity is obtained, the middle-orbit communication satellite takes the available target observed quantity as an observation equation and takes the space-time reference as a state quantity, the value of the space-time reference of the middle-orbit communication satellite is estimated by solving the equation, namely, the estimated navigation state quantity of the middle-orbit communication satellite at the current epoch moment is determined by solving the equation, and after the estimated navigation state quantity is obtained, the clock error between the middle-orbit communication satellite and the navigation satellite constellation is further calculated by combining the obtained navigation observed quantity. The clock difference may be understood as a Time difference, for example, if the Time of the target medium-orbit communication satellite is UTC (Coordinated Universal Time )08:00:12.016.005, and the Time of the navigation satellite constellation is UTC Time 08:00:12.016.009, it is known that the target medium-orbit communication satellite is 4 microseconds slower than the navigation satellite constellation, and the clock difference is 4 microseconds slower.

And step S16, calibrating parameters in the estimated navigation state quantity based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity.

And step S18, determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration.

In order to make the positioning and timing result of the target medium-orbit communication satellite more accurate, the parameters in the estimated navigation state quantity need to be calibrated according to the connection relationship between the target medium-orbit communication satellite and the ground gateway station, the first clock difference and the target observation quantity, and the target navigation state quantity of the target medium-orbit communication satellite at the current epoch moment is determined according to the estimated navigation state quantity after calibration.

In an alternative embodiment, the navigation observations comprise at least one of: a pseudorange observation and a carrier phase observation.

The first observation comprises at least one of: the first range observation represents a distance between the target medium orbit communication satellite and a medium orbit communication satellite adjacent thereto, and the second clock offset represents a clock offset between the target medium orbit communication satellite and a medium orbit communication satellite adjacent thereto.

The second observation comprises at least one of: a second range observation representing a distance between the target mid-orbit communication satellite and the ground gateway station, and a third clock difference representing a clock difference between the target mid-orbit communication satellite and the ground gateway station.

The third observation comprises at least one of: the third distance observation represents the distance between the target medium orbit communication satellite and the target Beidou satellite visible to the target medium orbit communication satellite, and the fourth clock error represents the clock error between the target medium orbit communication satellite and the target Beidou satellite.

It should be noted that, in the navigation observation obtained by the target medium-orbit communication satellite from the navigation satellite constellation through the satellite-borne navigation receiver, the pseudo-range observation is not a real distance affected by the first clock error, and the distance observation in the remaining several observations (the first distance observation, the second distance observation, and the third distance observation) is an actual distance.

In an optional embodiment, in the step S14, the calculating, based on the target observed quantity, the first clock difference and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time specifically includes the following steps:

step S141, obtaining an adjacent satellite navigation state quantity, where the adjacent satellite navigation state quantity represents a navigation state quantity of an intermediate orbit communication satellite adjacent to the target intermediate orbit communication satellite at the last epoch time.

In the embodiment of the invention, the adjacent satellite is an intermediate orbit communication satellite adjacent to the target intermediate orbit communication satellite, that is, the intermediate orbit communication satellite with an inter-satellite link with the target intermediate orbit communication satellite, the navigation state quantity of the target intermediate orbit communication satellite at the current epoch moment needs to be calculated, the navigation state quantity of the adjacent satellite at the last epoch moment needs to be acquired, the navigation state quantity of the adjacent satellite at the current epoch moment is obtained through orbit dynamics prediction, and then effective data support can be provided for calculating the estimated navigation state quantity of the target intermediate orbit communication satellite at the current epoch moment according to the first distance observation quantity.

And step S142, performing epoch normalization on the latest target observed quantity in the target observed quantities at the historical epoch time to obtain the cooperative observed quantity at the current epoch time.

As can be seen from the foregoing description, the measurement frequency of each observed quantity is different, and therefore, when calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time, it is further required to perform epoch normalization on the latest target observed quantity in the target observed quantities at the historical epoch time, where the latest target observed quantity includes at least one of: and performing epoch normalization on the latest target observation quantity to obtain the cooperative observation quantity at the current epoch moment.

For ease of understanding, it is noted that the measurement frequency of the navigation observation is 1 time per second, and the measurement is started from the whole second, but the measurement frequency of the third observation is 1 time every 5 minutes, that is, one navigation observation can be obtained every second, but one third observation can be obtained every 5 minutes in the target observation of the target medium orbit communication satellite at the historical epoch time. Assuming that a third observation quantity is obtained before 2 minutes, the third observation quantity before 2 minutes is the latest third observation quantity after 3 minutes is needed for the next measurement, and if the third observation quantity before 2 minutes is directly used as the third observation quantity at the current epoch time, a large data error is inevitably caused, so that epoch normalization needs to be performed on the third observation quantity before 2 minutes to obtain the third observation quantity at the current epoch time, and the same epoch normalization principle is adopted for the first observation quantity and the second observation quantity, which is not repeated herein, because the measurement time of the navigation observation quantity is started in whole second, the latest navigation observation quantity is the navigation observation quantity at the current epoch time, and the rest of target observation quantities are all normalized to the current epoch time.

And S143, calculating the first clock error and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the target observed quantity, the adjacent satellite navigation state quantity and the cooperation observed quantity at the historical epoch moment.

After the cooperative observation quantity of the target medium orbit communication satellite at the current epoch time is obtained, the first clock error and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time can be calculated by combining the target observation quantity at the historical epoch time and the adjacent satellite navigation state quantity. The pre-estimated navigation state quantity is an organic unity of the motion prediction result of the historical state at the current epoch moment and the cooperative observation quantity at the current epoch moment in the probability sense, and belongs to the nonlinear Bayesian inference problem.

In an optional embodiment, in step S142, performing epoch normalization on the latest target observation in the target observations at the historical epoch time to obtain the cooperative observation at the current epoch time, specifically includes the following steps:

step S1421, perform epoch normalization on the latest first observed quantity in the target observed quantity at the historical epoch time, to obtain the first observed quantity at the current epoch time.

Step S1422, perform epoch normalization on the latest second observed quantity in the target observed quantity at the historical epoch time, to obtain the second observed quantity at the current epoch time.

Step S1423, perform epoch normalization on the latest third observed quantity in the target observed quantity at the historical epoch time, to obtain the third observed quantity at the current epoch time.

The significance of performing epoch normalization has been described above, and when performing epoch normalization on the latest first observation, the latest second observation, and the latest third observation, in particular, the latest first distance observation in the latest first observation, the latest second distance observation in the latest second observation, and the latest third distance observation in the latest third observation are performed epoch normalization, and since the latest first distance observation and the latest third distance observation both represent the distances between the satellite and the satellite, the same method can be used when performing epoch normalization.

The process of performing epoch reckoning on the latest first distance observation and the process of performing epoch reckoning on the latest second distance observation are explained below, and the process of performing epoch reckoning on the latest third distance observation refers to the process of processing the latest first distance observation, which is not described herein again.

The embodiment of the invention provides two methods for reducing first distance observed quantities, wherein the method 1 comprises the following steps:

the latest first distance observation may be represented as:

wherein,

position information of the target medium orbit communication satellite m at the ith epoch time,

the location information of the inter-orbit communication satellite n adjacent to the target inter-orbit communication satellite m at the ith epoch time is shown, and i represents the observation time of the latest first observed quantity.

When performing epoch normalization, first, the arithmetic expression is used

Calculating the inter-satellite distance change rate between the target medium orbit communication satellite m and the medium orbit communication satellite n adjacent to the target medium orbit communication satellite m, wherein delta v₁The amount of inter-satellite velocity variation is represented,

representing a first range observation (latest first range observation) between the target mid-orbit communication satellite m and the mid-orbit communication satellite n adjacent thereto at the instant of the ith epoch,

representing the rate of change of the inter-satellite distance between the target mid-orbit communication satellite m and the mid-orbit communication satellite n adjacent thereto.

Then, the latest distance change rate between the satellites is used for correctingA distance observation quantity, obtaining a first distance observation quantity of the current epoch time, specifically, using a formula

A first distance observation at a current epoch time k is calculated.

And finally, taking the first distance observation quantity of the current epoch time and the second clock difference carried in the latest first observation quantity as the first observation quantity of the current epoch time.

The method 2 comprises the following steps:

the expression of the latest first distance observation is as in method 1

In the epoch reduction, the inter-satellite distance variation error between the target medium orbit communication satellite m and the medium orbit communication satellite n adjacent to the target medium orbit communication satellite m is calculated

Wherein,

indicating the position information of the orbiting communication satellite m in the target at the current epoch time k,

indicating the position information of the medium orbit communication satellite n adjacent to the target medium orbit communication satellite m at the current epoch time k,

the position information of the medium orbit communication satellite n at the ith epoch time is represented, i represents the observation time of the latest first observation quantity, and it should be noted that the position information of the medium orbit communication satellite used in the embodiment of the present invention is obtained by forecasting the orbit dynamics and obtained by the inertial navigation measurementErrors are smaller compared to the position information.

Then, the latest first distance observed quantity is corrected by using the inter-satellite distance change error to obtain the first distance observed quantity of the current epoch time, specifically, by using a formula

A first distance observation at a current epoch time k is calculated.

The process of performing epoch-reduction on the latest first range observation is described in detail above, and the process of performing epoch-reduction on the latest second range observation is described in detail below.

The latest second distance observation may be represented as: y is_j＝r_j+c(t_g-t^s) B, where t_gIs the clock error of the ground gateway station, t^sIs the satellite clock error and is the measurement error. r is_jIs the linear distance, y, between the target medium orbit communication satellite and the ground gateway station_jDenoted as the latest second distance observation, j denotes the observation time of said latest second observation.

When performing epoch reduction, first, the position coordinate of the ground gateway station in the ground-fixed coordinate system is set as R₀The position of the ground gateway station in the J2000 coordinate system is r₀＝(HG)R₀Wherein, (HG) represents a coordinate conversion matrix from the earth-fixed coordinate system to the J2000 coordinate system.

Then, the formula can be used

Calculating a rate of change of satellite-to-ground distance between the target medium orbit communication satellite and the ground gateway station, wherein r_sRepresenting the position coordinates of the orbiting communication satellite in the target,

indicating the speed of the satelliteThe amount of change is such that,

representing a rate of change of satellite-to-ground distance between the target medium orbit communication satellite and a ground gateway station.

Then, the latest second distance observed quantity is corrected by using the satellite-ground distance change rate to obtain the second distance observed quantity of the current epoch time, specifically, by using a formula

A second distance observation at the current epoch time k is calculated.

And finally, taking the third clock difference carried in the second distance observed quantity and the latest satellite-ground observed quantity of the current epoch time as the satellite-ground observed quantity of the current epoch time.

Step S1424, determining a cooperative observation at the current epoch time based on the first observation at the current epoch time, the second observation at the current epoch time, the third observation at the current epoch time, and the navigation observation at the current epoch time.

As can be seen from the above, the latest navigation observation is the navigation observation at the current epoch time, and therefore, after performing epoch normalization on the latest first distance observation, the latest third distance observation and the latest second distance observation, the obtained first observation, the obtained third observation, the obtained second observation and the obtained navigation observation at the current epoch time can be used as the cooperative observation at the current epoch time.

In the above, a detailed description is given to how to perform epoch normalization so as to obtain the cooperative observed quantity at the current epoch time, and a detailed description is given to a calculation manner of calculating the first clock difference and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time based on the target observed quantity, the adjacent satellite navigation state quantity and the cooperative observed quantity at the historical epoch time in the above step S143.

Firstly, a probability density function of the estimated navigation state quantity is constructed based on the target observed quantity, the adjacent satellite navigation state quantity and the cooperation observed quantity of the historical epoch moment.

Wherein the probability density function is expressed as

Representing a set of navigation state quantities of satellites in the medium orbit communication satellite constellation except the target medium orbit communication satellite m from a previous epoch time k-1 to a current epoch time k, p representing a probability density function,

representing the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time k,

representing a set of target observations of the medium orbit communication satellite constellation M at all epoch times,

indicating that the orbiting communication satellite m receives pseudorange observations from navigation satellites at the current epoch time k,

representing an observation other than the navigation observation at the current epoch time among the collaborative observations at the current epoch time k.

Specifically, first, a set of target observations of a medium orbit communication satellite constellation M at all epoch times is known

Establishing a mathematical model for solving the estimated navigation state quantity, wherein the mathematical model of the problem is as follows: there is a set M of M (medium orbit communication satellite constellation) medium orbit communication satellites, and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time k

Is a backlog and includes an estimate bitThe probability density function of the estimated navigation state quantity can be preliminarily expressed as follows:

wherein p represents a probability density function,

represents the estimated navigation state quantity of the target medium orbit communication satellite m at the current epoch time k,

set of target observations, X, representing the Medium orbit communication satellite constellation M at all epoch instants_k-1:kRepresenting a set of navigation state quantities for all communication satellites in the medium orbit communication satellite constellation from a last epoch time k-1 to a current epoch time k,

representing a set of navigation state quantities for satellites in the medium orbit communication satellite constellation other than the target medium orbit communication satellite m from the last epoch time k-1 to the current epoch time k.

Assuming independent motion of the medium orbit communication satellite and independent observation noise, the above formula can further adopt the above formula

Is decomposed into

Wherein,

representing an observation (first observation) other than the navigation observation at the current epoch time among the cooperative observations at the current epoch time kA second observation, a third observation).

Carry the decomposed formula into

The probability density function of the estimated navigation state quantity can be obtained. According to the expression of the probability density function, the estimated navigation state quantity is an organic unity of the motion prediction result of the historical state at the current epoch moment and the cooperative observation quantity at the current epoch moment in the probability sense, and belongs to the nonlinear Bayesian inference problem.

And then, calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the probability density function.

After the probability density function of the estimated navigation state quantity of the target medium orbit communication satellite is obtained, the statistical expectation is calculated according to the probability density function, and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment can be obtained, and can be specifically expressed as

And finally, determining a first clock error based on the estimated navigation state quantity and the navigation observed quantity of the current epoch moment.

As indicated above, in the navigation observed quantity from the navigation satellite constellation obtained by the target medium orbit communication satellite through the satellite-borne navigation receiver, the pseudo-range observed quantity is not a true distance affected by the first clock error, so that the first clock error can be obtained through calculation by combining the pseudo-range observed quantity in the navigation observed quantity at the current epoch time after the estimated navigation state quantity of the target medium orbit communication satellite is solved.

Further, the method for calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the probability density function specifically comprises the following steps:

step a, constructing a discrete nonlinear system of the estimated navigation state quantity based on a probability density function.

Wherein the discrete nonlinear system is represented as

Representing the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time k, f (-) representing a system state equation,

representing random system noise at the time of the k-1 epoch,

representing the cooperative observation quantity of the target medium orbit communication satellite at the current epoch moment, h (-) representing the system observation equation,

representing the estimated navigation state quantities of satellites in the medium orbit communication satellite constellation except the target medium orbit communication satellite m at the current epoch time k,

representing the random observed noise at the current epoch time.

And b, calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the discrete nonlinear system.

Because the probability density function can not be directly utilized to obtain the statistical expectation, a discrete nonlinear system for estimating the navigation state quantity is constructed by utilizing the probability density function, and then the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment is obtained by solving the discrete nonlinear system. In the case of a discrete non-linear system,

representing the cooperative observations of the target medium orbit communication satellite at the current epoch time,

can be expressed as

A pseudo-range observation is represented and,

a third distance observation is represented and,

a first distance observation is represented and,

representing a second distance observation.

The estimated navigation state quantity of the satellites except the target medium orbit communication satellite m in the medium orbit communication satellite constellation at the current epoch moment k is represented, and the requirement of the estimated navigation state quantity is met

Random system noise W at current epoch time_k～N(0,Q^(m)) Random observed noise of current epoch

f (-) represents a system state equation, the expression of the discrete nonlinear system is known, the second mode is that the state prediction is carried out by using an orbit dynamics equation, and h (-) represents a system observation equation and specifically comprises a navigation pseudo-range observation equation, an inter-satellite observation equation, a satellite-north (a target middle orbit satellite and a visible target Beidou satellite) observation equation and a satellite-ground (a target middle orbit satellite and a ground gateway station) observation equation.

Specifically, pseudorange observations

Satisfying a navigation pseudorange observation equation

Wherein,

indicating the position coordinates of the ith navigation satellite at the k-th epoch time,

the position coordinate of the orbit communication satellite m in the target at the time of the kth epoch is shown, c is the speed of light,

representing the clock offset (first clock offset) of the satellite-borne receiver of the target medium orbit communication satellite and the constellation of navigation satellites,

and indicating the Gaussian noise of the navigation pseudo range of the ith navigation satellite.

Third distance observed quantity

Satisfy the star north observation equation (after epoch return)

Wherein,

the position coordinates of a Beidou satellite q adjacent to the target medium orbit communication satellite m at the k epoch moment are shown,

represents the clock offset (fourth clock offset) of the satellite-borne receiver of the target medium orbit communication satellite and the Beidou satellite q,

and expressing the north-star distance Gaussian noise of the target middle orbit communication satellite and the Beidou satellite q.

First distance observed quantity

Satisfy the inter-satellite observation equation (after epoch return)

Wherein,

indicating the position coordinates of the medium orbit communication satellite n adjacent to the target medium orbit communication satellite m at the k-th epoch time,

representing the clock offset (second clock offset) of the on-board receiver of the target medium orbit communication satellite and the medium orbit communication satellite n,

and the inter-satellite distance Gaussian noise of the target medium orbit communication satellite and the medium orbit communication satellite n is represented.

Second distance observed quantity

Satisfy the star-earth observation equation (after epoch return)

Wherein,

represents the position coordinates of the ground gateway station at the time of the k epoch,

representing the clock offset (third clock offset) of the satellite-borne receiver of the target medium orbit communication satellite with the ground gateway station,

representing the satellite-to-ground distance gaussian noise of the target medium orbit communication satellite and the ground gateway station. Obviously, due to the similarity of the four observation equations, the four observation equations can be combined into a matrix for common use.

There are many solutions for the discrete nonlinear system, and optionally, a Cubature Kalman Filter (CKF) is used to perform inference and solution, and the CKF state updating method is as follows:

for state updates, the posterior probability density of k-1 epochs is assumed

Known, to-state covariance matrix

Cholesky decomposition is carried out by

Then the cubage sample point can be calculated as follows, for i ═ 1, 2, …, 2n, n is the state vector dimension:

wherein,

the propagation to the kth epoch is:

the state prediction for the kth epoch is estimated as:

the state error covariance prediction estimate is:

for observation updates, error covariance

Cholesky decomposition is carried out by

Then the Cubature sample point may be calculated as follows:

propagating Cubasic sampling points, have

The observed prediction estimate for the k epoch is:

the observation error auto-covariance prediction estimation value is as follows:

the observation error cross covariance prediction estimation value is as follows:

and (3) estimating Kalman gain:

the final state estimate is:

the state covariance matrix at the kth epoch time is:

in order to improve the filtering performance, the state covariance matrix of q adjacent stars at the time of k-1 epoch is used

The trace of the target medium orbit communication satellite is used as an initial random observation noise covariance matrix R at the k epoch moment^(m)The diagonal elements of the row and column corresponding to the respective observation equation.

And determining the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment according to the final state estimation value, and then combining the navigation pseudo-range observation equation to obtain the first clock error.

In an optional implementation manner, in step S16, the calibrating the parameter in the estimated navigation state quantity based on the connection relationship between the target medium orbit communication satellite and the ground gateway station, the first clock difference, and the target observed quantity specifically includes:

step S161, calibrating the estimated time based on the connection relationship between the target medium orbit communication satellite and the ground gateway station, the first clock error, the first observed quantity, the second observed quantity, and the third observed quantity, to obtain the target satellite time.

In the embodiment of the invention, the calibration of the estimated navigation state quantity specifically means the calibration of the estimated time in the estimated navigation state quantity, and the calibration needs to be carried out by combining the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock difference, the second clock difference in the first observed quantity, the third clock difference in the second observed quantity and the fourth clock difference in the third observed quantity, so that the calibration of the estimated time is finally realized, and the target satellite time is obtained after the calibration.

In an alternative embodiment, in order to minimize the error between the time of the target medium orbit communication satellite and the world coordination, as shown in fig. 3, the step S161 of calibrating the estimated time based on the connection relationship between the target medium orbit communication satellite and the ground gateway station, the first clock error, the first observed quantity, the second observed quantity, and the third observed quantity specifically includes the following steps:

step S1611, judging whether a feeder link at the current epoch moment is available or not based on the connection relation between the target medium orbit communication satellite and the ground gateway station;

if available, go to step S1612, and if not, go to step S1613.

Step S1612, calibrating the estimated time based on the third clock difference carried in the second observed quantity, to obtain the target satellite time.

Step S1613, determine whether the first clock difference is consistent with the fourth clock difference carried in the third observed quantity.

If they match, step S1614 is executed, and if they do not match, step S1615 is executed.

And step S1614, calibrating the estimated time based on the first clock difference to obtain the target satellite time.

Step S1615, it is determined whether there is a clock difference that is consistent with the second clock difference carried by the first observation amount in the first clock difference and the fourth clock difference.

If yes, step S1616 is executed, and if not, step S1617 is executed.

And step S1616, calibrating the estimated time based on the clock difference consistent with the second clock difference to obtain the target satellite time.

And step S1617, calibrating the estimated time based on the fourth clock difference to obtain the target satellite time.

Specifically, when the estimated time is calibrated, whether a feed link at the current epoch time is available is judged according to the connection relationship between the target medium orbit communication satellite and the ground gateway station, and if the feed link is determined to be available, the target medium orbit communication satellite calibrates the estimated time by using a third clock difference uploaded by the feed link, so that the target satellite time is obtained; otherwise, comparing whether the first clock difference is consistent with the fourth clock difference (in the embodiment of the invention, if the difference value of the first clock difference and the fourth clock difference is less than 1 microsecond, the clock differences are considered to be consistent), and if the difference value is consistent, calibrating the estimated time by using the first clock difference to obtain the target satellite time; if the clock difference is inconsistent, judging whether a clock difference result consistent with the second clock difference exists in the first clock difference and the fourth clock difference; if so, calibrating the estimated time by using the clock difference consistent with the second clock difference, wherein the consistent judgment condition is that the difference value is less than 1 microsecond; if the first clock difference and the fourth clock difference are not consistent with the second clock difference, the navigation signal is considered to be possibly interfered, and the estimated time is calibrated by using the fourth clock difference based on the link between the Beidou satellites to obtain the time of the target satellite.

Fig. 4 shows a schematic diagram of a satellite internal second pulse generation mechanism, and if a feeder link is available, that is, when a target medium orbit communication satellite receives a third clock difference result of a satellite-ground feeder link, a specific method for calibrating the estimated time by using the third clock difference is as follows:

and obtaining third clock differences Δ T from the satellite-ground feeder link by the target medium orbit communication satellite every T periods, and calculating a frequency increment control word and a phase control word according to the third clock differences Δ T, wherein: the frequency increment control word is inverted for the slope of Δ t and the phase control word is inverted for the intercept of Δ t.

In an optional embodiment, in step S18, the determining, based on the estimated navigation state quantity after calibration, a target navigation state quantity of the target medium orbit communication satellite at the current epoch time specifically includes: and determining a target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated position vector, the estimated speed vector and the target satellite time, namely, after the target satellite time is obtained, taking the target satellite time, the estimated position vector and the estimated speed vector as the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment.

In the above description, describing how to determine the target navigation state quantity (spatio-temporal reference) of the target medium orbit communication satellite, the method of the present invention further includes the following steps for the system realizable integrity:

the target medium orbit communication satellite stores all the above measurements on board the satellite when communication with the ground gateway station is not available, and then transmits the above measurements back to the ground gateway station when communication with the ground gateway station is available.

The ground gateway station calculates ephemeris information of the satellite by using the measurement data, and transmits the ephemeris information to the communication satellite and the ground communication user for the communication satellite and the ground communication user to use in communication.

The ephemeris information includes a 16-root format and a two-row root format. 16 in the form of

The physical meanings of the parameters are shown in Table 1:

physical meaning of the ephemeris for the parameters of Table 116

For a medium orbit communication satellite, the orbit period is about 12 hours, the satellite can be seen once in 24 hours, ephemeris can be represented by 1 group of 16-parameter ephemeris every 4 hours, the whole day is divided into 6 groups, and the ephemeris is uploaded to the satellite for use after ground calculation is completed.

When the ground terminal calculates the beam direction, two rows of roots are needed, and compared with a 16-parameter ephemeris, the two-row root ephemeris has a longer valid period. The two-row root form generally adopts a format issued by the north american command department, and specifically comprises the following steps:

line 0: AAAAAAAAAAAAAAAAAAAAAAAA

Line 1: 1NNNNNU NNNAAA NNNNNNN.NNNNNNNNNN +. NNNNNNNNNNNN + NNNNN-N + NNNNN-N NNNNNNNNNN

Line 2: 2 NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN

Wherein, line 0 has 24 characters, which are the common names of catalogued satellites; lines 1 and 2 have 69 characters each, and the meaning of each parameter is shown in tables 2 and 3:

TABLE 2 two lines radical number 1 line each character meaning

TABLE 3 two lines radical 2 line each character meaning description

Column(s) of	Examples of such applications are	Description of the invention
			1	2	Line number
3-7	NNNNN	Satellite numbering
			9-16	NNN.NNNN	Track inclination (degree)
18-25	NNN.NNNN	Ascending crossing point Chijing (rotation)
			27-33	NNNNNNN	Eccentricity (assuming a decimal point before the first digit)
35-42	NNN.NNNN	Breadth of approachAngle (degree)
			44-51	NNN.NNNN	Mean angle of approach (degree) representing the specific position of the satellite in orbit
53-63	NN.NNNNNNNN	Average movement (circles around the earth every day)
			64-68	NNNNN	Number of turns flown since launch
69	N	Check bit

In summary, the method for positioning and timing by an intermediate orbit communication Satellite according to the embodiment of the present invention combines with Global Navigation Satellite System (GNSS) measurement, inter-Satellite link measurement (ISL), feeder link measurement, and ranging and timing service of the beidou core network to perform high-precision positioning and timing on a target intermediate orbit communication Satellite, so that the target communication Satellite can still obtain a high-precision time-space reference when a Navigation signal is unavailable or the ground is invisible.

For the Bayesian inference problem, the existing method basically aims at ground low-speed even quasi-static scenes, and the state equation can be solved among nodes in a networked iteration mode.

Example two

The embodiment of the invention also provides a middle-orbit communication satellite positioning and timing device, which is mainly used for executing the middle-orbit communication satellite positioning and timing method provided by the embodiment of the invention, and the middle-orbit communication satellite positioning and timing device provided by the embodiment of the invention is specifically introduced below.

Fig. 5 is a functional block diagram of a middle orbit communication satellite positioning and time service apparatus according to an embodiment of the present invention, and as shown in fig. 5, the apparatus mainly includes: an acquisition module 10, a calculation module 20, a calibration module 30, and a determination module 40, wherein:

the obtaining module 10 is configured to obtain a target observation quantity of a target medium orbit communication satellite to be positioned and timed at a historical epoch time, where the target observation quantity includes at least one of the following: a navigation observation, a first observation, a second observation, and a third observation; the first observation quantity represents an observation quantity between a target medium orbit communication satellite and a medium orbit communication satellite adjacent to the target medium orbit communication satellite, the second observation quantity represents an observation quantity between the target medium orbit communication satellite and a ground gateway station, and the third observation quantity represents an observation quantity between the target medium orbit communication satellite and a target Beidou satellite visible to the target medium orbit communication satellite.

A calculating module 20, configured to calculate, based on the target observed quantity, a first clock difference and an estimated navigation state quantity of the target medium-orbit communication satellite at the current epoch time, where the first clock difference represents a clock difference between the target medium-orbit communication satellite and a constellation of navigation satellites, and the estimated navigation state quantity includes at least one of: estimating a position vector, a speed vector and time; the satellites in the navigation satellite constellation are capable of providing navigation signals to communication satellites.

And the calibration module 30 is configured to calibrate parameters in the estimated navigation state quantity based on the connection relationship between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity.

And the determining module 40 is used for determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration.

The invention provides a middle orbit communication satellite positioning and time service device, which comprises: the obtaining module 10 is configured to obtain a target observation quantity of a target medium orbit communication satellite to be positioned and timed at a historical epoch time, where the target observation quantity includes at least one of the following: a navigation observation, a first observation, a second observation, and a third observation; the first observation quantity represents the observation quantity between a target medium orbit communication satellite and a medium orbit communication satellite adjacent to the target medium orbit communication satellite, the second observation quantity represents the observation quantity between the target medium orbit communication satellite and a ground gateway station, and the third observation quantity represents the observation quantity between the target medium orbit communication satellite and a target Beidou satellite visible to the target medium orbit communication satellite; a calculating module 20, configured to calculate, based on the target observed quantity, a first clock difference and an estimated navigation state quantity of the target medium-orbit communication satellite at the current epoch time, where the first clock difference represents a clock difference between the target medium-orbit communication satellite and a constellation of navigation satellites, and the estimated navigation state quantity includes at least one of: estimating a position vector, a speed vector and time; satellites in the navigation satellite constellation can provide navigation signals for communication satellites; the calibration module 30 is configured to calibrate parameters in the estimated navigation state quantity based on the connection relationship between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity; and the determining module 40 is used for determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration.

The positioning and time service device for the medium-orbit communication satellite, provided by the invention, combines the navigation observation quantity obtained by the satellite-borne navigation receiver, the first observation quantity between the target medium-orbit communication satellite and the medium-orbit communication satellite adjacent to the target medium-orbit communication satellite, the second observation quantity between the target medium-orbit communication satellite and the ground gateway station and the third observation quantity between the target medium-orbit communication satellite and the target Beidou satellite visible to the target medium-orbit communication satellite in the positioning and time service process of the target medium-orbit communication satellite, realizes high-precision positioning and time service of the medium-orbit communication satellite, enables the medium-orbit communication satellite to still obtain high-precision space-time reference when a navigation signal is unavailable or the ground is invisible, and effectively relieves the technical problem of higher difficulty in obtaining the space-time reference of the medium-orbit communication satellite in the prior art.

Optionally, the navigation observations comprise at least one of: a pseudorange observation and a carrier phase observation.

Optionally, the calculation module 20 includes:

the device comprises an acquisition unit, a processing unit and a display unit, wherein the acquisition unit is used for acquiring the navigation state quantity of the adjacent satellite, and the navigation state quantity of the adjacent satellite represents the navigation state quantity of the middle orbit communication satellite adjacent to the target middle orbit communication satellite at the last epoch moment.

And the return unit is used for performing epoch return on the latest target observed quantity in the target observed quantities at the historical epoch time to obtain the cooperative observed quantity at the current epoch time.

And the calculation unit is used for calculating the first clock error and the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the target observed quantity, the adjacent satellite navigation state quantity and the cooperation observed quantity at the historical epoch moment.

Optionally, the reduction unit is specifically configured to:

and performing epoch normalization on the latest first observed quantity in the target observed quantity at the historical epoch time to obtain the first observed quantity at the current epoch time.

And performing epoch normalization on the latest second observed quantity in the target observed quantity at the historical epoch time to obtain the second observed quantity at the current epoch time.

And performing epoch normalization on the latest third observed quantity in the target observed quantity at the historical epoch time to obtain the third observed quantity at the current epoch time.

And determining the cooperative observation quantity of the current epoch moment based on the first observation quantity of the current epoch moment, the second observation quantity of the current epoch moment, the third observation quantity of the current epoch moment and the navigation observation quantity of the current epoch moment.

Optionally, the computing unit includes:

a construction subunit, configured to construct a probability density function of the estimated navigation state quantity based on the target observed quantity, the adjacent satellite navigation state quantity and the cooperation observed quantity at the historical epoch time, where the probability density function is expressed as

is shown in the current epochThe target medium orbit communication satellite m receives pseudorange observations from navigation satellites at time k,

And the calculating subunit is used for calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the probability density function.

And the determining subunit is used for determining a first clock error based on the estimated navigation state quantity and the navigation observed quantity of the current epoch moment.

Optionally, the calculating subunit is specifically configured to:

constructing a discrete nonlinear system for estimating the navigation state quantity based on a probability density function, wherein the discrete nonlinear system is represented as

representing random system noise at the time of the k-1 epoch,

representing the random observed noise at the current epoch time.

And calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on a discrete nonlinear system.

Optionally, the calibration module 30 includes:

and the time calibration unit is used for calibrating the estimated time based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock error, the first observed quantity, the second observed quantity and the third observed quantity to obtain the target satellite time.

Optionally, the determining module 40 is specifically configured to:

and determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated position vector, the estimated speed vector and the target satellite time.

Optionally, the time calibration unit is specifically configured to:

and judging whether the feeder link at the current epoch moment is available or not based on the connection relation between the target medium orbit communication satellite and the ground gateway station.

And if the estimated time is available, calibrating the estimated time based on the third clock difference carried in the second observed quantity to obtain the target satellite time.

And if not, judging whether the first clock difference is consistent with a fourth clock difference carried in the third observed quantity.

And if the estimated time is consistent with the target satellite time, calibrating the estimated time based on the first clock error to obtain the target satellite time.

And if not, judging whether a clock difference consistent with a second clock difference carried by the first observation quantity exists in the first clock difference and the fourth clock difference.

And if so, calibrating the estimated time based on the clock difference consistent with the second clock difference to obtain the target satellite time.

And if not, calibrating the estimated time based on the fourth clock difference to obtain the target satellite time.

EXAMPLE III

Referring to fig. 6, an embodiment of the present invention provides an electronic device, including: a processor 60, a memory 61, a bus 62 and a communication interface 63, wherein the processor 60, the communication interface 63 and the memory 61 are connected through the bus 62; the processor 60 is arranged to execute executable modules, such as computer programs, stored in the memory 61.

The memory 61 may include a high-speed Random Access Memory (RAM) and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory. The communication connection between the network element of the system and at least one other network element is realized through at least one communication interface 63 (which may be wired or wireless), and the internet, a wide area network, a local network, a metropolitan area network, and the like can be used.

The bus 62 may be an ISA bus, PCI bus, EISA bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one double-headed arrow is shown in FIG. 6, but that does not indicate only one bus or one type of bus.

The memory 61 is used for storing a program, the processor 60 executes the program after receiving an execution instruction, and the method executed by the apparatus defined by the flow process disclosed in any of the foregoing embodiments of the present invention may be applied to the processor 60, or implemented by the processor 60.

The processor 60 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 60. The Processor 60 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the device can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, or a discrete hardware component. The various methods, steps and logic blocks disclosed in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory 61, and the processor 60 reads the information in the memory 61 and, in combination with its hardware, performs the steps of the above method.

The computer program product of the method and the device for positioning and time service of the medium orbit communication satellite provided by the embodiment of the invention comprises a computer readable storage medium storing a nonvolatile program code executable by a processor, wherein instructions included in the program code can be used for executing the method described in the foregoing method embodiment, and specific implementation can refer to the method embodiment, and is not described herein again.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a non-volatile computer-readable storage medium executable by a processor. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or the orientations or positional relationships that the products of the present invention are conventionally placed in use, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A middle orbit communication satellite positioning and time service method is characterized by comprising the following steps:

the method comprises the steps of obtaining a target observation quantity of a target medium orbit communication satellite to be positioned and timed at a historical epoch moment, wherein the target observation quantity comprises at least one of the following: a navigation observation, a first observation, a second observation, and a third observation; the first observation represents an observation between the target medium orbit communication satellite and a medium orbit communication satellite adjacent to the target medium orbit communication satellite, the second observation represents an observation between the target medium orbit communication satellite and a ground gateway station, and the third observation represents an observation between the target medium orbit communication satellite and a target Beidou satellite visible to the target medium orbit communication satellite;

calculating a first clock error and an estimated navigation state quantity of the target middle-orbit communication satellite at the current epoch moment based on the target observed quantity, wherein the first clock error represents the clock error between the target middle-orbit communication satellite and a navigation satellite constellation, and the estimated navigation state quantity comprises at least one of the following: estimating a position vector, a speed vector and time; the satellites in the navigation satellite constellation can provide navigation signals for communication satellites;

calibrating parameters in the estimated navigation state quantity based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity;

determining a target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration;

calculating a first clock error and an estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the target observed quantity, wherein the method comprises the following steps:

acquiring an adjacent satellite navigation state quantity, wherein the adjacent satellite navigation state quantity represents the navigation state quantity of a middle orbit communication satellite adjacent to the target middle orbit communication satellite at the last epoch moment;

performing epoch normalization on the latest target observed quantity in the target observed quantities at the historical epoch time to obtain the cooperative observed quantity at the current epoch time;

and calculating a first clock error and an estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the target observed quantity at the historical epoch moment, the adjacent satellite navigation state quantity and the cooperation observed quantity.

2. The method of claim 1,

the navigation observations comprise at least one of: pseudo-range observations and carrier phase observations;

the first observation comprises at least one of: a first distance observation representing a distance between the target medium orbit communication satellite and a medium orbit communication satellite adjacent thereto, and a second clock offset representing a clock offset between the target medium orbit communication satellite and a medium orbit communication satellite adjacent thereto;

the second observation comprises at least one of: a second range observation representing a distance between the target mid-orbit communication satellite and a ground gateway station, and a third clock difference representing a clock difference between the target mid-orbit communication satellite and the ground gateway station;

the third observation comprises at least one of: a third distance observation representing a distance between the target mid-orbit communication satellite and a target Beidou satellite visible to the target mid-orbit communication satellite, and a fourth clock error representing a clock error between the target mid-orbit communication satellite and the target Beidou satellite.

3. The method of claim 1, wherein performing epoch normalization on a latest target observation in the target observations at the historical epoch time to obtain the collaborative observation at the current epoch time comprises:

performing epoch normalization on the latest first observed quantity in the target observed quantity at the historical epoch time to obtain the first observed quantity at the current epoch time;

performing epoch normalization on the latest second observed quantity in the target observed quantity at the historical epoch time to obtain the second observed quantity at the current epoch time;

performing epoch normalization on the latest third observed quantity in the target observed quantity at the historical epoch time to obtain the third observed quantity at the current epoch time;

4. The method of claim 1, wherein calculating a first clock offset and an estimated navigation state quantity of the target medium orbit communication satellite at a current epoch time based on the target observations at the historical epoch time, the neighbor navigation state quantity and the collaborative observations comprises:

constructing a probability density function of the estimated navigation state quantity based on the target observed quantity, the adjacent satellite navigation state quantity and the cooperation observed quantity at the historical epoch moment, wherein the probability density function is expressed as

A set of navigation state quantities representing satellites in a constellation of mid-orbit communication satellites other than the target mid-orbit communication satellite m from a previous epoch time k-1 to a current epoch time k, p represents the probability density function,

a set of target observations representing the mid-orbit communication satellite constellation M at all epoch times,

indicating that the target medium orbit communication satellite m receives data from the satellite at the current epoch time kA pseudorange observation for a satellite of interest,

representing an observation other than the navigation observation at the current epoch time among the collaborative observations at the current epoch time k;

calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the probability density function;

and determining the first clock error based on the estimated navigation state quantity and the navigation observed quantity of the current epoch moment.

5. The method of claim 4, wherein calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch time based on the probability density function comprises:

constructing a discrete nonlinear system of the estimated navigation state quantity based on the probability density function, wherein the discrete nonlinear system is represented as

representing random system noise at the time of the k-1 epoch,

representing a cooperative observation of the target medium orbit communication satellite at the current epoch time, h (-) representing a system observation equation,

representing mid-orbit communications in a mid-orbit communications satellite constellation except for a target mid-orbit communicationEstimated navigation state quantities of satellites other than the satellite m at the current epoch time k,

representing random observation noise at the current epoch time;

and calculating the estimated navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the discrete nonlinear system.

6. The method of claim 1, wherein calibrating the parameters in the estimated navigation state quantity based on the connection relationship between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observation comprises:

and calibrating the estimated time based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock error, the first observed quantity, the second observed quantity and the third observed quantity to obtain the target satellite time.

7. The method of claim 6, wherein determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch time based on the estimated navigation state quantity after calibration comprises:

8. The method of claim 6, wherein calibrating the estimated time based on the connection of the target medium orbit communication satellite to a ground gateway station, the first clock offset, the first observation, the second observation, and the third observation comprises:

judging whether a feeder link at the current epoch moment is available or not based on the connection relation between the target medium orbit communication satellite and the ground gateway station;

if the estimated time is available, calibrating the estimated time based on a third clock difference carried in the second observed quantity to obtain the target satellite time;

if not, judging whether the first clock difference is consistent with a fourth clock difference carried in the third observation quantity;

if the estimated time is consistent with the target satellite time, calibrating the estimated time based on the first clock error to obtain the target satellite time;

if not, judging whether a clock difference consistent with a second clock difference carried by the first observation quantity exists in the first clock difference and the fourth clock difference;

if so, calibrating the estimated time based on the clock difference consistent with the second clock difference to obtain the target satellite time;

and if the estimated time does not exist, calibrating the estimated time based on the fourth clock difference to obtain the target satellite time.

9. An intermediate orbit communication satellite positioning and time service device is characterized by comprising:

the acquisition module is used for acquiring a target observation quantity of a target medium orbit communication satellite to be positioned and timed at a historical epoch moment, wherein the target observation quantity comprises at least one of the following: a navigation observation, a first observation, a second observation, and a third observation; the first observation represents an observation between the target medium orbit communication satellite and a medium orbit communication satellite adjacent to the target medium orbit communication satellite, the second observation represents an observation between the target medium orbit communication satellite and a ground gateway station, and the third observation represents an observation between the target medium orbit communication satellite and a target Beidou satellite visible to the target medium orbit communication satellite;

a calculating module, configured to calculate, based on the target observation, a first clock difference and an estimated navigation state quantity of the target medium orbit communication satellite at a current epoch time, where the first clock difference represents a clock difference between the target medium orbit communication satellite and a navigation satellite constellation, and the estimated navigation state quantity includes at least one of: estimating a position vector, a speed vector and time; the satellites in the navigation satellite constellation can provide navigation signals for communication satellites;

the calibration module is used for calibrating parameters in the estimated navigation state quantity based on the connection relation between the target medium orbit communication satellite and the ground gateway station, the first clock error and the target observed quantity;

the determining module is used for determining the target navigation state quantity of the target medium orbit communication satellite at the current epoch moment based on the estimated navigation state quantity after calibration;

wherein, the calculation module includes:

the system comprises an acquisition unit, a processing unit and a processing unit, wherein the acquisition unit is used for acquiring an adjacent satellite navigation state quantity, and the adjacent satellite navigation state quantity represents the navigation state quantity of a middle orbit communication satellite adjacent to the target middle orbit communication satellite at the last epoch moment;

the return unit is used for performing epoch return on the latest target observed quantity in the target observed quantities at the historical epoch time to obtain the cooperative observed quantity at the current epoch time;

and the calculation unit is used for calculating a first clock error and an estimated navigation state quantity of the target middle orbit communication satellite at the current epoch moment based on the target observed quantity at the historical epoch moment, the adjacent satellite navigation state quantity and the cooperation observed quantity.