CN116996115B

CN116996115B - Low-orbit satellite receiving time window calculation method, device and equipment

Info

Publication number: CN116996115B
Application number: CN202311249043.9A
Authority: CN
Inventors: 刁宁辉; 吴奎桥; 孙从容; 马小峰; 腾和丽; 郭振宇; 韩静雨
Original assignee: NATIONAL SATELLITE OCEAN APPLICATION SERVICE
Current assignee: NATIONAL SATELLITE OCEAN APPLICATION SERVICE
Priority date: 2023-09-26
Filing date: 2023-09-26
Publication date: 2023-12-22
Anticipated expiration: 2043-09-26
Also published as: CN116996115A

Abstract

The invention discloses a method, a device and equipment for calculating a low-orbit satellite receiving time window, relates to the technical field of satellite application, and aims to solve the problem that the calculation efficiency and the result precision cannot be considered in the prior art. Comprising the following steps: acquiring ground station position information and satellite nominal orbit height information; determining a visible range of the low-orbit satellite; classifying ground stations of the low-orbit satellite in a visible range, selecting corresponding satellite orbit segmentation methods for different ground station types to carry out orbit segmentation, determining orbit filtering boundary conditions corresponding to different types of ground stations, and carrying out orbit filtering on segmented orbit arc segments based on the orbit filtering boundary conditions to obtain a filtering result; and calculating the starting time and the ending time of the low orbit satellite receiving by using a dynamic step-by-step method according to the filtering result to obtain a receiving time window. The calculation efficiency of the low-orbit satellite receiving time window can be improved at the same time, and the accuracy of the calculation result can be improved.

Description

Low-orbit satellite receiving time window calculation method, device and equipment

Technical Field

The present invention relates to the field of satellite application technologies, and in particular, to a method, an apparatus, and a device for calculating a low-orbit satellite receiving time window.

Background

Low orbit satellites are primarily satellite systems that operate on low orbit platforms. Satellites can be divided into high, medium and low rails according to platform altitude. Low orbit satellites, also called near earth orbit satellites, refer in particular to a satellite set with an orbit flight height of 200-2000 km. Satellites are classified according to the difference of orbit heights, and besides low-orbit satellites, medium-orbit satellites (2000 km-20000 km) and high-orbit satellites (20000 km or more) are also included.

The satellite visible range refers to the area visible to the satellite where the minimum altitude of the ground station is set, i.e., the coverage area where the ground station to satellite altitude is greater than the minimum altitude in the range of orientations of 0-360 ° to the ground station.

The method of low-orbit satellite receiving time window used in the current business is mainly a traditional method of tracking propagation. The main principle of the method is to set a fixed time step and calculate the altitude and azimuth angle of the satellite relative to the ground station point by point. And when the altitude angle is larger than the set minimum altitude angle, recording the start time and the end time of the satellite entering and exiting. The method can obtain the maximum height angle of the satellite in the time window and the antenna tracking point position of the ground station while obtaining the satellite receiving time window. However, the existing low-orbit satellite receiving time window calculation method does not solve the problems of low calculation efficiency and low result precision at the same time.

Accordingly, there is a need to provide a more reliable low-orbit satellite receiving time window calculation scheme.

Disclosure of Invention

The invention aims to provide a low-orbit satellite receiving time window calculating method, device and equipment, which are used for solving the problem that the calculating efficiency and the result precision cannot be considered in the prior art.

In order to achieve the above object, the present invention provides the following technical solutions:

in a first aspect, the present invention provides a method for calculating a low-orbit satellite receiving time window, the method comprising:

acquiring ground station position information and satellite nominal orbit height information;

determining a range of visibility for a low-orbit satellite based on the ground station location information and the satellite nominal orbit height information;

classifying the ground stations of the low-orbit satellite in the visible range to obtain the type of the ground station; the ground station type at least comprises a polar station, a hemispherical station and an equatorial station;

selecting corresponding satellite orbit segmentation methods for different ground station types to carry out orbit segmentation to obtain segmented orbit arcs;

determining track filtering boundary conditions corresponding to different types of ground stations, and performing track filtering on the segmented track arc segments based on the track filtering boundary conditions to obtain a filtering result;

And calculating the starting time and the ending time of low-orbit satellite receiving by using a dynamic step-by-step method according to the filtering result to obtain a receiving time window.

Compared with the prior art, the low-orbit satellite receiving time window calculating method provided by the invention is used for calculating the low-orbit satellite receiving time window. Acquiring ground station position information and satellite nominal orbit height information; determining a visible range of the low-orbit satellite based on the ground station position information and the satellite nominal orbit height information; classifying the ground stations of the low-orbit satellite in the visible range to obtain the types of the ground stations; selecting corresponding satellite orbit segmentation methods for different ground station types to carry out orbit segmentation to obtain segmented orbit arcs; determining track filtering boundary conditions corresponding to different types of ground stations, and performing track filtering on the segmented track arc segments based on the track filtering boundary conditions to obtain a filtering result; and calculating the starting time and the ending time of the low orbit satellite receiving by using a dynamic step-by-step method according to the filtering result to obtain a receiving time window. On the premise of ensuring the calculation precision of parameters such as a low-orbit satellite receiving time window, an altitude angle, an azimuth angle and the like, the orbit outside the visible range of the ground station is filtered, then the time window and the tracking point position information are calculated by changing the sampling time interval, the calculation step length is dynamically changed by the visible condition and the prediction distance, the calculation number of sampling points is greatly reduced under the condition that the result precision is not lost, the calculation efficiency is improved, and the calculation efficiency of the low-orbit satellite receiving time window and the calculation result precision can be simultaneously improved.

In a second aspect, the present invention provides a low-orbit satellite receiving time window calculating apparatus, the apparatus comprising:

the basic information acquisition module is used for acquiring the position information of the ground station and the nominal orbit height information of the satellite;

a visibility range determining module for determining a visibility range of a low-orbit satellite based on the ground station position information and the satellite nominal orbit height information;

the ground station classification module is used for classifying the ground stations of the low-orbit satellites in the visible range to obtain the types of the ground stations; the ground station type at least comprises a polar station, a hemispherical station and an equatorial station;

the satellite orbit segmentation module is used for selecting corresponding satellite orbit segmentation methods for orbit segmentation aiming at different ground station types to obtain segmented orbit arc segments;

the track filtering module is used for determining track filtering boundary conditions corresponding to different types of ground stations, and carrying out track filtering on the segmented track arc segments based on the track filtering boundary conditions to obtain a filtering result;

and the receiving time window calculation module is used for calculating the starting time and the ending time of the low orbit satellite receiving by utilizing a dynamic step length method according to the filtering result to obtain a receiving time window.

In a third aspect, the present invention provides a low-orbit satellite receiving time window computing device, the device comprising:

the communication unit/communication interface is used for acquiring the ground station position information and satellite nominal orbit height information;

a processing unit/processor for determining a range of visibility of a low-orbit satellite based on the ground station position information and the satellite nominal orbit height information;

In a fourth aspect, the present invention provides a computer storage medium having instructions stored therein, which when executed, implement the above-described low-orbit satellite receiving time window calculation method.

Technical effects achieved by the apparatus class scheme provided in the second aspect, the device class scheme provided in the third aspect, and the computer storage medium scheme provided in the fourth aspect are the same as those achieved by the method class scheme provided in the first aspect, and are not described herein.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:

FIG. 1 is a schematic view of azimuth and elevation angles;

FIG. 2 is a schematic view of the satellite's visible range;

FIG. 3 is a flowchart of a method for calculating a low-orbit satellite receiving time window according to the present invention;

FIG. 4 is a schematic diagram of an overall process of calculating a low-orbit satellite time window according to the present invention;

fig. 5 is a schematic diagram of a visual range determining principle in the low-orbit satellite receiving time window calculating method provided by the invention;

FIG. 6 is a schematic view of the range of a polar ground station to an HY-1C satellite provided by the invention;

FIG. 7 is a schematic diagram of determination of hemispherical station orbit filtering boundary conditions provided by the present invention;

FIG. 8 is a schematic representation of equatorial station orbit filtering provided by the present invention;

Fig. 9 is a schematic structural diagram of a low-orbit satellite receiving time window calculating device according to the present invention;

fig. 10 is a schematic diagram of a low-orbit satellite receiving time window computing device according to the present invention.

Detailed Description

In order to clearly describe the technical solution of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second", etc. are used to distinguish the same item or similar items having substantially the same function and effect. For example, the first threshold and the second threshold are merely for distinguishing between different thresholds, and are not limited in order. It will be appreciated by those of skill in the art that the words "first," "second," and the like do not limit the amount and order of execution, and that the words "first," "second," and the like do not necessarily differ.

In the present invention, the words "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

In the present invention, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (one) of a, b or c may represent: a, b, c, a and b, a and c, b and c, or a, b and c, wherein a, b, c can be single or multiple.

Firstly, explanation is made on the corresponding technical concept in the technical scheme provided by the invention:

(1) Two rows of element track report:

Two-Line Element orbit (TLE) is a parameter file for predicting satellite orbit position, TLE is a flat number, and the periodic disturbance term is removed by a specific method in consideration of earth's flat rate, long-term and periodic perturbation influence of solar-lunar attraction, attraction resonance and orbit decay generated by an atmospheric resistance model. The TLE consists of two rows of parameters, wherein the first row of parameters comprise an orbit report number, a satellite classification identifier, a satellite transmission year, a satellite transmission serial number in the current year, an epoch year, epoch time, a first-order time derivative of average motion, a second-order time derivative of average motion, a BSTAR drag modulation coefficient, an ephemeris type, an ephemeris number and a checksum; the second row of parameters comprises orbit report number, satellite number, orbit inclination angle, ascending intersection point right ascent, eccentricity, near-place angular distance, flat near-point angle, number of turns of the satellite around the earth within 24 hours, orbit circle number and checksum.

(2) SGP4 orbit prediction model:

the conventional perturbation model (Simplified General Perturbations-4, SGP4 model for short) is simplified and is used for forecasting the orbit of the near-earth spacecraft with the orbit period less than or equal to 225 minutes. Substituting TLE into SGP4 model can calculate position and speed of satellite at any time. The prediction precision of the model within 24 hours is 1-3 km, and the longer the prediction period, the larger the error is due to the influence of the non-spherical gravitational force of the earth, the gravitational force of the sun and the moon, the atmosphere, the solar pressure and other perturbation forces. Therefore, in business work, the TLE (two-row element track report) of the current day is generally used to calculate the reception time window and the tracking point.

The coordinate system of the SGP4 model calculation result is True equatorial plane spring point coordinate system (True editor, mean Equinox, abbreviated as tee). In practice, it is necessary to calculate the greenish flat stars and to use polar motion two-component to convert satellite position and velocity from the TEME (real equatorial plane spring point coordinate system) coordinate system to the traditional Earth Centered Earth Fixed (ECEF).

(3) Satellite azimuth and altitude calculation

The satellite azimuth is the horizontal angle from the north-pointing direction line at a point, in the clockwise direction, to the satellite direction line. The satellite altitude is the angle between the horizontal plane and the direction line from a point to the satellite.

For example: knowing the ground pointsAnd satellite->The coordinates of the earth system at the earth center are +.>And->The earth-fixed coordinates of the satellites need to be converted into station-center horizontal coordinates. The origin of the station horizon coordinate is ground point D +.>The axis points to the zenith along the normal direction of the origin, < > the zenith>The axis pointing north in the meridian direction, +.>The axis is in the right hand direction as shown in fig. 1. In FIG. 1, ->For satellite->In the station horizon coordinate system->Projection of plane->For satellite->Azimuth angle of->For satellite->Is a height angle of (2). />And->Ground points->Geodetic longitude and geodetic latitude.

SatelliteThe conversion formula from the geodetic system to the station-centric horizontal coordinate system is formula (1):

（1）

Satelliteazimuth angle +.>And height angle->The calculation formula of (a) is formula (2) and formula (3):

（2）

（3）

(4) Visible range and time window

The satellite visibility range refers to an area visible to the satellite in the case where the minimum altitude of the ground station is set, that is, a coverage area in which the altitude of the ground station to the satellite is greater than the minimum altitude in the azimuth range of 0 to 360 ° of the ground station. As shown in fig. 2,is a satellite orbit arc section->For ground station->For satellite altitude, +.>Is the corresponding geocentric angle. Assuming that the minimum altitude is set to 5 °, in a certain orbital arc of the satellite, when +. >When 5 DEG or more, the satellite enters the station, i.e. the satellite is visible to the ground station, when +.>And when the angle is less than or equal to 5 degrees, the satellite is out of the station, namely the satellite is invisible to the ground station. The time interval in which the satellite is visible to the ground station (when 5 ° or more) is called the time window.

In the prior art, the method of low-orbit satellite receiving time window used in the current service is mainly a traditional method of tracking propagation. The main principle of the method is to set a fixed time step and calculate the altitude and azimuth angle of the satellite relative to the ground station point by point. And when the altitude angle is larger than the set minimum altitude angle, recording the start time and the end time of the satellite entering and exiting. The method can obtain the maximum height angle of the satellite in the time window and the antenna tracking point position of the ground station (namely the altitude angle and the azimuth angle obtained by point-by-point calculation) while obtaining the satellite receiving time window. The method comprises the following specific steps of;

(1) Satellite orbit extrapolation

And pushing TLE of a certain satellite to a specified path, checking the legality of TLE data, and starting an SGP4 model when the legality check is passed, and calculating the position and the speed of the satellite in a specified time period.

(2) Coordinate system conversion

Because the SGP4 model is utilized for track extrapolation, the coordinate frame of the result is a TEME coordinate system, and a Greenner flat star hour angle needs to be rotated around a Z axis, and the TEME coordinate is converted into a quasi-ground fixed system (Pseudo Earth Fixed, PEF for short) coordinate; the polar-shift two components are then rotated about the X-axis and Y-axis, respectively, to convert the PEF coordinates to ECEF coordinates. The conversion formula is shown as follows, Representing a rotation matrix +.>The first parameter of (2) represents the coordinate axis and the second parameter is the angle of rotation around the coordinate axis, +.>Position vector representing satellite>Velocity vector representing satellite>Represents the time angle of the Greenwich mean star,and->Representing the polar-shift component.

（4）

（5）

(3) Altitude and azimuth calculation

Knowing the position of the ground station and the satellite in the ECEF coordinate system, converting the ECEF coordinate of the satellite into the station center horizontal coordinate by using a formula (1), and then calculating the altitude and azimuth angle of the satellite relative to the ground station point by using formulas (2) - (3).

(4) Time window calculation

And screening N time windows in a satellite specified time period according to the set minimum altitude angle, and searching the maximum value of the altitude angle in each time to obtain the maximum altitude angle of the satellite in each time window. The smaller the maximum height angle, the further the track arc is from the ground station, the greater the impact on wireless communication quality, and therefore the maximum height angle is an important indicator for selecting a good quality time window.

However, in the above prior art, the existing low-orbit satellite receiving time window calculating method does not solve the problems of low calculating efficiency and low result accuracy at the same time. Specifically:

The tracking propagation method is simple to realize and high in result precision as only the position of the satellite is calculated, the position relation between the satellite and the ground station is judged, and the sampling interval can be adjusted at will; the low orbit satellite winds around the earth 14 circles a day, for the ground station with middle and low latitude, the visible time window of the satellite is about 4-5 times a day, and each time window is about 12 minutes, so that the indiscriminate continuous tracking sampling is carried out, the calculated amount is increased, and the efficiency is reduced.

The main idea of the orbit-changing cross-circle compensation algorithm is to find a satellite under-satellite point in a visual window, then approximate the under-satellite point track in the visual window by using a large circle passing through the under-satellite point and having an inclination angle different from the inclination angle of the satellite orbit, and improve the algorithm precision by using a compensation algorithm. The algorithm adopts a mathematical approximation method, and has the problems of low accuracy although the calculated amount is greatly reduced, and the algorithm is only aimed at circular tracks and has low applicability.

Dynamic step-size fast algorithm defines the satellite-to-satellite visibility range of a ground station as a cone shapeThe vertical distance of the conical sides is referred to as the "predicted distance". The minimum altitude angle when the ground station is visible to the satellite is set to The cone half angle of the visual field is +.>Is included in the above-mentioned range. Calculating a sampling point at the starting moment of the satellite, calculating a time step according to the 'prediction distance' of the sampling point to obtain a sampling point at the next moment, iterating continuously, calculating the sampling point and the starting moment which meet the visual condition as the step is closer to the visual range, gradually increasing the step until the step approaches the boundary of the visual range, starting to decrease the step to obtain the sampling point and the ending moment which meet the visual condition, and then entering an increasing process again, and repeating the process continuously until the calculation is ended. Compared with a tracking propagation method, the algorithm dynamically changes the calculation step length through visual conditions and the prediction distance, greatly reduces the calculation number of sampling points under the condition of not losing the result precision, and improves the calculation efficiency. However, this method also calculates a number of arc segments of the track that are not likely to enter the visible range, adding some computational effort.

Therefore, the present invention is based on the defects in the prior art, and needs to solve the problems of low calculation efficiency or low result accuracy in the current low-orbit satellite receiving time window calculation. And constructing a computer system to quickly calculate a receiving time window of a satellite in a plurality of ground stations in a specified time interval.

Next, the scheme provided by the embodiments of the present specification will be described with reference to the accompanying drawings:

as shown in fig. 3, the process may include the steps of:

step 310: ground station position information and satellite nominal orbit height information are acquired.

The nominal orbit is the optimal orbit derived from the actual orbital positions of the individual satellites in the current constellation. The instantaneous nominal orbit of the navigation satellite can be used as a reference target for satellite launching and position maintenance to guide the establishment of an orbit control strategy of the navigation satellite.

Ground stations are an important component of satellite communication systems. The ground station basically functions to transmit signals to satellites, or to receive downlink signals or retransmitted signals from satellites.

Step 320: a range of visibility for the low-orbit satellites is determined based on the ground station location information and the satellite nominal orbit height information.

The visible range is shown in fig. 2, and has been described in the previous discussion, and will not be described again here, the visible range of the low-orbit satellite can be determined according to the ground station information obtained in step 310 and the satellite nominal orbit height information.

Step 330: classifying the ground stations of the low-orbit satellite in the visible range to obtain the type of the ground station; the ground station types include at least polar stations, hemispherical stations, and equatorial stations.

Step 340: and selecting corresponding satellite orbit segmentation methods for different ground station types to carry out orbit segmentation to obtain segmented orbit arcs.

The relationship between the ground station and the satellite orbit segmentation method is:

when the ground station is a polar station or a hemispherical station, adopting a rising intersection point segmentation method, and carrying out track segmentation by taking a rising intersection point as a segmentation point to obtain segmented track arc sections;

when the ground station is an equatorial station or other types of ground stations except for polar stations, hemispherical stations and equatorial stations, a pole segmentation method is adopted, and poles are used as segmentation points for track segmentation, so that segmented track arc segments are obtained.

Step 350: and determining the track filtering boundary conditions corresponding to the ground stations of different types, and performing track filtering on the segmented track arc segments based on the track filtering boundary conditions to obtain a filtering result.

The boundary conditions of track filtering and the track filtering method are related to the types of the ground stations, and different ground station types correspond to different track filtering conditions and track filtering methods.

Step 360: and calculating the starting time and the ending time of low-orbit satellite receiving by using a dynamic step-by-step method according to the filtering result to obtain a receiving time window.

The method of fig. 3 by acquiring ground station position information and satellite nominal orbit height information; determining a visible range of the low-orbit satellite based on the ground station position information and the satellite nominal orbit height information; classifying the ground stations of the low-orbit satellite in the visible range to obtain the types of the ground stations; selecting corresponding satellite orbit segmentation methods for different ground station types to carry out orbit segmentation to obtain segmented orbit arcs; determining track filtering boundary conditions corresponding to different types of ground stations, and performing track filtering on the segmented track arc segments based on the track filtering boundary conditions to obtain a filtering result; and calculating the starting time and the ending time of the low orbit satellite receiving by using a dynamic step-by-step method according to the filtering result to obtain a receiving time window. On the premise of ensuring the calculation precision of parameters such as a low-orbit satellite receiving time window, an altitude angle, an azimuth angle and the like, the orbit outside the visible range of the ground station is filtered, then the time window and the tracking point position information are calculated by changing the sampling time interval, the calculation step length is dynamically changed by the visible condition and the prediction distance, the calculation number of sampling points is greatly reduced under the condition that the result precision is not lost, the calculation efficiency is improved, and the calculation efficiency of the low-orbit satellite receiving time window and the calculation result precision can be simultaneously improved.

Based on the method of fig. 3, the embodiments of the present disclosure further provide some specific implementations of the method, and next, the technical solution of the present disclosure will be described with reference to the overall flowchart of the calculation of the low-orbit satellite time window of fig. 4.

In determining the visible range based on the minimum altitude angle of the ground station position and the satellite nominal orbit parameter, in particular, determining the visible range of the low orbit satellite based on the ground station position information and the satellite nominal orbit altitude information may specifically include:

and calculating the visible boundary of the satellite by taking the ground station as the center based on the preset minimum altitude angle of the satellite to the ground station and the sampling interval of the azimuth angle, thereby obtaining the visible range of the low-orbit satellite.

Specifically, the determination of the visual range may be achieved based on the following method:

the visible position of the satellite can be determined based on information such as the ground station position and the nominal orbit height of the satellite. Setting the minimum altitude angle of the satellite to the ground station asSetting a sampling interval of azimuth angles, and calculating a visible boundary of a satellite by taking a ground station as a center, wherein the method comprises the following steps of:

as shown in fig. 5, the ground stationAnd satellite point->Is>The calculation formula of (2) is as follows:

（6）

Wherein,is the average radius of the earth>Is the satellite altitude.

The latitude of the visible boundary point can be obtained by the cosine formula of the spherical triangle PDN:

（7）

in the formula (7), the amino acid sequence of the compound,is the latitude of the visible boundary point, +.>Latitude of ground station>Is the satellite azimuth.

The longitude of the visible boundary can be obtained from the sine formula of the spherical triangle PDN:

（8）

（9）

longitude, +.>For ground station->Longitude of->For the point on the earth's surface->Meridian plane to->The angle of meridian plane is equal to azimuth angle +.>And continuously sampling from 0 to 360 degrees to obtain the visual range of the low-orbit satellite by calculation.

Regarding ground stations that include poles in the range of view to the satellite, it is necessary to determine the geocentric angleLatitude>Is used to determine the visual boundary. Fig. 6 shows the range of a certain polar earth station from the determination method to the HY-1C satellite. Based on the requirements of satellite orbit filtering algorithm, the method not only can calculate the visible range of the ground station to the satellite, but also can classify the ground station. The global ground stations can be divided into four categories, the ground stations whose visual range contains poles of north and south are called polar stations, identified as 0; the ground station with the visual range completely located in the north-south hemisphere is called a hemisphere station and is marked as 1; the ground station with the ground station at the equator is called the equator station, identified as 2; ground stations whose visual range spans the north-south hemisphere are called other stations, identified as 3.

The method for determining the visible range is suitable for calculating the visible range of any ground station to the satellite.

After the visibility range is determined, in step 340, input parameters are provided for satellite orbit filtering due to the main fact that the satellite orbit is segmented. The orbit dividing method is related to the type of a ground station, and the satellite orbit dividing method adopts two modes, namely a rising intersection point of the orbit is taken as a dividing point, and the satellite is divided once every round of the earth, namely the rising intersection point dividing method; the other is a pole segmentation method, in which the position of the satellite flying to the south and north ends of the earth is used as a segmentation point, and the satellite is segmented once every half circle around the earth.

The segmentation method can be respectively described for different ground stations:

(1) When the ground station is a polar station or a hemispherical station, adopting a lifting intersection point segmentation method to carry out track segmentation:

setting a time interval for carrying out orbit segmentation, reading TLE files of satellites, checking the legality of the files, and analyzing the number of the orbits of the satellites. Inputting the satellite orbit number into an SGP4 model, calculating to obtain the TEME coordinate of the satellite at the starting time, and converting the TEME coordinate of the satellite into a J2000 inertial coordinate through coordinate conversion. Then calculating by using inertial coordinates of the current moment of the satellite to obtain a satellite orbit semi-path Semi-major axis->Eccentricity of track->Track inclination->The ascending intersection is the right direction>Near-site angular distance->True near point angle->And instantaneous orbit parameters.

The time interval from the start time to the dividing point is calculated using these parameters. The specific formula is as follows:

（10）

（11）

wherein,is latitude and amplitude angle>For the time interval from the current satellite position to the next intersection point position, < >>Is the average angular velocity of the satellite.

According to the start time andthe longitude and latitude of the first division point can be calculated. Due to->Is the average angular velocity, requires multiple iterations of calculating the latitude argument +.>Until the latitude of the division point differs from the equatorial level by less than a threshold value +.>. Calculation of the nth split point requires adding time to one track period +.>Repeating the above steps.

The results of the intersection-up segmentation method are stored in the following table, and in table 1, the first turn and the last turn in the calculation time interval may be less than half a turn, and the present turn may not have intersection-down points, so the intersection-down time may be empty.

TABLE 1 results storage means table of increasing intersection point dividing method

(2) When the ground station is an equatorial station or other types of ground stations except polar stations, hemispherical stations and equatorial stations, a pole segmentation method is adopted:

The pole segmentation method is similar to the lifting intersection segmentation method, and the instantaneous orbit parameters of the satellite starting time are calculated through TLE files, SGP4 models and coordinate system conversion. And judging the position relation between the current position of the satellite and the nearest pole through the latitude amplitude angle, further calculating the satellite position near the pole, setting a time sampling interval, and calculating longitude and latitude coordinates of three continuous sampling points. If the latitude of the middle sampling point is greater or less than the latitude of the two side sampling points, then that point is considered to be a pole. The subsequent calculation of N poles requires 1/2 track period steps, and the steps of calculating three continuous sampling points to search the poles are repeated.

The pole division method is stored in the following table, and the data corresponding to the start time 2 and the end time 1 in table 2 are the same, the data corresponding to the start time 3 and the end time 2 are the same, and so on.

TABLE 2 results storage means table of pole splitting method

In the method, different track segmentation methods are adopted for different ground stations to segment, so that preparation is made for rapid and effective filtration of subsequent tracks.

In addition, the determination method of the track filtering boundary condition is different for different ground stations, and different types of ground stations adopt different track filtering boundary conditions, which can be respectively described as follows:

(1) Polar station orbit filtering boundary condition determination

The polar region stations are divided into a southern hemispherical polar region station and a northern hemispherical polar region station, the orbit filtering boundary condition of the northern hemispherical polar region station is an ascending intersection point, and the orbit filtering boundary condition of the southern hemispherical polar region station is a descending intersection point.

(2) Hemispherical station orbit filtering boundary condition determination

The boundary condition of hemispherical station orbit filtering is determined, firstly, the orbit arc sections tangential to the two sides of the visible boundary are found, and the intersection point of the orbit and the equator can be used as the boundary condition of the orbit filtering.

As shown in fig. 7, in the hemispherical station orbit filtering boundary condition determination diagram,Din the case of a ground station,E0、E1、E2and E3 are the points of maximum latitude, maximum longitude, minimum latitude and minimum longitude on the ground station's visual boundary to the HY-1C satellite,EC1to take the following measuresEDIs a circle of radiusEA tangent to the point at which,EC2perpendicular to the equator,C1C2C3are all located at the equator.EThe point being at the boundary arc sectionE3E0Up-sampling continuously, calculating tangent lineEC1Included angle with the equatorWhen->When the inclination angle is closest to the orbit inclination angle of the satellite, then the satellite is considered to be at the momentC1The point is the left boundary point of hemispherical station orbit filtering. The calculation formula is as follows:

（12）

（13）

（14）

in the above-mentioned method, the step of,、/>respectively areDLongitude and latitude of the point +.>、/>Respectively areEThe longitude and latitude of the point, Is thatC1Dots and dotsC2Longitude difference of point ++>Is thatC1Longitude of the point. />

Similarly, the right boundary point of hemispherical station orbit filtering can be obtained by using the method.

(3) Equatorial station orbit and other station orbit filtering boundary condition determination method the equatorial station orbit filtering boundary condition determination method is similar to hemispherical station, only the included angle isIs slightly different.

As shown in figure 8 of the drawings,Din order to be located at the equatorial ground station,E0、E1the points with the largest latitude and the largest longitude on the visible boundary of the ground station to the HY-1C satellite are respectively.EThe point being at the boundary arc sectionE0 E1Up-sampling continuously, calculating tangent lineEC2Included angle with the equatorWhen (when)When the inclination angle is closest to the orbit inclination angle of the satellite, then the satellite is considered to be at the momentC2The point is the right boundary point of the hemispherical station orbit filter.

（15）

（16）

Similarly, the left boundary point of the equatorial station orbit filter can be obtained by the method.

The orbit filtering boundary condition determination method of other stations is the same as that of the hemispherical station.

For different ground stations, track filtering can be described separately:

(1) Polar station track filtration

For a northern hemisphere polar station, selecting a time interval of a first rising intersection point and a first falling intersection point of each turn in a rising intersection point segmentation method result, and filtering out half track turns positioned in a southern hemisphere in each turn.

For the southern hemisphere polar station, selecting a time interval of a descending intersection point and a second ascending intersection point of each circle in the ascending intersection point segmentation method result, and filtering out a half track circle of each circle, which is positioned in the northern hemisphere. This results in a track arc that may pass through the viewable range of the polar station.

(2) Hemispherical station orbit filtering

Firstly, filtering out track circle numbers of ascending intersection points and descending intersection points which are positioned outside boundary points of left and right sides in an ascending intersection point segmentation method result, and filtering out half track circle numbers of a hemisphere station positioned in a northern hemisphere; for a hemispherical station of the southern hemisphere, filtering out a half track circle number positioned in the northern hemisphere; this results in a track arc that passes through the viewable range of the hemispherical station.

(3) Equatorial station orbit filtering

And judging the longitude of the arc section passing through the equatorial point and the longitude of the left and right boundary points as a result of the pole segmentation method, and filtering the arc section to the track arc section positioned outside the left and right boundary points, thereby obtaining the track arc section passing through the visual range of the equatorial station. The other station orbit filtering is the same as the equatorial station orbit filtering method.

Finally, after the target satellite orbit is obtained through filtering, a receiving time window needs to be calculated, a minimum altitude angle can be set during calculation, and the starting time and the ending time of satellite receiving are calculated by utilizing a dynamic step length method according to the orbit arc section of the orbit filtering result.

And setting stepping time according to service requirements, and continuously sampling and calculating satellite altitude and azimuth in a time window. The point location information can be used as an initial parameter for the ground station antenna to start tracking the satellite, and the maximum height angle in the time window can be used as a basis for selecting a high-quality time window.

Dynamic step algorithm: the range of visibility of the ground station to the satellite is defined as a conical shape with the vertical distance of the satellite to the side of the cone as the "predicted distance". The minimum altitude angle when the ground station is visible to the satellite is set toThe cone half angle of the visual field is +.>Is included in the above-mentioned range. Calculating sampling points at the starting time of the satellite, calculating time step according to the predicted distance of the sampling points to obtain the sampling point at the next time, and iterating continuously to obtain the distance between the sampling points and the visible lightThe closer the range is, the smaller the step length is, so that the sampling point and the starting moment which meet the visual condition can be calculated, then the step length is gradually increased until the step length approaches the boundary of the visual range, the step length starts to be reduced, the sampling point and the ending moment which meet the visual condition are obtained, then the step length enters the increasing process, and the process is repeated until the calculation is ended.

According to the technical scheme provided by the invention, the method for determining the satellite visible range by the ground station and the satellite orbit filtering can simultaneously solve the problems of low calculation efficiency and low result precision. The satellite positions satisfying the minimum altitude angle are calculated in the omnibearing direction of the ground station, and the visible range of any position on the earth to the satellites can be easily obtained. The visibility range is related to the altitude of the satellite, the higher the satellite orbit altitude, the larger the visibility range. It is particularly noted that the visible range of ground stations with higher latitudes may contain poles. For this situation, a solution is proposed, i.e. to determine if the spherical arc of the ground station and the satellite's understar point is larger than the spherical arc of the ground station and the pole, and if so, the visible range contains the pole. In this way, the correct range of visibility of the ground station to the satellite is obtained. Different track splitting methods are employed depending on the type of ground station. The scheme provided by the invention can be used for quickly and effectively carrying out orbit filtering, the boundary conditions of the orbit filtering are determined by utilizing the visible range of the ground station to the satellite and the orbit parameters of the satellite, and the arc sections of the orbit outside the visible range can be quickly and effectively filtered according to the filtering boundary conditions and the orbit segmentation result, so that a foundation is laid for quick calculation of a subsequent time window.

The technical scheme provided by the invention aims to realize rapid orbit filtering on the premise of ensuring the calculation accuracy of parameters such as a low orbit satellite receiving time window, an altitude angle, an azimuth angle and the like, has simple implementation principle, is easy to implement and has high calculation accuracy, and can be directly used for the business works such as the calculation of time windows and tracking points of a ground receiving station network.

The low orbit satellite winds around the earth 14 circles each day, the visible orbit of the medium-low latitude ground station to the low orbit satellite is 4-6 circles each day, and the visible orbit of the high latitude ground station to the low orbit satellite is 11-12 circles each day, or even more. If the satellite position is continuously sampled and calculated by using the tracking propagation method, a large amount of redundant calculation is generated, and the technical scheme provided by the invention firstly filters out the orbit outside the visible range of the ground station, then calculates the time window and tracking point position information by changing the sampling time interval, can rapidly and effectively filter out the orbit arc segments outside the visible range, and lays a foundation for the rapid calculation of the subsequent time window.

Based on the same thought, the invention also provides a low-orbit satellite receiving time window calculating device, as shown in fig. 9, which can comprise:

a base information acquisition module 910, configured to acquire ground station location information and satellite nominal orbit height information;

A visibility range determining module 920 configured to determine a visibility range of the low-orbit satellite based on the ground station position information and the satellite nominal orbit height information;

the ground station classification module 930 is configured to classify the ground station of the low-earth satellite in the visible range, so as to obtain a ground station type; the ground station type at least comprises a polar station, a hemispherical station and an equatorial station;

the satellite orbit segmentation module 940 is configured to select corresponding satellite orbit segmentation methods for different ground station types to perform orbit segmentation, so as to obtain segmented orbit arcs;

the track filtering module 950 is configured to determine track filtering boundary conditions corresponding to different types of ground stations, and perform track filtering on the segmented track arc segments based on the track filtering boundary conditions to obtain a filtering result;

and a receiving time window calculating module 960, configured to calculate, according to the filtering result, a start time and an end time of low-orbit satellite receiving by using a dynamic step-length method, and obtain a receiving time window.

Based on the apparatus in fig. 9, some specific implementation units may also be included:

optionally, the visual range determining module 920 may specifically be configured to:

Based on a preset minimum altitude angle of the satellite to the ground station and a sampling interval of an azimuth angle, calculating a visible boundary of the satellite by taking the ground station as a center:

ground stationAnd satellite point->Is>The calculation formula of (2) is as follows:

；

wherein,is the average radius of the earth>For satellite altitude, +.>Minimum altitude for satellites to ground stations;

the latitude of the visible boundary point is obtained by the cosine formula of the spherical triangle PDN:

；

wherein,is the latitude of the visible boundary point, +.>Latitude of ground station>Is the satellite azimuth;

the longitude of the visual boundary is calculated from the sine formula of the spherical triangle PDN:

；

Optionally, the satellite orbit splitting module 940 may specifically include:

the intersection point raising and dividing unit is used for carrying out track division by taking intersection points as dividing points by adopting an intersection point raising and dividing method when the ground station is a polar station or a hemispherical station, so as to obtain divided track arc sections;

and the pole segmentation unit is used for carrying out track segmentation by taking poles as segmentation points by adopting a pole segmentation method when the ground station is an equatorial station or other types of ground stations except for the polar station, the hemispherical station and the equatorial station, so as to obtain segmented track arc sections.

Optionally, the rising intersection point dividing unit may specifically be configured to:

setting a time interval for carrying out orbit segmentation, reading TLE files of satellites, checking the legality of the files, and analyzing to obtain the number of the orbits of the satellites;

calculating to obtain a TEME coordinate of a satellite starting moment based on the satellite orbit number;

converting the TEME coordinates of the satellite into inertial coordinates through coordinate conversion;

calculating to obtain instantaneous orbit parameters of the satellite orbit by using inertial coordinates of the current moment of the satellite;

based on the instantaneous orbit parameters, the formula is adopted:

；

calculating to obtain a time interval from the starting time to the dividing point; wherein,for the near-spot angular distance->For true near point angle, +.>Is latitude and amplitude angle>For the time interval from the current satellite position to the next intersection point position, < >>Is the average angular velocity of the satellite; according to the start time and->Calculating to obtain the longitude and latitude of the first division point; multiple iterative calculation of latitude argument +.>Until the latitude of the division point differs from the equatorial level by less than a threshold value +.>。

Optionally, the pole segmentation unit may specifically be configured to:

determining the position relation between the current position of the satellite and the nearest pole through the instantaneous orbit parameters, and calculating to obtain the position of the satellite near the pole;

setting a time sampling interval, and calculating longitude and latitude coordinates of three continuous sampling points;

if the latitude of the middle sampling point is larger or smaller than the latitude of the sampling points at the two sides, determining the sampling points as poles;

and performing track segmentation by taking the poles as segmentation points to obtain segmented track arc segments.

Optionally, when the ground station is a polar station, the orbit filtering boundary condition of the northern hemisphere polar station of the polar station is an ascending intersection point, and the orbit filtering boundary condition of the southern hemisphere polar station of the polar station is a descending intersection point;

when the ground station is a hemispherical station, determining the arc sections of the orbit tangential to the two sides of the visible boundary, and determining the intersection point of the orbit and the equator as the boundary condition of orbit filtering.

Optionally, the track filtering module 950 may specifically include:

The first filtering unit is used for selecting a time interval of a first rising intersection point and a falling intersection point of each circle in a rising intersection point segmentation method result for a northern hemisphere polar station when the ground station is a polar station, and filtering out half track circle numbers positioned in a southern hemisphere in each circle; for a polar region station of the southern hemisphere, selecting a time interval of a descending intersection point and a second ascending intersection point of each circle in a ascending intersection point segmentation method result, and filtering out half track circle times positioned in the northern hemisphere in each circle to obtain a track arc section passing through a visible range of the polar region station;

the second filtering unit is used for filtering track circle times of which the rising intersection point and the falling intersection point are positioned outside the boundary points of the left side and the right side in the rising intersection point segmentation method result when the ground station is a hemispherical station; for a hemisphere station located in the northern hemisphere, filtering a half orbit number located in the southern hemisphere; for a hemispherical station of a southern hemisphere, filtering a half track circle number of the northern hemisphere to obtain a track arc section passing through a visible range of the hemispherical station;

and the third filtering unit is used for determining the longitude of the arc section passing through the equatorial point and the longitude of the left and right boundary points in the pole segmentation method result when the ground station is an equatorial station or other types of ground stations except the polar station, the hemispherical station and the equatorial station, and filtering the track arc section positioned outside the left and right boundary points to obtain the track arc section passing through the visual range of the equatorial station or other types of ground stations except the polar station, the hemispherical station and the equatorial station.

Based on the same thought, the embodiment of the specification also provides a low-orbit satellite receiving time window computing device. As shown in fig. 10, may include:

As shown in fig. 10, the terminal device may further include a communication line. The communication line may include a pathway to communicate information between the aforementioned components.

Optionally, as shown in fig. 10, the terminal device may further include a memory. The memory is used for storing computer-executable instructions for executing the scheme of the invention, and the processor is used for controlling the execution. The processor is configured to execute computer-executable instructions stored in the memory, thereby implementing the method provided by the embodiment of the invention.

In a specific implementation, as an embodiment, as shown in FIG. 10, the processor may include one or more CPUs, such as CPU0 and CPU1 in FIG. 10. In a specific implementation, as an embodiment, as shown in fig. 10, the terminal device may include a plurality of processors, such as the processor in fig. 10. Each of these processors may be a single-core processor or a multi-core processor.

Based on the same thought, the embodiments of the present disclosure further provide a computer storage medium corresponding to the above embodiments, where instructions are stored, and when the instructions are executed, the method in the above embodiments is implemented.

The above description has been presented mainly in terms of interaction between the modules, and the solution provided by the embodiment of the present invention is described. It is understood that each module, in order to implement the above-mentioned functions, includes a corresponding hardware structure and/or software unit for performing each function. Those of skill in the art will readily appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is implemented as hardware or computer software driven hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The embodiment of the invention can divide the functional modules according to the method example, for example, each functional module can be divided corresponding to each function, or two or more functions can be integrated in one processing module. The integrated modules may be implemented in hardware or in software functional modules. It should be noted that, in the embodiment of the present invention, the division of the modules is schematic, which is merely a logic function division, and other division manners may be implemented in actual implementation.

Although the invention has been described in connection with specific features and embodiments thereof, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the invention. Accordingly, the specification and drawings are merely exemplary illustrations of the present invention as defined in the appended claims and are considered to cover any and all modifications, variations, combinations, or equivalents that fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A method for calculating a low orbit satellite receiving time window, the method comprising:

calculating the starting time and the ending time of low orbit satellite reception by using a dynamic step length method according to the filtering result to obtain a receiving time window;

the method for performing orbit segmentation by selecting corresponding satellite orbit segmentation methods according to different ground station types to obtain segmented orbit arc segments specifically comprises the following steps:

When the ground station is an equatorial station or other types of ground stations except for a polar station, a hemispherical station and the equatorial station, adopting a pole segmentation method, and carrying out track segmentation by taking poles as segmentation points to obtain segmented track arc segments;

when the ground station is a polar station or a hemispherical station, a rising intersection point segmentation method is adopted, and a track segmentation is carried out by taking the rising intersection point as a segmentation point, so that a segmented track arc section is obtained, and the method specifically comprises the following steps:

setting a time interval for carrying out orbit segmentation, reading two-line element orbit report TLE files of a satellite, checking the legality of the files, and analyzing to obtain the number of the satellite orbits;

calculating to obtain real equatorial plane spring point TEME coordinates of the satellite starting time based on the satellite orbit number;

converting the real equatorial plane spring point TEME coordinates of the satellite into inertial coordinates through coordinate conversion;

based on the instantaneous orbit parameters, the formula is adopted:

；

calculating to obtain a time interval from the starting time to the dividing point; wherein,for the near-spot angular distance->For true near point angle, +.>Is latitude and amplitude angle>For the time interval from the current satellite position to the next intersection point position, < > >Is the average angular velocity of the satellite;

according to the start time andcalculating to obtain the longitude and latitude of the first division point; multiple iterative calculation of latitude argument +.>Until the latitude of the division point differs from the equatorial level by less than a threshold value +.>；

When the ground station is an equatorial station or other types of ground stations except polar stations, hemispherical stations and equatorial stations, a pole segmentation method is adopted, and poles are used as segmentation points for track segmentation, so that segmented track arc segments are obtained, and the method specifically comprises the following steps:

performing track segmentation by taking the poles as segmentation points to obtain segmented track arc segments;

the track filtering boundary condition is used for carrying out track filtering on the segmented track arc segments to obtain a filtering result, and the method specifically comprises the following steps:

when the ground station is a polar station, for the northern hemisphere polar station, selecting a time interval of a first rising intersection point and a falling intersection point of each circle in a rising intersection point segmentation method result, and filtering out a half track circle number positioned in the southern hemisphere in each circle; for a polar region station of the southern hemisphere, selecting a time interval of a descending intersection point and a second ascending intersection point of each circle in a ascending intersection point segmentation method result, and filtering out half track circle times positioned in the northern hemisphere in each circle to obtain a track arc section passing through a visible range of the polar region station;

when the ground station is a hemispherical station, filtering a half track circle number of a hemispherical station positioned in a southern hemisphere for the hemispherical station positioned in a northern hemisphere; for a hemispherical station of a southern hemisphere, filtering a half track circle number positioned in the northern hemisphere, and then filtering track circle numbers with a rising intersection point and a falling intersection point positioned outside boundary points of left and right sides in a rising intersection point segmentation method result to obtain a track arc section passing through a visual range of the hemispherical station;

When the ground station is an equatorial station or other types of ground stations except for the polar station, the hemispherical station and the equatorial station, determining the longitude of the arc section passing through the equatorial point and the longitude of the left and right boundary points in the pole segmentation method result, and filtering the track arc section positioned outside the left and right boundary points to obtain the track arc section passing through the visual range of the equatorial station or other types of ground stations except for the polar station, the hemispherical station and the equatorial station.

2. The method of claim 1, wherein determining the visible range of the low-orbit satellite based on the ground station position information and the satellite nominal orbit height information, specifically comprises:

；

wherein,is the average radius of the earth>For the satellite height, the spherical arc length of the receiving ring is +.>，/>Minimum altitude for satellites to ground stations;

；

wherein,is the latitude of the visual border +. >Latitude of ground station>Is the satellite azimuth;

；

longitude, +.>For ground station->Longitude of->For the point on the earth's surface->From the meridian plane toThe angle of meridian plane is equal to azimuth angle +.>And continuously sampling from 0 to 360 degrees to obtain the visual range of the low-orbit satellite by calculation.

3. The method for calculating a low-orbit satellite receiving time window according to claim 1, wherein determining the orbit filtering boundary conditions corresponding to different types of ground stations comprises:

when the ground station is a polar station, the orbit filtering boundary condition of the northern hemisphere polar station of the polar station is an ascending intersection point, and the orbit filtering boundary condition of the southern hemisphere polar station of the polar station is a descending intersection point;

4. A low-orbit satellite reception time window computing device, the device comprising:

the receiving time window calculation module is used for calculating the starting time and the ending time of low orbit satellite receiving by utilizing a dynamic step length method according to the filtering result to obtain a receiving time window;

the satellite orbit segmentation module specifically comprises:

The pole segmentation unit is used for carrying out track segmentation by taking poles as segmentation points by adopting a pole segmentation method when the ground station is an equatorial station or other types of ground stations except for a polar station, a hemispherical station and an equatorial station, so as to obtain segmented track arc sections;

the rising intersection point dividing unit is specifically configured to:

based on the instantaneous orbit parameters, the formula is adopted:

；

calculating to obtain a time interval from the starting time to the dividing point; wherein,for the near-spot angular distance->For true near point angle, +.>Is latitude and amplitude angle>For the time interval from the current satellite position to the next intersection point position, < >>Is the average angular velocity of the satellite;

according to the start time andcalculating to obtain the longitude and latitude of the first division point; multiple iterative calculation of latitude argument +. >Until the latitude of the division point differs from the equatorial level by less than a threshold value +.>；

The pole segmentation unit is specifically configured to:

the track filtration module specifically comprises:

5. A low-orbit satellite reception time window computing device, the device comprising:

based on the instantaneous orbit parameters, the formula is adopted:

；

according to the start time andcalculating to obtain the longitude and latitude of the first division point; multiple iterative calculation of latitude argument +.>Until the latitude of the division point differs from the equatorial level by less than a threshold value +. >；

6. A computer storage medium having instructions stored therein which, when executed, implement the low orbit satellite receiving time window calculation method according to any one of claims 1 to 3.