A method for inter-satellite communication in a cluster of satellites in the same orbital plane

Abstract

The application discloses an antenna switching method for inter-satellite networking. When the included angle between the direction vector of any antenna in a closed state and the direction vector of the opposite satellite is less than or equal to a preset value within a continuous specified time length, the antenna is opened, and the currently opened antenna is closed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerospace technology, in particular to an antenna switching method for inter-satellite networking. BACKGROUND

[0002] Satellite on-orbit networking is a development trend of space-based systems, and it is the key to exert the effectiveness of space-based systems. To realize satellite on-orbit networking, a reliable inter-satellite communication link needs to be formed. The inter-satellite communication link is used for communication between satellites, which can interconnect multiple satellites together to realize information transmission and exchange between satellites. The introduction of the inter-satellite communication link makes the satellite communication system less dependent on the ground network, and thus makes the satellite communication system more flexible in routing selection and network management, and reduces the transmission delay.

[0003] During the on-orbit period of the satellite, the attitude of the satellite will change continuously, and the beam direction of the antenna on the satellite will also change accordingly, which will cause the communication link formed between the single antenna and the opposite satellite to be interrupted. To solve this problem, one way is to install multiple sets of antennas on the satellite, and the beam directions of the antennas form a complement to each other to ensure that at any moment and in any attitude, the satellite has an antenna that can establish a communication link with the opposite satellite. How to control the switching between the sets of antennas becomes the key to ensuring the continuity of inter-satellite communication. SUMMARY

[0004] To ensure the continuity of inter-satellite communication, the present application provides an antenna switching method for inter-satellite networking, comprising:

[0005] If any antenna in the closed state has an included angle with the direction vector of the opposite satellite less than or equal to a preset value within a continuous specified time length, the antenna is turned on and the currently turned-on antenna is turned off.

[0006] Further, the specified time length is 3 seconds.

[0007] Further, the preset value is 45°.

[0008] Further, the included angle with the direction vector of the opposite satellite is calculated according to the received orbit position information of the opposite satellite.

[0009] Further, the antenna switching method further comprises:

[0010] If the inter-satellite communication link interruption time exceeds a threshold value, the search for link establishment is restarted.

[0011] Further, the threshold value is 1 minute.

[0012] Further, the search for link establishment comprises:

[0013] sequentially turn on each antenna on the satellite, and keep for a second specified time length to search for the opposite satellite signal, wherein any antenna is in the on state and the rest of the antennas are in the off state; and

[0014] After the opposite satellite signal is searched, a communication link is established.

[0015] Further, the second specified time length is 15 seconds.

[0016] The present application provides an antenna switching method for inter-satellite networking, which sets the on and off of each antenna according to the azimuth between the antenna and the opposite satellite, realizes antenna switching, and effectively ensures the continuity of the inter-satellite communication link. BRIEF DESCRIPTION OF DRAWINGS

[0017] To further clarify the above and other advantages and features of the present application, a more particular description of embodiments thereof will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the application and are therefore not to be considered limiting of its scope. In the drawings, like or similar components are denoted by the same or similar reference signs.

[0018] Figure 1 A flowchart of an antenna switching method for inter-satellite networking according to one embodiment of the present application is shown; and

[0019] Figures 2a-2b A schematic diagram of the antenna beams on a satellite according to one embodiment of the present application is shown. DETAILED DESCRIPTION

[0020] In the following description, the present application is described with reference to various embodiments. However, one skilled in the art will recognize that the various embodiments can be practiced without one or more of the specific details, or with other replacement and / or additional methods.

[0021] In the present application, each embodiment is only intended to illustrate the scheme of the present application, and should not be understood as limiting.

[0022] In the present application, the quantifier "one", "a" does not exclude the scenario of multiple elements, unless specifically indicated.

[0023] In the present specification, the reference to "one embodiment" or "the embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. The phrase "in one embodiment" appearing in various places in the specification does not necessarily all refer to the same embodiment.

[0024] It should also be pointed out herein that, within the scope of the present application, the expressions "same", "equal", "identical" and the like do not mean that the values are absolutely equal, but allow for a certain reasonable error, that is to say, the expressions also encompass "substantially same", "substantially equal", "substantially identical".

[0025] A reliable inter-satellite communication link is the key to the on-orbit networking of satellites. Designing a reasonable switching strategy for a satellite communication antenna and ensuring that the antenna can realize inter-satellite communication at any time can ensure the continuity of inter-satellite communication. Based on this, the present application provides an antenna switching method for inter-satellite networking, which determines the opening and closing of the antenna according to the relative position of the antenna and the opposite satellite. The scheme of the present application will be further described below in combination with the embodiment drawings.

[0026] Figure 1 A flowchart of an antenna switching method for inter-satellite networking according to an embodiment of the present application is shown. As shown in Figure 1 , an antenna switching method for inter-satellite networking comprises:

[0027] Real-time calculation of the direction vector angle Ψ i between each antenna i on the satellite and the opposite satellite; in an embodiment of the present application, the direction vector angle Ψ i between the antenna i and the opposite satellite is calculated according to the received orbit position information of the opposite satellite, and the specific calculation is as follows:

[0028]

[0029] Ψ = arccos (V

[0030] · V i_J2000 ), where V is the direction vector of the antenna i in the J2000 coordinate system, A bi is the attitude conversion matrix from the J2000 system to the body system, and V i_body is the axial direction of the antenna i in the body system, all of which are known quantities; and

[0031] V df_J2000 is the direction vector of the opposite satellite relative to the satellite in the J2000 coordinate system, V df_J2000 = R df_J2000 -R wx_J2000 , where:

[0032] R df_J2000 = (R df_J2000_x , R df_J2000_y , R df_J2000_z ) Tthe orbit position of the counterpart star in the J2000 coordinate system is calculated according to the orbit information of the counterpart star successively received by the satellite most recently, and a mature J2 model orbit extrapolation algorithm is used to calculate the orbit position of the counterpart star in the J2000 coordinate system;

[0033] and

[0034] R wx_J2000 = (R wx_J2000_x , R wx_J2000_y , R wx_J2000_z ) T is the orbit position of the satellite itself in the J2000 coordinate system at the current time; and

[0035] the calculated direction vector angle Ψ i is compared with a preset value:

[0036] if any antenna L in the closed state has an angle with the direction vector of the counterpart star less than or equal to the preset value within a continuous specified time length, the antenna L is turned on, and the currently turned-on antenna is turned off. In an embodiment of the present application, the specified time length is 3 seconds, and / or the preset value is 45°. Thus, the switching of the antenna is completed once, and the above process is repeated continuously during the in-orbit period of the satellite. It should be understood that in other embodiments of the present application, the specified time length and / or the preset value can also be set to different values according to requirements.

[0037] In order to quickly re-establish the communication link after the inter-satellite link is interrupted, in an embodiment of the present application, if the inter-satellite communication link interruption event exceeds a threshold value, the search for link establishment is restarted, and the threshold value can be, for example, 1 minute, or other values can be set according to requirements. The search for link establishment includes:

[0038] each antenna on the satellite is turned on successively and kept for a second specified time length to search for the counterpart star signal, wherein any antenna in the turned-on state is closed, and the second specified time length can be, for example, 15 seconds, or other values can be set according to requirements; and after the counterpart star signal is searched, the communication link is established.

[0039] The antenna switching method for inter-satellite networking provided by the present application is especially suitable for the switching of communication antennas between member stars and a center node star in a star cluster on the same orbital plane, wherein the inter-satellite distance between the member stars and the center node star is not more than 1500 km. In order to better illustrate the antenna switching method, the specific process of the antenna switching method used between the member stars and the center node star in the star cluster on the same orbital plane is described in detail below.

[0040] The member star runs on a sun-synchronous orbit with an altitude of 500km and a descending node local time of 12:00. The member star adopts a sailboard to direct at the sun to supplement energy during non-mission period, and switches to fly straight to the earth to make observation during mission period. The coordinate system O c -X sun Y sun Z sun As the system, the member star takes the center of mass as the origin O c , the Z axis O c Z sun is parallel to the vector of the member star pointing to the sun, but opposite to its direction, the X axis O c X sun is obtained by the cross product of the +Y axis of the orbit coordinate system (VVLH coordinate system) and O c Z sun , and the Y axis O c Y sun is determined according to the right-hand rule. In the system, the orbit coordinate system takes the center of mass of the member star as the origin, the Z axis points to the center of the earth, the Y axis points to the negative normal direction of the orbit plane, and the X axis is determined according to the right-hand rule. Generally, for a circular orbit, the X axis direction points to the flight direction. Based on the system, the member star flies straight to the earth so that the attitude is: +Z points to the center of the earth, and +X points to the flight direction.

[0041] Four pairs of interstellar communication antennas are installed on the member star, which are installed in the ±X and ±Z directions of the star body respectively, and the beam half-cone angle of each antenna is 46°. Figures 2a-2b A schematic diagram of the antenna beam on the member star is shown. As shown in the figure, the axial direction of the four pairs of antennas corresponds to the direction vector of the system as follows:

[0042] +X antenna: the axial direction is along the +X direction of the member star body, and the unit direction vector in the system is V tx_Xpos_body =(1, 0, 0) T ;

[0043] -X antenna: the axial direction is along the -X direction of the member star body, and the unit direction vector in the system is V tx_Xneg_body =(-1, 0, 0) T ;

[0044] +Z antenna: the axial direction is along the +Z direction of the member star body, and the unit direction vector in the system is V tx_Zpos_body =(0, 0, 1) T ; and

[0045] -Z antenna: the axial direction is along the -Z direction of the member star body, and the unit direction vector in the system is V tx_Zneg_body =(0, 0, -1) T .

[0046] The interstellar communication antenna of the member star has two states: one is that the ±X antenna is turned on and the ±Z antenna is turned off; the other is that the ±X antenna is turned off and the ±Z antenna is turned on.

[0047] The member star needs to communicate with the center node star, and the center node star is located at a distance of about 1000 km in front of the member star and continuously broadcasts its real-time orbital position and velocity information in the earth-fixed system, wherein the broadcast period is better than 1 minute. In an embodiment of the application, the member star can periodically receive the orbital position and velocity information with time stamp broadcast by the center node star, wherein the information format of the orbital position is shown in Table 1.

[0048]

[0049] Table 1

[0050] Therefore, the switching of the interstellar networking antenna of the member star includes:

[0051] Firstly, the member star searches for the broadcast signal of the center node star to establish a link. The four pairs of antennas +X, +Z, -X and -Z of the member star are switched in turn, and each pair of antennas is switched every 15s to search for the center node star signal, and after the signal is searched, a communication link is established;

[0052] Next, the member star calculates the included angle between the +X antenna, -X antenna, +Z antenna and -Z antenna of the member star and the direction vector of the center node star at the current time, which are respectively Ψ tx_Xpos , Ψ tx_Xneg , Ψ tx_Zpos and Ψ tx_Zneg , and the specific calculation method is as follows:

[0053] Firstly, the center node star is extrapolated. After the member star receives the orbital position and velocity information with time stamp broadcast by the center node star, the last received orbital position of the center node star is taken as the starting point, and the mature J2 model orbit extrapolation algorithm is used to calculate the orbital position R * of the center node star in the J2000 coordinate system at the current time T ZS_J2000 :

[0054] R ZS_J2000 = (R ZS_J2000_x , R ZS_J2000_y , R ZS_j2000_z ) T ;

[0055] Next, the direction of the center node star is determined. The orbital position R GP_j2000 of the member star itself in the J2000 coordinate system at the current time is known.

[0056] R GP_j2000 =(R GP_J2000_x ,R GP_J2000_y ,R GP_J2000_z ) T ,

[0057] Then, the direction vector of the central node star relative to the member star in the J2000 coordinate system at the current time is calculated as follows:

[0058] And

[0059] Finally, the angle between the central node star direction and each antenna is calculated. The attitude conversion matrix A from the J2000 system to the current system is bi is a known quantity, and the +X, -X, +Z, and -Z antenna axes in the current system are vectors V tx_Xpos_body , V tx_Xneg_body , V tx_Zpos_body , and V tx_Zneg_body , respectively. Then, the direction vectors of the +X, -X, +Z, and -Z antenna axes in the J2000 coordinate system are:

[0060]

[0061]

[0062] And

[0063]

[0064] Then, the calculation of the angle between the +X, -X, +Z, and -Z antenna axes and the direction vector of the central node star is as follows:

[0065]

[0066]

[0067] And

[0068] And

[0069] Finally, according to the calculated angles between the +X antenna, -X antenna, +Z antenna, and -Z antenna and the direction vector of the central node star, the antenna switching logic is determined as follows:

[0070] If the current ±Z antenna is on, if min(Ψ tx_Xpos , Ψ tx_Xneg ) ≤ 45° for 3 consecutive seconds, switch to the ±X antenna, i.e., turn on the ±X antenna and turn off the ±Z antenna, and in other cases, keep the ±Z antenna on.

[0071] If the current ±X antenna is on, if min(Ψ tx_Zpos ,Ψ tx_Zneg )≤45° in 3 seconds, switch to ±Z antenna, i.e. turn on ±Z antenna,

[0072] At the same time, turn off ±X antenna, and keep other antennas on.

[0073] In addition, once the inter-satellite communication link is interrupted for more than 1 minute, the search for the link establishment process is restarted according to the foregoing steps, i.e. the four pairs of antennas of the member satellite, +X, +Z, -X, -Z are switched in turn, and the center node satellite signal is searched every 15 seconds, and after the signal is searched, the communication link is established.

[0074] The application provides an antenna switching method for inter-satellite networking, which switches the antennas according to the azimuth between the antennas and the opposite satellite, and effectively ensures the continuity of the inter-satellite communication link.

[0075] Although the embodiments of the application are described above, it should be understood that they are presented only as examples, and not as limitations. It is obvious for those skilled in the art that various combinations, modifications and changes can be made without departing from the spirit and scope of the application. Therefore, the width and scope of the application disclosed herein should not be limited by the above disclosed exemplary embodiments, but should be defined only according to the appended claims and their equivalent replacements.

Claims

1. A method for inter-satellite communication in a cluster of satellites in the same orbital plane, characterized in that, The method comprises the steps of: Switching the four pairs of antennas of the member satellite +X, +Z, -X, -Z in turn, searching for the center node satellite signal, and establishing a communication link; After the member satellite receives the orbit position and speed information with time stamp broadcast by the center node satellite, the orbit position of the center node satellite under the J2000 coordinate system at the current time is calculated by using the J2 model orbit extrapolation algorithm; According to the orbit position of the center node satellite under the J2000 coordinate system, the vector angle between the four pairs of antennas +X, +Z, -X, -Z and the direction of the center node satellite is calculated in real time; and According to the vector angle, the antenna is switched to maintain the inter-satellite communication link: if the currently opened antenna on the member satellite is the ±X direction antenna, if the vector angle between the ±Z direction antenna and the center node satellite is less than or equal to 45° within a continuous specified time length, the ±Z direction antenna is opened and the ±X direction antenna is closed, otherwise the ±X direction antenna is kept open; and If the currently opened antenna on the member satellite is the ±Z direction antenna, if the vector angle between the ±X direction antenna and the center node satellite is less than or equal to 45° within a continuous specified time length, the ±X direction antenna is opened and the ±Z direction antenna is closed, otherwise the ±Z direction antenna is kept open, wherein the specified time length is 3 seconds.

2. The inter-satellite communication method of claim 1, wherein, The four pairs of antennas of the member satellite are switched every 15 seconds.

3. The inter-satellite communication method of claim 1, wherein, the angle between the vector and the direction of the star of the central node is calculated as follows: Wherein, is the direction vector of the axis of the antenna in the J2000 coordinate system, wherein is the attitude transformation matrix from the J2000 system to the body system, and is the direction vector of the axis of the antenna in the body system, all being known quantities; and a direction vector of the central node star relative to the member star in the J2000 coordinate system, wherein: is the orbital position of the central node in the J2000 coordinate system for the current time; and The orbital position of the member star itself in the J2000 coordinate system for the current time.

4. The inter-satellite communication method of claim 1, wherein, Further comprising: If the inter-satellite communication link interruption time exceeds 1 minute, the searching and link establishment are restarted.

Images