Random access measurement and control method suitable for medium-orbit relay satellite

Abstract

The invention provides a spacecraft random access measurement and control method suitable for a medium-orbit relay satellite. According to the method, the beam of a multi-beam antenna is automatically controlled to point to a user spacecraft by using user spacecraft orbit information pre-stored on a medium orbit relay satellite, so that in-orbit random access of the user spacecraft is realized; forward and reverse link resources of the medium-orbit relay satellite are autonomously managed on the satellite, and cooperative work between the user spacecraft and the ground and between different user spacecrafts can be achieved. According to the method, random access of the low-orbit spacecraft can be realized, autonomous management of conventional measurement and control tasks and inter-satellite cooperative work is realized, the difficulty and complexity of ground task scheduling can be effectively reduced, and the efficiency of a measurement and control system is improved.

Description

Technical Field

[0001] The invention relates to an on-demand access measurement and control method suitable for a medium-orbit relay satellite, which can be applied to spacecraft relay communication and measurement and control based on the medium-orbit relay satellite and belongs to the technical field of spacecraft measurement and control. Background Art

[0002] At present, there are two main methods for spacecraft to access the measurement and control link: one is the method of access by ground stations according to task scheduling, and the other is the method of spacecraft access as needed. However, with the rapid growth of the number of low-orbit spacecraft, the amount of spacecraft measurement, control and management tasks is also increasing exponentially. The method of requiring manual intervention by ground stations according to task scheduling will become complicated or even difficult to complete. Therefore, the only way to solve this problem is to use spacecraft access as needed, reduce dependence on ground measurement and control management, and improve the automation level of measurement and control management.

[0003] At present, there are two random access methods used in the field of spacecraft measurement and control in my country: one is the ground-based measurement and control random access method, and the other is the panoramic beam method based on GEO relay satellites.

[0004] 1. Random access method for ground-based measurement and control

[0005] The ground-based random access method refers to the automatic access to the TT&C network to provide TT&C services when the spacecraft enters the coverage of the ground-based TT&C network antenna beam. The ground-based random access has the following characteristics: (1) The service coverage is limited to the visible arc of the ground station; (2) Random access is used to access the channel, and then transfer to the service channel after access; (3) The random access process is complicated, and the spacecraft terminal needs to apply for network access and network exit. (4) The ground station needs to continuously send broadcast information to maintain the access link.

[0006] 2. Panoramic beam method based on GEO relay satellite

[0007] The panoramic beam is formed by overlapping and combining static beams to form continuous coverage of the visible area in time and space. The relay satellite in the GEO orbit transmits all in-band signals received by the SMA (S-band Multiple Access) phased array antenna elements to the ground station through the downlink feeder link. At the ground station, the ground-based digital beamforming (GDBF) technology can form a cellular wide-area static beam, thereby achieving global coverage. The panoramic beam method based on GEO relay satellite has the following characteristics: (1) The panoramic beam is only applicable to the return tracking and control link. (2) The panoramic beam is a static beam, and the relay satellite must be located in the GEO orbit. Summary of the invention

[0008] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a random access method applicable to a medium-orbit relay satellite, and to enable a low-orbit spacecraft to randomly access a measurement and control link based on a medium-orbit relay satellite. A low-orbit user spacecraft can periodically report its status in all orbital arcs, and by applying to a relay satellite, the relay satellite autonomously allocates measurement and control link resources to achieve communication with a ground station or other user spacecraft.

[0009] The technical solution of the present invention is:

[0010] A random access measurement and control method applicable to a medium-orbit relay satellite, comprising:

[0011] The medium-orbit relay satellite pre-stores and maintains a user spacecraft list on board, wherein the user spacecraft list includes the orbital element number of the user spacecraft, the spread spectrum code used by the user spacecraft, and the authentication information of the user spacecraft;

[0012] The medium-orbit relay satellite calculates the real-time position of the user spacecraft according to the orbital elements of the user spacecraft, and automatically controls the return tracking beam of the multi-beam antenna to point to different user spacecraft in the service area in turn;

[0013] The medium-orbit relay satellite captures and tracks the short message signal sent by the user terminal on the user spacecraft. The onboard measurement and control payload demodulates and decodes the signal and determines the legitimacy of the user spacecraft based on the authentication data in the short message.

[0014] The medium-orbit relay satellite determines the type of short message based on the short message information sent by the user terminal of the legitimate user spacecraft. When the short message is a periodic status report short message, it forwards the demodulated periodic status report data to the ground station and ends the service. When the short message is a resource application short message, the medium-orbit relay satellite allocates link resources to the user spacecraft, establishes a relay measurement and control link, and sends a resource plan short message to the user spacecraft after the relay measurement and control link is established. The medium-orbit relay satellite allocates the duration of the relay link when the link is established. When the allocated duration ends, it automatically releases the relay link resources and ends the service.

[0015] Preferably, at the beginning of each service, the medium-orbit relay satellite searches the list of user spacecraft in the service area to find the current service object; for users of the same priority, measurement and control services are provided to each user spacecraft in turn in a polling manner.

[0016] Preferably, the user terminal of the user spacecraft needs to continuously send short message signals during operation, so that the medium-orbit relay satellite can immediately receive the short message information after pointing the return tracking beam to the user terminal of the user spacecraft.

[0017] Preferably, the forward and return short message signals between the user terminal of the user spacecraft and the medium-orbit relay satellite adopt the BPSK+coherent spread spectrum modulation method, and different user spacecraft are distinguished by code division multiple access combined with phased array beam space division.

[0018] Preferably, different types of short message data adopt a unified format and length, and all include two parts: a synchronization segment and a data segment. The synchronization segment is used to capture and synchronize signals, and the data segment contains user spacecraft authentication data, short message type and other data.

[0019] Preferably, after receiving the periodic status report short message information sent by the user terminal of a user spacecraft, if the medium-orbit relay satellite is in the visible arc segment within the country, the demodulated data is forwarded to the ground station through the satellite-to-ground feeder link of the medium-orbit relay satellite; if the medium-orbit relay satellite is not in the visible arc segment within the country, it is first sent to the adjacent medium-orbit relay satellite through the inter-satellite link. When the demodulated data is transmitted to the medium-orbit relay satellite located in the visible arc segment within the country, the medium-orbit relay satellite sends the demodulated data to the ground station through the satellite-to-ground feeder link.

[0020] Preferably, the resource application short message includes two types, one is to apply for return link resources only, and the information transmission direction is user spacecraft->relay satellite->ground station; the other is to apply for bidirectional link resources, and the information transmission direction is user spacecraft A<->relay satellite<->user spacecraft B or ground station.

[0021] Preferably, the medium-orbit relay satellite determines whether the resource application of the user spacecraft is approved based on the resource situation. When the resource application of the user spacecraft can be met, relay link resources are allocated to the user spacecraft and the resource usage time is directly determined. After the medium-orbit relay satellite allocates link resources and duration to the user spacecraft, it points the transmit beam of the multi-beam antenna to the user spacecraft and sends a resource planning short message to the user spacecraft. The resource planning short message includes the link resource allocation duration. After the allocation duration ends, the medium-orbit relay satellite automatically disconnects the link, releases the resources, and the user spacecraft automatically leaves the network.

[0022] The beneficial effects of the present invention compared with the prior art are:

[0023] (1) The relay satellite (TDRS) systems currently used at home and abroad are all composed of synchronous orbit relay satellites, and the orbital position of the relay satellites is relatively limited. The present invention can be used in a relay satellite system composed of medium-orbit relay satellites. The relay satellites do not need to occupy synchronous orbit resources, and the number of relay satellites can be increased according to the mission volume, which has a wider adaptability.

[0024] (2) In the present invention, the access requirements generated by the periodic status report of the user spacecraft can be realized by transmitting a return short message. Periodic status reporting is the most important requirement of spacecraft measurement and control, accounting for more than 90% of the measurement and control data transmission. Compared with the method of ground-based measurement and control that requires handshake before entering the service channel, this method greatly improves the efficiency of the relay satellite system in space-based measurement and control applications.

[0025] (3) At present, the ground-based measurement and control random access method is limited to ground measurement and control stations within the country. For a low-orbit satellite with an orbital altitude of 500km, its visible arc is less than 5% of the total arc. The present invention is a random access method based on medium-orbit relay satellites. By forming a constellation of multiple medium-orbit relay satellites, it can meet the full-time and full-domain measurement and control needs of user spacecraft.

[0026] (4) In the present invention, compared with the ground-based measurement and control random access method, the medium-orbit relay satellite allocates the duration of relay link resource use when accessing, and the user spacecraft automatically leaves the network after the time expires, thereby simplifying the process of processing the off-network application on the medium-orbit relay satellite.

[0027] (5) In the present invention, compared with the ground-based measurement and control random access method, the medium-orbit relay satellite does not need to continuously send a broadcast signal, which can reduce power consumption and the impact on the space electromagnetic environment.

[0028] (6) In the present invention, the resource request of the user spacecraft is directly processed by the relay satellite, which can realize both unidirectional data transmission of the return link and bidirectional data transmission of the forward and return links. The bidirectional tracking and control link can be used not only for tracking and control between low-orbit spacecraft and ground stations, but also for inter-satellite collaborative operations between different low-orbit spacecraft, and has a wider application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a simplified diagram of the composition of a typical medium-orbit relay satellite random access measurement and control system;

[0030] Figure 2 It is a short message frame structure;

[0031] Figure 3 A workflow diagram for user spacecraft access at any time;

[0032] Figure 4 Workflow diagram for requesting bidirectional link resources for user spacecraft. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0034] The present invention provides a random access method applicable to a medium-orbit relay satellite, comprising the following steps:

[0035] S1, the onboard TT&C payload of the medium-orbit relay satellite stores and maintains a list of user spacecraft in the service area, including user spacecraft terminal identification, spread spectrum code, orbital element number and other information. The service object with the highest priority in the current service area is found by searching the list. The onboard TT&C payload of the medium-orbit relay satellite calculates the real-time position of the user spacecraft based on the pre-stored orbital element number of the user spacecraft, and controls the receiving beam of the multi-beam antenna to point to the user spacecraft.

[0036] S2, the medium-orbit relay satellite captures and tracks the short message signal sent by the user spacecraft. The onboard measurement and control payload demodulates and decodes the signal and determines the legitimacy of the user based on the authentication data in the short message.

[0037] S3, the medium-orbit relay satellite determines the type of short message based on the short message information sent by the user spacecraft. When the short message received by the relay satellite is a periodic status report short message, the demodulated periodic status report data is forwarded to the ground station and the service is terminated. When the short message received by the relay satellite is a resource application short message, the relay satellite allocates link resources to the user spacecraft, establishes a relay measurement and control link, and sends a resource plan short message to the user spacecraft after the relay link is established. The relay satellite allocates the duration of the relay link when the link is established. When the allocated duration ends, the relay link resources are automatically released and the user spacecraft leaves the network.

[0038] Figure 1 This is a simplified diagram of the composition of the random access measurement and control system for medium-orbit relay satellites.

[0039] In step S2, the user terminal of the user spacecraft needs to continuously send short message signals during operation so that the relay satellite can immediately receive the short message after the receiving beam is directed to the user spacecraft. The forward and return short message signals between the user spacecraft and the relay satellite adopt the modulation method of BPSK+coherent spread spectrum. Different user spacecraft adopt code division multiple access combined with phased array beam space division to distinguish them. Figure 2 As shown in the figure, different types of short message data use a unified format and length, including a synchronization segment and a data segment. The synchronization segment is used to capture and synchronize signals, and the data segment contains user spacecraft authentication data, short message type, and other data. Authentication data is used to correctly identify users and avoid illegal access to the measurement and control link. There are two types of short messages: one is a periodic status report short message, and the other is a resource request short message.

[0040] In step S3, the data segment of the periodic status report short message sent by the user spacecraft includes the telemetry information of the current health status of the satellite. After receiving the periodic status report short message information sent by the user spacecraft, if the relay satellite is in the visible arc segment within the territory, the telemetry information is forwarded to the ground station through the relay satellite satellite-to-ground feeder link; if the relay satellite is not in the visible arc segment within the territory, it is first sent to the adjacent relay satellite through the intersatellite link. When the telemetry information is transmitted to the relay satellite located in the visible arc segment within the territory, the relay satellite sends the telemetry information to the ground station through the satellite-to-ground feeder link.

[0041] In S3, the user spacecraft sends a short message for resource application, and the data segment includes resource application information. There are two types of resource applications: one is to apply for return link resources only, and the information transmission direction is user spacecraft->relay satellite (constellation)->ground station; the other is to apply for bidirectional link resources, and the information transmission direction is user spacecraft A<->relay satellite (constellation)<->user spacecraft B (or ground station). The relay satellite determines whether the resource application of the user spacecraft is approved based on the resource situation. When the resource application of the user spacecraft needs to be met, the relay link resources are allocated to the user, and the resource usage time is directly determined. After the relay satellite allocates link resources and time to the user spacecraft, it points the transmit beam of the multi-beam antenna to the user spacecraft and sends a resource plan short message to the user spacecraft. The short message contains the link resource allocation time. After the allocation time ends, the relay satellite automatically disconnects the link, releases the resources, and the user spacecraft automatically leaves the network.

[0042] Example:

[0043] like Figure 3 As shown, the workflow of the user spacecraft random access in this embodiment is as follows:

[0044] (1) At the beginning of each service, the relay satellite searches the list of user spacecraft in the service area and finds the current service object. For users with the same priority, it provides measurement and control services to each user spacecraft in turn in a polling manner.

[0045] (2) The relay satellite directs the return tracking beam of the multi-beam antenna to the location of the user spacecraft. The location of the user spacecraft is calculated using the pre-stored orbital elements.

[0046] (3) The user terminal on the user spacecraft periodically and continuously sends short message signals, and the relay satellite's return tracking beam searches and tracks the user's location. If the relay satellite does not receive the short message sent by the user spacecraft within the predetermined time, the service is terminated.

[0047] (4) After receiving the short message sent by the user spacecraft, the relay satellite performs despreading, demodulation and authentication, and performs corresponding processing according to the type of short message. There are two types of short messages: one is a periodic status report short message, and the other is a resource request short message.

[0048] (5) After receiving the periodic status report short message, the relay satellite directly forwards the demodulated status report data to the ground station and ends the service. If the relay satellite is not currently within the visible arc of the ground station, the data is sent to other relay satellites via the intersatellite link, and other relay satellites send the data to the ground station via the satellite-to-ground feeder link.

[0049] (6) After receiving the resource request short message, the relay satellite checks the current resource situation and determines whether the resource request of the user spacecraft is approved based on the resource situation. When the resource request of the user spacecraft needs to be met, the relay link resources are allocated to the user and the resource usage duration is directly determined. After allocating link resources and duration to the user spacecraft, the relay satellite points the transmit beam of the multi-beam antenna toward the user spacecraft and sends a resource plan short message to the user spacecraft, which contains the link resource allocation duration.

[0050] (7) During the relay link establishment period, the relay satellite phased array beam dynamically tracks the user spacecraft. After the allocated time period ends, the relay satellite automatically disconnects the link, releases resources, and the user spacecraft automatically leaves the network.

[0051] like Figure 4 As shown in the figure, when a user spacecraft applies for bidirectional link resources, the process is as follows:

[0052] (1) The relay satellite receives a two-way link resource request from user spacecraft A, requesting two-way relay communication with user spacecraft B. If user spacecraft B is within the service range of the same relay satellite, the relay satellite points another set of antenna beams toward user spacecraft B and sends a request for relay communication to user spacecraft B. If user spacecraft B is not within the service range of the current relay satellite, the relay satellite is required to send the relay communication request to a relay satellite that can serve user spacecraft B via an intersatellite link.

[0053] (2) If the relay satellite does not receive the relay communication confirmation from user spacecraft B within the predetermined time, the relay satellite sends a short message rejecting the request to user spacecraft A. If the relay satellite receives the relay communication confirmation from user spacecraft B, it allocates resources and establishes a relay communication link.

[0054] (3) The relay satellite sends resource plans to user spacecraft A and B respectively, which include the resource usage time.

[0055] (4) During the use of the relay communication link, the two different beams of the relay satellite dynamically track user spacecraft A and B. After the allocated duration of the relay communication link ends, the link resources are released, user spacecraft A and B automatically leave the network, and the relay communication service ends.

[0056] The present invention proposes a spacecraft random access measurement and control method suitable for medium-orbit relay satellites. The method uses the user spacecraft orbit information pre-stored on the medium-orbit relay satellite to automatically control the beam of the multi-beam antenna to point to the user spacecraft, so as to achieve random access of the user spacecraft in orbit; the forward and return link resources of the medium-orbit relay satellite are autonomously managed on the satellite, and the user spacecraft can work with the ground and different user spacecraft. The method can achieve random access of low-orbit spacecraft, realize autonomous management of conventional measurement and control tasks and inter-satellite collaborative work, effectively reduce the difficulty and complexity of ground task scheduling, and improve the efficiency of the measurement and control system.

[0057] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

Claims

1. A random access measurement and control method applicable to a medium-orbit relay satellite, characterized in that: include: The medium-orbit relay satellite pre-stores and maintains a user spacecraft list on board, wherein the user spacecraft list includes the orbital element number of the user spacecraft, the spread spectrum code used by the user spacecraft, and the authentication information of the user spacecraft; The medium-orbit relay satellite calculates the real-time position of the user spacecraft according to the orbital elements of the user spacecraft, and automatically controls the return tracking beam of the multi-beam antenna to point to different user spacecraft in the service area in turn; The medium-orbit relay satellite captures and tracks the short message signal sent by the user terminal on the user spacecraft. The onboard measurement and control payload demodulates and decodes the signal and determines the legitimacy of the user spacecraft based on the authentication data in the short message. The medium-orbit relay satellite determines the type of short message based on the short message information sent by the user terminal of the legitimate user spacecraft. When the short message is a periodic status report short message, it forwards the demodulated periodic status report data to the ground station and ends the service. When the short message is a resource application short message, the medium-orbit relay satellite allocates link resources to the user spacecraft, establishes a relay measurement and control link, and sends a resource plan short message to the user spacecraft after the relay measurement and control link is established. The medium-orbit relay satellite allocates the duration of the relay link when the link is established. When the allocated duration ends, it automatically releases the relay link resources and ends the service.

2. The random access measurement and control method applicable to a medium-orbit relay satellite according to claim 1, characterized in that: At the beginning of each service, the medium-orbit relay satellite searches the list of user spacecraft in the service area to find the current service object; for users of the same priority, it provides measurement and control services to each user spacecraft in turn in a polling manner.

3. The random access measurement and control method applicable to a medium-orbit relay satellite according to claim 1, characterized in that: During operation, the user terminal of the user spacecraft needs to continuously send short message signals so that the medium-orbit relay satellite can immediately receive the short message information after pointing the return tracking beam to the user terminal of the user spacecraft.

4. The random access measurement and control method applicable to a medium-orbit relay satellite according to claim 1, characterized in that: The forward and return short message signals between the user terminal of the user spacecraft and the medium-orbit relay satellite adopt the BPSK+coherent spread spectrum modulation method. Different user spacecraft are distinguished by code division multiple access combined with phased array beam space division.

5. The random access measurement and control method applicable to a medium-orbit relay satellite according to claim 1, characterized in that: Different types of short message data use a unified format and length, and all include two parts: a synchronization segment and a data segment. The synchronization segment is used to capture and synchronize signals, and the data segment contains user spacecraft authentication data, short message type, and other data.

6. The random access measurement and control method applicable to a medium-orbit relay satellite according to claim 1, characterized in that: After receiving the periodic status report short message information sent by the user terminal of a user spacecraft, if the medium-orbit relay satellite is in the domestic visible arc, the demodulated data will be forwarded to the ground station through the satellite-to-ground feeder link of the medium-orbit relay satellite; if the medium-orbit relay satellite is not in the domestic visible arc, it will first be sent to the adjacent medium-orbit relay satellite through the inter-satellite link. When the demodulated data is transmitted to the medium-orbit relay satellite located in the domestic visible arc, the medium-orbit relay satellite will send the demodulated data to the ground station through the satellite-to-ground feeder link.

7. The random access measurement and control method applicable to a medium-orbit relay satellite according to claim 1, characterized in that: There are two types of resource application short messages: one is to apply for return link resources only, and the information transmission direction is user spacecraft->relay satellite->ground station; the other is to apply for bidirectional link resources, and the information transmission direction is user spacecraft A<->relay satellite<->user spacecraft B or ground station.

8. The random access measurement and control method applicable to a medium-orbit relay satellite according to claim 7, characterized in that: The medium-orbit relay satellite determines whether the resource application of the user spacecraft is approved based on the resource situation. When the resource application of the user spacecraft can be met, it allocates relay link resources to the user spacecraft and directly determines the resource usage time. After allocating link resources and duration to the user spacecraft, the medium-orbit relay satellite points the transmit beam of the multi-beam antenna to the user spacecraft and sends a resource planning short message to the user spacecraft. The resource planning short message includes the link resource allocation duration. After the allocation duration ends, the medium-orbit relay satellite automatically disconnects the link, releases resources, and the user spacecraft automatically leaves the network.

Images