A random access measurement and control method suitable for medium-orbit relay satellites

Abstract

This invention proposes a method for on-the-spot access tracking and control of spacecraft applicable to medium-Earth orbit relay satellites. This method utilizes pre-stored user spacecraft orbit information on the medium-Earth orbit relay satellite to automatically control the beam direction of the multi-beam antenna to point at the user spacecraft, enabling on-orbit on-the-spot access for the user spacecraft. The forward and return link resources of the medium-Earth orbit relay satellite are autonomously managed on-board, enabling collaborative work between user spacecraft and the ground, as well as between different user spacecraft. This method can also achieve on-the-spot access for low-Earth orbit spacecraft, realize autonomous management of routine tracking and control tasks and inter-satellite collaborative work, effectively reduce the difficulty and complexity of ground mission scheduling, and improve the efficiency of the tracking and control system.

Description

Technical Field

[0001] This invention relates to an on-demand access telemetry and control method suitable for medium-Earth orbit relay satellites, which can be applied to spacecraft relay communication and telemetry and control based on medium-Earth orbit relay satellites, and belongs to the field of spacecraft measurement and control technology. Background Art

[0002] Currently, there are two main methods for spacecraft to connect to the telemetry, tracking, and command (TT&C) link: one is through ground stations scheduling connections according to mission requirements, and the other is through on-the-spot spacecraft connection. However, with the rapid increase in the number of low-Earth orbit spacecraft, the workload of spacecraft TT&C and management is also increasing exponentially. The method of ground stations scheduling connections according to mission requirements, which requires manual intervention, will become complex and even difficult to implement. Therefore, adopting on-the-spot spacecraft connection, reducing reliance on ground-based TT&C and management, and improving the automation level of TT&C and management is the only way to solve this problem.

[0003] Currently, my country uses two types of on-demand access methods in the field of spacecraft telemetry, tracking, and command (TT&C): one is the ground-based TT&C on-demand access method, and the other is the panoramic beam method based on GEO relay satellites.

[0004] I. Ground-based Measurement and Control Access Method

[0005] Ground-based on-demand telemetry and control (TT&C) refers to the automatic access to the TT&C network to provide TT&C services once the spacecraft enters the coverage area of ​​the ground-based TT&C network antenna beam. Ground-based on-demand TT&C access has the following characteristics: (1) The service coverage is limited to the line of sight of the ground station; (2) On-demand access is used for access channels, and then the spacecraft is transferred to the service channel after access; (3) The on-demand access process is complex, 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] II. Panoramic Beaming Method Based on GEO Relay Satellites

[0007] Panoramic beamforming is formed by overlapping and combining static beams to achieve continuous temporal and spatial coverage of the visible area. A relay satellite in GEO orbit transmits all in-band signals received by the SMA (S-band Multiple Access) phased array antenna elements to a ground station via a downlink feed link. At the ground station, ground-based digital beamforming (GDBF) technology is used to form a cellular wide-area static beam, thus achieving global coverage. The panoramic beamforming method based on GEO relay satellites has the following characteristics: (1) Panoramic beamforming is only applicable to return telemetry and control links. (2) Panoramic beamforming is a static beam, and the relay satellite must be located in GEO orbit. Summary of the Invention

[0008] The technical problem solved by this invention is to overcome the shortcomings of existing technologies and provide a method for on-demand access to medium-Earth orbit relay satellites, enabling low-Earth orbit spacecraft to access telemetry and control links based on medium-Earth orbit relay satellites. Low-Earth orbit user spacecraft can periodically report their status throughout the entire orbital arc and, by requesting access from the relay satellite, have the relay satellite autonomously allocate telemetry and control link resources to achieve communication with ground stations or other user spacecraft.

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

[0010] A method for on-the-fly access telemetry, tracking, and command (TT&C) for medium-Earth orbit relay satellites, comprising:

[0011] The medium-Earth orbit relay satellite stores and maintains a list of user spacecraft on-board. The list of user spacecraft includes the orbital elements of the user spacecraft, the spreading code used by the user spacecraft, and the authentication information of the user spacecraft.

[0012] The medium-Earth orbit relay satellite calculates the real-time position of the user spacecraft based on 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 sequence.

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

[0014] The medium-Earth 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 terminates the service. When the short message is a resource request short message, the medium-Earth orbit relay satellite allocates link resources to the user spacecraft, establishes a relay telemetry and control link, and sends a resource plan short message to the user spacecraft after the relay telemetry and control link is established. The medium-Earth orbit relay satellite allocates the relay link duration when the link is established, and automatically releases the relay link resources and terminates the service when the allocated duration expires.

[0015] Preferably, at the start of each service, the medium-Earth orbit relay satellite searches the list of user spacecraft within the service area to find the current service target; for users of equal priority, it provides telemetry, tracking and command services to each user spacecraft in a round-robin 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 at 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-Earth orbit relay satellite adopt the modulation method of BPSK + coherent spread spectrum. 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 uniform 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 a periodic status report short message from a user terminal of a user's spacecraft, if the medium-Earth orbit relay satellite is within the visible arc within the territory, it forwards the demodulated data to the ground station via the satellite-to-ground feeder link. If the medium-Earth orbit relay satellite is not within the visible arc within the territory, it first sends the data to an adjacent medium-Earth orbit relay satellite via an inter-satellite link. When the demodulated data is transmitted to a medium-Earth orbit relay satellite located within the visible arc within the territory, that medium-Earth orbit relay satellite sends the demodulated data to the ground station via the satellite-to-ground feeder link.

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

[0021] Preferably, the medium-Earth orbit relay satellite determines whether to approve the user spacecraft's resource request based on resource availability. When the user spacecraft's resource request can be met, relay link resources are allocated to the user spacecraft, and the resource usage duration is directly determined. After allocating link resources and duration to the user spacecraft, the medium-Earth orbit relay satellite points the transmission beam of its multi-beam antenna at the user spacecraft and sends a resource plan short message to the user spacecraft. The resource plan short message contains the link resource allocation duration. After the allocation duration ends, the medium-Earth orbit relay satellite automatically disconnects the link, releases the resources, and the user spacecraft automatically leaves the network.

[0022] The beneficial effects of this invention compared to the prior art are:

[0023] (1) Currently, all relay satellite (TDRS) systems used domestically and internationally consist of geostationary orbit relay satellites, whose orbital positions are relatively limited. This invention can be used in relay satellite systems composed of medium-Earth orbit relay satellites. The relay satellites do not need to occupy geostationary orbit resources, and the number of relay satellites can be increased according to the workload, thus having wider adaptability.

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

[0025] (3) Currently, the ground-based telemetry and control access method is limited to ground telemetry 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. This invention is an access method based on medium-orbit relay satellites. By forming a constellation of multiple medium-orbit relay satellites, it can meet the user's all-time and all-domain telemetry and control needs for spacecraft.

[0026] (4) In this invention, compared with the ground-based telemetry and control access method, the medium-orbit relay satellite allocates the time for using relay link resources when it accesses the network, and the user spacecraft automatically leaves the network after the time expires, which simplifies the process of processing the network leaving application on the medium-orbit relay satellite.

[0027] (5) In this invention, compared with the ground-based telemetry and control 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 this invention, the relay satellite directly processes the resource requests of the user's spacecraft, which can realize both one-way data transmission of the return link and two-way data transmission of the forward and return links. The two-way telemetry and control link can be used not only for telemetry and control between low-Earth orbit spacecraft and ground stations, but also for inter-satellite collaborative operations between different low-Earth orbit spacecraft, and has a wider range of application prospects. Attached Figure Description

[0029] Figure 1 A simplified diagram of a typical medium-orbit relay satellite on-demand access telemetry and control system;

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

[0031] Figure 3 A flowchart illustrating the workflow for on-demand access for user spacecraft;

[0032] Figure 4 Workflow diagram for requesting bidirectional link resources for user spacecraft. Detailed Implementation

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

[0034] This invention provides an on-demand access method suitable for medium-Earth orbit relay satellites, comprising the following steps:

[0035] S1, the onboard telemetry, tracking, and command (TT&C) payload of the medium-Earth orbit relay satellite stores and maintains a list of user spacecraft within its service area, including information such as user spacecraft terminal identifiers, spreading codes, and orbital elements. It retrieves the highest-priority service object within the current service area by searching the list. Based on the pre-stored orbital elements, the onboard TT&C payload of the medium-Earth orbit relay satellite calculates the real-time position of the user spacecraft and controls the receiving beam of the multi-beam antenna to point towards the user spacecraft.

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

[0037] S3, the medium-Earth orbit relay satellite determines the type of short message based on the information sent by the user spacecraft. When the relay satellite receives a periodic status report short message, it forwards the demodulated periodic status report data to the ground station and terminates the current service. When the relay satellite receives a resource request short message, it allocates link resources to the user spacecraft, establishes a relay telemetry 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 relay link duration when the link is established, and automatically releases the relay link resources when the allocated duration expires, and the user spacecraft disconnects from the network.

[0038] Figure 1 A simplified diagram of the composition of the on-demand access telemetry and control system for medium-orbit relay satellites.

[0039] In step S2, the user terminal on the user spacecraft needs to continuously send short message signals during operation so that the relay satellite can immediately receive the short messages after pointing its receiving beam at the user spacecraft. The forward and return short message signals between the user spacecraft and the relay satellite use BPSK + coherent spread spectrum modulation. Different user spacecraft are distinguished using code division multiple access combined with phased array beam space division. For example... Figure 2 As shown, different types of short message data use a unified format and length, comprising two parts: a synchronization segment and a data segment. The synchronization segment is used to capture and synchronize signals, while the data segment contains user spacecraft authentication data, short message type, and other data. Authentication data is used to correctly identify users and prevent unauthorized access to the telemetry, tracking, and command (TT&C) link. There are two types of short messages: periodic status reporting short messages and resource request short messages.

[0040] In step S3, the user spacecraft sends a periodic status report short message, the data segment of which includes telemetry information about the satellite's current health status. Upon receiving the periodic status report short message from the user spacecraft, if the relay satellite is within the visible arc within the country, it forwards the telemetry information to the ground station via the relay satellite-to-ground feeder link. If the relay satellite is not within the visible arc within the country, it first sends the information to a neighboring relay satellite via an inter-satellite link. When the telemetry information reaches a relay satellite within the visible arc within the country, the relay satellite then transmits the telemetry information to the ground station via the satellite-to-ground feeder link.

[0041] In S3, the resource request short message sent by the user spacecraft includes resource request information in its data segment. There are two types of resource requests: one is a request for return link resources only, with the information transmission direction being user spacecraft -> relay satellite (constellation) -> ground station; the other is a request for bidirectional link resources, with the information transmission direction being user spacecraft A <-> relay satellite (constellation) <-> user spacecraft B (or ground station). The relay satellite determines whether to approve the user spacecraft's resource request based on resource availability. When the user spacecraft's resource request needs to be fulfilled, 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 its multi-beam antenna at the user spacecraft and sends a resource plan short message to the user spacecraft. This short message contains the link resource allocation duration. After the allocated duration 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 for a user spacecraft's one-time random access in this embodiment is as follows:

[0044] (1) At the start of each service, the relay satellite searches the list of user spacecraft within the service area to find the current service target. For users of equal priority, telemetry, tracking, and command services are provided to each user spacecraft in turn using a polling method.

[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 from 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 a short message from the user spacecraft within the predetermined time, the service will be terminated.

[0047] (4) After receiving a short message from a user's spacecraft, the relay satellite performs despreading, demodulation, and authentication verification, and processes the message according to its type. There are two types of short messages: periodic status reporting short messages and resource request short messages.

[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 terminates the current service. If the relay satellite is not currently within the line of sight of the ground station, it sends the data to other relay satellites via the inter-satellite link, and the other relay satellites then 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 status and determines whether the user spacecraft's resource request should be approved based on the resource status. If the user spacecraft's resource request needs to be met, the relay satellite allocates relay link resources to the user and directly determines the resource usage duration. After allocating link resources and duration to the user spacecraft, the relay satellite points the transmit beam of its multi-beam antenna at the user spacecraft and sends a resource plan short message to the user spacecraft, which includes the link resource allocation duration.

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

[0051] like Figure 4 As shown, when a user spacecraft requests 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 will point another set of antenna beams at user spacecraft B and send a relay communication request to user spacecraft B. If user spacecraft B is not within the service range of the current relay satellite, the relay satellite needs to send the relay communication request to a relay satellite that can serve user spacecraft B through an inter-satellite link.

[0053] (2) If the relay satellite does not receive a relay communication acknowledgment from user spacecraft B within the predetermined time, the relay satellite will send a short message of rejection request to user spacecraft A. If the relay satellite receives a relay communication acknowledgment from user spacecraft B, it will allocate resources and establish a relay communication link.

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

[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 respectively. After the allocated time of the relay communication link ends, the link resources are released, user spacecraft A and B automatically disconnect from the network, and the relay communication service ends.

[0056] This invention proposes a method for on-the-spot access tracking and control of spacecraft applicable to medium-Earth orbit relay satellites. This method utilizes pre-stored user spacecraft orbit information on the medium-Earth orbit relay satellite to automatically control the beam direction of the multi-beam antenna to point at the user spacecraft, enabling on-orbit on-the-spot access for the user spacecraft. The forward and return link resources of the medium-Earth orbit relay satellite are autonomously managed on-board, enabling collaborative work between user spacecraft and the ground, as well as between different user spacecraft. This method can also achieve on-the-spot access for low-Earth orbit spacecraft, realize autonomous management of routine tracking and control tasks and inter-satellite collaborative work, effectively reduce the difficulty and complexity of ground mission scheduling, and improve the efficiency of the tracking and control system.

[0057] The parts of this invention not described in detail are common knowledge to those skilled in the art.

Claims

1. A method for on-the-spot access telemetry and control suitable for medium-Earth orbit relay satellites, characterized in that, include: The medium-Earth orbit relay satellite stores and maintains a list of user spacecraft on-board. The list of user spacecraft includes the orbital elements of the user spacecraft, the spreading code used by the user spacecraft, and the authentication information of the user spacecraft. The medium-Earth orbit relay satellite calculates the real-time position of the user spacecraft based on 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 sequence. The medium-Earth orbit relay satellite captures and tracks short message signals sent by user terminals on user spacecraft. The onboard telemetry and control payload demodulates and decodes the signals and determines the legitimacy of the user spacecraft based on the authentication data in the short message. The medium-Earth 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 terminates the service. When the short message is a resource request short message, the medium-Earth orbit relay satellite allocates link resources to the user spacecraft, establishes a relay telemetry and control link, and sends a resource plan short message to the user spacecraft after the relay telemetry and control link is established. The medium-Earth orbit relay satellite allocates the relay link duration when the link is established, and automatically releases the relay link resources and terminates the service when the allocated duration expires.

2. The on-demand access telemetry and control method for medium-Earth orbit relay satellites according to claim 1, characterized in that, At the start of each service, the medium-Earth orbit relay satellite searches the list of user spacecraft within the service area to find the current service target; for users of equal priority, it provides telemetry, tracking and command services to each user spacecraft in turn through a polling process.

3. The on-the-spot access telemetry and control method for medium-Earth orbit relay satellites 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-Earth orbit relay satellite can immediately receive the short message information after pointing the return tracking beam at the user terminal of the user spacecraft.

4. The on-the-spot access telemetry and control method for medium-Earth orbit relay satellites 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-Earth orbit relay satellite adopt the modulation method of BPSK + coherent spread spectrum. Different user spacecraft use code division multiple access combined with phased array beam space division to distinguish them.

5. A method for on-the-spot access telemetry and control of medium-Earth orbit relay satellites according to claim 1, characterized in that, Different types of short message data use a uniform 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 on-the-spot access telemetry and control method for medium-Earth orbit relay satellites according to claim 1, characterized in that, After receiving a periodic status report short message from a user terminal of a user's spacecraft, if the medium-Earth orbit relay satellite is within the visible arc within China, it will forward the demodulated data to the ground station via the satellite-to-ground feeder link. If the medium-Earth orbit relay satellite is not within the visible arc within China, it will first send the data to an adjacent medium-Earth orbit relay satellite via an inter-satellite link. When the demodulated data is transmitted to a medium-Earth orbit relay satellite located within the visible arc within China, that medium-Earth orbit relay satellite will then send the demodulated data to the ground station via the satellite-to-ground feeder link.

7. A method for on-the-spot access telemetry and control of medium-Earth orbit relay satellites according to claim 1, characterized in that, There are two types of resource request short messages: one is to request only return link resources, with the information transmission direction being user spacecraft -> relay satellite -> ground station; the other is to request bidirectional link resources, with the information transmission direction being user spacecraft A <-> relay satellite <-> user spacecraft B or ground station.

8. A method for on-the-spot access telemetry and control of medium-Earth orbit relay satellites according to claim 7, characterized in that, The medium-Earth orbit relay satellite determines whether to approve the user spacecraft's resource request based on resource availability. When the user spacecraft's resource request can be met, relay link resources are allocated to the user spacecraft, and the resource usage duration is directly determined. After allocating link resources and duration to the user spacecraft, the medium-Earth orbit relay satellite points the transmission beam of its multi-beam antenna at the user spacecraft and sends a resource plan short message to the user spacecraft. The resource plan short message contains the link resource allocation duration. After the allocation duration ends, the medium-Earth orbit relay satellite automatically disconnects the link, releases the resources, and the user spacecraft automatically leaves the network.

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