CN111654325A

CN111654325A - Satellite laser communication method

Info

Publication number: CN111654325A
Application number: CN202010446554.XA
Authority: CN
Inventors: 向晓霞; 杨峰; 任维佳; 杜志贵
Original assignee: Changsha Tianyi Space Technology Research Institute Co Ltd
Current assignee: Changsha Tianyi Space Technology Research Institute Co Ltd
Priority date: 2018-11-07
Filing date: 2018-11-07
Publication date: 2020-09-11
Anticipated expiration: 2038-11-07
Also published as: CN109698721A; CN111654326B; CN111654325B; CN109698721B; CN111654326A

Abstract

The invention relates to a satellite laser communication method, which comprises the following steps: when the aircraft attempts to establish a laser communication link with a first low earth orbit satellite, the aircraft emits a laser beam directed at a first synchronization satellite having a determined position to request establishment of the laser communication link of the first synchronization satellite of the aircraft; after determining the attitude and position of the aerial vehicle, attempting to establish a laser communication link between the aerial vehicle and the first low-earth-orbit satellite based at least on the determined attitude and position of the aerial vehicle, and transmitting data directly between the aerial vehicle and the first low-earth-orbit satellite via the established laser communication link between the aerial vehicle and the first low-earth-orbit satellite.

Description

Satellite laser communication method

The invention relates to a divisional application of a satellite laser communication system, which has the application number of 201811321886.4, the application date of 2018, 11 and 7, and the application type of the invention.

Technical Field

The invention relates to the field of satellite communication, in particular to a satellite laser communication system.

Background

Satellite communication is a combination of aerospace, communication, information and new material technologies, is one of the world high-precision technologies, and embodies the comprehensive strength of the state in the high and new technology fields in the information age. The satellite communication industry, as an important component of the information communication industry, plays an increasingly important role in the construction of national information infrastructure, the realization of universal services, the creation of a harmonious information society, and the national security strategy.

Currently, airborne communication is mainly achieved by microwave satellites. In the case of communication by microwave radio, since radio frequency is a base for normal communication between an aircraft and a satellite and is a channel for information transmission, in order to prevent electromagnetic interference between satellites, it is necessary to maintain a certain interval of communication frequency for frequency isolation, and thus the radio spectrum is strictly regulated by the International Telecommunications Union (ITU) and governments of various countries. In addition, radio communication has the problems of frequency spectrum saturation and limited communication bandwidth, and is difficult to meet the high-speed transmission requirement of mass data, and the real-time transmission of mass flight data of an aircraft cannot be realized. Accordingly, techniques for aircraft to communicate with satellites have emerged. For example, chinese patent publication No. CN108337041A discloses an aircraft communication system, which relates to the technical field of laser communication, and mainly aims to implement laser communication between an aircraft and a satellite, and includes at least one aircraft-satellite laser communication terminal device, an electric cabinet, a fairing, and a bracket with a vibration reduction function; the aircraft-satellite laser communication terminal equipment is communicated with a satellite communication system through a laser link; the electric cabinet is used for supplying power to the aircraft-satellite laser communication terminal equipment and providing control instructions and information flow; the fairing is of an at least partially transparent structure and covers the outer side of the aircraft-satellite laser communication terminal equipment. The invention is mainly used for data transmission of the aircraft. However, it does not consider the problem of how quickly to establish a lower delay laser communication link with geostationary and non-geostationary satellites. In the laser communication between the aircraft and the satellite, if the aircraft directly establishes a laser communication link with the geostationary satellite, although the geostationary satellite is fixed in position and the laser communication link is established faster, the laser communication link is established between the aircraft and the geostationary satellite, but the laser communication link is relatively delayed due to the longer distance between the aircraft and the geostationary satellite. However, if the aircraft directly tries to establish the laser communication link with the low-orbit satellite, the time of the position and attitude changes due to the fact that the low-orbit satellite moves, although the position and attitude of the satellite at the corresponding time can be known by ephemeris data, the accuracy range of the attitude and position determined by the ephemeris data is not accurate enough compared with the establishment of the laser communication link, and the aircraft can also be in a moving state, which further increases the difficulty of directly establishing the laser communication link between the aircraft and the low-orbit satellite, and although the establishment is possible, the establishment time is long. Accordingly, there is a need for improvements in the art to establish a communication link between an aircraft and a low earth orbit satellite in a shorter amount of time.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a satellite laser communication system, which can firstly establish a laser communication link between an aircraft and a synchronous satellite when the aircraft needs to establish the laser communication link with a first low-orbit satellite, determine the position of the aircraft which is more accurate than the position determined by the traditional positioning modules such as GPS, Beidou and the like at least partially based on an ATP device of the aircraft, determine the attitude of the aircraft, and try to establish the laser communication link between the aircraft and the first low-orbit satellite according to the determined attitude and position of the aircraft, thereby greatly shortening the time for establishing the laser communication link between the aircraft and the first low-orbit satellite.

According to a preferred embodiment, a satellite laser communication system comprises: a first synchronous satellite and a first low earth orbit satellite; when the aircraft attempts to establish a laser communication link with a first low earth orbit satellite, the aircraft emits a laser beam directed at a first synchronization satellite having a determined position to request establishment of a laser communication link between the aircraft and the first synchronization satellite; determining an attitude and a position of the aerial vehicle based at least in part on a first ATP device of the aerial vehicle pointing and tracking the first synchronization satellite after establishing the laser communication link between the aerial vehicle and the first synchronization satellite; after determining the attitude and position of the aerial vehicle, attempting to establish a laser communication link between the aerial vehicle and the first low-earth-orbit satellite based at least on the determined attitude and position of the aerial vehicle, and transmitting data directly between the aerial vehicle and the first low-earth-orbit satellite via the established laser communication link between the aerial vehicle and the first low-earth-orbit satellite.

According to a preferred embodiment, before the aircraft emits the laser beam to point at the first synchronous satellite with the determined position, the aircraft selects a synchronous satellite capable of establishing a laser communication link with the aircraft and the first low-orbit satellite as the first synchronous satellite according to the ephemeris data, and sends the selected first synchronous satellite to the first low-orbit satellite through a non-optical communication mode together with a message that the aircraft requests to establish the laser communication link with the first low-orbit satellite; the first low earth orbit satellite responds to the selected first synchronous satellite and the message that the aircraft requests to establish the laser communication link with the first low earth orbit satellite, and a laser communication link is established between the first low earth orbit satellite and the first synchronous satellite; determining an attitude and a position of a first low-orbit satellite based at least in part on a second ATP device pointing and tracking the first low-orbit satellite of the first synchronous satellite after establishing a laser communication link between the first low-orbit satellite and the first synchronous satellite; after determining the attitude and position of the first low-earth satellite, attempting to establish a laser communication link between the aerial vehicle and the first low-earth satellite based at least on the determined attitude and position of the first low-earth satellite, and transmitting data directly between the aerial vehicle and the first low-earth satellite via the established laser communication link between the aerial vehicle and the first low-earth satellite.

According to a preferred embodiment, the determination of the attitude and position of at least one of the aerial vehicle and the first low-earth satellite is done before the establishment of the laser communication link between the aerial vehicle and the first low-earth satellite, and after the determination of the attitude and position of the aerial vehicle or the first low-earth satellite is done, the first low-earth satellite or the aerial vehicle of which the attitude and position is not determined emits a laser beam scan toward the aerial vehicle of which the attitude and position is determined or the first low-earth satellite in an attempt to establish the laser communication link between the aerial vehicle and the first low-earth satellite; in the process that the first low-earth satellite or the aircraft of which the attitude and the position are not determined emits the laser beam toward the aircraft of which the attitude and the position are determined or the first low-earth satellite to attempt to establish the laser communication link between the aircraft and the first low-earth satellite, the determination process of the first low-earth satellite or the aircraft of which the attitude and the position are not determined is not terminated until the attempt to establish the laser communication link between the aircraft and the first low-earth satellite is successful or the system determines the attitude and the position of the first low-earth satellite or the aircraft of which the attitude and the position are not determined.

According to a preferred embodiment, after the laser communication link is established between the aerial vehicle and the first low-orbit satellite, the first synchronization satellite maintains the laser communication link established with the aerial vehicle and/or the first low-orbit satellite until the data transmission between the aerial vehicle and the first low-orbit satellite is completed, and the first synchronization satellite identifies a link state of the laser communication link established between the aerial vehicle and the first low-orbit satellite and a transmission state of the data transmitted through the laser communication link, and in the case where the transmission state is an uncompleted state and the link state is an unavailable state, the first synchronization satellite transmits a request for assistance in transmitting the data to the aerial vehicle and the first low-orbit satellite, and after both the aerial vehicle and the first low-orbit satellite receive the request for assistance in transmitting the data transmitted by the first synchronization satellite, the aerial vehicle and the first low-orbit satellite transmit the data through the laser communication link established between the aerial vehicle and the first synchronization satellite and the laser communication link established by the first synchronization satellite and the first low-orbit satellite The optical communication link indirectly transfers data.

According to a preferred embodiment, when the aircraft and the first low-earth orbit satellite directly transmit data through the laser communication link established between the aircraft and the first low-earth orbit satellite, the data is transmitted in clear or encrypted by using a first encryption algorithm; and/or when the aircraft and the first low-orbit satellite transmit data through the laser communication link established by the aircraft and the first synchronous satellite and the laser communication link established by the first synchronous satellite and the first low-orbit satellite, encrypting the transmitted data by adopting a second encryption algorithm different from the first encryption algorithm; wherein the key used to encrypt the data for the first encryption algorithm and/or the second encryption algorithm is transmitted directly over the laser communication link established between the aerial vehicle and the first low-earth satellite when the link state of the laser communication link established between the aerial vehicle and the first low-earth satellite is in an available state.

According to a preferred embodiment, after the laser communication link is established between the aircraft and the first low-orbit satellite and before the data to be encrypted is transmitted, the aircraft and the first low-orbit satellite need to perform a key generation process and a key transmission process; the key generation process comprises the following steps: the aircraft or the first low orbit satellite generates a symmetric key for the first encryption algorithm, the aircraft generates a first asymmetric key for the second encryption algorithm, the first low orbit satellite generates a second asymmetric key for the second encryption algorithm, the first asymmetric key comprises a first public key and a first private key, and the second asymmetric key comprises a second public key and a second private key; the key transmission process comprises the following steps: the aircraft or the first low-orbit satellite transmits the generated symmetric key to the first low-orbit satellite or the aircraft through a laser communication link established between the aircraft and the first low-orbit satellite, the aircraft transmits the generated first public key to the first low-orbit satellite through a laser communication link established between the aircraft and the first low-orbit satellite, and the first low-orbit satellite transmits the generated second public key to the aircraft through a laser communication link established between the aircraft and the first low-orbit satellite.

According to a preferred embodiment, the aircraft is configured to: generating at least two symmetric keys corresponding to at least two security levels and generating at least two groups of first asymmetric keys corresponding to the at least two security levels, wherein the symmetric keys or the first asymmetric keys with higher security levels are distributed with longer key lengths, before the aircraft transmits data to the first low-orbit satellite through a laser communication link established between the aircraft and the first low-orbit satellite, the aircraft determines the security level required for transmitting the data to the first low-orbit satellite, and selects the keys required for encrypting the data according to the security level determined by the aircraft and required for transmitting the data to the first low-orbit satellite; and/or the first low earth satellite is configured to: generating at least two sets of second asymmetric keys corresponding to at least two security levels, the second asymmetric keys with higher security levels being assigned longer key lengths, the first low-orbit satellite determining a security level required for transmitting data to the aircraft before the first low-orbit satellite transmits data to the aircraft via the laser communication link established between the aircraft and the first low-orbit satellite, and selecting the key required for encrypting the data according to the security level determined by the first low-orbit satellite for transmitting data to the aircraft.

According to a preferred embodiment, the aircraft is configured to: after selecting a key required for encrypting data according to the determined security level required for transmitting the data to the first low-orbit satellite and before transmitting the encrypted data to the first low-orbit satellite, transmitting the security level required for transmitting the data to the first low-orbit satellite determined by the aircraft to enable the first low-orbit satellite to enable a decryption key adapted thereto; and/or the first low earth satellite is configured to: after selecting the key required for encrypting the data according to the determined security level required for transmitting the data to the aircraft and before transmitting the encrypted data to the aircraft, the security level determined by the first low earth orbit satellite required for transmitting the data to the aircraft is transmitted to the aircraft to enable the aircraft to use the decryption key adapted thereto.

According to a preferred embodiment, the aircraft is further configured to: before the aircraft sends the determined security level required for transmitting data to the first low-orbit satellite, the first private key corresponding to the highest security level generated by the aircraft and the second public key corresponding to the highest security level generated by the first low-orbit satellite are used for encrypting the security level required for transmitting data to the first low-orbit satellite determined by the aircraft and then sending the encrypted security level to the first low-orbit satellite; and/or the first low earth satellite is further configured to: before the first low-orbit satellite sends the determined security level required for transmitting data to the aircraft, the second private key corresponding to the highest security level generated by the first low-orbit satellite and the first public key corresponding to the highest security level generated by the aircraft are used for encrypting the security level required for transmitting data to the aircraft and determined by the first low-orbit satellite, and then the encrypted security level is sent to the aircraft.

According to a preferred embodiment, the aircraft is further configured to: decrypting the security level determined by the received first low-orbit satellite and required for transmitting data to the aircraft by using a first private key which is generated by the aircraft and corresponds to the highest security level and a second public key which is generated by the first low-orbit satellite and corresponds to the highest security level, and enabling a decryption secret key adapted to the first private key to decrypt the corresponding data transmitted by the first low-orbit satellite; and/or the first low earth satellite is further configured to: and decrypting the security level determined by the received aircraft and required for transmitting the data to the first low-orbit satellite by using the second private key which is generated by the first low-orbit satellite and corresponds to the highest security level and the first public key which is generated by the aircraft and corresponds to the highest security level, and enabling the decryption key adapted to the second private key to decrypt the corresponding data transmitted by the aircraft.

Drawings

Fig. 1 is a simplified schematic diagram of a preferred embodiment of the present invention.

List of reference numerals

100: the aircraft 110: first ATP device

120: third ATP device 210: first low earth orbit satellite

211: second ATP device 212: fourth ATP device

310: the first sync satellite 320: second geostationary satellite

400: the ground station 410: microwave station

420: optical station

Detailed Description

This is explained in detail below with reference to fig. 1.

In the description of the present invention, it is to be understood that the terms "first", "second", and the like, if any, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, the term "plurality", if any, means two or more unless specifically limited otherwise.

Example 1

The embodiment also discloses a communication method, which may be a laser communication method, or a laser communication method based on a satellite, or an air-ground laser communication method based on a satellite, or a satellite laser communication method, or a laser communication method for communication between an aircraft and a satellite, and the method may be implemented by the system of the present invention and/or other alternative components. For example, the method of the present invention may be implemented using various components of the system of the present invention.

According to a preferred embodiment, the method may comprise: when the aerial vehicle 100 attempts to establish a laser communication link with the first low earth orbit satellite 210, the aerial vehicle 100 may emit a laser beam directed at the first synchronization satellite 310 having a determined location to request establishment of a laser communication link between the aerial vehicle 100 and the first synchronization satellite 310. After the laser communication link is established between the aircraft 100 and the first sync satellite 310, the attitude and position of the aircraft 100 may be determined based at least in part on the first ATP device 110 of the aircraft 100 pointing and tracking the first sync satellite 310. After determining the attitude and position of the aerial vehicle 100, an attempt may be made to establish a laser communication link between the aerial vehicle 100 and the first low-earth satellite 210 based at least on the determined attitude and position of the aerial vehicle 100, and data may be transmitted directly between the aerial vehicle 100 and the first low-earth satellite 210 over the established laser communication link between the aerial vehicle 100 and the first low-earth satellite 210. Preferably, determining the attitude and position of the aircraft 100 based at least in part on the first ATP device 110 of the aircraft 100 pointing and tracking the first sync satellite 310 may be determining the attitude and position of the aircraft 100 from the positioning module and the first ATP device 110. Preferably, after determining the attitude and position of the aerial vehicle 100 based at least in part on the first ATP device 110 of the aerial vehicle 100 pointing and tracking the first synced satellite 310, the aerial vehicle 100 and the first low earth orbit satellite 210 can scan each other accordingly to shorten the time to establish the laser communication link. Preferably, determining the attitude and position of the aircraft may be updated in real time via a laser communication link established between the first low earth orbit satellite and the first geostationary satellite. The invention can at least realize the following beneficial technical effects by adopting the mode: first, since the laser inter-satellite link is established if the aircraft points directly to the first low-orbit satellite using the position of the position fix by the position fix module and the position of the first low-orbit satellite in the ephemeris data, since the relative change in position of both is relatively coarse with respect to the position at which the ATP device is located, and the positions of both relative to the earth may be in variance, the time of laser scanning is greatly increased, after the invention is adopted, the aircraft and a synchronous satellite establish a laser communication link, and the position of the aircraft which is more accurate than the position determined by the traditional positioning modules such as GPS, Beidou and the like is determined at least partially based on the ATP device of the aircraft, and the attitude of the aircraft can also be determined, then attempting to establish a laser communication link between the aerial vehicle and the first low-earth satellite based on the determined attitude and position of the aerial vehicle, thereby greatly reducing the time to create a laser communication link between the aircraft and the first low-orbit satellite; secondly, the determined attitude and position of the aircraft can be updated in real time through a laser communication link established between the first low-orbit satellite and the first synchronous satellite, so that the first low-orbit satellite can quickly know the attitude and position of the aircraft to point to the aircraft more accurately and quickly, and the laser communication link between the first low-orbit satellite and the first synchronous satellite is established more efficiently. Preferably, the aircraft 100 emitting a laser beam directed at the first synchronization satellite 310 having a determined position to request establishment of the determined position in the laser communication link between the aircraft 100 and the first synchronization satellite 310 is fixed relative to the earth. Preferably, in the present invention, because the point-to-point establishment of the spatial laser communication does not have a high success rate like the optical fiber communication, the attempt to establish may be a way to seek to establish the laser communication with the other side in a case where the scanning direction of the laser beam is adjusted.

According to a preferred embodiment, the aircraft 100 may select a sync satellite that can establish a laser communication link with the aircraft 100 and the first low-earth satellite 210 as the first sync satellite 310 based on the ephemeris data before the aircraft 100 transmits a laser beam directed at the first sync satellite 310 having a determined position. The aircraft 100 may send the selected first synchronization satellite 310 to the first low-earth satellite 210 in a non-optical communication manner along with a message that the aircraft 100 requests that a laser communication link be established with the first low-earth satellite 210. The first low earth satellite 210 may initially establish a laser communication link between the first low earth satellite 210 and the first low earth satellite 310 in response to a message from the selected first low earth satellite 310 and the aircraft 100 requesting that a laser communication link be established with the first low earth satellite 210. After the laser communication link is established between the first low-earth satellite 210 and the first sync satellite 310, the attitude and position of the first low-earth satellite 210 may be determined based at least in part on the second ATP device 211 pointing and tracking the first low-earth satellite 210 of the first sync satellite 310. After determining the attitude and position of the first low-earth satellite 210, an attempt may be made to establish a laser communication link between the aerial vehicle 100 and the first low-earth satellite 210 based at least on the determined attitude and position of the first low-earth satellite 210, and to transmit data directly between the aerial vehicle 100 and the first low-earth satellite 210 via the established laser communication link between the aerial vehicle 100 and the first low-earth satellite 210. Preferably, determining the attitude and position of the first low-orbiting satellite 210 based at least in part on the second ATP device 211 of the first low-orbiting satellite 210 pointing and tracking the first sync satellite 310 may be based on the position determined by the first low-orbiting satellite in communication with its neighboring satellites or ground stations and the second ATP device 211 together determining the attitude and position of the aircraft 100. Preferably, after determining the attitude and position of the first low-orbiting satellite 210 based at least in part on the second ATP device 211 pointing at and tracking the first low-orbiting satellite 210 of the first geostationary satellite 310, the aerial vehicle 100 and the first low-orbiting satellite 210 may scan each other accordingly to reduce the time to establish the laser communication link. If the attitude and position of the first low earth orbit satellite 210 and the attitude and position of the aircraft 100 are determined, the two can be directed towards each other and a laser communication link can be established quickly. The invention can at least realize the following beneficial technical effects by adopting the mode: because the laser communication link is also established with the first geostationary satellite after the first low-earth satellite has obtained the request for the aircraft, because the first low-earth satellite 210 is generally in a predetermined orbit, unlike an aircraft that can change its flight trajectory at will, it is possible that the attitude and position of the first low-earth satellite 210 is determined prior to the attitude and position of the aircraft, and in such a case attempting to establish a laser communication link between the aircraft 100 and the first low-earth satellite 210 based at least on the determined attitude and position of the first low-earth satellite 210 can also reduce the time to establish a laser communication link between the aircraft and the first low-earth satellite.

According to a preferred embodiment, determining the attitude and position of at least one of the aerial vehicle 100 and the first low earth orbit satellite 210 is done before establishing the laser communication link between the aerial vehicle 100 and the first low earth orbit satellite 210, and after determining the attitude and position of the aerial vehicle 100 or the first low earth orbit satellite 210 is done, the first low earth orbit satellite 210 or the aerial vehicle 100 for which the attitude and position is not determined may emit a laser beam scan toward the aerial vehicle 100 or the first low earth orbit satellite 210 for which the attitude and position is determined in an attempt to establish the laser communication link between the aerial vehicle 100 and the first low earth orbit satellite 210. In the process in which the first low-earth satellite 210 or the aircraft 100 of which the attitude and position are not determined emits the laser beam toward the aircraft 100 or the first low-earth satellite 210 of which the attitude and position are determined in an attempt to establish the laser communication link between the aircraft 100 and the first low-earth satellite 210, the determination process of the first low-earth satellite 210 or the aircraft 100 of which the attitude and position are not determined may not be terminated until the attempt to establish the laser communication link between the aircraft 100 and the first low-earth satellite 210 is successful or the system determines the attitude and position of the first low-earth satellite 210 or the aircraft 100 of which the attitude and position are not determined. The invention can at least realize the following beneficial technical effects by adopting the mode: when the posture and position of one party are determined and before the posture and position of the other party are not determined, the laser communication link is established by first trying to establish the laser communication link according to the posture and position of the other party, and the determination process of the posture and position of the other party with no determined posture and position is not terminated.

According to a preferred embodiment, after the laser communication link is established between the aerial vehicle 100 and the first low-earth satellite 210, the first synchronization satellite 310 may maintain the laser communication link established with the aerial vehicle 100 and/or the first low-earth satellite 210 until the data transmission between the aerial vehicle 100 and the first low-earth satellite 210 is completed. The first sync satellite 310 may identify a link state of a laser communication link established between the aircraft 100 and the first low earth orbit satellite 210 and a transmission state of data transmitted through the laser communication link. In the event that the transmission status is an incomplete status and the link status is an unavailable status, the first synchronous satellite 310 may send a request to the aircraft 100 and the first low earth orbit satellite 210 to assist in transmitting data. After both the aerial vehicle 100 and the first low-earth satellite 210 receive the request from the first synchronization satellite 310 to assist in transmitting data, the aerial vehicle 100 and the first low-earth satellite 210 may transmit data indirectly via the laser communication link established by the aerial vehicle 100 and the first synchronization satellite 310 and the laser communication link established by the first synchronization satellite 310 and the first low-earth satellite 210. The invention can at least realize the following beneficial technical effects by adopting the mode: data may be transmitted indirectly through the first geostationary satellite when the laser communication link between the aircraft and the first low earth satellite is unstable.

According to a preferred embodiment, the data may be transmitted in clear or encrypted using a first encryption algorithm while the aircraft 100 and the first low earth orbit satellite 210 transmit the data directly over the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210. Preferably, while the aerial vehicle 100 and the first low-earth satellite 210 transmit data over the laser communication link established by the aerial vehicle 100 and the first synchronization satellite 310 and the laser communication link established by the first synchronization satellite 310 and the first low-earth satellite 210, the transmit data may be encrypted using a second encryption algorithm different from the first encryption algorithm. Preferably, the key used to encrypt the data for the first encryption algorithm and/or the second encryption algorithm may be transmitted directly over the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210 when the link status of the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210 is in an available state. The invention can at least realize the following beneficial technical effects by adopting the mode: first, a key used for encrypting data by the first encryption algorithm and/or the second encryption algorithm is transmitted directly through the laser communication link established between the aircraft 100 and the first low-earth satellite 210 when the link state of the laser communication link established between the aircraft 100 and the first low-earth satellite 210 is in an available state, and is not transmitted through an intermediate satellite, so that the security is extremely high; secondly, data are transmitted in an encryption mode, so that interception by other satellites can be prevented; thirdly, when the two are directly transmitted, the first encryption algorithm with relatively lower decryption difficulty is adopted for encryption or clear code transmission, and when the two are transmitted through the first synchronous orbit satellite, the second encryption algorithm with relatively higher decryption difficulty is adopted for encryption, so that the method has higher safety.

According to a preferred embodiment, the aircraft 100 and the first low-earth satellite 210 may perform a key generation process and a key transmission process after the laser communication link is established between the aircraft 100 and the first low-earth satellite 210 and before the data to be encrypted is transmitted. The key generation process may include: at least one of the aircraft 100 or the first low-earth satellite 210 generating a symmetric key for a first encryption algorithm, the aircraft 100 generating a first asymmetric key for a second encryption algorithm, and the first low-earth satellite 210 generating a second asymmetric key for the second encryption algorithm. The first asymmetric key may include a first public key and a first private key. The second asymmetric key may include a second public key and a second private key. The key transmission process may include: the symmetric key generated by the aircraft 100 or the first low-earth satellite 210 may be transmitted to the first low-earth satellite 210 or the aircraft 100 via a laser communication link established between the aircraft 100 and the first low-earth satellite 210. The aerial vehicle 100 may transmit the generated first public key to the first low-earth satellite 210 via a laser communication link established between the aerial vehicle 100 and the first low-earth satellite 210. The first low-earth satellite 210 may transmit the generated second public key to the aerial vehicle 100 via a laser communication link established between the aerial vehicle 100 and the first low-earth satellite 210. The invention can at least realize the following beneficial technical effects by adopting the mode: in the traditional asymmetric secret key, the public key is required to be forwarded to a specific object through intermediate equipment, and the possibility of being stolen is also provided, although the public key cannot be directly used for cracking a communication file, one layer of difficulty is also reduced, and the first public key and the second public key are both sent point to point, so that the security is extremely high.

According to a preferred embodiment, the aircraft 100 may be configured to: at least two symmetric keys corresponding to the at least two security levels are generated and at least two sets of first asymmetric keys corresponding to the at least two security levels are generated. A symmetric key or first asymmetric key with a higher security level may be assigned a longer key length. Before the aerial vehicle 100 transmits data to the first low-earth satellite 210 over the laser communication link established between the aerial vehicle 100 and the first low-earth satellite 210, the aerial vehicle 100 may determine the level of security required to transmit data to the first low-earth satellite 210. The key required to encrypt the data is preferably selected based on the security level determined by the aircraft 100 to be required to transmit the data to the first low earth satellite 210. The first low-earth satellite 210 may be configured to: at least two sets of second asymmetric keys corresponding to the at least two security levels are generated. The higher the security level, the longer the key length may be allocated to the second asymmetric key. Prior to the first low earth satellite 210 transmitting data to the aircraft 100 via the laser communication link established between the aircraft 100 and the first low earth satellite 210, the first low earth satellite 210 may determine a level of security required to transmit data to the aircraft 100 and select a key required to encrypt the data based on the level of security determined by the first low earth satellite 210 to be required to transmit data to the aircraft 100. The invention can at least realize the following beneficial technical effects by adopting the mode: and the data with higher security level is encrypted by adopting a longer secret key, so that the security is further improved.

According to a preferred embodiment, the aircraft 100 may be configured to: after selecting the key required to encrypt the data according to the determined security level required to transmit the data to the first low-orbiting satellite 210 and before transmitting the encrypted data to the first low-orbiting satellite 210, the security level required to transmit the data to the first low-orbiting satellite 210 determined by the aircraft 100 is transmitted to the first low-orbiting satellite 210 to enable the first low-orbiting satellite 210 to have the decryption key adapted thereto. Preferably, the first low-earth satellite 210 may be configured to: after selecting the keys required to encrypt the data according to the determined level of security required to transmit the data to the aircraft 100 and before transmitting the encrypted data to the aircraft 100, the determined level of security required to transmit the data to the aircraft 100 by the first low earth orbit satellite 210 is transmitted to the aircraft 100 to enable the aircraft 100 to have the decryption key adapted thereto.

According to a preferred embodiment, the aircraft 100 may be configured to: before the aircraft 100 sends the determined security level required for transmitting data to the first low-orbit satellite 210, the security level required for transmitting data to the first low-orbit satellite 210, which is determined by the aircraft 100, is encrypted by using a first private key corresponding to the highest security level generated by the aircraft 100 and a second public key corresponding to the highest security level generated by the first low-orbit satellite 210 and then sent to the first low-orbit satellite 210. Preferably, the first low-earth satellite 210 may be configured to: before the first low-earth satellite 210 transmits the determined security level required for transmitting data to the aircraft 100, the security level required for transmitting data to the aircraft 100 determined by the first low-earth satellite 210 is encrypted by the second private key corresponding to the highest security level generated by the first low-earth satellite 210 and the first public key corresponding to the highest security level generated by the aircraft 100 and then transmitted to the aircraft 100. The invention can at least realize the following beneficial technical effects by adopting the mode: the asymmetric secret key with the highest security level is used for encrypting the security level, the decryption difficulty is further improved, but for two communication parties, the decryption secret key matched with the two communication parties can be quickly started according to the public key and the private key of the two communication parties.

According to a preferred embodiment, the aircraft 100 may be configured to: the first private key corresponding to the highest security level generated by the aircraft 100 and the second public key corresponding to the highest security level generated by the first low-earth satellite 210 are used for decrypting the security level determined by the received first low-earth satellite 210 and required for transmitting data to the aircraft 100, and accordingly, the decryption key adapted to the first low-earth satellite is used for decrypting the corresponding data transmitted by the first low-earth satellite 210. The first low-earth satellite 210 may be configured to: the received security level determined by the aircraft 100 to be required for transmitting data to the first low-orbit satellite 210 is decrypted using the second private key corresponding to the highest security level generated by the first low-orbit satellite 210 and the first public key corresponding to the highest security level generated by the aircraft 100, and the decryption key adapted thereto is enabled to decrypt the corresponding data transmitted by the aircraft 100 accordingly.

Example 2

This embodiment may be a further improvement and/or a supplement to embodiment 1, and repeated contents are not described again. The preferred embodiments of the present invention are described in whole and/or in part in the context of other embodiments, which can supplement the present embodiment, without resulting in conflict or inconsistency.

According to a preferred embodiment, the method may comprise: when the aerial vehicle 100 attempts to establish a laser communication link with the first low earth orbit satellite 210, the aerial vehicle 100 may emit a laser beam directed at the first synchronization satellite 310 having a determined location to request establishment of a laser communication link between the aerial vehicle 100 and the first synchronization satellite 310. The laser communication link between the aircraft 100 and the first synchronization satellite 310 may be followed by determining the attitude and position of the aircraft 100 based at least in part on the first ATP device 110. The first sync satellite 310 scans the first low-orbit satellite 210 at a possible position with the laser beam until the laser beam irradiates the first low-orbit satellite 210. The attitude and position of the first low-earth satellite 210 may be determined based at least in part on the second ATP device 211 after the laser communication link is established between the first synchronization satellite 310 and the first low-earth satellite 210. Preferably, a laser communication link is established between the aerial vehicle 100 and the first low-earth satellite 210 based on the determined attitude and position of the aerial vehicle 100 and the attitude and position of the first low-earth satellite 210, and data is transmitted between the aerial vehicle 100 and the first low-earth satellite 210 via the established laser communication link between the aerial vehicle 100 and the first low-earth satellite 210. Preferably, the vehicle of one or both of the aircraft 100 and the first low earth satellite 210 is capable of moving on land or on the water, and the vehicle of the other or both of the aircraft 100 and the first low earth satellite 210 is capable of moving in the air. For example, one of the craft 100 and the first low earth satellite 210 may be at least one of a land vehicle, a watercraft, and a portable device. The other of the aerial vehicle 100 and the first low earth satellite 210 or the carrier of the other may be, for example, at least one of an airplane, a rocket, a helicopter, and a drone.

Preferably, ATP may be referred to as Acquisition, Tracking and Pointing, i.e., capture Tracking and targeting. Preferably, the ATP device may also be referred to as an APT device, a capture aiming tracker, a capture tracking and aiming system, an aiming capture tracking device, and/or a capture tracking and aiming device. For example, in the case of ground stations and satellites, in order to achieve reliable communication between satellites or between satellites and other communication devices, it is first required that one satellite captures a light beam from another satellite or ground station 400, called beacon light, and focuses the light beam to the center of a detector or antenna, which is called an acquisition or capture body. After the acquisition is complete, the receiving satellite also emits a beam that is required to be accurately directed to another satellite or ground station 400 that emits the beacon light, a process known as pointing or aiming. After receiving the beacon light, the satellite emitting the beacon light needs to complete the acquisition process accordingly, so that the two satellites or the satellite and the ground station 400 can finally reach the communication connection state. To ensure that the two satellites or satellites are in communication with the ground station 400 at all times, this precise connection must be maintained at all times, a process known as tracking or tracking.

Preferably, there are a plurality of mathematical expressions for determining the attitude and position of the object, such as at least one of an Euler angle, an Euler-Rodrigue parameter, a Rodrigue-Gilles vector, a quaternion, and a dual quaternion.

Preferably, the method may comprise: generating an optical frequency comb and a pump signal at a satellite transmitter; modulating an optical frequency comb at a transmitter to produce a data signal and an idle signal that is a phase conjugate of the data signal; attenuating the pump signal at the transmitter; transmitting a communication signal having a data signal, an idle signal, and a pump signal from a satellite through free space; receiving at a receiver a transmitted communication signal from a satellite, the communication signal having a data signal, an idle signal, and an attenuated pump signal; amplifying the data signal and the idle signal at a phase sensitive amplifier in the receiver; and/or demodulating the data signal and the idle signal at the receiver to extract the data.

According to a preferred embodiment, determining the attitude and position of at least one of the aerial vehicle 100 and the first low-earth satellite 210 is done before the laser communication link is established between the aerial vehicle 100 and the first low-earth satellite 210. After determining the attitude and position of the aerial vehicle 100 or the first low earth orbit satellite 210 is completed, the first low earth orbit satellite 210 or the aerial vehicle 100 for which the attitude and position is not determined may emit a laser beam scan toward the aerial vehicle 100 or the first low earth orbit satellite 210 for which the attitude and position is determined in an attempt to establish a laser communication link between the aerial vehicle 100 and the first low earth orbit satellite 210. Preferably, in the process in which the first low-earth satellite 210 or the aircraft 100 of which the attitude and position are not determined emits the laser beam toward the aircraft 100 or the first low-earth satellite 210 of which the attitude and position are determined in an attempt to establish the laser communication link between the aircraft 100 and the first low-earth satellite 210, the determination process of the first low-earth satellite 210 or the aircraft 100 of which the attitude and position are not determined is not terminated until the attempt to establish the laser communication link between the aircraft 100 and the first low-earth satellite 210 is successful or the system determines the attitude and position of the first low-earth satellite 210 or the aircraft 100 of which the attitude and position are not determined. The invention can at least realize the following beneficial technical effects by adopting the mode: first, the other party whose position is not determined, although not determining the attitude and position by the ATP device, can determine attitude and position information that is relatively coarser than the attitude and position determined by the ATP device by the positioning module, thereby attempting to establish communication, so the present invention can try to shorten the establishment time of a laser communication link between two movable communication platforms in an additional way, because the present invention, when establishing a laser communication link, in the case where the position of one party is determined and the position of the other party is not determined, the other party whose position is not determined determines the idle time of its attitude and position by using the system, sends a laser beam scan to the party whose attitude and position is determined to attempt to establish a laser communication link, and attempts to establish communication quickly if success; second, even if the attempt fails, after the posture and position of the other party are determined, communication can be established between the two parties using the determined posture and position of the two parties.

Preferably, after determining the attitude and position of the aircraft 100 based at least in part on the first ATP device 110, an open loop search for the first low earth orbit satellite 210 may be initiated by the aircraft 100 and there may be no step of gaze searching during the initial second preset length of open loop search.

According to a preferred embodiment, the aircraft 100 may comprise a third ATP device 120. The first low earth satellite 210 may include a fourth ATP device 212. After the laser communication link is established between the aerial vehicle 100 and the first low-earth satellite 210, the first synchronization satellite 310 may selectively disconnect the laser communication link established between it and the aerial vehicle 100 and/or the first low-earth satellite 210. After at least one of the aerial vehicle 100 and the first low-earth satellite 210 disconnects its established laser communication link with the first synchronization satellite 310, the attitude and position of each other between the aerial vehicle 100 and the first low-earth satellite 210 may be determined, at least in part, by the third ATP device 120 and the fourth ATP device 212. The invention can at least realize the following beneficial technical effects by adopting the mode: firstly, after the laser communication link is directly established between the aircraft 100 and the first low-earth satellite 210, the aircraft 100 and the first low-earth satellite 210 can determine the attitude and the position of each other according to the laser communication link without establishing the laser communication link with the first synchronous satellite 310, so that the later-stage calculation overhead and energy consumption can be greatly reduced by adopting the method; second, because the resources carried by the satellite are limited and valuable, a portion of the device occupancy may be freed after disconnection, thereby more efficiently utilizing system resources and providing services to more devices.

Preferably, the aircraft, the first low earth satellite or the first geostationary satellite in the system of the present invention may establish a laser communication link using at least one of a green laser, a blue laser and a red laser. For example, the laser communication link established between the aircraft and the first low earth orbit satellite, the uplink of the data transmitted by the aircraft to the first low earth orbit satellite may be the green laser, and the downlink of the data transmitted by the first low earth orbit satellite to the aircraft may be the red laser.

Preferably, the first synchronization satellite 310 may maintain the laser communication link established with the aerial vehicle 100 and the first low-earth satellite 210 while the aerial vehicle 100 is in motion relative to earth and changing its orbit with the first low-earth satellite 210. The first geostationary satellite 310 may disconnect its laser communication link with the aircraft 100 or the first low earth satellite 210 while the aircraft 100 is stationary relative to earth or the first low earth satellite 210 is orbiting.

Preferably, a request to disconnect the laser communication link may be sent to the aircraft 100 or the first low-earth satellite 210 before the first synchronization satellite 310 disconnects its established laser communication link with the aircraft 100 or the first low-earth satellite 210. In response to the request to disconnect the laser communication link, at least one of the aerial vehicle 100 and the first low-earth satellite 210 may predict a disconnection condition of the laser communication link established between the aerial vehicle 100 and the first low-earth satellite 210 within a first preset time period after the disconnection based on the geographic information model and the trajectory prediction. The aircraft 100 or the first low-earth satellite 210 may reject the request of the first sync satellite 310 when at least one of the aircraft 100 and the first low-earth satellite 210 predicts that the number of disconnections of the laser communication link established between the aircraft 100 and the first low-earth satellite 210 within a first preset time period after the disconnection is greater than or equal to a preset number threshold based on the geographic information model and the trajectory prediction. The aircraft 100 or the first low-earth satellite 210 may receive the request of the first synchronization satellite 310 when at least one of the aircraft 100 and the first low-earth satellite 210 predicts that the number of disconnections of the laser communication link established between the aircraft 100 and the first low-earth satellite 210 within a first preset time period after the disconnection is less than a preset number threshold value based on the geographic information model and the trajectory prediction. Preferably, the geographic information model is a GIS model. The system may map and/or update a geographic information model based on geographic information acquired by at least some of the plurality of satellites. The system may also plot and/or update the cloud model on the geographic information model based on cloud information acquired by at least some of the plurality of satellites. Preferably, the cloud layer model can also be used to predict the disconnect condition.

Preferably, the first synchronization satellite 310 may selectively disconnect its laser communication link established with the aerial vehicle 100 and/or the first low-earth orbit satellite 210 based on the reliability and/or error rate of communication between the aerial vehicle 100 and the first low-earth orbit satellite 210. Preferably, the first synchronizing satellite 310 can analyze the reliability of the communication by means of geographic conditions, meteorological conditions, the degree of beam drift of the laser beam emitted by the first low-orbit satellite 210 detected by the third ATP device 120 and the degree of beam drift of the laser beam emitted by the aircraft 100 detected by the fourth ATP device 212.

Preferably, the process of determining the attitude and position of aircraft 100 based at least in part on first ATP device 110 may include: obtaining the position of the first synchronization satellite 310 from the ephemeris data and/or the registry, obtaining the velocity and geolocation of the aircraft 100, obtaining the position of the first synchronization satellite 310 as viewed by the first ATP device 110, and/or calculating the attitude and position of the aircraft 100 based on the position of the first synchronization satellite 310 obtained from the ephemeris data and/or the registry, the obtained velocity and geolocation of the aircraft 100, and the obtained position of the first synchronization satellite 310 as viewed by the first ATP device 110.

Preferably, the process of determining the attitude and position of the first low-earth satellite 210 based at least in part on the second ATP device 211 may comprise: the method may include obtaining a position of the first low-orbiting satellite 310 from the ephemeris data and/or the registry, obtaining a velocity and a geolocation of the first low-orbiting satellite 210, obtaining a position of the first low-orbiting satellite 310 as viewed by the second ATP device 211, and/or calculating an attitude and a position of the first low-orbiting satellite 210 based on the position of the first low-orbiting satellite 310 obtained from the ephemeris data and/or the registry, the obtained velocity and the geolocation of the first low-orbiting satellite 210, and the obtained position of the first low-orbiting satellite 310 as viewed by the second ATP device 211.

According to a preferred embodiment, after determining the attitude and position of the aerial vehicle 100 based at least in part on the first ATP device 110 and the attitude and position of the first low-earth satellite 210 based at least in part on the second ATP device 211, the aerial vehicle 100 and the first low-earth satellite 210 may transmit laser beams toward each other to establish a laser communication link between the aerial vehicle 100 and the first low-earth satellite 210. Preferably, the aerial vehicle 100 and the first low-earth satellite 210 transmit laser beams toward each other in an open-loop manner to establish a laser communication link between the aerial vehicle 100 and the first low-earth satellite 210 within 9 seconds.

According to a preferred embodiment, the aircraft 100 may select the first synchronization satellite 310 from ephemeris data or a registry before the aircraft 100 transmits a laser beam directed at the first synchronization satellite 310 having a determined position to request establishment of a laser communication link between the aircraft 100 and the first synchronization satellite 310. Preferably, the selected first sync satellite 310 is within a 10mrad field of view, particularly preferably a 4mrad field of view, of the first ATP device 110 of the aircraft 100 at the time of selection.

According to a preferred embodiment, beam drift of the aerial vehicle 100 may be compensated for by establishing absolute attitude and heading using the first ATP device 110 and the second ATP device 211 before a successful establishment of a laser communication link between the aerial vehicle 100 and the first low earth satellite 210. Preferably, before the successful establishment of the laser communication link between the aerial vehicle 100 and the first low-earth satellite 210, the absolute attitude of the aerial vehicle 100 and the absolute pointing direction toward the first low-earth satellite 210 may be established by using the first ATP device and the third ATP device to compensate for beam drift of the laser beam emitted by the aerial vehicle 100. Before the laser communication link is successfully established between the aerial vehicle 100 and the first low-orbit satellite 210, the absolute attitude and the absolute pointing direction of the first low-orbit satellite 210 toward the aerial vehicle 100 may be established by using the second ATP device and the fourth ATP device to compensate for the beam drift of the laser beam emitted by the first low-orbit satellite 210. Preferably, because the laser is affected by the thermal deformation, the environmental vibration, the air disturbance and other factors of the laser, the emitted laser beam often drifts in the propagation process, and the further improvement of the collimation precision of the laser is limited, and the drift is called as the beam drift.

Example 3

This embodiment may be a further improvement and/or a supplement to embodiments 1, 2 or a combination thereof, and repeated contents are not described again. The preferred embodiments of the present invention are described in whole and/or in part in the context of other embodiments, which can supplement the present embodiment, without resulting in conflict or inconsistency.

According to another preferred embodiment, after the laser communication link is established between the aerial vehicle 100 and the first low-earth satellite 210, the first synchronization satellite 310 may maintain the laser communication link established with the aerial vehicle 100 and/or the first low-earth satellite 210 until the data transmission between the aerial vehicle 100 and the first low-earth satellite 210 is completed. The first sync satellite 310 may identify a link state of a laser communication link established between the aircraft 100 and the first low earth orbit satellite 210 and a transmission state of data transmitted through the laser communication link. In the event that the transmission status is an incomplete status and the link status is an unavailable status, the first synchronous satellite 310 may send a request to the aircraft 100 and the first low earth orbit satellite 210 to assist in transmitting data. After both the aerial vehicle 100 and the first low-earth satellite 210 receive the request from the first synchronization satellite 310 to assist in transmitting data, the aerial vehicle 100 and the first low-earth satellite 210 may transmit data via the laser communication link established by the aerial vehicle 100 and the first synchronization satellite 310 and the laser communication link established by the first synchronization satellite 310 and the first low-earth satellite 210. Preferably, at least one of the aircraft 100 and the first low-earth satellite 210 may transmit the link state of the laser communication link established between the aircraft 100 and the first low-earth satellite 210 and the transmission state of data transmitted through the laser communication link to the first synchronous satellite 310.

Preferably, after the laser communication link established between the aerial vehicle 100 and the first low-earth satellite 210 is in an unavailable state, the attitude and position of the aerial vehicle 100 and the first low-earth satellite 210 may be determined to each other at least in part by the first geostationary satellite 310, and/or an attempt may be made to reestablish the laser communication link between the aerial vehicle 100 and the first low-earth satellite 210 accordingly.

According to a preferred embodiment, the aircraft 100 and the first low earth orbit satellite 210 may transmit data in clear or encrypted form while transmitting data via the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210. When the aircraft 100 and the first low-earth satellite 210 transmit data through the laser communication link established between the aircraft 100 and the first synchronous satellite 310 and the laser communication link established between the first synchronous satellite 310 and the first low-earth satellite 210, the data is transmitted in an encrypted manner, and neither the aircraft 100 nor the first low-earth satellite 210 transmits a secret key for decrypting the data transmitted between the aircraft 100 and the first low-earth satellite 210 to the first synchronous satellite 310.

According to a preferred embodiment, while the aircraft 100 and the first low earth orbit satellite 210 transmit data through the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210, the transmission data is encrypted using a first encryption algorithm; while the aircraft 100 and the first low-earth satellite 210 transmit data via the laser communication link established by the aircraft 100 and the first geostationary satellite 310 and the laser communication link established by the first geostationary satellite 310 and the first low-earth satellite 210, the transmitted data is encrypted using a second encryption algorithm that is different from the first encryption algorithm. Preferably, the first calculation amount of the first encryption algorithm is smaller than the second calculation amount of the second encryption algorithm. More preferably, the first encryption algorithm is a symmetric encryption algorithm and the second encryption algorithm is an asymmetric encryption algorithm.

According to a preferred embodiment, the aircraft 100 and the first low-earth satellite 210 may perform a key generation process and a key transmission process after the laser communication link is established between the aircraft 100 and the first low-earth satellite 210 and before the data to be encrypted is transmitted.

Preferably, the key generation process may include: the aircraft 100 or the first low-orbit satellite 210 generates a symmetric key for the first encryption algorithm, the aircraft 100 generates a first asymmetric key for the second encryption algorithm, and the first low-orbit satellite 210 generates a second asymmetric key for the second encryption algorithm, the first asymmetric key comprising a first public key and a first private key, and the second asymmetric key comprising a second public key and a second private key.

Preferably, the key transmission process may include: the aircraft 100 or the first low earth orbit satellite 210 transmits the generated symmetric key to the first low earth orbit satellite 210 or the aircraft 100 through the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210, the aircraft 100 transmits the generated first public key to the first low earth orbit satellite 210 through the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210, and the first low earth orbit satellite 210 transmits the generated second public key to the aircraft 100 through the laser communication link established between the aircraft 100 and the first low earth orbit satellite 210. Preferably, while the aerial vehicle 100 and the first low-earth satellite 210 transmit data over the laser communication link established between the aerial vehicle 100 and the first low-earth satellite 210, the aerial vehicle 100 and the first low-earth satellite 210 encrypt the transmitted data by a symmetric key. Preferably, when the aircraft 100 and the first low earth orbit satellite 210 transmit data through the laser communication link established by the aircraft 100 and the first geostationary satellite 310 and the laser communication link established by the first geostationary satellite 310 and the first low earth orbit satellite 210, the data transmitted by the aircraft 100 is encrypted by the first private key and the second public key and then is indirectly transmitted to the first low earth orbit satellite 210 through the first geostationary satellite 310, and the first low earth orbit satellite 210 unlocks the received data transmitted by the aircraft 100 through the first public key and the second private key. When the aircraft 100 and the first low earth orbit satellite 210 transmit data through the laser communication link established by the aircraft 100 and the first geostationary satellite 310 and the laser communication link established by the first geostationary satellite 310 and the first low earth orbit satellite 210, the data transmitted by the first low earth orbit satellite 210 is encrypted by the second private key and the first public key and then is indirectly transmitted to the aircraft 100 through the first geostationary satellite 310, and the aircraft 100 unlocks the received data transmitted by the first low earth orbit satellite 210 through the second public key and the first private key.

Example 4

This embodiment may be a further improvement and/or a supplement to embodiments 1, 2, and 3 or a combination thereof, and repeated details are not repeated. The embodiment discloses a communication system, which may also be a laser communication system, or a laser communication system based on a satellite, or a satellite laser communication system, or a laser communication system for aircraft and satellite communication, and the system is adapted to perform the steps of the method described in the present invention to achieve the intended technical effect. The preferred embodiments of the present invention are described in whole and/or in part in the context of other embodiments, which can supplement the present embodiment, without resulting in conflict or inconsistency.

According to a preferred embodiment, the system may comprise: a satellite communications network of satellites. The number of satellites may include a number of geostationary satellites and/or a number of low earth orbit satellites. The plurality of sync satellites may include a first sync satellite and a second sync satellite. The number of low earth satellites may include, for example, a first low earth satellite 210 and a second low earth satellite 220. Preferably, when the first low-earth satellite 210 leaves or is about to leave the communication range of the aircraft and/or the first synchronization satellite that is capable of communicating, the first synchronization satellite is able to reselect one of the low-earth satellites as the first low-earth satellite based on the position of the first synchronization satellite and the position of the aircraft. For example, the second low-orbiting satellite 220 in the figure is taken as the new first low-orbiting satellite 210. Preferably, the aircraft 100 may include a first ATP device 110 and the first low earth orbit satellite 210 may include a second ATP device 211.

According to a preferred embodiment, the system may comprise: at least one of a first synchronous satellite, a first low-orbit satellite, and an aircraft. When the aerial vehicle 100 attempts to establish a laser communication link with the first low earth orbit satellite 210, the aerial vehicle 100 transmits a laser beam directed at the first synchronization satellite 310 having a determined position to request establishment of a laser communication link between the aerial vehicle 100 and the first synchronization satellite 310. After the laser communication link is established between the aircraft 100 and the first sync satellite 310, the attitude and position of the aircraft 100 is determined based at least in part on the first ATP device 110 of the aircraft 100 pointing and tracking the first sync satellite 310. After determining the attitude and position of the aerial vehicle 100, an attempt is made to establish a laser communication link between the aerial vehicle 100 and the first low-earth satellite 210 based at least on the determined attitude and position of the aerial vehicle 100, and data is transmitted directly between the aerial vehicle 100 and the first low-earth satellite 210 via the established laser communication link between the aerial vehicle 100 and the first low-earth satellite 210.

Preferably, the laser beam generated by the system of the invention is narrow, and the divergence angle of the laser beam can be 12-95 μ rad. Particularly preferably 15 to 20 mu rad. The divergence angle of the laser transmitting antenna adopted by the invention can be adjustably set, and the adjustment range is 15-20 mu rad or 12-95 mu rad. A narrow laser beam is advantageous because it can provide high directivity by providing higher watts per square meter at the target and can achieve high data rates over long distances. However, since the laser beam is narrow, it must be pointed very precisely to establish reliable and stable communication.

Preferably, the system of the invention tracks and aims the moving target under the condition of compensating the wave front distortion brought to the laser beam by the atmosphere by adopting a nonlinear optical phase conjugation mode. The aiming light energy can be better concentrated in a small area, and higher precision aiming is provided.

Preferably, the system of the invention can adopt a discontinuous laser emitting mode to carry out discontinuous communication. In the system, any two devices establishing a laser communication link only endow one device with a state of not emitting laser at the same time in the discontinuous communication process in a discontinuous laser emitting mode.

According to a preferred embodiment, the system may include several ground stations 400. The first synchronizing satellite 310 may invoke at least one of the plurality of satellites and/or at least one of the plurality of ground stations 400 to scan the first low earth satellite 210 with a laser beam at a possible location until one of the satellites or one of the ground stations 400 illuminates the first low earth satellite 210 with a laser beam and notifies the first synchronizing satellite 310, whereupon the first low earth satellite 210 is illuminated with a laser beam to establish a laser communication link between the first synchronizing satellite 310 and the first low earth satellite 210. Preferably, the first sync satellite 310 may divide up different scan areas for at least one of the invoked satellites and/or at least one ground station 400 of the ground stations 400. Preferably, the different scan areas may have partially overlapping areas. Preferably, the plurality of satellites may include a microwave star that communicates with microwaves, an optical star that communicates with lasers, and/or a microwave optical common star that can communicate with lasers or microwaves. Preferably, the number of ground stations 400 may include a number of microwave stations 410 and/or a number of optical stations 420. The possible position may be a larger area than the exact optically determined position, which is determined non-optically, and then the laser beam is further scanned within this possible position to search for the first low-earth satellite 210. For example, microwaves from the satellite and/or microwave station 410 may first locate the possible position of the first low earth orbit satellite 210. The first geostationary satellite 310 then requests to invoke the second geostationary satellite 320 and/or the optical station 420 to scan with a laser within a possible location to determine a relatively more accurate location of the first low earth satellite 210 in order to establish a laser communication link between the first geostationary satellite 310 and the first low earth satellite 210.

The word "module" as used herein describes any type of hardware, software, or combination of hardware and software that is capable of performing the functions associated with the "module".

It should be noted that the above-mentioned embodiments are exemplary, and that those skilled in the art, having benefit of the present disclosure, may devise various arrangements that are within the scope of the present disclosure and that fall within the scope of the invention. It should be understood by those skilled in the art that the present specification and figures are illustrative only and are not limiting upon the claims. The scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for satellite laser communication, the method comprising: when the aircraft (100) attempts to establish a laser communication link with the first low earth orbit satellite (210), the aircraft (100) transmits a laser beam directed at a first synchronization satellite (310) having a determined position to request establishment of a laser communication link between the aircraft (100) and the first synchronization satellite (310);

after determining the attitude and position of the aircraft (100), attempting to establish a laser communication link between the aircraft (100) and the first low-earth satellite (210) based at least on the determined attitude and position of the aircraft (100), and transmitting data directly between the aircraft (100) and the first low-earth satellite (210) over the established laser communication link between the aircraft (100) and the first low-earth satellite (210).

2. The satellite laser communication method of claim 1, wherein determining the attitude and position of at least one of the aerial vehicle (100) and the first low-earth satellite (210) is accomplished prior to establishing the laser communication link between the aerial vehicle (100) and the first low-earth satellite (210),

after determining the attitude and position of the aerial vehicle (100) or the first low earth orbit satellite (210) is completed, the first low earth orbit satellite (210) or the aerial vehicle (100) of which the attitude and position is not determined transmits a laser beam scan toward the aerial vehicle (100) of which the attitude and position is determined or the first low earth orbit satellite (210) to attempt to establish a laser communication link between the aerial vehicle (100) and the first low earth orbit satellite (210);

in the process that the first low-earth satellite (210) or the aircraft (100) of which the attitude and the position are not determined emits the laser beam toward the aircraft (100) of which the attitude and the position are determined or the first low-earth satellite (210) in an attempt to establish the laser communication link between the aircraft (100) and the first low-earth satellite (210), the determination process of the first low-earth satellite (210) or the aircraft (100) of which the attitude and the position are not determined is not terminated until the attempt to establish the laser communication link between the aircraft (100) and the first low-earth satellite (210) is successful or the system determines the attitude and the position of the first low-earth satellite (210) or the aircraft (100) of which the attitude and the position are not determined.

3. The satellite laser communication method according to claim 2, wherein after the laser communication link is established between the aircraft (100) and the first low-orbit satellite (210), the first synchronization satellite (310) maintains the laser communication link established between the aircraft (100) and/or the first low-orbit satellite (210) until the data transmission between the aircraft (100) and the first low-orbit satellite (210) is completed, and the first synchronization satellite (310) identifies a link state of the laser communication link established between the aircraft (100) and the first low-orbit satellite (210) and a transmission state of the data transmitted through the laser communication link, and in the case where the transmission state is an uncompleted state and the link state is an unavailable state,

the first synchronous satellite (310) sends a request for assisting data transmission to the aircraft (100) and the first low-orbit satellite (210), and after the aircraft (100) and the first low-orbit satellite (210) both receive the request for assisting data transmission sent by the first synchronous satellite (310), the aircraft (100) and the first low-orbit satellite (210) indirectly transmit data through a laser communication link established by the aircraft (100) and the first synchronous satellite (310) and a laser communication link established by the first synchronous satellite (310) and the first low-orbit satellite (210).

4. A satellite laser communication method according to claim 3, wherein before the aircraft (100) emits the laser beam directed to the first geostationary satellite (310) having the determined position, the aircraft (100) selects a geostationary satellite capable of establishing a laser communication link with both the aircraft (100) and the first low-earth satellite (210) as the first geostationary satellite (310) based on the ephemeris data, and transmits the selected first geostationary satellite (310) to the first low-earth satellite (210) together with a message that the aircraft (100) requests to establish a laser communication link with the first low-earth satellite (210) in a non-optical communication manner;

the first low earth satellite (210) establishing a laser communication link between the first low earth satellite (210) and the first synchronization satellite (310) in response to the selected first synchronization satellite (310) and the message that the aircraft (100) requests that a laser communication link be established with the first low earth satellite (210);

determining an attitude and a position of a first low-orbit satellite (210) based at least in part on a second ATP device (211) pointing and tracking the first low-orbit satellite (210) of the first synchronous satellite (310) after establishing a laser communication link between the first low-orbit satellite (210) and the first synchronous satellite (310);

after determining the attitude and position of the first low-earth satellite (210), attempting to establish a laser communication link between the aerial vehicle (100) and the first low-earth satellite (210) based at least on the determined attitude and position of the first low-earth satellite (210), and transmitting data directly between the aerial vehicle (100) and the first low-earth satellite (210) over the established laser communication link between the aerial vehicle (100) and the first low-earth satellite (210).

5. The satellite laser communication method according to claim 4, wherein when the aircraft (100) and the first low earth orbit satellite (210) directly transmit data through the laser communication link established between the aircraft (100) and the first low earth orbit satellite (210), the transmitted data is transmitted in clear or encrypted using a first encryption algorithm; and/or

Encrypting the transmission data using a second encryption algorithm different from the first encryption algorithm while the aircraft (100) and the first low-earth satellite (210) transmit the data over the laser communication link established by the aircraft (100) and the first synchronization satellite (310) and the laser communication link established by the first synchronization satellite (310) and the first low-earth satellite (210);

wherein the key for encrypting the data of the first encryption algorithm and/or the second encryption algorithm is transmitted directly over the laser communication link established between the aircraft (100) and the first low earth orbit satellite (210) when the link status of the laser communication link established between the aircraft (100) and the first low earth orbit satellite (210) is in the available state.

6. The satellite laser communication method according to claim 5, wherein after the laser communication link is established between the aerial vehicle (100) and the first low-earth satellite (210) and before the data to be encrypted is transmitted, the aerial vehicle (100) and the first low-earth satellite (210) need to perform a key generation process and a key transmission process;

the key generation process comprises the following steps: the aircraft (100) or the first low-orbit satellite (210) generates a symmetric key for a first encryption algorithm, the aircraft (100) generates a first asymmetric key for a second encryption algorithm, the first low-orbit satellite (210) generates a second asymmetric key for the second encryption algorithm, the first asymmetric key comprises a first public key and a first private key, and the second asymmetric key comprises a second public key and a second private key;

the key transmission process comprises the following steps: the aircraft (100) or the first low-orbit satellite (210) transmits the generated symmetric key to the first low-orbit satellite (210) or the aircraft (100) through a laser communication link established between the aircraft (100) and the first low-orbit satellite (210), the aircraft (100) transmits the generated first public key to the first low-orbit satellite (210) through a laser communication link established between the aircraft (100) and the first low-orbit satellite (210), and the first low-orbit satellite (210) transmits the generated second public key to the aircraft (100) through a laser communication link established between the aircraft (100) and the first low-orbit satellite (210).

7. The satellite laser communication method of claim 6, further comprising:

the aircraft (100) generates at least two symmetric keys corresponding to the at least two security levels and generates at least two sets of first asymmetric keys corresponding to the at least two security levels, the higher the security level the symmetric keys or the first asymmetric keys are assigned the longer the key length,

prior to the aircraft (100) transmitting data to the first low-orbit satellite (210) over the laser communication link established between the aircraft (100) and the first low-orbit satellite (210), the aircraft (100) determining a level of security required to transmit data to the first low-orbit satellite (210), and selecting a key required to encrypt the data based on the level of security determined by the aircraft (100) to be required to transmit data to the first low-orbit satellite (210); and/or

The first low earth orbit satellite (210) generates at least two sets of second asymmetric keys corresponding to at least two security levels, the higher the security level, the longer the second asymmetric keys are assigned, the first low earth orbit satellite (210) determines a security level required to transmit data to the aircraft (100) before the first low earth orbit satellite (210) transmits data to the aircraft (100) over the laser communication link established between the aircraft (100) and the first low earth orbit satellite (210), and selects the key required to encrypt the data based on the security level determined by the first low earth orbit satellite (210) to transmit data to the aircraft (100).

8. The satellite laser communication method according to claim 7, wherein after selecting the key required to encrypt the data according to the determined security level required to transmit the data to the first low-orbit satellite (210) and before transmitting the encrypted data to the first low-orbit satellite (210), the aircraft (100) transmits the security level determined by the aircraft (100) required to transmit the data to the first low-orbit satellite (210) to enable the decryption key adapted thereto; and/or

After selecting the key required for encrypting the data according to the determined security level required for transmitting the data to the aircraft (100) and before transmitting the encrypted data to the aircraft (100), the first low-earth satellite (210) transmits the security level determined by the first low-earth satellite (210) required for transmitting the data to the aircraft (100) for the aircraft (100) to enable the decryption key adapted thereto.

9. The satellite laser communication method according to claim 8, wherein before the aircraft (100) transmits the determined security level required for transmitting data to the first low-orbit satellite (210), the security level required for transmitting data to the first low-orbit satellite (210) determined by the aircraft (100) is transmitted to the first low-orbit satellite (210) after being encrypted by a first private key corresponding to the highest security level generated by the aircraft (100) and a second public key corresponding to the highest security level generated by the first low-orbit satellite (210); and/or

Before the first low-orbit satellite (210) sends the determined security level required for transmitting the data to the aircraft (100), the security level required for transmitting the data to the aircraft (100) and determined by the first low-orbit satellite (210) is encrypted by using a second private key corresponding to the highest security level and a first public key corresponding to the highest security level and generated by the aircraft (100) and sent to the aircraft (100).

10. The satellite laser communication method according to claim 9, wherein the received security level determined by the first low earth orbit satellite (210) to be required for transmitting data to the aircraft (100) is decrypted using a first private key corresponding to the highest security level generated by the aircraft (100) and a second public key corresponding to the highest security level generated by the first low earth orbit satellite (210) and the decryption key adapted thereto is enabled to decrypt the corresponding data transmitted by the first low earth orbit satellite (210) accordingly; and/or

The first low-earth satellite (210) is further configured to: and decrypting the security level determined by the received aircraft (100) and required for transmitting the data to the first low-orbit satellite (210) by using the second private key corresponding to the highest security level generated by the first low-orbit satellite (210) and the first public key corresponding to the highest security level generated by the aircraft (100) and enabling the decryption key adapted to the second private key to decrypt the corresponding data transmitted by the aircraft (100).