Integrated data transfer system between satellites and from satellites to earth

Abstract

(57) The present invention relates to an integrated system for data transfer between satellites and from satellites to Earth, which will find application in the satellite industry, more particularly for increasing the useful data that can be received from satellites, and reducing the execution time of commands sent from a ground station to satellites. The designed integrated communication system is comprised of a software- defined radio (1) with numerical computation capability and algorithms for determination and control of relative orientation and Doppler offset compensation, an inter-satellite radio frequency unit (2) in the S-band, a high-speed radio frequency transmitter block (3) in the X-band or K-band, and interfaces for data transmission over existing optical terminals. The system shall also include the appropriate S-band (2.2) and X-band or K-band (3.2) antennas to implement free-space radio wave propagation, as well as manoeuvre planning algorithms to control orientation for precision guidance.

Description

[0001] Integrated data transfer system between satellites and from satellites to Earth

[0002] Technical field

[0003] The present invention relates to an integrated data transfer system between satellites and from satellites to Earth, which will find application in the satellite industry and more particularly to increase the useful data that can be received from satellites, and to reduce the execution time of tasks and / or commands sent from a ground station to satellites.

[0004] Background of the invention

[0005] Space exploration and related infrastructure are becoming increasingly important to the modem world. The space sector is evolving at an extraordinary speed and this will lead to major changes in many industries in the coming years. Globally, more than 7 000 new micro and small artificial satellites are expected to be launched in the next ten years. Micro-satellites are traditionally defined as those with a mass between 10-200 kg and small satellites with a mass between 200-600 kg. These classes of satellites are increasingly being used for Earth observation, communications, information transfer, research and education. The development of launch vehicles over the last 10 years and the reduction in the launch cost of this class of satellites has contributed to their significantly increased capabilities for applications where multiple satellites perform a single mission, in the form of a so- called satellite constellation. The largest such constellations involve hundreds or even thousands of satellites that are designed to monitor the Earth's surface, connect remote points without access to a GSM network, provide accurate time, and assist navigation systems such as GPS, among many others. The main problem with utilizing such networks of satellites is that they all still communicate separately with the ground segment of the mission. In the absence of communication between satellites, all data transfer and operations prioritization decisions, as well as the actual transfer of useful data to Earth, are limited by the contact time that a satellite has with the ground segment of the network. This time is typically less than 7% of the mission lifetime, which brings with it a host of problems, the most common of which can be listed as the deletion of the oldest data on board, even if it is useful, due to the lack of ability to download everything to Earth; the dropping of service delivery capabilities (imaging, communication, etc.) due to inability to send a command to the satellite in time, and strong inhomogeneity in the resources used such as memory and computing power of satellite constellations, i.e. lack of sharing of resources for optimal use.

[0006] Technical summary of the invention

[0007] The object of the invention is to provide an integrated data transfer system between satellites and from satellites to Earth that is autonomous, secure, and fully ready for integration by providing: a radio link between individual satellites for command execution and telemetry data transfer at any relative orientation; an optical link between individual satellites for transfer of large volumes of useful data; and a high-speed radio link to Earth for transfer of large volumes of useful data.

[0008] The problem is solved by creating an integrated system for data transfer between satellites and from satellites to the Earth, which is composed of a software- defined radio bidirectionally connected to an inter-satellite radio frequency unit through a serial communication interface and through a radio interface. On the other hand, the software-defined radio is bidirectionally coupled to the high-speed radio frequency unit via a second serial communication interface and unidirectionally coupled to the high-speed radio frequency unit via a modulated signal radio interface. The software-defined radio is composed of a transceiver with two radio frequency (RF) channels and a module for determining and controlling relative orientation between satellites. The inter-satellite radio frequency unit shall include an S-band radio frequency transceiver, bidirectionally connected via a second radio interface to an S-band antenna, for bidirectional radio frequency communication with other satellites. The high-speed radio-frequency unit includes an X-band or K- band radio-frequency transceiver unidirectionally coupled via a radio interface to a converted X-band or K-band antenna for communication with a ground station via electromagnetic waves. The software-defined radio is also bidirectionally coupled to a satellite orientation control subsystem via a third serial communications interface.

[0009] In one preferred embodiment, the software-defined radio via a serial interface for high-speed data transmission is bidirectionally coupled to an integrated optical terminal, for bidirectional optical communication with other satellites.

[0010] The first and second radio interfaces are implemented either by a diplexer or by two separate physical interfaces.

[0011] An advantage of the integrated system created is that it allows sharing of communication and computational resources across satellites to reduce the time to download data to Earth, and to increase the usable data for a constellation in proportion to a power function of the number of satellites in it. Another advantage is that the system is fully integrated and also allows internal data transmission between different satellites of the network to improve pointing accuracy by receiving only a radio signal, without requiring the mandatory use of external navigation services, but only regular updates of the orbital parameters of all satellites in the system.

[0012] Description of the attached figures The present invention is illustrated in the attached Figure 1, which is a schematic diagram of the integrated data transfer system between satellites and from satellites to the Earth according to the invention.

[0013] Examples of embodiments of the invention

[0014] The designed integrated data transfer system between satellites and from satellites to the Earth, shown in Fig. 1, is composed of a software-defined radio 1 that is bidirectionally connected to an inter-satellite radio frequency unit 2 via serial communication interface 6.1 and via radio interface 7.1. On the other hand, the software-defined radio 1 via a second serial communication interface 6.2 is bidirectionally connected to the high-speed radio frequency unit 3 and via a modulated signal radio interface 7.3 is unidirectionally connected to the high-speed radio frequency unit 3. The software-defined radio 1 is composed of a dualfrequency transceiver 1.1 and a module for determining and controlling relative orientation between satellites 1.2. The inter-satellite radio frequency unit 2 comprises an S-band 2.1 radio frequency transceiver, bidirectionally connected via a second radio interface 7.2 to an S-band 2.2 antenna, for bidirectional 9.2 radio frequency communication with other satellites. The high-speed radio frequency unit 3 includes an X-band or K-band 3.1 radio frequency transmitter unidirectionally coupled via a 7.4 converted signal radio interface to an X-band or K-band 3.2 antenna, for communication with a ground station via 9.3 electromagnetic waves. The software-defined radio 1 is also bidirectionally coupled to a satellite orientation control subsystem 5 via a third serial communications interface 6.3.

[0015] In one preferred embodiment, the software-defined radio 1 via a high-speed serial data interface 8.1 is bidirectionally coupled to an integrated optical terminal 4, for bidirectional optical communication 9.1 with other satellites. The radio interfaces 7.1 and 7.2 are implemented either by a diplexer or by two separate interfaces - 7.1.1, 7.1.2, and 7.2.1, 7.2.2, respectively.

[0016] An external power supply is required for the system to function, which is not part of it, but is always an integral part of any satellite.

[0017] The principle operation of the system is not limited to any particular frequency, but the logical implementation of the scheme uses the S-band frequency range for radio frequency inter-satellite links and the X-band or K-band frequency range for downloading data to ground stations, due to the legal and purely physical advantages of these bands. It is possible to use alternative bands, including the IJHF or C-band band for radio-frequency inter-satellite links and the Ka / Ku / W-band for downloading data to earth stations.

[0018] The modules of the established SD-IRS integrated data transfer system have the following functions and features:

[0019] The software-defined radio 1 is a transceiver with two radio frequency channels 1.1, each capable of modulating / demodulating and encoding / decoding digital radio signals, by means of programmable logic (FPGA), and performing the calculations necessary to determine relative pointing and relative position, and velocity by means of the module for determining and controlling relative orientation between satellites 1.2. Software-defined radio 1 consists of a main processor and a dedicated field programmable logic (FPGA) chip, associated program memories and long-term data storage memory, a radio transceiver chip, high-speed digital-to- analogue converters (DACs) and analogue-to-digital converters (ADCs), high- power amplifiers and low-noise amplifiers operating in the main frequency range of software-defined radio 1.

[0020] The inter-satellite radio frequency unit 2 includes an S-band 2.1 radio frequency transceiver, which is intended to amplify the signal coming from the transceiver 1.1 of the software-defined radio 1 , to a power suitable for transmission to the S-band antenna 2.2 and send to other satellites, and to amplify signals coming from other satellites via the same S-band antenna 2.2 to a power that the input channel of the software-defined radio 1 can use.

[0021] The high-speed radio frequency unit 3 includes an X-band or K-band radio frequency transmitter 3.1, which is designed to convert the signal frequency produced by the software-defined radio l's transceiver 1.1 to a higher one, and amplify it to a power suitable for transmission to the X-band or K-band antenna 3.2 and sending to Earth. The high-speed radio frequency transmitter unit 3 consists of a conversion circuit with frequency mixers and filters as well as power amplifiers.

[0022] The 2.2 and 3.2 antennas are passive or active antennas that are intended to focus (and further amplify in the case of active antennas) the signals from the 2.1 transceiver and 3.1 transmitter and to transmit / receive the modulated signals to / from free space. These consist of microstrip and potentially high-power amplifiers or low noise amplifiers in some particular implementations.

[0023] In addition to these mandatory components, the system optionally includes an integrated optical terminal 4 for inter-satellite communication, which is a laser transceiver terminal designed to communicate with another similar terminal on another satellite. Such a terminal type consists of an optical part (telescope), an optical diplexer and separate receiving and transmitting circuitry using optocouplers to convert optical signals to electrical ones and vice versa, and basic electronics consisting of a microcontroller, programmable logic and communication peripherals.

[0024] A mandatory part of the system is the ability to interface with the attitude determination and control subsystem (ADCS) of the satellite 5, which has the purpose of determining the orientation of the satellite with respect to a predefined reference system, and the ability to maintain a given orientation or sequence of orientations with respect to that reference system. Such a subsystem shall consist of, as a minimum, a set of orientation sensors (solar sensors, infrared sensors, star counters, at least three gyroscopes and magnetometers), actuators to change the orientation of the satellite (at least 3 reaction wheels and at least 3 magnetic moment of force coils, or 3 motors on different axes), and algorithms to determine and control the orientation inherent to each satellite.

[0025] The serial communication interfaces 6.1, 6.2 and 6.3 provide the data exchange between the main modules of the communication system in order to configure and transmit parameters for the correct operation of all radio elements. These communication interfaces may be a single bus or different serial interfaces. The serial communication interfaces 6.1 and 6.2 are used to configure the parameters of the RF transceiver 2.1 and the RF transmitter 3.1, including the exact receive / transmit frequency, the output power of the final amplifier and other parameters, and to receive telemetry data on the status of the transceivers. After calculating the relative Doppler effect, the communication interface 6.1 is also used to compensate the receive / transmit frequency in order to reduce the frequency error to a limit that can be compensated by the software-defined radio 1. On the other hand, the third communication interface 6.3 is used to receive the satellite orientation and attitude information from the attitude control subsystem 5, by means of standard formats (projection matrix, quaternions, modified Rodrigues parameters and other equivalents for orientation, and orbital elements or orbital state vector for attitude / velocity) which are fed to the software-defined radio 1. In addition, the third communication interface 6.3 is used to transmit the required orientation for pointing the satellite in equivalent formats as commands from the software-defined radio 1 to the orientation subsystem 5 after the corresponding relative orientations have been computed. In this way, the control subsystem 5 does not need to implement specific algorithms, but only executes a given trajectory, with all algorithmic calculations for the relative pointing performed internally in the system. Serial communication interfaces 6.1, 6.2 and 6.3 are bidirectional telemetry and data interfaces with typical speeds <1 Mbps.

[0026] The radio interfaces 7.1 / (7.1.1 and 7.1.2), 7.2 / (7.2.1 and 7.2.2), 7.3 and 7.4 are used to transmit and receive modulated signals between the software-defined radio 1, the respective transceiver radio frequency modules and their associated antennas.

[0027] Interface 7.1 is bidirectional as it is implemented either by a diplexer or by physically two separate interfaces 7.1.1 and 7.1.2. The 7.1.1 interface transmits a modulated low frequency signal from the software-defined radio 1 transceiver 1.1 to the radio frequency transceiver 2.1 when transmitting to another satellite. At interface 7.1.2, a signal modulated and amplified by a low-noise amplifier is transmitted from the radio-frequency transceiver 2.1 to the software-defined radio 1 transceiver 1.1 when received from another satellite. The logic behind switching between receive and transmit (in a half-duplex system) is implemented as part of the software-defined radio 1 .

[0028] Interface 7.2 is bidirectional, which is again implemented by a diplexer, or by two physically separate interfaces 7.2.1 and 7.2.2. The 7.2.1 interface transmits the already amplified modulated signal from the RF transceiver 2.1 to the S-band antenna 2.2 for inter-satellite communication, which sends it into free space via RF communication 9.2 to another satellite. On interface 7.2.2, a signal is transmitted from the S-band antenna 2.2 for inter-satellite communication, after receiving RF communication 9.2 from another satellite to the low-noise amplifier in RF transceiver 2.1, where it is amplified before transmission on interface 7.1.2 for demodulation by software-defined radio 1.

[0029] The 7.3 radio interface is used to transmit a modulated signal in the base frequency of the software-defined radio 1 from the 1.1 transceiver to the 3.1 radio frequency transmiter for conversion to a higher frequency and signal amplification. The radio interface 7.4, in turn, transmits the signal already converted to a higher frequency and amplified from the radio frequency transmiter 3.1 to the output X- band or K-band antenna 3.2 for data transmission, which in turn realizes the output of the signal in the form of free electromagnetic waves 9.3 to the ground station in one of the frequency ranges mentioned above.

[0030] The High-Speed Data Link Interface 8.1 is a bidirectional communication channel that allows both the transmission of telemetry data and commands from the software-defined radio 1 to the integrated optical terminal 4 for pointing to other satellites based on the computed relative orientations, and the bidirectional transmission of payload data over a high-speed link (e.g., Ethernet 1000 BASE-T) to re-transmit the data between different satellites of a satellite constellation.

[0031] The functionalities for data transfer between satellites for command and telemetry transfer for decision making, as well as data transfer from the pay load to the ground station, via high-speed radio frequency link, are embedded in the core of the system, which includes all the necessary calculations and algorithms to perform the corresponding manoeuvres from the Doppler effect control and compensation subsystem in inter-satellite communication and under available orbital parameters. On the other hand, the high-speed data transfer functionality between satellites is optional and is guaranteed by an external laser terminal, which is not necessary for all applications of the system. When using such a terminal, the system determines all necessary commands based on the above-mentioned algorithms, this capability makes the system integrated and creates added value beyond that of individual components such as software-defined radio and RF transceivers, which are available as stand-alone devices for much more limited purposes.

[0032] The functionality of the system is as follows: The system created allows data to be transmitted at low rates (up to several Mbps) at any time for the purpose of exchanging telemetry or sending commands between individual satellites in direct line-of-sight, and with any relative orientation in low Earth orbit, as long as they are equipped with the cited system. This functionality is supported by the permanently operating software-defined radio 1, RF transceivers and 2.1 and 2.2 antennas. The added value of this functionality is proportional to the power function of the number of satellites equipped with the system, since they are the points of information transfer to each other.

[0033] In addition to this functionality, the system allows the download of high-speed data (up to Gbps) to different ground stations under the condition of contact between a satellite and the respective ground station. This functionality is supported by the same software-defined radio 1, but with a different (parallel) radio frequency transmitter 3.1 and its corresponding antenna 3.2, as well as the attitude control subsystem 5.

[0034] The system also allows the use of standard optical laser terminals for highspeed (up to several Gbps) data transfer between satellites, in order to reduce the download time of priority data by transmitting it from a satellite other than the one that generated it, when earlier contact with a ground station is available for it (the data carrier). For this functionality, in addition to the software-defined radio 1 and the attitude control system 5, an external integrated optical terminal 4 is used, which acts as a transparent interface between the satellites of the system, for which the software-defined radio 1 remains the controller.

[0035] The integration of the platform lies in the fact that it performs all the necessary calculations for contact determination, prioritization for maneuvers, calculations of the maneuvers themselves, and calculations of compensations for frequencies and their Doppler offsets, transmitting this data to the individual components to achieve end-to-end communication, both between individual satellites and between the satellite and the Earth, without the need for any additional implementation on the client’s side beyond securing the interfaces.

[0036] The security of the system lies in the fact that all radio channels for communication between individual satellites and between the satellite and the Earth are encrypted. This makes it possible to exchange data between different satellites (owned by different operators) without the risk of data leakage.

Claims

PATENT CLAIMS1. An integrated system for data transfer between satellites and from satellites to Earth, characterized in that it is composed of a software-defined radio (1) that is bidirectionally coupled to an inter-satellite radio frequency unit (2) on the one hand via a serial communication interface (6.1) and via a radio interface (7.1), on the other hand, the software-defined radio (1) via a second serial communication interface (6.2) is bidirectionally coupled to the high-speed radio frequency unit (3), and via a modulated signal radio interface (7.3) is unidirectionally coupled to the high-speed radio frequency unit (3), wherein the software-defined radio (1) comprises a transceiver with two radio frequency channels (1.1) and an inter-satellite relative attitude determination and control module (1.2), wherein the inter-satellite radio frequency unit (2) comprises an S-band radio frequency transceiver (2.1) bidirectionally coupled via a second radio interface (7.2) to an S-band antenna (2.2) for bidirectional radio frequency communication (9.2) with other satellites, wherein the high-speed radio frequency unit (3) includes an X-band or K-band radio frequency transceiver (3.1) unidirectionally coupled via a converted signal radio interface (7.4) to an X-band or K-band antenna (3.2) for communication with a ground station via electromagnetic waves (9.3), wherein the software-defined radio (1) is bidirectionally coupled to a satellite attitude control subsystem (5) via a third serial communication interface (6.3).

2. An integrated data transfer system between satellites and from satellites to Earth, according to claim 1, characterized in that the software- defined radio (1) is bidirectionally connected via a high-speed serial data transfer interface (8.1) to an integrated optical terminal (4) for bidirectional optical communication (9.1) with other satellites.

3. An integrated system for data transfer between satellites and from satellites to Earth according to claims 1 and 2, characterized in that the radio interfaces (7.1) and (7.2) are implemented either by a diplexer or by two separate interfaces, respectively (7.1.1, 7.1.2) and (7.2.1, 7.2.2).

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