High rate payload management between ground segment and satellite

Abstract

To provide a technique for constructing a payload of a satellite at high rate and low waiting time between a ground segment and a satellite and recovering telemetry data of the payload.SOLUTION: In a communication system, a satellite comprises: a platform; and a payload. The ground segment comprises at least one satellite control center configured to generate or process data associated with the satellite platform and directly communicate with the satellite platform on a dedicated platform channel; and at least one mission control center different from the satellite control center. A method includes a step of directly communicating on a signaling channel between the mission control center and an on board processing unit which is configured to manage at least a part of the payload of the satellite, telecommand or telemetry data of the part of the payload of the satellite. The signaling channel and the platform channel are different.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] METHOD OF COMMUNICATION BETWEEN A SATELLITE AND A GROUND SEGMENT FIELD OF THEINVENTION The present invention relates to the field of satellite communications, and more particularly to the field of communications payload management. [Background technology]

[0002] In the space communications market, the demands of end users (i.e., communications operators) are becoming increasingly complex in terms of real-time in-flight configurability, in-flight mission upgrades and flexibility. For example, one of the requirements of communications operators is to be able to instantly adapt their services to current market demands. However, these demands must be met while addressing the mass and bulkiness requirements of on-board payload management equipment.

[0003] Until now, the payload of a communication satellite has been managed through the same channel devoted to platform management (or spacecraft management), also called the Telemetry, Tracking and Command (TT&C) channel, as disclosed in documents WO 2004 / 107185 A1 and CA 2862019 A1. The uplink telecommand and downlink telemetry of the platform (as well as the payload) are managed by the Spacecraft Control Center (also called the Platform Control Center). In the uplink, the Spacecraft Control Center formulates the platform and payload control programs and instructions, and the corresponding telecommand data is uploaded by the satellite to configure the satellite and the payload. In the downlink, the satellite transmits telemetry data to the Spacecraft Control Center, which is used to determine the health and location of the satellite and the status of the payload. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2004 / 107185 [Patent Document 2] Canadian Patent Application Publication No. 2862019 Summary of the Invention [Problem to be solved by the invention]

[0005] The TT&C channel is highly secured to ensure that the satellites can always communicate with the ground segment, therefore the antennas of satellites dedicated to platform management must be omnidirectional and the power transmitted on this channel is not optimized for point-to-point links.

[0006] Due to these security requirements, the channel has a very low data rate (on the order of a few kbits / sec) for constructing the payload and for retrieving the telemetry data from the payload.

[0007] Moreover, when a communication operator needs a new configuration of the payload (e.g., to adapt the service to the development of market demand), the communication operator transmits the new configuration to the spacecraft control center, which in turn communicates with the spacecraft. Due to the low data rate, the communication may take some time (usually several days), which may be problematic for the communication operator.

[0008] Therefore, there is a need to overcome the aforementioned deficiencies, particularly to configure satellite payloads and retrieve payload telemetry data at a high rate and with low latency. [Means for solving the problem]

[0009] According to one aspect of the invention, a method for performing communication between a satellite and a ground segment, the satellite including a platform and a payload, the ground segment including at least one satellite control center configured to generate or process data associated with the satellite platform, the satellite control center communicating directly with the satellite platform on a dedicated channel called a platform channel, and at least one mission control center different from said satellite control center, is proposed, characterized in that the method includes a step of communicating directly between the mission control center and an on-board processing unit configured to manage at least a part of the satellite's payload and / or telecommand or telemetry data of a part of the satellite's payload, on another dedicated channel called a signaling channel, the signaling channel and the platform channel being different.

[0010] In a preferred embodiment, the payload portion receives multiple telecommand signals from N mission control centers, N≧2, the signaling channel includes N sub-channels, the same telecommand signal is modulated onto a different carrier wave for each mission control center on each sub-channel, the carrier waves having different non-overlapping spectral bands, the payload portion includes an RF filter having a predefined bandwidth and an adjustable center frequency, and the step of directly communicating includes: a1) adjusting a center frequency of an RF filter for a first carrier among the N carriers; b1) filtering the received signal using an RF filter to determine whether a first condition related to a received signal power level and / or a signal-to-noise ratio of the received signal is satisfied; c1) if the first condition is met, demodulating the filtered signal and determining whether a second condition related to the quality of demodulation of the received signal is met; d1) issuing a command to the payload portion according to the telecommand signal if the second condition is met; e1) if the first condition or the second condition is not satisfied, adjusting the center frequency of the filter to another carrier among the N carriers and repeating substeps b1) to d1); Includes.

[0011] In a preferred embodiment, the method includes the sub-step of generating, by the processing unit, an error message if neither the first condition nor the second condition is met for any of the N carriers, and transmitting the error message to the N mission control centers.

[0012] In a preferred embodiment, in sub-step b1) it is determined whether the power level and / or the signal-to-noise ratio of the received signal is greater than a predefined threshold.

[0013] In a preferred embodiment, in sub-step b1) it is determined whether the carrier is centered on the center frequency of the RF filter.

[0014] In a preferred embodiment, the processing unit receives a number of different payload telecommand signals, each of which is transmitted by a number of user terminals and retransmitted by at least one mission control center to the satellite over a signaling channel, said at least one mission control center being associated with at least one user, each telecommand signal being modulated onto a different carrier for each user on the signaling channel, and said step of directly communicating comprises: a2) demodulating each received signal in a hardware module specific to each user terminal, said hardware modules being managed by a common programmable logic device; b2) storing the demodulated telecommand signals in respective mailboxes in a common memory of the programmable logic devices, said memory being accessible by a common microprocessor; c2) indicating to the microprocessor by the programmable logic device that a message specific to one of the user terminals is present in one of the mailboxes; d2) reading the contents of each of the mailboxes by a microprocessor and controlling the payload portion according to the telecommand signals; Includes.

[0015] In a preferred embodiment, the method includes a preliminary sub-step of storing security keys associated with each user in a memory external to the programmable logic device, called external memory, and in sub-steps a2) to d2) the programmable logic device communicates with the external memory so that one security key can be accessed by only one user, and the method comprises the steps: - inserting a key, called the transmit key, into the Telecommand signal; - comparing the security key with the transmission key; - controlling the payload according to a result of said comparison; Further includes:

[0016] In a preferred embodiment, the step of directly communicating comprises: - a3) transmitting, by the mission control center, a telecommand signal on a signaling channel; - b3) extracting time data from the telecommand signal; - c3) updating the on-board time embedded in the payload based on the time data; Includes.

[0017] In a preferred embodiment, sub-step b3) comprises generating a set of symbols comprising time data by a first numerically controlled oscillator based on the telecommand signal, the first numerically controlled oscillator being synchronized with the symbol duration determination unit.

[0018] In a preferred embodiment, sub-step c3) is performed by using a second numerically controlled oscillator, which synchronizes the time data with a clock signal generated in the payload.

[0019] In a preferred embodiment, the method comprises a sub-step d3) of controlling the payload according to the updated on-board time.

[0020] In a preferred embodiment, the time data is calculated based on a global navigation satellite system.

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments of the invention and, together with the general description of the invention provided above and the detailed description of the embodiments provided below, serve to explain embodiments of the invention. [Brief description of the drawings]

[0022] [Figure 1] 1 illustrates the relationship between the ground segment and the satellite, including signaling channels and platform channels. [Diagram 2] 1 shows a functional diagram of a payload management processing unit, including main modules and service modules. [Diagram 3] 1 illustrates a first embodiment of a communication method according to the present invention, in which a payload portion receives multiple telecommand signals from a single user terminal, the multiple telecommand signals being retransmitted to the payload portion by N mission control centers. [Figure 4] 1 shows a frequency spectrum including three carriers of a telecommand signal transmitted from a single user terminal. [Diagram 5] A second embodiment of the communication method according to the invention is shown, in which a programmable logic device common to all users interacts with a microprocessor to separate the streams of several users. [Figure 6]4 illustrates a third embodiment of a communication method according to the present invention for updating an on-board time embedded in a payload. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In FIG. 1, the satellite control center SCC communicates with the satellite management unit on the platform channel Lnk-PF. The platform channel Lnk-PF is used for spacecraft configuration and housekeeping processes. It can also be used as a troubleshooting tool for payload configuration and housekeeping processes in the case of advanced communication systems. Data for on-board activities of the satellite's platform (e.g., propulsion, thermal control, power supply, attitude command and control) is transmitted on the platform channel. Communication between the satellite control center SCC and the satellite management unit can include, for example, the transmission of telemetry data (on the downlink) and the transmission of telecommand data (on the uplink). Both the platform and the payload transmit or receive telemetry and telecommand data to / from the ground segment.

[0024] The satellite control centre SCC communicates with the satellite platforms PF to send or receive telecommands and / or telemetry data associated with the satellite platforms on dedicated channels called platform channels.

[0025] A typical communication link between a satellite platform and the satellite control center (SCC) is disclosed in the article "Telemetry, Tracking and Command Systems of Spacecraft", SN Prasad & S Pal FIETE (2003), IETE Technical Review, 20:6, 561-576.

[0026] A mission control centre MCC associated with an appropriate user (also called customer or operator) communicates directly with a payload management processing unit PRU configured to control and monitor the main elements of the payload (channeliser / payload processor or other payload units) on another dedicated channel called the signalling channel. It is essential for the implementation of the method that the signalling channel and the platform channel are distinct.

[0027] Due to the method for performing the communication between the ground segment and the satellite, the communication between the payload and the ground segment does not go through the satellite control center SCC. Actually, the communication between the payload and the ground segment occurs on a channel dedicated to the payload, called the signaling channel. Each operator has its own signaling channel. For example, in FIG. 1, up to three signaling channels (Lnk-S1, Lnk-S2, Lnk-S3) are managed by their respective operators. Since each communication operator has its own signaling channel, each operator can monitor and control the payload independently of the other operators. The platform channel and the signaling channel are different. The ground segment includes a mission control center, which is also different from the satellite control center SCC. The mission control center is operated and managed by the telecom operator. Due to the configuration, the payload can be managed with a high degree of flexibility.

[0028] Moreover, security and availability requirements are lower for signaling channels than for platform channels, and therefore data rates can be significantly higher than current rates for telecommand and telemetry data when transmitted to or from the satellite control center SCC.

[0029] FIG. 2 shows a functional diagram of a payload management processing unit PRU, which is configured to communicate with a mission control centre MCC and also configured to manipulate the payload according to commands of the mission control centre MCC.

[0030] The payload management processing unit PRU includes a main module MMO for processing and setting up the received telemetry and / or telecommand signals, and a service module SMO, which includes a power supply such as a DC / DC board to provide the power required by the main module MMO. The payload management processing unit PRU may also include expansion boards and additional interfaces.

[0031] The main module is responsible for receiving the radio frequency signals (RF input) from the ground segment (after a previous frequency conversion, if necessary). The RF filter FLT1 performs the necessary filtering before digitizing the information. The digitization is performed by the sampler ADC. The demultiplexer DEMUX extracts the individual signaling channels, filtered and sampled. The demodulator DEMOD outputs the binary I (in-phase) and Q (quadrature) components from the individual signaling channels by using timing and phase tracking loops. The decoder DECOD then detects and corrects possible errors in the signaling channels.

[0032] After decryption, decryption can be performed. Decryption can be performed in the uplink using a set of keys securely uploaded and managed in the units (Decryptor / Encryptor CRY and Key Manager KMN). In addition, decryption can be bypassed or performed by an external unit with commercial or military encryption algorithms.

[0033] Finally, the received telecommand signal reaches the last processing element and all selected mission functions are performed. The payload management processing unit PRU also includes a clock generator CLK, which provides clock signals to all digital components of the payload management processing unit PRU based on an external clock reference, so that all gates of the digital components (such as the sampler ADC, the demultiplexer DEMUX, the demodulator DEMOD and the decoder DECOD) can be driven synchronously. The payload management processing unit PRU also includes a satellite management unit interface SMU_IF for communicating with the platform, a payload interface PL_IF for sending telecommand signals to the payload or receiving telemetry signals from the payload, and a synchronization element SYNC for controlling fine synchronization between different elements of the payload (e.g., between different sources for beam hopping).

[0034] Similar to how telecommands are processed, the payload telemetry data (configuration reports, spectrum analysis, event logs) follow the reverse procedure to enable its transmission to the ground. The telemetry data is first sent to an internal or external decryptor / encryptor CRY of the payload management processing unit PRU, then continues the different transmission steps such as encoding (coder COD), modulation (modulator MOD) and multiplexing (multiplexer MUX) of the different user channels, and finally converted to high frequency using a direct conversion technique (converter DAC). Finally, after RF filtering (RF filter FLT), the signal is transmitted to the ground segment.

[0035] The service module SMO can perform the functions of generating a secondary voltage from the platform's primary voltage to be used for the processing boards, over-voltage, under-voltage and over-current protection functions, and discrete telecommand and telemetry line functions for housekeeping processing and expansion capabilities in terms of interfaces and processing capabilities.

[0036] Redundancy of the payload management processing unit PRU can be implemented. In fact, the flight segments are in a fully-contributed manner to maximize the reliability of its operation as a payload computer. The unit is connected to the main spacecraft elements, to the on-board computer to ensure consistency in the received commands, and to the different elements of the payload for their control, management and monitoring.

[0037] To guarantee reliability, it undertakes operation with cold redundancy of two identical halves, while at the same time minimizing the switchover time between the two halves to guarantee very high availability. Each of the two halves contains all the elements necessary to perform the required services and functions.

[0038] Figures 3 and 4 show a first embodiment of the present invention. In Figure 3, an operator OP (e.g. a communication operator) communicates with at least two mission control centers (three in Figure 3: MCC1, MCC2, MCC3). The communication is performed by using multiple mission control centers to enhance the reliability of the communication. In fact, each mission control center includes a satellite gateway, which has its own carrier (C1, C2, C3). The different carriers have different non-overlapping spectrum bands.

[0039] The non-overlapping spectral bands of the carriers of the ground stations are shown in Figure 4. The total bandwidth BW (e.g., 50 MHz) allocated to the signaling channels is the result of a trade-off between the ability to manage several carriers at the desired data rate for the telecommand and telemetry links and the fact that the total bandwidth should be negligible compared to the user bandwidth (i.e., that devoted to the communication signals transmitted through the satellite).

[0040] Each carrier (C1, C2, C3) has a center frequency (Fc1, Fc2, Fc3) that is separated by a guard fundamental bandwidth (Gbw1, Gbw2, Gbw3, Gbw4, e.g., 7 MHz each) to specifically avoid overlapping subchannels.

[0041] The RF filter FLT1 shown in Figure 2 has a predefined bandwidth and an adjustable center frequency, and the filter is automatically tuned to one of the carriers. To do so, the following steps are performed:

[0042] In a first step a1), the RF filter FLT1 is tuned: the center frequency of the RF filter FLT1 is adjusted for a first carrier among the N carriers. The first carrier to which the adjustment is performed is called the default carrier.

[0043] In a second step b1), once the RF filter FLT1 has been adjusted, the received signal is filtered using the RF filter to determine whether a first condition related to the received signal power level and / or the signal-to-noise ratio of the received signal is fulfilled. In a preferred embodiment, it is determined whether the power level and / or the signal-to-noise ratio of the received signal is greater than a predefined threshold. It is also determined whether the carrier is centered on the center frequency of the RF filter FLT1. Step b1) is performed by a demultiplexer DEMUX as shown in FIG. 2.

[0044] According to a third step c1), if the first condition is fulfilled, the filtered signal is demodulated by a demodulator DEMOD (see FIG. 2) and it is determined whether a second condition related to the quality of demodulation of the received signal is fulfilled. For example, the second condition may determine whether the locking of the demodulator to the carrier can be successfully achieved.

[0045] If the first and second conditions are met, in a fourth step d1) commands are issued to the payload according to the telecommand signal.

[0046] If the first or second condition is not met, then in a fifth step e1), the center frequency of the RF filter is adjusted to another carrier among the N carriers and sub-steps b1) to d1) are repeated for the other carrier, thus repeating the same process for all sub-channels.

[0047] If it is found that locking cannot be achieved for one of the N sub-channels (meaning that neither the first nor the second condition is met for any of the sub-channels), a report indicating that the carrier was not detected correctly is provided to the Satellite Management Unit SMU, which then sends the report to the N Mission Control Centers MCC.

[0048] Thus, a single user / communications operator can operate with several satellite gateways by using several mission control centers.

[0049] This process allows unwanted signals (e.g., jamming signals) to be discarded. For example, in the ground segment, the ground station may decide to transmit a telecommand signal not at the center frequency of the filter, but at a slight offset (e.g., 1 kHz above the center frequency of the filter). Then, if the locked carrier is exactly at the center frequency of the basic bandwidth, it may be determined that the signal is not the signal expected to come from the ground station. Therefore, the signal should be discarded.

[0050] This is made possible by a direct link between the payload and the mission control center.

[0051] According to a second embodiment of the invention, a separation scheme between different users can be implemented.Figure 5 shows a block diagram of the main module MMO of the payload management processing unit PRU also shown in figure 2.

[0052] The payload management processing unit PRU includes a common programmable logic device PLD, which may be, for example, an FPGA (Field Programmable Gate Array) and has the advantage of being reprogrammable, so that the configured design can be modified even in flight. The common programmable logic device PLD is directly coupled to an analog-to-digital converter ADC and a digital-to-analog converter DAC, which are coupled to the RF filters FLT1 and FLT2. The common programmable logic device PLD is also coupled to a clock generator CLK, which serves as an internal clock reference for all elements of the payload management processing unit PRU.

[0053] Thus, a set of digital data containing data of N users (i.e. telecommand signals of N communication operators (each operator is connected to one mission control center)) is filtered and digitized all together. At this stage, the telecommand data is mixed and separation needs to be ensured in order to process this data and split it into N streams (one for each user). A common programmable logic device PLD contains a number of hardware modules such as a demultiplexer DEMUX, a demodulator DEMOD and a decoder DECOD, so that each telecommand signal can be processed independently in a dedicated demultiplexer, demodulator and decoder.

[0054] Thus, in a first substep a2), each received signal is demodulated in a specific hardware module of the programmable logic device PLD.

[0055] Then, in step b2), the demodulated telecommand signals are stored in mailboxes. Each mailbox is associated with a user. The implementation of barriers between the design of the programmable logic device PLD ensures that the data streams coming from different mission control centers are separated. The mailboxes are separated while being located in a common memory MEM of the programmable logic device PLD.

[0056] The memory MEM can be accessed through a first memory controller MCO1 by a common microprocessor MPR, which is responsible for interpreting the data and routing them in the form of physical elements through a corresponding physical interface (payload interface PL_IF) to their destination.

[0057] There is only one physical link LNK between the common programmable logic device PLD and the common microprocessor MPR, so it must be ensured that the separate data are sent separately to the common microprocessor MPR.

[0058] In a third substep c2), the common programmable logic device PLD notifies the microprocessor MPR that a message specific to one of the user terminals is present in one of the mailboxes.

[0059] Then, in a fourth substep d2), the common microprocessor MPR reads the content of each of the mailboxes and controls the payload portion according to the telecommand signals.

[0060] The processor maintains data isolation by using a supervisor to divide the processing of data into different threads of execution. The supervisor also ensures that no conflicts are seen in the physical elements of the system (storage in different memory areas, access to interfaces through their specific drivers). The supervisor is a specific piece of software that runs on the microprocessor MPR and creates N independent threads.

[0061] An additional separation of the streams of the N users can also be considered. An external memory MEMext is coupled to the programmable logic device PLD. The external memory MEMext is a non-volatile memory, for example an EEPROM (Electrically Erasable Programmable Read Only Memory). The external memory MEMext stores N security keys, each security key being associated with one of the users. The security keys can be preloaded into the external memory MEMext by the users before the launch of the satellite.

[0062] Then, in sub-steps a2) to d2), the programmable logic device PLD communicates with the external memory MEMext through the second memory controller MCO2. A key, called the transmit key, is inserted into the telecommand signal by the mission control centre. The security key is compared with the transmit key and, if they are identical, the payload is controlled according to the telecommand signal. The keys are managed by the aforementioned decryptor / encryptor CRY and key manager KMN, which are shown diagrammatically by FIG. 2.

[0063] Thus, the satellite provides user isolation while at the same time providing multi-user capability.

[0064] The third embodiment of the present invention illustrated by Figure 6 allows for the handling of enhanced communication services that require very precise timing, and is made possible by a signaling channel that has a high data rate compared to state-of-the-art payload telecommand methods.

[0065] In a method for performing communication between the satellite SAT and the ground segment GS, the following substeps are performed:

[0066] In a first substep a3), the mission control centre MCC transmits a telecommand signal TC to the satellite on a signalling channel. The payload management processing unit PRU receives the telecommand signal.

[0067] In a second sub-step b3), the programmable logic device PLD extracts time data from the telecommand signal. In a preferred embodiment, the time data is calculated based on a satellite geolocalization system, for example based on a global navigation satellite system (such as GPS or Galileo). The mission control centre MCC therefore has very precise knowledge of the time data and transmits it on the signalling channel.

[0068] In a third sub-step c3) the on-board time OBT embedded in the payload is updated based on the time data, so that the on-board time of the payload can be updated whenever the time data is transmitted by the mission control centre MCC.

[0069] Thus, end-to-end synchronization between ground and flight segments allows for correct management of the elements to meet the beam hopping requirements. A synchronization delay of less than 1 ms is recommended to send commands to the RF switches and payload processor drivers to implement the beamforming technique.

[0070] In the programmable logic device PLD, a first numerically controlled oscillator NCO1, which is also coupled to a clock generator CLK, controls the symbol time of the received telecommand signal on the signaling channel.

[0071] Advantageously, sub-step b3) comprises generating a set of symbols comprising time data based on the telecommand signal, the set of symbols being generated by a first numerically controlled oscillator NCO1, the first numerically controlled oscillator being synchronized with a symbol duration determination unit SDU, the first numerically controlled oscillator NCO1 and the symbol duration determination unit SDU being located in a programmable logic device PLD.

[0072] Advantageously, sub-step c3) is implemented by using a second numerically controlled oscillator NCO2, which synchronizes the time data with a clock signal generated in the payload, the second numerically controlled oscillator NCO2 also being located in the programmable logic device PLD.

[0073] According to the third embodiment, the telecommand signal can provide data on the next pulses per second PPS and the delay from the last PPS to the start of the command frame. This specific telecommand is interpreted on-board to allow synchronization. The frequency soft-steering is performed based on the uplink symbol rate, in the same way that the absolute time soft-steering is based on the telecommand data and calibration coefficients that depend on the satellite delays stored and processed by the programmable logic device PLD, and also on the ground delay clock for the antenna data introduced in the telecommand.

[0074] The relative radial velocity of the satellite compared to the mission control center and / or weather conditions such as rain can generate frequency shifts on the signaling channel due to the Doppler effect, in which case corrections to the on-board clock are made based on the motion of the satellite and / or based on the determined weather conditions.

[0075] Advantageously, the method comprises a substep d3) of controlling the payload according to the updated on-board time OBT. By means of the aforementioned fine synchronization mechanism, a very precise control of the payload can be achieved, for example for beam hopping. Indeed, beam hopping requires a tight control of the synchronization between the commands to the different elements of the payload.

[0076] Similar to how telecommand signals are processed for the method described above, payload telemetry data follows the reverse procedure.

Claims

1. A method for performing communications between a satellite (SAT) and a ground segment (GS), the satellite (SAT) including a platform (PF) and a payload (PL), the ground segment including at least one satellite control center (SCC) configured to generate or process data associated with the satellite platform (PF), the satellite control center (SCC) communicating directly with the satellite platform (PF) on a dedicated channel called a platform channel, and at least one mission control center (MCC) different from the satellite control center (SCC), characterized in that the method includes a step of communicating directly between the mission control center (MCC) and an on-board processing unit (PRU) configured to manage at least a part of the payload of the satellite and / or telecommand or telemetry data of the part of the payload of the satellite, the signaling channel being different from the platform channel, the signaling channel being different from the platform channel, the payload portion receiving multiple telecommand signals from N mission control centers (MCCs), N≧2, the signaling channel including N sub-channels, the same telecommand signal being modulated onto different carriers on each sub-channel for each mission control center (MCC), the carriers (C1, C2, C3) having different non-overlapping spectral bands, the payload portion including an RF filter (FLT1) having a predefined bandwidth and an adjustable center frequency, the step of directly communicating a1) tuning the center frequency of the RF filter (FLT1) for a first carrier among the N carriers; b1) filtering the received signal using the RF filter to determine whether a first condition related to the received signal power level and / or the signal-to-noise ratio of the received signal is satisfied; c1) if the first condition is met, demodulating the filtered signal and determining whether a second condition related to the quality of the demodulation of the received signal is met; d1) if the second condition is met, issuing a command to the payload portion according to the telecommand signal; e1) if the first condition or the second condition is not satisfied, adjusting the center frequency of the filter to another carrier among the N carriers and repeating substeps b1) to d1); A method comprising:

2. 2. The method of claim 1, further comprising the substep of generating an error message by said processing unit (PRU) and transmitting said error message to said N mission control centers (MCCs) if neither the first condition nor the second condition is met for any of said N carriers.

3. 3. The method according to claim 1 or 2, wherein in sub-step b1) it is determined whether the power level and / or the signal-to-noise ratio of the received signal is greater than a predefined threshold.

4. The method according to any one of claims 1 to 3, wherein in sub-step b1) it is determined whether the carrier is centred on the centre frequency of the RF filter (FLT1).

5. A method for performing communications between a satellite (SAT) and a ground segment (GS), the satellite (SAT) including a platform (PF) and a payload (PL), the ground segment including at least one satellite control center (SCC) configured to generate or process data associated with the satellite platform, the satellite control center (SCC) communicating directly with the satellite platform (PF) over a dedicated channel called a platform channel, and at least one mission control center (MCC) distinct from the satellite control center (SCC), the method comprising the steps of: communicating directly between the mission control center (MCC) and an on-board processing unit (PRU) configured to manage at least a portion of the payload of the satellite and / or telecommand or telemetry data for the portion of the payload of the satellite over another dedicated channel called a signaling channel, the signaling channel and the platform channel being distinct. said processing unit (PRU) receiving a number of different payload telecommand signals, each of said number of different payload telecommand signals being transmitted by a number of user terminals and retransmitted to said satellite over said signaling channel by at least one mission control center (MCC), said at least one mission control center (MCC) being associated with at least one user, each telecommand signal being modulated onto a different carrier for each user over said signaling channel to communicate directly; a2) demodulating each received signal in a hardware module specific to each user terminal, said hardware modules being managed by a common programmable logic device (PLD); b2) storing the demodulated telecommand signals in respective mailboxes in a common memory (MEM) of the programmable logic devices (PLDs), the memory (MEM) being accessible by a common microprocessor (MPR); c2) indicating, by said programmable logic device (PLD), to said microprocessor (MPR) that a message specific to one of said user terminals is present in one of said mailboxes; d2) reading the contents of each of said mailboxes by said microprocessor (MPR) and controlling said payload portions according to said telecommand signals; A method comprising:

6. 6. The method of claim 5, further comprising the preliminary sub-step of storing security keys associated with each user in a memory external to the programmable logic device, called an external memory (MEMext), and in sub-steps a2) to d2), the programmable logic device (PLD) communicates with the external memory (MEMext) such that each security key is accessible to only one user, - inserting a key, called a transmission key, into said telecommand signal; - comparing said security key with said transmission key; - controlling said payload according to a result of said comparison; The method further comprising:

7. A method for performing communications between a satellite (SAT) and a ground segment (GS), the satellite (SAT) including a platform (PF) and a payload (PL), the ground segment including at least one satellite control center (SCC) configured to generate or process data associated with the satellite platform, the satellite control center (SCC) communicating directly with the satellite platform (PF) over a dedicated channel called a platform channel, and at least one mission control center (MCC) distinct from the satellite control center (SCC), the method comprising the steps of: communicating directly between the mission control center (MCC) and an on-board processing unit (PRU) configured to manage at least a portion of the payload of the satellite and / or telecommand or telemetry data for the portion of the payload of the satellite over another dedicated channel called a signaling channel, the signaling channel and the platform channel being distinct. said step of directly communicating with - a3) transmitting, by said Mission Control Center (MCC), a telecommand signal on said signaling channel; - b3) extracting time data from said telecommand signal; - c3) updating an on-board time (OBT) embedded in the payload based on the time data; A method comprising:

8. 8. The method according to claim 7, wherein said sub-step b3) comprises generating a set of symbols including said time data by a first numerically controlled oscillator (NCO1) based on said telecommand signal, said first numerically controlled oscillator (NCO1) being synchronized with a symbol duration determination unit (SDU).

9. 9. The method according to claim 7 or 8, wherein sub-step c3) is performed by using a second numerically controlled oscillator (NCO2), said second numerically controlled oscillator (NCO2) synchronizing said time data with a clock signal generated in the payload.

10. The method according to any one of claims 7 to 9, comprising a sub-step d3) of controlling the payload according to the updated on-board time (OBT).

11. The method according to any one of claims 7 to 10, wherein the time data is calculated based on a global navigation satellite system.

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