FR3056305B1 - FLIGHT IN TRAINING OF AEROSPATIAL VEHICLES - Google Patents

Abstract

Flight in aerospace vehicle formation A primary aerospace vehicle (SM), capable of communicating with one or more secondary aerospace vehicles (SE1, SE2, ..., SEi, ..., SEN) of an aerospace vehicle formation (10). ), comprising an antenna configured to receive GNSS signals, a digitizer configured to digitize the GNSS signals received by the antenna, a communication system configured to receive data including GNSS signals digitized by one or more secondary aerospace vehicles, and transmitting data including flight instructions for one or more secondary aerospace vehicles and an on-board GNSS signal processor configured to determine a training navigation state based on the digitized GNSS signals from the digitizer as well as those from, via the communication system, one or more aerospace vehicles of the f raining. The invention will be of interest to all stakeholders interested in aerospace training flights.

Description

TECHNICAL FIELD [0001] In general, the invention relates to aerospace vehicles designed to be able to fly in formation under the supervision of a particular aerospace vehicle.

BACKGROUND [0002] The realization of a formation flight by aerospace vehicles is a very studied subject at present. In particular, safe and autonomous training flights could pave the way for the realization of a variety of applications such as, for example, space or air telescopes with large aperture, very precise space or airborne interferometers, opening synthesis, complex maneuvers by aerospace vehicles, etc.

US 2010/0032528 discloses a deployment control system of at least two spacecraft intended to move in formationsous control stations on the ground. Each machine is connected to a ground station by a communication link. The maneuvers to be performed by each spacecraft are determined on the ground in order to place the formation in a chosen configuration. The instructions for performing the maneuvers are sent separately to each plant by the ground stations.

The object of the present invention is to overcome the disadvantages of existing solutions.

GENERAL DESCRIPTION OF THE INVENTION [0005] According to one aspect of the invention, the aerospace vehicles are configured to allow a global approach to the supervision and / or management of the training so that the implementation of the control system as well as the management of the the information is not significantly more complicated or costly than that of a single aerospace vehicle.

In the context of this document, the term "aerospace vehicles" includes space vehicles (eg satellites, probes, etc.) as well as aeronautical vehicles (eg drones, airplanes). , etc.). The term "primary aerospace vehicle" refers to an aerospace vehicle responsible for one or more other aerospace vehicles assigned to it, called "secondary aerospace vehicles". Secondary aerospace vehicles may be supervised and / or managed by the primary aerospace vehicle. The aerospace vehicles covered by this document are designed to fly in formation, that is to say to achieve a coordinated flight. Preferably, the secondary aerospace vehicles of the formation are distant, at most 500 km, preferably at most 100 km, more preferably at most 50 km, still more preferably at most 10 km, the aerospaceprimaire vehicle.

A first aspect of the present invention relates to a primary aerospace vehicle, capable of communicating with one or more aerospace vehicles secondary aerospace vehicle formation. The primary aerospace vehicle comprises an antenna configured to receive radio navigation signals also called GNSS signals (GNSS for "GlobalNavigation Satellite System" in English), a digitizer configured to digitize the GNSS signals received by the antenna, a communication system configured to receive data comprising GNSS signals digitized by one or more secondary aerospace vehicles and for transmitting data including flight instructions for one or more secondary aerospace vehicles and a GNSS-embarked signal processor. The embedded GNSS signal processor is configured to determine a navigation state of the formation based on the digitized GNSS signals from the digitizer as well as those from the communication system of one or more aerospace vehicles of the formation.

[0008] A GNSS signal corresponds to a radionavigation signal emitted by unsatellite GNSS (GPS, GLONASS, Galileo, etc.) in a certain frequency band. The GNSS signal comprises a code modulated carrier, data (except in the case of a pilot signal), and, optionally, a subcarrier. The carrier is sinusoidal at a certain frequency (for example at a frequency of 1575.42 MHz in the frequency band L1). The code is a pseudo-random binary code ("Pseudo-Random Noise (PRN) sequences" or "PRN code" in English) identifying the transmitting satellite. The data includes navigation data including, for example, ephemeris of the transmitting GNSS satellite and "almanac" type data on the GNSS constellation. The modulation of the carrier by the pseudo-randombinary code and the data causes a spectrum spread around the (central) carrier frequency (for example, for a GPSC / A code signal, the spread around the center frequency is 1575.42 ± 1.023 MHz for the main lobe). The pseudo-random codes of the different GNSS satellites are orthogonal, resulting in a code division multiple access (TDMA) system to the frequency resource shared by all GNSS satellites (ie the carrier frequency) .

Upon receipt (in our case at a primary or secondary aerospace vehicle), GNSS signals from "visible" GNSS satellites (ie, non-eclipsed from the receiving antenna) are mixed. Their reception and processing comprise several steps, the first including the digitization (possibly after transposition to an intermediate frequency) by a radiofrequency head ("RF front end" in English) equipped with an analogue-digital converter. After the digitization follows the acquisition and tracking step, which is performed on several parallel processing channels for different GNSS signals, and which produces observables, eg observables decode, phase observables, etc. The observables are processed in a navigation step, configured to estimate position, speed and / or time.

In the context of the present invention, the GNSS signals digitized andtransmitted by one or more secondary aerospace vehicles correspond GNSS signals delivered by an analog-digital converter of the radiofrequency headstage, before any subsequent processing acquisition or prosecution . The data packets containing digitized GNSS signals transmitted to the primary aerospace vehicle of the formation may be understood as "snapshots" of GNSS signals received in a certain frequency band, taken by the secondary aerospace vehicles of the formation for a certain period of time. In practice, the GNSS signal processing equipment on board an aerospace vehicle can be limited to an antenna and an RF front end stage equipped with an analog-to-digital converter.

The communication system may be any wireless communication system suitable for communication between aerospace vehicles.According to one embodiment of the invention, the communication can be performed on a radio frequency band, through radio frequency antennas present on each Aerospace vehicle training. According to a preferred embodiment of the invention, the communication system of the primary aerospace vehicle is an optical communication system, comprising a laser for transmitting the data and an optical receiver for receiving data. The data to be transmitted to one or more secondary aerospace vehicles may include, for example, flight instructions. Flight instructions can include, for example, commands for propulsion system actuators, solar panel actuators for deploying panels in a certain direction, and so on. The data, from one or more secondary aerospace vehicles, to be transmitted to the primary aerospace vehicleincludes in particular the digitized GNSS signals (the "snapshots" mentioned above).

By "navigation state" of the formation is meant all thepositions of the aerospace vehicles of the formation. Optionally, the navigation status may also include, among other things, speeds and / or accelerations of one or more (and preferably all) aerospace vehicles of the formation. According to one embodiment of the invention, the physical quantities related to the navigation state (positions, speeds, etc.) are relative magnitudes with respect to a reference aerospace vehicle of the formation. The reference vehicle is preferably the primary aerospace vehicle. It will be appreciated that the navigation state of the formation is determined centrally on the primary aerospace vehicle. In fact, any processing of GNSS signals relating to the determination of the navigation state of the formation (eg acquisition / pursuit steps etc.) downstream of the digitization of the GNSS signals (which is carried out on all the vehicles of training), is performed centrally on the primary aerospace vehicle. In other words, only the aerospaceprimary vehicle has a complete GNSS receiver. It goes without saying that the GNSS receiver is more developed than a standard GNSS receiver, since it must be able to support the GNSS signals received by all GNSS antennas distributed on the aerospace vehicles of the formation.

According to one embodiment of the invention, the aerospace vehicles of the formation each comprise several antennas configured to receive the GNSS signals in space. The use of several GNSS antennas on an aerospace vehicle of the formation makes it possible to determine the attitude (orientation in space) of this aerospace vehicle as part of the determination of the navigation state of the formation.

[0014] Preferably, the GNSS signal processor of the aerospaceprimary vehicle is configured to determine the navigation state using known constraints on the formation. A constraint determination allows, among other things, to restrict the number of possible solutions of the navigation state. Otherwise, a determination of the navigation state of the constraint formation can substantially increase the accuracy of the determined navigation state. These constraints may include, for example, prior positions of the aerospace vehicles in the formation, positions obtained by ancillary systems (for example by telemetry and / or through the optic communication medium). According to one embodiment of the invention, the constraints comprise approximate positions and speeds (absolute or relative) of the aerospace vehicles of the formation.

The determination of the navigation state may comprise a demodulation of the GNSS signals received in order to obtain observables of code and phase. The different GNSS signals can be combined to obtain observables of other types. Eg there are possibilities of observable "iono-free". The estimation of the navigation state can also include the use of differences between GNSS signals received by different aerospace vehicles from the formation (simple differences in receivers). Another example of a relative determination of the navigation state includes making differences between GNSS signals from different GNSS satellites (simple differences between GNSS satellites). There is also the possibility of observing "double differences" corresponding to differences between GNSS signals from different GNSS satellites and different receivers.

According to one embodiment of the invention, the GNSS signal processor of the primary aerospace vehicle is configured for determining the navigation state of the formation by the kinematic method in real time. This method uses doubly differentiated carrier phase observables. The real-time kinematic method can be the mobile baseline real-time kinematics (RTK) variant or the fixed base variant if there is a Ground reference station. Since the signal of the carrier is at high frequency, it makes it possible to achieve a high degree of accuracy in determining the state of navigation. The RTK method determines relative physical quantities (e.g., relative positions) relative to a reference station (which may be an aerospace vehicle of the formation). In the case where the aerospace vehicle of the formation acts as the reference station, it is preferable to combine, in the context of the determination of the navigation state, the RTK method with a determination, at least, of the absolute position of the station. reference.

According to one embodiment of the invention, the primary aerospace vehicle comprises an on-board computer configured to communicate, via the communication system, with one or more secondary aerospace vehicles of the formation in order to coordinate and / or supervise training. based on, among other things, the navigation status of the formation. Training coordination may include, for example, "day-to-day" management of training in accordance with higher-level instructions. These instructions of higher level can be, for example, a particular geometry (static or dynamic) to be respected. These instructions can be set and transmitted by a ground station and the primary aerospace vehicle then acts to maintain this geometry. The primary aerospace vehicle may, for example, send instructions to a secondary aerospace vehicle to deploy its solar panels in some direction. The primary aerospace vehicle may also, for example, request a report on the operating status and / or health of a component of a secondary aerospace vehicle (for example on its propulsion). It will be appreciated that the primary aerospace vehicle can be considered as the focal point of the formation, at least as far as the coordination of flight formation is concerned.

According to one embodiment of the invention, the onboard computer of the primary aerospace vehicle is configured to assign (add) an aerospace secondary vehicle to the formation or to decommission (withdraw) a secondary aerospace vehicle from the formation, optionally on the basis of data relating to the operational status of the secondary aerospace vehicle concerned.

The primary aerospace vehicle preferably comprises a single internal clock, shared with each of its components, and an onboard computer or embedded GNSS signal processor. The unique and shared clock provides a time stamp for events taking place onboard the aerospace vehicle (eg scientific measurements, reports operations) consistently and unique to the aerospace vehicle. The onboard computer or GNSS signal processor embedded are configured to determine a bias between a clock of an aerospace vehicle (primary or secondary) of the formation and a reference clock. According to an advantageous embodiment of the invention, this bias can be determined by means of the GNSS signals received by the training vehicles (i.e. thanks to the GNSS signal images received by the training). Preferably, all the biases between the clocks and the reference clock are determined. According to a preferred embodiment of the invention, the reference clock is the clock of the primary aerospace vehicle. According to another embodiment of the invention, the reference clock may be that of a secondary aerospace vehicle training.The clock on the primary aerospace vehicle is adapted to restrictions imposed by aerospace vehicles. It can be, for example, a quartz clock or an atomic clock (for example a maser, an ion trap, etc.) orother.

[0020] A second aspect of the present invention relates to a secondary aerospace vehicle, capable of communicating with a primary aerospace vehicle of an aerospace vehicle formation, comprising an antenna configured to receive GNSS signals, a digitizer configured to digitize the received GNSSignals by said antenna, a communication systemconfigured to transmit data including digitized GNSS signals to the primary aerospace vehicle and to receive data including flight instructions from the primary aerospace vehicle. According to one advantageous embodiment of the invention, the digitizer is configured to dynamically adapt its operating parameters, such as its sampling frequency, in order, for example, to release bandwidth for other data to be transmitted (for example data harvested by an instrument from the payload of the secondary aerospace vehicle).

According to one embodiment of the invention, the communication system of the secondary aerospace vehicle is an optical communication system comprising a laser for transmitting data comprising GNSS signals and an optical receiver for receiving data comprising aerospace vehicle devol instructions. primary.

[0022] Preferably, the secondary aerospace vehicle comprises an on-board computer as well as a single internal clock, shared with the components of the secondary aerospace vehicle. The on-board computer is preferably configured to timestamp, by means of the clock, the data to be transmitted. The time stamp may include, for example, a number of ticks since the clock is turned on, received GNSS signals, and so on. The clock present on the aerospace secondary vehicle is adapted to the restrictions imposed by aerospace vehicles. It can be, for example, a quartz clock or an atomic clock (for example a maser, an ion trap, etc.) or other. According to a preferred embodiment of the invention, all the data that the aerospace-secondary vehicles transmit to the primary aerospace vehicle are time-stamped.

According to a preferred embodiment of the invention, each aerospace vehicle (primary or secondary) of the formation is equipped with a single internal clock. This configuration allows each aerospace vehicle to clock all the measurements or observations made with this clock. In particular, each aerospace vehicle is preferably configured to timestamp the GNSS signals digitized using this clock. Since the digitized GNSS signals allow a determination of the GNSS time, it will be possible to precisely determine the bias of each clock with respect to the GNSS time and thus to indicate the GNSS time for any measurement made on any of the vehicles of the formation. With this configuration, a problem of distributed measurement systems is solved or at least greatly reduced.

A third aspect of the present invention relates to a control software for aerospace vehicle training, stored on a computer medium, comprising commands, which, when executed by a computer hardware comprising a GNSS signal processor, ensure that the GNSS signal processor implements a method comprising determining the navigation state of a formation of aerospace vehicles based on digitized GNSS signals from the formation. Computer equipment may also include an on-board computer.

According to one embodiment of the invention, the software includes, in addition, commands, which, when executed by the computer hardware, cause the computer hardware to determine a bias between an interneunique clock present on An aerospace vehicle and a reference clock. Preferably, all bias, between each clock of the formation and the reference clock, are determined.

[0026] A fourth aspect of the invention relates to an aerospace vehicle formation which comprises a primary aerospace vehicle according to the first aspect of the invention, one or more secondary aerospace vehicles according to the second aspect of the invention. In addition, the onboard computer of the primary aerospace vehicle is preferably configured to execute software, according to the third aspect of the invention, loaded into a computer hardware.

According to one embodiment of the invention, the formation of primary and secondary aerospace vehicles is a formation of aircraft or drones.According to another preferred embodiment of the invention, the formation of primary and secondary aerospace vehicles is a formation of satellites.

BRIEF DESCRIPTION OF THE DRAWINGS [0028] Other features and characteristics of the invention will become apparent from the detailed description of certain advantageous embodiments presented below, by way of illustration, with reference to the appended drawings which show:

Fig. 1: a constellation of satellites flying in formation comprising several slave satellites under the control of a master satellite;

Fig. 2: a possible structure of a master satellite and a slave satellite;

Fig. 3: a schematic representation of the different processing channels of the GNSS signal processor present on the master satellite;

Fig. 4: a graphical representation of measurements made on different satellites of the formation and the determination of the delays between each clock of the formation and the clock of the master satellite.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS OF THE INVENTION [0029] FIG. 1 shows a constellation 10 of satellites flying in formation 18. According to a preferred embodiment of the invention, this constellation 10 comprises a primary or master satellite and one or more secondary or slave satellites. In the following, and without limiting the scope of the invention, a preferred embodiment of the invention will be described wherein the constellation 10 is composed of Λ / slave satellites SE), SE2, ..., SE /, SE / v, numbered from 1 to Λ / (ού N is a positive integer, i = 1, 2, N). The master satellite SM is responsible for the management and / or supervision of the formation 18. In other words, the master satellite co-ordinates the constellation. The slave satellites SE / relay to the masterSM satellite, via a wireless communication link 22, all the raw dataconcerning them, for example, the state of health and / or operation of their components, one or more indicators of their positioning, deradionavigation signals received and digitized etc. All data are processed on the master satellite SM, which, based on these data, sends, via a wireless communication link 22, flight instructions to the slave satellites SE / of the training 18. These instructions may include, for example, instructions for the actuators of the propulsion to correct a deviation of the position of one or more satellites to the desired geometry of the formation 18. By way of example in FIG. 1, the SE / v satellite deviates from the formation 18. The constellation is said to be "autonomous", in the sense that the management is carried out and centralized by the satellite master SM and not satellite by satellite, for example, by agents in ground stations, or as described in US 2010/0032528. According to a particular embodiment of the invention, the geometry of the formation 18 is a star, the master satellite SM being in the center of the formation 18 (as shown in Fig. 1). According to a particular embodiment of the invention, the slave entities SE; are arranged around the master satellite SM on an ellipse.According to a preferred embodiment of the invention, the geometry of the formation 18 is a close formation ("cluster formation" in English). In the approached formation considered in the preferred embodiment of the invention, the distance between the satellites is typically a few kilometers.

The master satellite SM comprises a radiofrequency antenna 12 for establishing and / or maintaining a communication link 20 with a ground station 16comprenant, too, a radiofrequency antenna 14. Even if the constellation 10is autonomous, a ground station 16 can communicating with it and, in particular, sending instructions through the master satellite SM in order, for example, to change formation geometry 18. It will be appreciated that, from the point of view of the ground station 16, the constellation 10 can be managed as a unique satellite.

SE slave satellites; can be designed in such a way as to only ship the bare minimum outside the payload in order to make their design and launch as inexpensive as possible.This mass reduction also offers the advantage of increasing the chances of being able to launch these SE / slave satellites into satellite slots known as nanosatellites or microsatellites. The absence of a control center embarked in the slave satellites SE, makes it possible to have a better report chargeutile on total mass of the satellite. The control is delegated to the master satellite SM. A slave satellite SE / is thus incapable of functioning alone and even less to manage, alone, its formation flight within a constellation. It will be appreciated later that the delegation of control is advantageous for the coordination of the constellation 10. It will also be appreciated in the following that the delegation of control is advantageous to reduce the redundancy of components in the formation (for example Λ / GNSS signal processors , Λ / protection boxes for GNSS processors, etc.).

The payload as well as the other components of the slave satellites SE are determined according to the function and / or mission within the constellation 10. Lessatellites can include, for example, a telescope, cameras (IR, UV,. ..), a radar, a propulsion module specific to their needs, etc. Provided that the constellation 10 is accurately known, the payload elements, such as telescopes, can work together to achieve equivalent performance and likely to exceed that of a single satellite comprising a single large telescope (ie a satellite with a large payload). Indeed, disturbances (for example vibrations) coming from ancillary components in the payload of the single satellite (for example a very powerful propulsion necessary to maintain in orbit) can throw other components (telescopes, interferometers, ...). The constellation 10 desatellites is also much more diversified because the geometry of the formation 18 thereof can change, if necessary.

The master satellite SM can be considered as the nerve center of the formation 18. In fact, the master satellite centralizes all the data received, generated, captured, etc. 18. In particular, the SM master satellite centralizes all the GNSS 24 signals received by the training after scanning. On the basis, among other things, of these GNSS signals 24 received, the master satellite determines the navigation state of the formation 18. The navigation state comprises, among other things, the positions and the speeds of the satellites of the formation 18. The navigational state may also include the acceleration of the satellites of the formation.

[0034] FIG. 2 represents a possible structure of a master satellite SM and a slave unsatellite SE /. Each satellite of the constellation may comprise a power supply module 32 comprising, for example, solar panels, batteries, etc. Each satellite may also include an environmental control module 34 operable to facilitate or prohibit passive or active heat exchangers, a propulsion system 36, and an altitude orbit control system 38 (SCOA for Altitude and Orbital Control

System (AOCS) "comprising, for example, solar collectors, star sensors, reaction wheels, etc. According to another embodiment of the invention, the satellites of the constellation comprise only part of the components mentioned in the preferred embodiment. According to another embodiment of the invention, the components (including the payload 42) can be different satellite satellite constellation and include other or other components mentioned above.

The determination of the navigation state of the constellation is based on the reception of GNSS signals 24 emitted by transmitters of a positioning system (for example satellites of the GPS constellation, Galileo, GLONASS, etc.) and their interpretation. For this purpose, the satellites of the constellation each comprise a radio frequency antenna 26 receiving GNSS signals 24. The GNSS 24 signals received are digitized in an RF head stage 30. The slave satellites SE / transmit to the master satellite SM via a communication link 22 established by a communication system 28, the GNSSignals 24 received and digitized. The GNSS signal processor 48, present on the master satellite SM deduces the navigation state of the overbase constellation of the GNSS signals 24 received by the constellation. Alternatively, all the GNSS signals can be transferred via the radiofrequency antenna (12, see Fig. 1) from the master satellite SM to the ground station for determining the navigation state of the constellation. It should be noted that the master satellite SM can also send, via the radiofrequency antenna (12, see Fig. 1), data other than the GNSS signals 24 received for ground processing by the station. In this case, the satellite master SM acts as an aggregator of satellite constellation information.

The satellites of the constellation comprise a front end-of-frequency (RF) stage connected to the antenna 26 which receives the GNSS signals 24 in one or more frequency bands used for the transmission of the signals. , reduces the frequency of signals (normally to an intermediate frequency) and converts them to digital format through an analog-to-digital converter. The converter is preferably configured to dynamically adapt its operating parameters (such as the sampling frequency or the number of sampled frequencies) according to the available bandwidth of the communication system. According to a preferred embodiment of the invention, the RF head stage 30 reduces the central frequency of the GNSS signals 24 to an intermediate frequency (F1, "IF"). According to embodiments of the invention, the binned bit rate of the digitized GNSS signals can vary between 2 Mbits / s and 1200 Mbits / s depending, inter alia, operating parameters of the converter. The raw GNSS signals, received by a satellite SE / constellation slave and passed through the RF head stage 30, are sent to the master satellite SM via the communication system 28.

The determination of the navigation state, comprising the processing of raw GNSS signals from the slave satellites of the constellation, is, in fact, deported to the master satellite SM, on which is embedded a GNSS signal processor 48. The satellite Master SM receives all the raw GNSS signals from the constellation through the communication system 28. The GNSS signal processor 48 determines the navigation state. It comprises a baseband processing stage comprising GNSS signal acquisition / tracking channels. The baseband processing stage determines a set of GNSS observables (for example, carrier phase measurements, code measurements) through demodulation of the carrier and, inter alia, the use of the pseudo bit code. -random. The determination of GNSS observables is performed in parallel on the different channels. The number of channels of the GNSS signal processor 48 may be chosen sufficiently high to allow the processing of all the GNSS signals of the constellations simultaneously. Alternatively, the number of channels of the GNSS signal processor 48 can be chosen according to the one or more missions to be carried out by the satellites constellation. A schematic representation of the channels 44 processing of the GNSS signals is given in FIG. 3.

Downstream of the acquisition / prosecution stage is a floor called step of navigation or browser. On this floor, the observables and possibly the navigation data extracted from the GNSS signals are combined (eg in an extended Kalman filter or by a least squares method, etc.) to provide an estimate of the navigation state 46. That includes, eg, position, speed, and time, etc. of each satellite of the constellation.

The number of channels allocated to one satellite may be different from the number of channels allocated to another (for example M channels for the master satellite and pecs for the first slave satellite, see Fig. 3) according to, inter alia, the number of channels allocated to one satellite. signals picked up by the satellite in question. By way of example, 32 dual channels for GPS and Galileo navigation systems could process the GNSS signals received by the master satellite SM and each time 8 channels, for the GPS navigation system, could process the GNSS signals received by the slave satellites SE /. Channel allocation may change over time as needed. It will be appreciated that an advantage of the invention lies in the fact that a single cryptographic module for all training is sufficient to determine the navigation state of the training based on encrypted GNSS signals.

The a priori knowledge of constraints on the formation, for example on the geometry of the constellation (ie the a priori knowledge of the approximate positions of each satellite of the constellation) makes it possible to substantially increase the precision of the estimation of the navigation state. As an example, the navigation stage could implement an (extended) Kalman filter whose model supplemented by the set of constraints and / or a priori deconscessions of the constellation allows the increase of the constellation. accuracy of the results given in the browser. It will be appreciated that the determination of the navigation state of the constellation is done in a global manner, and not singly satellite satellite. According to a preferred embodiment of the invention, the position and speed of the master satellite is determined in a terrestrial orgeocentric reference frame and the positions and the speeds of the slave satellites are determined in a relative manner relative to the master satellite.

The determination of the navigation state 46 for the slave satellites of the constellation can rest (among other things) on the kinematic method in real time. The carrier signal is at a higher frequency than the code signals for determining the navigation status of the more accurate constellation. This embodiment of the invention may be particularly advantageous in case of tight formation, in which the satellites generally have the same GNSS satellites in view. Optionally, measurements with attached systems, such as telemetry measurements, can be used to increase the accuracy, for example, of the positioning of the constellation satellites.

With reference to FIG. 2 and according to an advantageous and preferred embodiment of the invention, the communication system 28 is an optical communication system comprising a laser and an optical receiver. The interest of an optical communication system is twofold. Indeed, compared to a radiofrequency communication, the optical communication makes it possible, in the first place, to avoid interference with radio frequency signals and thus to increase the electromagnetic compatibility (EMC) in the local level. the satellite constellation globally at the level of the international radio frequency spectrum management. Secondly, this communication system makes it possible to achieve high data rates for a size, weight and reduced and / or low power ("lowSize, Weight and Power "or" low SWaP "in English) compared to the radio frequency system.

The onboard computer 40 of the master satellite SM is also configured to determine flight instructions to be executed by the slave satellites SE /. These instructions are determined on the basis, among other things, of the state of navigation of the constellation. The instructions may include, for example, commands to restore compliance of the actual geometry of the formation with the desired geometry. These commands may comprise, for example, an order of operation for the actuators of a propulsion system of an ES satellite; in order to restore the conformity of the geometry of the formation. The instructions determined on the master satellite SM are sent by the master satellite to the slave satellites SE; via the communication system 28. The instructions are executed by an on-board computer 40 of the slave satellite SE /.

[0044] Preferably, the on-board computer of the master satellite SM is configured to decommission a slave satellite SE; based on, among other things, information on the health status transmitted by the slave satellite SE /. Indeed, when the SE satelliteclave; is no longer able to perform its function (for example when its propulsion 36 is faulty), it becomes unnecessary in the formation and the master satelliteaffects the satellite SE / training. The onboard processor is configured to allocate a new slave satellite SEy (/ # /) available to the formation and luidonner, for example, the position of the old defective satellite SE; in the constellation.

Preferably, each satellite of the constellation comprises an internal clock, unique and shared with each component of the satellite. All components of a satellite have access to the same clock to time stamp, for example, scientific measurements 49, data describing the health status of a component, a signal notifying a defective RF antenna, etc., and in particular the GNSS signals received and digitized 52. All the events taking place on a satellite of the formation are therefore timestamped by the onboard and unique computer. Fig. 4 shows measurements 49 of components of two satellites SE; and SEy over time by the timestamp 51 provided by their respective internal timers 50. The data transmitted to the master satellite, via the communication system 54, comprises, in the illustrated case, the scientific measures 49 and the digitized GNSS signals 52 received in parallel with the measurements 49. Preferably, the onboard computer time stamps all the data to be transmitted.

The processor of the on-board computer 40 of the master satellite SM performs synchronization of the internal clocks of all the satellites. This synchronization is possible because the digitized GNSS signals transmitted by each slave satellite make it possible to exactly determine the moment of their reception at the antennas in the GNSS time (eg in the GPS time) and therefore also the moment of their time stamp at the same time. using the internal clock. All the desatellite internal clocks are thus referenced with respect to the GNSS time (ie their biases and possibly their drifts are known with respect to a clock indicating the GNSS times). As shown in FIG. 4, the on-board computer processor 40 may optionally determine an Afy bias 56 between the internal slave satellite timer SEj of the constellation and the clock of the master satellite SM. In this case the master satellite clock SM can serve as a reference clock. Itself is also calibrated on the GNSS time. Optionally, the clock of the master satellite SM could be set to GNSS time by a servo loop. The clocks of the slave satellites could also be set to the GNSS time or be slaved to the clock of the master satellite. In this case, the clock corrections (the setting controls) would be determined by the processor of the onboard computer 40 of the master satellite SM and transmitted to the slave satellites via the communication means. When all the clocks are synchronized (ie when all the biases of the clocks 50 are determined), all the measurements49 and events recorded by the formation (on any satellite thereof) are dated (or at least datable). ) in a single time reference (the GNSS time and / or the time indicated by the reference clock).

While particular embodiments have just been described in detail, those skilled in the art will appreciate that various modifications and alternatives to them can be developed in light of the overall teaching provided by the present disclosure of the invention. . Therefore, the specific arrangements and / or processes described herein are intended to be given solely for the purpose of illustration, without intention to limit the scope of the invention.

Claims (6)

claims 1. A primary aerospace vehicle (SM), capable of communicating with one or more secondary aerospace vehicles (SEi, SE2, ..., SE /, ..., SE / v) of an aerospace vehicle formation (10), comprising an antenna (12) configured to receive GNSS signals (24); a digitizer (30) configured to digitize the GNSS signals received by said antenna; a communication system (28) configured to receive data comprising GNSS signals (24) digitized by one or more secondary aerospace vehicles (SE ?, SE2, ..., SE /, ..., SE / v) and to transmit data including flight instructions for one or more secondary aerospace vehicles; an on-board GNSS signal processor (48) configured to determine a navigation state of said formation based on digitized GNSS signals from the digitizer as well as those from, via the communication system, one or more aerospace vehicles of said formation; and an on-board computer (40) configured to determine the flight instructions to be executed by the one or more secondary aerospace vehicles (SEi, SE2, SE /, ..., SE / v), the flight instructions being determined on the basis of the state of navigation. 2. The primary aerospace vehicle (SM) according to claim 1, wherein the determination of the navigation state of the formation is done using constraints known on the formation (10). The primary aerospace vehicle (SM) according to any one of claims 1 and 2, configured to determine the navigation state by the kinematic method in real time with a mobile base. The primary aerospace vehicle (SM) according to any one of claims 1 to 3, wherein said communication system (28) is an optical communication system comprising a laser for transmitting data including flight instructions to one or more secondary aerospace vehicles. and an optical receiver for receiving data comprising digitized GNSS signals from one or more secondary aerospace vehicles (SEi, SE2, ..., SE /, ..., SEn). The primary aerospace vehicle (SM) according to any one of claims 1 to 4, comprising an on-board computer (40) configured to communicate with the one or more secondary aerospace vehicles (SEi, SE2) to a communication system (28). , ..., SE /, SE / v) of said formation to decoordinate said formation on the basis, inter alia, of said state of navigation of the formation. The primary aerospace vehicle (SM) according to claim 5, wherein the onboard computer (40) is configured to decommission a secondary aerospace vehicle (SEy, SE2, .... SE /, ..., SE / v). of said formation or affect an aerospace vehicle secondary to said formation. The primary aerospace vehicle (SM) according to any one of claims 1 to 6, comprising a single internal clock (50) and wherein the board computer (40) or the onboard GNSS signal processor (48) are configured separately. determining a bias between a clock of an aerospace vehicle of said information and a reference clock, the reference clock beingpreferably the clock of the primary aerospace vehicle. 8. A secondary aerospace vehicle (SE1, SE2, ..., SE /, ..., SE / v), adapted to communicate with a primary aerospace vehicle (SM), according to any one of claims 1 to 7, of aerospace vehicle training (10), comprising an antenna (26) configured to receive GNSS signals (24); a digitizer configured to digitize the GNSS signals received by said antenna; a communication system (28) configured to transmit data comprising digitized GNSS signals to the primary aerospace vehicle (SM) and to receive data including primary air vehicle (SM) flight instructions. 9. The secondary aerospace vehicle (SE 2, SE 2,..., SE /,..., SE / v) according to claim 8, wherein said communication system (28) is an optical communication system comprising a laser for transmitting data comprising GNSS signals and an optical receiver for receiving data including flight instructions of the primary aerospace vehicle (SM). The secondary aerospace vehicle (SE 2, SE 2,..., SE /, ..., SE / v) according to any one of claims 8 and 9, comprising an on-board computer (40) and a clock single internal circuit (50), the on-board computer (40) being configured to timestamp, by means of the clock (50), the data to be transmitted. An aerospace vehicle formation (10) characterized in that it comprises a primary aerospace vehicle (SM) according to any one of claims 1 to 7; and one or more secondary aerospace vehicles (SEy, SE2, ..., SE /, ..., SE / v) according to any of claims 8 to 10. 12. The formation of aerospace vehicles (10) according to claim 11, in which the primary (SM) and secondary (SEv, SE2, ..., SE /, ..., SE / v) aerospace vehicles are aircraft or UAVs. The formation of aerospace vehicles (10) according to claim 11, wherein the primary (SM) and secondary aerospace (SE ?, SE2, ..., SE / ..... SE / v) vehicles are satellites .