Device and method for precisely pointing a decoy source.

Abstract

TITLE: Device and method for very precise pointing of a decoy source. Device for very precise pointing of a decoy source comprising one or more galaxies of geolocation satellites regularly emitting, for each satellite, a wave train, three GNSS antennas arranged more than one meter apart, said antennas forming a planar triangle, the three heights of said triangle each having a length greater than one meter, said three antennas being positioned on the aircraft in such a way that they receive the signals emitted by the geolocation satellites, a means of comparing, for each selected satellite and at each instant, the time difference values ​​allowing to determine, if these time difference values ​​are respectively substantially equal to a predetermined value, greater than a few tens of nanoseconds,and in this case to determine that the signals sent by this satellite are not spoofed, and that otherwise the signals sent by this satellite are spoofed, a calculation method allowing precise targeting of the spoofing satellite, in the case where the method has determined that the selected satellite is spoofed, by constructing a trihedron with the antennas as its base and a point as its vertex indicating the direction of the spoofing satellite. Figure for the abbreviation: Figure 1,

Description

Title of the invention: Device and method for precisely pointing a decoy source.

[0001] The present invention relates mainly to a device and a method of precise pinpointing of a source of decoy.

[0002] It also relates to a GNSS anti-spoofing device and method for aircraft.

[0003] It also relates to an autonomous GNSS anti-spoofing device and method for aircraft.

[0004] It also relates to a device and a method for navigation and piloting for vehicles.

[0005] It also relates to a GNSS anti-spoofing device and method for ground stations.

[0006] It relates mainly to a device and a method for piloting and navigating manned aircraft or drones or missiles.

[0007] It uses the absolute position with metric precision of at least three points of a mobile or a fixed station, relative to a fixed terrestrial reference frame and the very precise relative position with centimetric precision of the same points of said mobile, these said points being separated by a distance equal to several times the wavelength of the waves transmitted by the geolocation satellites.

[0008] It also relates to the real-time detection of a malicious attack modifying information sent from the ground or by one or more geolocation satellites.

[0009] It mainly concerns the real-time detection of a possible failure of one or more geolocation satellites.

[0010] Today, "GPS" (Global Positioning System) or "GNSS" (Global Navigation Satellite System) information is increasingly used. Indeed, the information provided by these systems is very precise and inexpensive.

[0011] For example, information from gyroscopic systems is regularly corrected by GNSS information. Indeed, all gyroscopic systems drift over time, which is not the case for GNSS information. GNSS information is already integrated into vital navigation systems, notably to correct the drift of gyroscopic systems.

[0012] In a few years, several other constellations will significantly increase the number of available geolocation satellites. Currently, about sixty satellites are available, whereas in five years it is likely that there will be 150 satellites. Geolocation data will be available. Accuracy and reliability will certainly be increased.

[0013] Satellite failures can easily be taken into account. Indeed, only four or five satellites are needed to obtain accurate information.

[0014] However, the use of GNSS data in vital aeronautical systems cannot be accepted today because the threat of malicious modification of GNSS information, although difficult, cannot be excluded.

[0015] Indeed, it is not impossible to conceive of the emission of malicious signals that would be slightly different from the original signals and that would have the effect of diverting the aircraft from its desired trajectory by correcting the gyroscopic information. Such a threat is very detrimental, particularly for civil aviation, but also for military aviation.

[0016] One of the main goals of this present patent is to define a very precise, simple, inexpensive, reliable, real-time and autonomous means of ensuring 100% authenticity of received GNSS signals.

[0017] Numerous systems have been proposed to try to overcome this problem:

[0018] It has been proposed to encrypt the GNSS signals emitted by the satellites so that no one can send signals of the same nature that would lead the mobile device astray. Unfortunately, this implies having control over and encrypting the signals emitted by the satellites. The cost of such a system is enormous and cannot be considered for civilian applications and is hardly conceivable for military applications. On the other hand, the possibility that a foreign power could decrypt and re-encrypt the messages sent cannot be ruled out.

[0019] It has been proposed to note the reception power of the received data in order to ensure that the signal comes from the intended satellite and not from a malicious source. Unfortunately, this criterion is not sufficiently conclusive to definitively characterize a malicious signal.

[0020] It has been proposed to use several constellations to verify the validity of the signals. Unfortunately, it is conceivable that a malicious foreign power could manage to alter the signals of several constellations.

[0021] The following publications also form part of the prior art:

[0022] From publication KR 2012 0025 027, a device comprising at least one DGPS is known for determining the location of a vessel and for accurately determining the values ​​of the location and movement of a vessel, in particular, the pitch and roll angles of said vessel. However, the GPS antennas of said device are not coordinated with each other.

[0023] From US publication 6,002,362, a position measurement and control system for a mobile device such as a truck is known, comprising at least one A GPS antenna capable of receiving a GPS signal and a relatively stationary GPS receiver, installed in a position where its geometric coordinates are precisely known. Unfortunately, the system is a DGPS and can therefore be excluded from the prior art of the relevant technical field.

[0024] US patents 2002 / 029110, US 4,990,922, US 2009 / 164067 and W0 98 / 29757 form part of the technological background. They describe other combinations of certain features of claim 1, but none of these documents describes all the features of claim 1 of the present invention.

[0025] Patent WO2017203108 describes a device comprising four GNSS antennas located on an aircraft. This patent neither describes nor even suggests using the position of the four antennas to calculate the position of geolocation satellites and to compare this calculated position with the actual position of these satellites obtained by other means, and thus to deduce whether the received GNSS signals are authentic or not.

[0026] There are also systems comprising two antennas spaced a few centimeters apart (approximately 18 centimeters), corresponding to the wavelength of the wave emitted by the decoy transmitter. The phase difference of the received signals makes it possible to define the plane in which the decoy transmitter is located. It is thus possible to determine whether the transmitter is a decoy transmitter or not. This system has the major drawback of requiring two antennas to be placed close together on the structure and separated by a distance equal to the wavelength of the received signal. The necessary proximity of the two antennas leads to a particularly imprecise direction for determining the plane where the decoy transmitter is located. Indeed, in this case, if the antennas are separated by more than one wavelength, the phase difference is no longer characteristic of the position of a potential decoy satellite.

[0027] These documents neither describe nor suggest the device or method presented in the claims of this patent of invention. These documents neither describe nor even suggest obtaining, at any given time, from the calculated actual position of each satellite and from the absolute and relative positions of the three GNSS antennas, and from the differential reception time of the same signal on each of the antennas, and by placing the antennas at a large distance from each other (a distance greater than one meter, corresponding to several times the wavelength, equal to approximately 18 centimeters), from the actual position of each satellite used, nor from the comparison of this calculated position with the actual position of each satellite.

[0028] Consequently, the invention can be considered as non-obviously attacking the assurance at every instant that the signals obtained are indeed valid signals and not emitted by a malicious source if the existing direction between the measured direction of each selected satellite and the actual direction of each satellite is below a predetermined value and to determine very precisely the direction of the decoy satellite.

[0029] It should be noted that vital piloting systems do not inherently possess the ability to verify the results they provide, as is the case, for example, with anemometer and gyroscopic systems. For this reason, two redundant elements are insufficient to ensure safety in the event of a failure of one element. It is necessary to use three identical elements to verify the failed element and those that are functioning.

[0030] Having a system with its own means of verifying proper functioning is a significant advantage in terms of mass, volume and price, because it only needs to be redundant twice instead of three times.

[0031] The main objective of the present invention is therefore to provide, at any given moment, 100% reliable, highly accurate, autonomous, and inexpensive information on the authenticity of received GNSS signals by comparing the actual direction of each satellite used with the measured direction of the same satellites obtained from the difference in reception times (accurate to within a few tens of nanoseconds) of the signals on the three antennas. This method efficiently uses the difference in reception times of the signals received on three antennas to deduce the direction of the transmitter relative to the reference frame of the three antennas and to verify whether this direction corresponds to the actual position of the selected satellite, which can be determined from the publicly available satellite ephemerides.

[0032] In the following description, the terms listed below shall have the following definitions:

[0033] Reference frame: A system of coordinates allowing a solid to be located in space and time. It ideally consists of a trihedron or spatial reference frame, and a clock or temporal reference frame.

[0034] Predefined reference frame: Ideally defined, precisely known reference system.

[0035] One-to-one correspondence: a relationship where one element of one set corresponds to one and only one element of the other set. For example, for an x ​​in one set, there corresponds to one and only one y in the other set, and vice versa.

[0036] Metric absolute position of a point of an aircraft relative to a fixed reference frame: precise three-dimensional positioning of said point to within one or a few meters.

[0037] Centimeter relative position of a point of an aircraft: three-dimensional relative positioning of a point of the aircraft with respect to another point of the aircraft and / or three-dimensional positioning in a fixed frame linked to the aircraft, these positionings being known to within one or a few centimeters.

[0038] Two planes are said to be substantially perpendicular if they are perpendicular to within five degrees.

[0039] “GPS”: called in English “Global Positioning System”: global system of Satellite positioning. We will use this term to encompass other existing or developing satellite positioning systems:

[0040] “GLONASS”: Soviet-origin satellite positioning system

[0041] “GALILEO”: satellite positioning system developed by the Union European.

[0042] “BEIDOU” also known as “COMPAS$” is a navigation system and Chinese satellite positioning system currently being deployed, which is now fully operational.

[0043] “GNSS signals”: ​​geolocation signals encompassing the “GPS” system and the other satellite geolocation systems.

[0044] “GNSS antennas”: antennas capable of receiving GNSS geolocation signals

[0045] “Airspeed”: speed of the aircraft relative to the air mass surrounding speed usually expressed in knots or Mach number.

[0046] “Pressure altitude”: altitude relative to sea level calculated from a value of static pressures.

[0047] “Aneometric incidence”: angle of incidence of the aircraft with respect to the mass of surrounding air, usually expressed in degrees, also called angle of attack or incidence, generally obtained from an incidence probe.

[0048] “Air-speed vertical speed”: vertical speed of the aircraft relative to the surrounding air mass, generally expressed in feet per minute and obtained from variations in static pressure,

[0049] “anemometric slip”: slip angle relative to the air mass surrounding, generally expressed in degrees, and obtained from a skid probe or left / right static pressure differences or using a woolen thread on gliders.

[0050] “Winglet”: wingtip continuing the wing upwards and / or downwards.

[0051] “Wing tip”: part of the wing located in the outer half of the wing. For example, if a wing has a wingspan of 30 meters relative to the aircraft's plane of symmetry, the wingtip is located between 15 and 30 meters from the aircraft's plane of symmetry.

[0052] “Sharlets”: wingtip structure improving aerodynamic performance of the sail.

[0053] “Pseudo-distance”: this is the distance calculated between two points based on time measured the time it takes for an electromagnetic wave to reach these two points by estimating the speed of this electromagnetic wave traveling through the medium considered.

[0054] “Two line segments” are said to be substantially perpendicular if the angle formed The distance between these two segments is equal to 90 degrees plus or minus 5 degrees.

[0055] “Position” a position is defined by three coordinates measured on a reference frame terrestrial.

[0056] "Precise relative position of two or three antennas" these are relative positions precise known to better than one meter.

[0057] “Approximate absolute position” is an absolute position known to better than 10 to the nearest meter.

[0058] “Angular coordinates” in geometry the angular coordinates of a point (P) denoted (TETAI : TETA2 : TET A3) with respect to a given triangle, are, up to an additive constant, the oriented angles they form with the vertices of a triangle. For a triangle A1, A2, A3, angle O1 is the oriented angle, and so on by permutation on A1, A2, A3. These angles, and those formed by addition, are considered modulo θ.

[0059] “Units used”: in this document we will preferably use the system measurement units as follows: distances in meters, time in seconds, speeds in meters per second.

[0060] “Precise date”: precise date to within a few microseconds.

[0061] “very precise date”: precise date to within a few nanoseconds.

[0062] “precise relative position”: precise relative position to within a few centimeters.

[0063] “approximate absolute position” precise absolute position to within a few tens of to the nearest meter.

[0064] It is important to note that the dimensions of a mobile device are small compared to the distances between the satellites and the mobile device. For example, the wingspan of a large passenger aircraft is on the order of 80 meters and the fuselage length is approximately 70 meters (for the Airbus A380, for example), while the distance between the satellites and the mobile device is on the order of 20,000 kilometers. The ratio between the distance separating the antennas of an aircraft and the distance between the aircraft's antennas and the satellites is 20,000,000 / 80, or 250,000, which is very significant. Furthermore, the errors in measuring the time of flight of electromagnetic waves are mainly due to atmospheric phenomena. Electromagnetic rays emanating from a satellite and arriving at several points on the mobile device are subject to the same perturbations.Consequently, relative position measurements between two points on a moving object are very precise insofar as the antennas are "coordinated". The accuracy of relative coordinates between two points on a moving object is estimated to be one or a few centimeters, although the absolute accuracy of coordinate measurements is several meters.

[0065] It should be noted that, in space, two points can be connected by a single straight segment, three points can be connected by three straight segments and four points can be connected by six straight segments.

[0066] It is very important for security reasons, on the one hand, to know if one or more geolocation satellites are being deceived, and on the other hand, to be able to know the direction in which this deceiving satellite or these deceiving satellites are located in order to eliminate the source of deceiving, or in order to eliminate the signals coming from this direction.

[0067] Brief description of the drawing:

[0068] Figure 1 is a schematic representation, indicated by crosses, of a galaxy of several geolocation satellites, including the selected satellite (SS), three GNSS antennas (A1), (A2), and (A3), and the time difference (DELTA2-1) of the paths joining the satellite (SS) with antenna (A2) and the path joining the satellite (SS) with antenna (A1). Also shown are the decoy satellite (SL) and the time difference (DIFF2-1) of the paths joining the satellite (SL) with antenna (A2) and the path joining the satellite (SS) with antenna (A1).

[0069] The invention solves the technical problems stated above by proposing a very precise pointing device for an aircraft decoy source comprising:

[0070] one or more geolocation satellite galaxies regularly emitting, for each satellite, a wave train indicating at least the name of the satellite, the position of the satellite at the time of sending this wave train, and the very precise date, to within a few tens of nanoseconds, of the moment of sending this wave train,

[0071] three GNSS antennas (A1), (A2), and (A3) arranged more than one meter apart, said antennas forming a planar triangle, the three heights of said triangle each having a length greater than one meter, said three antennas being positioned on the aircraft in such a way that they receive the signals emitted by the geolocation satellites,

[0072] three receiving and analyzing units (B1), (B2) and (B3) for signals emitted by the geolocation satellites and received by the three antennas (A1), (A2) and (A3), said units being connected respectively to each of the antennas by a wired, radio or optical link,

[0073] a calculation means (Ml) determining the precise actual position of each selected satellite at each instant relative to a terrestrial reference frame,

[0074] a means of determining (M2), at each instant, the precise actual relative position of the three antennas (A1), (A2), and (A3) with respect to a terrestrial reference frame and the approximate absolute position, with respect to a terrestrial reference frame, of at least one antenna chosen from among the three antennas (A1), (A2), or (A3),

[0075] a calculation means (M3) for determining, at each instant, the difference in travel times (DIFF2-1), (DIFF3-2), and (DIFF1-3) of an electromagnetic wave between the selected satellite and, respectively, the antennas (A1), (A2), and (A3), based on the actual position of the selected satellite and the position The actual value of each antenna obtained by the determination method (M2), divided by a predefined value of the speed of light (c) chosen between 280000000 m / s and 310000000 m / s such that (DIFF2-1) is equal to the value of the distance (D2) separating antenna A2 from the selected satellite divided by the speed of light (c) minus the distance (Dl) separating antenna (A1) from the selected satellite divided by the speed of light (c), i.e., (DIFF2-1) = ((D2) - (Dl)) / (c), and (DIFF3-2) is equal to the value of the distance (D3) separating antenna A3 from the selected satellite divided by the speed of light (c) minus the distance (D2) separating antenna (A2) from the selected satellite divided by the speed of light (c), i.e. (DIFF3-2)=((D3)-(D2)) / (c),and (DIFF1-3) is equal to the value of the distance (Dl) separating the antenna A1 from the selected satellite divided by the speed of light (c) minus the distance (D3) separating the antenna (A3) from the selected satellite divided by the speed of light (c), i.e. (DIFF1-3)=((Dl)-(D3)) / (c), ,

[0076] a computing center connected to the three receiving and analysis units by three wired, radio or optical links, calculating at each instant for each selected satellite the very precise difference (DELTA2-1), (DELTA3-2), and (DELTA1-3) of the reception date by the three antennas of the wave train relating to that satellite, the difference (DELTA2-1) being equal to the difference between the reception date of the wave train on antenna (A2) and the reception date on antenna (A1), of the wave train relating to the selected satellite, the difference (DELTA3-2) being equal to the difference between the reception date of the wave train on antenna (A3) and the reception date on antenna (A2), of the wave train relating to the selected satellite, the difference (DELTA1-3) being equal to the difference between the reception date of the wave train on antenna (A1) and the reception date on antenna (A3), of the wave train relative to the selected satellite,

[0077] a comparison means (M4), for each selected satellite and at each instant, of the time difference values ​​(DIFF2-1) and (DELTA2-1), (DIFF3-2) and (DELTA3-2), as well as (DIFF1-3) and (DELTA1-3) respectively, making it possible to determine whether these time difference values ​​are respectively substantially equal to a predetermined value, greater than a few tens of nanoseconds, and in this case to determine that the signals sent by this satellite are not spoofed, and that otherwise the signals sent by this satellite are spoofed,

[0078] a computing means (M5) allowing precise pointing towards the decoy satellite, in the case where the means (M4) has determined that the selected satellite is decoyed, by constructing a trihedron (A1,A2,A3,P) having as its base the antennas (A1), (A2), and (A3) and as its vertex (P) designating the direction of the decoy satellite, and such that the difference in length (A2P)-(A1P) is equal to (DELTA2-1) multiplied by (c), that the the difference in length (A3P)-(A2P) is equal to (DELTA3-2) multiplied by (c), and the difference in length (A1P)-(A3P) is equal to (DELTA1-3) multiplied by (c).

[0079] It is advantageous that the means (M5) calculates the position of the point (P) by considering that the point (P) is the point of intersection of three spheres having respectively as counter antennas (Al), (A2), and (A3), and as radii (RI), (R2), and (R3), taking a fixed value DI for example equal to 10000 meters, and such that (R1)=D1, (R2)=D1+(DELTA2-1) x (c), and (R3)=D1+(DELTA2-1) x (c) +(DELTAl-3) x (c).

[0080] It is advantageous that the means (Ml) calculates the precise position of the selected geolocation satellites from a database defining at each instant the precise coordinates of the geolocation satellites, this database being regularly updated, or calculated from regularly updated algorithms.

[0081] It is advantageous that the time differences (DIFF2-1), (DIFF3-2), and (DIFF1-3), (DELTA2-1), (DELTA3-2), and (DELTA3-1) be expressed as a number of periods of the wave received by the antennas.

[0082] It is advantageous for the antennas to be placed on a structure fixed relative to the earth's surface.

[0083] It is advantageous for the antennas to be placed on the roof of a building in order to check that no decoy is in operation in the vicinity and that if this is the case, the direction of this decoy can be known precisely.

[0084] It is advantageous to propose a method for precisely targeting a decoy source using the device described above and comprising the following steps taken in this order or in a different order:

[0085] Step 1: Definition of the selected satellites,

[0086] Step 2: Verification that the coordinates of each selected satellite provided by the received wave train correspond to the coordinates calculated by the means (Ml),

[0087] Step 3: Verification whether the satellite is being deceived or not by means of M4,

[0088] Step 4: In the case where the selected satellite sends spoofed signals, we calculate the direction of the decoy satellite by means of (M5).

[0089] It is advantageous to propose a method for very precise pointing of a decoy source using the device described above, such that the point (P) is defined as follows:

[0090] a predefined distance (Dl) greater than ten meters is chosen, for example ten kilometers,

[0091] From the real coordinates of the antennas (Al), (A2), and (A3), we define the coordinates of the intersection (P) of the three circles having center respectively (Al), (A2), and (A3) and radius respectively (RI), (R2), (R3) with (R1)=D1, (R2)=D1+(DELTA2-1) x (c), and (R3)=D1+(DELTA2-1) x (c) +(DELTAl-3) x (c), the point P designating the direction of the decoy satellite.

[0092] Other features and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference should be made to the accompanying drawing in which:

[0093] A preferred embodiment is described below. This description uses [Fig. 1].

[0094] In this embodiment, three GNSS antennas (A1), (A2), and (A3) are mounted on the upper part of an aircraft. These three antennas receive GNSS signals sent by several constellations of geolocation satellites. At any given time, a satellite is selected. Figure 1 shows the selected satellite (SS). This satellite, in normal operation, sends a wave train including at least the satellite's name, its position, and the precise date of transmission. Antennas (A1), (A2), and (A3) receive the signals emitted by this satellite, which are transmitted respectively to three receivers that analyze these signals and record the date of reception of these signals on each antenna. These receivers communicate this information to a central computer, which calculates the difference in the reception dates of the signals received from this satellite (SS) for the three pairs of antennas.An independent system, in this example a gyroscopic system, allows for the precise determination of the three antennas' positions in space. A regularly updated database provides the position of the selected satellite at any given time. An onboard computer calculates the actual distances between the selected satellite and the three antennas at all times, using the actual coordinates of the selected satellite and the gyroscopic coordinates of the three antennas, and assuming a speed of light value of, for example, 2.99700000 m / s. The true time differences (DIFF2-1), (DIFF3-2), and (DIFF1-3) of the distances connecting the selected satellite to the three antennas (A1), (A2), and (A3), respectively, can then be determined. Furthermore, the central computer analyzes the time difference in the reception times of the signals on the three antennas (DELTA2-1), (DELTA3-2), and (DELTA1-3).If the time difference between (DIFF2-1) and (DELTA2-1), as well as the time difference between (DIFF3-2) and (DELTA3-2), and the time difference between (DIFF1-3) and (DELTA1-3), is close to zero within a tolerance chosen here as 40 nanoseconds, we can say that the SS satellite is not being spoofed. However, if at least one of the time differences between (DIFF2-1) and (DELTA2-1), as well as the time difference between (DIFF3-2) and (DELTA3-2), and the time difference between (DIFF1-3) and (DELTA1-3), is not close to zero within a tolerance chosen here as 40 nanoseconds, we can deduce that the signals do not originate from the SS satellite but from the SL satellite, which is a spoofing satellite. We can then solve the system of equations with three unknowns to find the coordinate of a point P indicating the direction of the decoy satellite relative to the antennas, taking as coordinates the centers of the spheres respectively. The three antennas (Al), (A2), and (A3) and the radii are the values ​​(RI), (R2), and (R3) calculated as follows: a predefined distance (Dl) greater than ten meters is chosen, for example ten kilometers. From the actual coordinates of the antennas (Al), (A2), and (A3), the coordinates of the intersection (P) of the three circles centered at (Al), (A2), and (A3) respectively, and with radii (RI), (R2), (R3) respectively, are defined, with (R1)=D1, (R2)=D1+(DELTA2-1) x (c), (R3)=D1+(DELTA2-1) x (c) +(DELTAl-3) x (c), the point (P) designating the direction of the decoy satellite relative to the antennas.

[0095] The use of existing components allows for rapid development and qualification / certification.

[0096] The device and method according to the invention are by no means limited to the embodiments described and illustrated, but those skilled in the art will be able to make any variation in accordance with their intent. For example, application on a helicopter, a ship, a land vehicle, or a drone is entirely conceivable. Furthermore, three antennas fixed to a building make it possible to secure a block of buildings deemed sensitive during, for example, major sporting events.

Claims

1. Demands A highly accurate aircraft decoy source pointing device characterized in that it comprises: one or more geolocation satellite galaxies regularly transmitting, for each satellite, a wave train indicating at least the name of the satellite, the position of the satellite at the time of transmission of this wave train, and the very precise date to within a few tens of nanoseconds of the time of transmission of this wave train; three GNSS antennas (A1), (A2), and (A3) arranged more than one meter apart, these antennas forming a planar triangle, the three heights of this triangle each having a length greater than one meter; these three antennas being positioned on the aircraft in such a way that they receive the signals emitted by the geolocation satellites. three receiving and analyzing units (B1), (B2) and (B3) for signals emitted by the geolocation satellites and received by the three antennas (A1), (A2) and (A3), these units being connected respectively to each of the antennas by a wired, radio or optical link, a calculation method (Ml) determining the precise actual position of each selected satellite at each instant relative to a terrestrial reference frame, a means of determining (M2), at each instant, the precise actual relative position of the three antennas (Al), (A2), and (A3) with respect to a terrestrial reference frame and the approximate absolute position, with respect to a terrestrial reference frame, of at least one antenna chosen from among the three antennas (Al), (A2), or (A3), A calculation means (M3) for determining, at each instant, the difference in travel times (DIFF2-1), (DIFF3-2), and (DIFF1-3) of an electromagnetic wave between the selected satellite and, respectively, the antennas (A1), (A2), and (A3), based on the actual position of the selected satellite and the actual position of each antenna obtained by the determination means (M2), divided by a predefined value of the speed of light (c) chosen between 280,000,000 m / s and 310,000,000 m / s such that (DIFF2-1) is equal to the value of the distance (D2) separating antenna A2 from the selected satellite divided by the speed of light (c) minus The distance (Dl) separating antenna (A1) from the selected satellite divided by the speed of light (c), i.e., (DIFF2-1) = ((D2) - (D1)) / (c), (DIFF3-2) is equal to the value of the distance (D3) separating antenna A3 from the selected satellite divided by the speed of light (c) minus the distance (D2) separating antenna (A2) from the selected satellite divided by the speed of light (c), i.e., (DIFF3-2) = ((D3) - (D2)) / (c), and (DIFF1-3) is equal to the value of the distance (Dl) separating antenna A1 from the selected satellite divided by the speed of light (c) minus the distance (D3) separating antenna (A3) from the selected satellite divided by the speed of light (c), i.e. (DIFFl-3)=((Dl)-(D3)) / (c), A computing center connected to the three receiving and analysis units by three wired, radio, or optical links calculates at every instant, for each selected satellite, the very precise difference (DELTA2-1), (DELTA3-2), and (DELTA1-3) of the reception date by the three antennas of the wave train relating to that satellite. The difference (DELTA2-1) is equal to the difference between the reception date of the wave train on antenna (A2) and the reception date on antenna (A1) of the wave train relating to the selected satellite. The difference (DELTA3-2) is equal to the difference between the reception date of the wave train on antenna (A3) and the reception date on antenna (A2) of the wave train relating to the selected satellite. The difference (DELTA1-3) is equal to the difference between the reception date of the wave train on antenna (A1) and the reception date on antenna (A3). wave train relative to the selected satellite, a means of comparison (M4),for each selected satellite and at each instant, time difference values ​​(DIFF2-1) and (DELTA2-1), (DIFF3-2) and (DELTA3-2), as well as (DIFF1-3) and (DELTA 1-3) respectively, allowing to determine, if these time difference values ​​are respectively substantially equal to a predetermined value, greater than a few tens of nanoseconds, and in this case to determine that the signals sent by this satellite are not spoofed, and that otherwise the signals sent by this satellite are spoofed, a computing means (M5) allowing to point precisely towards the spoofing satellite, in the case where the means (M4) has determined that the selected satellite is spoofed, by constructing a trihedron (A1,A2,A3,P) having as its base the antennas (A1), (A2), and (A3) and, as vertex (P) designating the direction of the decoy satellite, and such that the difference in length (A2P)-(A1P) is equal to (DELTA2-1) multiplied by (c), (A3P)-(A2P) is equal to (DELTA3-2) multiplied by (c), and (A1P)-(A3P) is equal to (DELTA1-3) multiplied by (c).

2. A very precise pointing device for a decoy source according to claim 1, characterized in that the means (M5) calculates the position of the point (P) by considering that the point (P) is the point of intersection of three spheres having respectively as centers the antennas (A1), (A2), and (A3), and as radii (R1), (R2), and (R3) respectively, taking a fixed value DI for example equal to 10000 meters, and such that (R1)=D1, (R2)=D1+(DELTA2-1) x (c), and (R3)=D1+(DELTA2-1) x (c) +(DELTA1-3) x (c)

3. A very precise pointing device for a decoy source according to one of the preceding claims, characterized in that the means (M1) calculates the precise position of the selected geolocation satellites from a database defining at each instant the precise coordinates of the geolocation satellites, this database being regularly updated, or calculated from regularly updated algorithms.

4. Accurate pointing device for a decoy source according to any one of the preceding claims, characterized in that the time differences (DIFF2-1), (DIFF3-2), and (DIFF1-3), (DELTA2-1), (DELTA3-2), and (DELTA3-1) are quantified in number of periods of the wave received by the antennas.

5. A device for very precise pointing of a decoy source according to any one of the preceding claims, characterized in that the antennas are placed on a structure fixed relative to the Earth's surface.

6. A device for very precise pointing of a decoy source according to one of the preceding claims, characterized in that the antennas are placed on the roof of a building in order to verify that no decoy is in operation in the vicinity and that if this is the case, the direction of this decoy can be known with precision.

7. A method for very precise pointing of a decoy source using the device described in the preceding claims and comprising the following steps taken in this order or in a different order: step 1: definition of the selected satellites, Step 2: Verification that the coordinates of each selected satellite provided by the received wave train correspond to the coordinates calculated by means (M1), Step 3: Verification whether the satellite is being spoofed or not by means M4, Step 4: In the case where the selected satellite sends spoofed signals, the direction of the spoofing satellite is calculated by means (M5)

8. A method for very precise pointing of a decoy source using the device described in claims 1 to 6, and according to the preceding claim characterized in that the point (P) is defined as follows: a predefined distance (Dl) greater than ten meters, for example ten kilometers, is chosen from the actual coordinates of the antennas (Al), (A2), and (A3), the coordinates of the intersection (P) of the three circles having center (Al), (A2), and (A3) respectively and radii (RI), (R2), (R3) respectively are defined with (R1)=D1, (R2)=D1+(DELTA2-1) x (c), and (R3)=D1+(DELTA2-1) x (c) +(DELTAl-3) x (c), the point P designating the direction of the decoy satellite.

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