Method and device for referencing an artificial satellite in a star ephemeris in order to detect GNSS spoofing

Abstract

The invention relates to a method (PREF) for referencing at least one artificial satellite (SAT) in a star catalogue (CTG) comprising the step of positioning at least one star projected onto a celestial sphere (SC). It comprises: - a step (E10) of obtaining the co-ordinates (Oqd, Â) of an observation location of the at least one artificial satellite (SAT) and the orbital parameters (TLE) of the at least one artificial satellite (SAT); - a step (E50) of projecting the satellite (SAT) onto the celestial sphere (SC) in a viewing direction determined from the orbital parameters (TLE) and the observation location; - a step (E80) of recording, in the catalogue (CTG), the co-ordinates of the satellite (SAT) projected onto the celestial sphere (CS), wherein the co-ordinates of the stars and the at least one artificial satellite (SAT) are expressed in the same geocentric reference frame, referred to as the star catalogue reference frame.

Description

[0001]Description Title of the invention: Method and device for referencing an artificial satellite in a star ephemeris for detecting GNSS spoofing. The present invention relates to a method and device for detecting GNSS (Global Navigation Satellite System) spoofing, such systems making it possible to determine in particular the position and speed of objects equipped with GNSS receivers using signals emitted by satellites orbiting the Earth. The invention can in particular be used to detect spoofing, namely an attack aimed at deceiving such a positioning system by sending falsified signals to a receiver.There are currently decoy detection systems that exploit a star ephemeris to detect the presence of falsified GNSS signals, for example by comparing the received GNSS signals with the expected positions of these stars, as calculated from the star ephemeris. A decoy device can for example be detected if the received signals do not correspond to the expected positions. Unfortunately, star finders or other observation devices used to observe stars have optronic performances, generally limited by the technology of the detector used (CMOS), which only allow the observation of the brightest stars, for example of magnitude less than 4. Consequently, current detection systems can only exploit a limited number of stars which negatively impacts the availability and accuracy of their measurements.The invention relates to a method for improving decoy detection, or more generally for improving the detection of a malfunction of a global positioning system. Purpose and summary of the invention Figure 1 shows geocentric or topocentric reference frames known to those skilled in the art of star or satellite observation and which will be used in certain embodiments of the invention. The International Terrestrial Reference Frame [ITRF] is a reference frame linked to Earth, identical to the [WGS84] reference frame to within a few centimeters. The [WGS84] reference frame is created from coordinates of a large number of measurement stations, in a similar manner to the [ICRF] reference frame but in a reference frame linked to Earth. This terrestrial reference frame is used to define the longitude and geographic latitude, used in GPS. Its origin is placed at the center of mass of the Earth.Its xITRF axis is oriented along the reference meridian of the International Earth Rotation and Reference Systems Service (IERS), a meridian almost equivalent to the Greenwich meridian to within 5.3 arcseconds. Its zITRF axis is collinear with the axis of revolution of the ellipsoid. The yITRF axis is defined to define a direct orthonormal reference frame. The Terrestrial Intermediate Reference System (TIRS) or Pseudo-Earth Fixed (PEF) reference frame is defined at date t by the equator of the Celestial Intermediate Pole (CIP), i.e. the true celestial pole, and an origin for longitude called the Terrestrial Intermediate Origin (TIO) and noted ϖ. This is a reference frame rotating with the Earth. The PEF reference frame is a geocentric reference frame whose zPEF axis follows the movements of the poles on the Earth's crust. This frame of reference is obtained by rotating the ITRF frame of reference around the xITRF and yITRF axes so that the zPEF axis follows the movement of the poles.Its principal plane PPEF is defined as the true equator at a date t and its xPEF axis defines the intermediate terrestrial origin TIO. The TEME (True Equator Mean Equinox) reference frame: a geocentric mean celestial reference frame used to track satellite trajectories around the Earth. Its principal plane PTEME is the true equator at date t and its xTEME axis points towards the mean vernal point (vernal point that does not take nutation into account). Its zTEME axis is aligned with the mean rotation axis of the Earth, in the direction of the North Pole. The SEZ (Southeast-Zenith) topocentric reference frame: reference frame linked to the observation location whose axes point towards the South, the East and the Zenith. Its OSEZ origin corresponds to the position of the observer. Its zSEZ axis is aligned with the local vertical in the sense of the WGS84 model, it points towards the zenith of the observer. The eSEZ axis is aligned eastward, and points in the direction of the horizon east of the observer.The sSEZ axis is aligned southward and points in the direction of the horizon south of the observer. Its principal plane PSEZ is tangent to the reference ellipsoid. The J2000.0 reference frame: geocentric reference frame Mean Equator / Mean Equinox at 12:00 on January 1, 2000. Star catalogs are expressed in this reference frame. Its xJ2000 axis is defined as the vector from the center of the Earth to the mean vernal point at J2000.0 (specific date corresponding to 1. erJanuary 2000 at 12h). Its zJ2000 axis is the mean celestial pole at J2000.0. It is aligned with the Earth's rotation axis at J2000.0 and points approximately towards the North Pole. The ICRF (International Celestial Reference Frame), a creation of the ICRS, is constructed from observations of distant quasars by VLBI (Very Long Baseline Interferometry). Its origin is the barycenter of the solar system, and its axes are fixed relative to these distant objects, quasars, objects that are assumed to have no angular motion perceptible from Earth. The axes of this frame are "non-rotating", although its center moves over time: it is a pseudo-inertial frame. The direction of the axes of the ICRF and J2000.0 frames are almost identical to within 0.02 arcseconds. The transformation matrix to go from one to the other is called the bias matrix and is: where ^^ ^ = −14.6 mas (offset on e of the ICRS reference frame relative to the equinox J2000.0), ^ ^ = −16.6170 mas, and ^ ^ = −6.8192 mas , where 1 mas is approximately 4.8481368110954×10 -9radians). The GCRS (Geocentric Celestial Reference System) is today the standard geocentric celestial reference system. It corresponds to a translation of the ICRS heliocentric reference frame constructed from the observation of distant quasars. The xGCRS, yGCRS, and zGCRS axes are fixed relative to these distant objects. The xGCRS axis is defined as the direction from the center of the Earth to the intersection of the celestial equator and the GCRS meridian plane. The yGCRS axis is defined as being perpendicular to the xGCRS axis in the GCRS meridian plane, pointing toward the vernal point. The zGCRS axis is defined as being perpendicular to the GCRS meridian plane, pointing toward the north celestial pole. The axes of the ICRF and GCRF reference frames are the same. Only the center changes: GCRF is centered on the Earth, ICRF is centered on the barycenter of the solar system. There is no rotation between the two markers.The axes of the GCRS reference frame are close to those of the J2000.0 reference frame at 0.02 arcseconds. Those skilled in the art may refer in particular to the document “Relativistic celestial mechanics of the solar system, Kopeikin, Efroimsky, & Kaplan, 2011, p. 773” or to the document “Fundamentals of astrodynamics and applications, 4th edition, David. A. Vallado, 2013.” Star catalogs express the coordinates of stars in the J2000.0 or ICRF reference frames in particular. According to a first aspect, the invention relates to a method for referencing at least one artificial satellite in a star catalog, this catalog comprising the position of at least one star projected onto a celestial sphere.This method comprises: - a step of obtaining coordinates of an observation location of said at least one artificial satellite and orbital parameters of said at least one artificial satellite; - a step of projecting the satellite onto said celestial sphere according to a direction of view determined from said orbital parameters and the observation location; - a step of recording, in said catalog, coordinates of the satellite projected onto the celestial sphere, the coordinates of the stars and of said at least one artificial satellite being expressed in the same geocentric reference frame, called the star catalog reference frame.Correlatively, the invention relates to a device for referencing at least one artificial satellite in a star catalogue comprising the position of at least one star projected onto a celestial sphere, this device comprising: - a module for obtaining coordinates of an observation location of said at least one artificial satellite and orbital parameters of said at least one artificial satellite; - a module for projecting the satellite onto said celestial sphere in a direction of view determined from said orbital parameters and the observation location; - a module for recording, in said catalogue, coordinates of the satellite projected onto the celestial sphere, the coordinates of the stars and of said at least one artificial satellite being expressed in the same reference frame, called the reference frame of the star catalogue.As is known, the celestial sphere is an astronomical concept that allows distant celestial bodies, including stars, to be represented on a sphere of very large arbitrary radius regardless of their actual distance. For example, but not limited to, a radius of one light year can be used for the celestial sphere. Thus, and in general, the invention proposes to use the orbital coordinates of artificial satellites to complete a star catalog or ephemeris. In the art prior to the invention, star ephemeris only include stars of low magnitude, observable by optronic performance of CMOS detectors of star finders.The invention advantageously makes it possible to supplement these catalogs with the position of artificial satellites so that these satellites can, in addition to stars, be used to detect decoy, while continuing to use the decoy detection methods which are based on these catalogs. In a particular embodiment, the geocentric reference frame of the star catalog is the J2000.0, ICRS or GCRS reference frame. For example, for ephemerides using the J2000.0 reference frame, the equatorial coordinates. ^ ^, ^ ^stars are given at a specific date called J2000.0: January 1, 2000 at 12:00, Earth Time. Note that Earth Time differs from the Coordinated Universal Time (UTC) used in everyday life by a certain number of whole seconds called leap seconds, which change each year. The number of stars listed varies depending on the type of catalog; it can reach several million. The transition from the equatorial coordinates of a star at the date J2000.0 to another date and time of observation is done by physical corrections of the movement of the Earth (precession, nutation) and of the stars themselves (proper motion) which are detailed in particular in the article by Meeus, J. (1998) entitled "Astronomical Algorithms" published by "Willmann-Bell". These physical corrections are not detailed here. On the other hand,the position of artificial satellites is known in the Earth geocentric reference frame and is defined by the Two-Line Elements (TLE) orbital parameters which correspond to a standardized representation of the orbital parameters of objects in Earth orbit and which are widely disseminated by NORAD (North American Aerospace Defense Command) and NASA. In a particular embodiment, the referencing method comprises: - a step of determining coordinates of the artificial satellite in the TEME reference frame from the orbital parameters and a date of said observation; - a step of determining coordinates of said artificial satellite in the ITRF reference frame from the coordinates of the artificial satellite in the TEME reference frame, and the position of the Earth's poles; - a step of determining, from the coordinates of the artificial satellite in the ITRF reference frame,coordinates of the artificial satellite in a topocentric reference frame centered on said observation location; - a step of projecting the artificial satellite onto a projection point of the celestial sphere in a direction of view defined from said coordinates of the artificial satellite in the topocentric reference frame; - a step of determining coordinates of said projection point in the ITRF geocentric reference frame; and - a step of determining coordinates of the artificial satellite in the geocentric reference frame of the catalog from said coordinates of said projection point in the ITRF reference frame. The invention also relates to a star catalog comprising: - for at least one object consisting of a star; and - for at least one object consisting of an artificial satellite; the position of these objects projected onto a celestial sphere,the coordinates of the positions of these objects being expressed in the same geocentric reference frame. This star catalog can be used in a decoy detection method. It advantageously makes it possible to improve the performance of such methods in that it makes it possible to exploit a much larger number of landmarks, that is to say not only stars but also artificial satellites, in a coordinate system compatible with ephemerides. Consequently, and according to another aspect, the invention relates to a decoy detection method, this method comprising: - at least one step of aiming at an object recorded in a catalog as mentioned above, said object being aimed using the coordinates of the position of said object as recorded in said catalog; and - if the targeted object is not observed at said position,a step of triggering a decoy alert. This targeted object may be a star or an artificial satellite referenced by a referencing method as presented above. Correlatively, the invention relates to a decoy detection device comprising: - a module for aiming and observing an object recorded in a catalog as mentioned above, said object being aimed using the coordinates of the position of said object as recorded in said catalog; and - a module for triggering an alert if the object (targeted) is not observed at said position. In a particular embodiment, the different steps of the referencing method or the decoy detection method are determined by computer program instructions or are implemented by a silicon chip which comprises transistors adapted to constitute logic gates of a non-programmable wired logic. Consequently,The invention also relates to a computer program on an information medium, this program being capable of being implemented in a controller computer, this program comprising instructions adapted to the implementation of the steps of a referencing method and / or a decoy detection method as described above. This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form. The invention also relates to an information medium readable by a computer, and comprising instructions of a computer program as mentioned above. The information medium can be any entity or device capable of storing the program. For example, the medium can comprise a storage means, such as a ROM,a non-volatile memory of the flash type or a magnetic recording means, for example a hard disk. On the other hand, the information carrier may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention may in particular be downloaded from a network of the Internet type. Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question. Brief description of the drawings: Other characteristics and advantages of the present invention will emerge from the description given below,with reference to the appended drawings which illustrate exemplary embodiments thereof without any limiting character. In the figures: [Fig. 1] Figure 1 already described shows reference systems used in certain embodiments of the invention. [Fig. 2] Figure 2 illustrates the projection of an artificial satellite onto a celestial sphere seen from two observation points; [Fig. 3] Figure 3 illustrates in the form of a flowchart,the main steps of a referencing method and a decoy detection method according to embodiments of the invention; [Fig. 4] Figure 4 represents the functional architecture of a referencing device according to a particular embodiment of the invention; [Fig. 5] Figure 5 represents the functional architecture of a decoy detection device according to a particular embodiment of the invention; [Fig. 6] Figure 6 represents the hardware architecture of a referencing device according to a particular embodiment of the invention; [Fig. 7] Figure 7 represents the hardware architecture of a decoy detection device according to a particular embodiment of the invention. Detailed description of embodiments In the remainder of the description, the term "equatorial coordinates of the projected object" will be used.the coordinates that correspond to the geocentric equatorial coordinates of the target object if it were projected onto the celestial sphere from the observation location. These coordinates are similar to the standard geocentric equatorial coordinates for stars located far from Earth. Figure 2 illustrates, in the ITRF reference system, the projection of an artificial satellite SAT onto a celestial sphere SC seen from two observation points LO1, LO2 on the surface of the Earth T. In this figure 2, CT is referenced to the center of the Earth T and CE1, CE2 to the equatorial coordinates of the satellite SAT projected onto the celestial sphere CS from the two observation locations LO1,LO2. It is clear that these equatorial coordinates CEi are extremely different depending on the observation point LOi. Figure 3 represents the main steps of a method for referencing at least one satellite according to a particular embodiment of the invention. The referencing of a satellite will be described here but it can be used in the same way to reference several satellites. In the embodiment described here, this method implements a loop comprising steps E10 to E70 to calculate the equatorial coordinates of the satellite projected onto the celestial sphere from an observation point in the same reference frame as the star catalogs and to update the CTG catalog (step E80) with these coordinates. It should be noted that these coordinates do not correspond to the actual equatorial coordinates of the satellite in the catalog reference frame (J2000.0 for example). If these coordinates can be confused for distant stars,for artificial satellites, the equatorial coordinates of the projected object depend directly on the observation location. This loop is for example implemented every second of observation so as to keep the satellite's referencing updated in real time. A satellite can thus be treated as a star with zero proper motion for stellar navigation. It should be remembered that the proper motion of stars corresponds to their apparent motion on the celestial sphere seen from Earth. The coordinates of stars evolve over time by this proper motion given in star catalogs. Subsequently, we will designate ^, ^, ^ ^ and ^ " the x, y and z axis rotations. During a step E10, we obtain: - the coordinates of the observation location of the artificial satellite SAT. These coordinates include, for example, the geodetic latitude Φ $%of this place, its longitude and its altitude; - the current date of observation ' ()*in the Coordinated Universal Time (UTC) format; - the two-line orbital parameters +, - of the artificial satellite as updated daily by NORAD; the position of the poles . / and 0 / on the Earth's crust at that time, as determined by the IERS (International Earth Rotation and Reference Systems Service). During a step E20, the coordinates of the artificial satellite SAT are determined in the TEME reference frame, from the TLE orbital parameters and the date of observation in Coordinated Universal Time. For this, the SGP4 algorithm provided by David Vallado, and available at http: / / celestrak.org / software / vallado-sw.php, is used, for example. Those skilled in the art may also refer to the algorithm (C code) detailed in the reference Vallado, David A.; Paul Crawford; Richard Hujsak; TS Kelso (August 2006). “Revisiting Spacetrack Report #3”. Astrodynamics Specialist Conference or the document “Felix R. Hoots, Ronald L.Roehrich, SPACETRACK REPORT NO. 3 Models for Propagation of NORAD Element Sets. December 1980” which presents the SGP4 algorithm from a theoretical point of view. We will denote by t the instant of observation. This instant can be expressed in different time scales, indicated by subscript, according to the definition of the time considered in the different changes of reference points: in UTC time scale denoted '. ()* , in terrestrial time scale noted ' 11 . Noting ' ()* Coordinated Universal Time civil time and +,- the orbital parameters of the artificial satellite at time ' ()* we obtain the coordinates 2 )343 ^'^ of the satellite in the TEME reference frame: 2 )343 ^'^ = 5674^+,-, ' ()* ^ (1) During a step E30, from the coordinates of the artificial satellite in the TEME reference frame, and the position of the poles . / and 0 / , the coordinates of the satellite in the ITRF reference frame are calculated. First, a rotation of angle θ is carried out 94:)along the zTEME axis with the GMST angle (Greenwich Mean Sidereal Time) calculated at the time of observation, to bring the xTEME axis towards xPEF. Remember that the GMST angle (mean sidereal time) corresponds to the angle between the mean vernal point and the Greenwich meridian. In this embodiment, we use the equation provided by the book “Fundamentals of Astrodynamics and Application” by David A Vallado (1997), page 188: θ 94:) = ^67310.54841 + ^8766000 ∗ 3600 + 8640184.812866^ ∗ + ()^ + 0.093104 ∗ + ( ^ )^ − With: - θ 94:) OF 2F^; - + ()^ the date in Julian centuries since January 1, 2000, expressed in terms of the Julian date UT1 HI ()^ : H I ^ − 24515450 Coordinates 2 J3K ^ ' ^ of the satellite in the PEF reference frame are obtained by a rotation R3 along the zTEME axis of angle L 94:) 2 J3K ^'^ = ^ " ^L 94:) ^2)343 ^'^ (3) Coordinates 2 M)NK ^ ' ^ of the satellite are obtained by a rotation of the RPEF reference frame along the yPEF and xPEF axes of angles −. O and −0 O to lead the zPEF axis perpendicular to the true equator towards the mean axis of rotation of the Earth considered in ITRF. During a step E40, the coordinates of the satellite are defined in a topocentric reference frame relative to the observation location (for example LO1). As explained with reference to Figure 2, the viewing angles impact the equatorial coordinates of the projected satellite. In one embodiment, the position is in the topocentric reference frame SEZ. Alternatively, the position is in another topocentric reference frame, for example in the Northwest-Zenith reference frame. The ITRF vector defined by the center of the Earth and the observation location 2 is first calculated. PQ1Rdepending on the latitude, longitude and altitude of this location. We then calculate the vector 2 M)NK1SOS from the observation site to the artificial satellite: 2 M)NK1SOS = 2 M)NK − 2 PQ1R (5) We then apply a rotation to this vector around the zITRF axis by an angle &, the longitude of the observation location to align the xITRF axis with the south axis. We then perform a rotation along the yITRF axis by an angle 90 − Φ $% with Φ $% the geodetic latitude of the observation location to align the zITRF axis with the zenith axis. where 2 :3T ^'^ corresponds to the vector connecting the observation location to the satellite expressed in the Southeast-Zenith topocentric reference frame. During a step E50, the artificial satellite SAT is projected onto the celestial sphere SC in the direction of sight. The topocentric SEZ vector is arbitrarily multiplied by 1 light year to obtain the coordinates in the SEZ reference frame of the projected satellite. In Figure 2, the direction of sight is the straight line (L01, SAT). During a step E60, the reverse reference frame change to that performed in step E40 is then performed to determine the coordinates of the point targeted by the SEZ vector extended in the ITRF geocentric reference frame. The coordinates thus determined are the ITRF geocentric coordinates of the satellite projected onto the celestial sphere SC from the observation location. These coordinates make it possible to assimilate it to a star in the context of stellar navigation at the observation location. Adding 2 PQ1R in the equation actually does not matter. After extending the SEZ vector, the geocentric and topocentric vectors of the projected satellite become comparable. Therefore, equivalently: During a step E70, the coordinates of the satellite projected onto the celestial sphere SC are obtained in a coordinate system used by star catalogs. For example, the coordinates of the satellite are determined in the GCRS reference frame. Note that this GCRS reference frame is close to the J2000.0 reference frame at 0.02 arcseconds. In the context of satellite tracking where this position accuracy is not achieved, these two reference frames can be confused. In the embodiment described here, this conversion is performed using the Ter2Cel algorithm from the Novas (Naval Observatory Vector Astrometry Software) library, Kaplan et al. (2012), available at https: / / ascl.net / 1202.003. Other methods described in the Kaplan (2011) or Meeus (1998) references mentioned above can be used. This algorithm allows to move from the ITRF reference frame to the GCRS reference frame depending on the position of the celestial poles. / and 0 / relative to the Earth's poles, precession, nutation (parameters ^`, ^a provided by IERS), coordinated universal time'. ()* and earthly time' 11 provided by IERS. Two equivalent methods are possible to carry out this change of reference by Ter2Cel: Equinox-based transformation and CIO-based transformation. A different change of reference can be applied depending on the desired final reference. In the embodiment described here, the coordinates of the artificial satellite SAT are stored in the star catalog CTG during a step E80. This satellite SAT can thus be treated as a star with zero proper motion for stellar navigation. The CTG catalog can be used by a PDL decoy detection method according to the invention. According to the invention, this catalog includes both star positions (natural celestial objects) and positions of artificial satellites SAT projected onto the celestial sphere CS. The coordinates of these different objects OBJi are expressed in the same reference frame. During a step E90, an observation instrument (star finder, telescope, etc.) obtains the coordinates of an object (star or artificial satellite) recorded in the catalog and aims at this object according to the coordinates of this object recorded in the CTG catalog to observe it.When the targeted object is detected at the expected position, the result of a test E100 is positive, and another object in the catalog is targeted during a new iteration of step E90. On the contrary, if the targeted object is not at the expected position, the result of the test E100 is negative, a decoy alert is triggered during a step E110, because jamming signals may be the cause of the disturbance of the instrument's measurements. Figure 4 represents the functional architecture of a DREF referencing device according to the invention. It makes it possible to reference artificial satellites in a star catalog (or ephemeris) which includes the position of at least one star projected onto a celestial sphere. This DREF device includes an input module M10 configured to obtain the parameters necessary for implementing the invention, and in particular the coordinates ^Φ. $%, &^ of an observation location of an artificial satellite, its TLE orbital parameters, and the observation date. The DREF device also comprises a module M50 configured to determine the coordinates of the artificial satellite in the different reference frames, using for example the equations (1) to (9) described previously. This module M50 is in particular configured to calculate the projection of an artificial satellite on the celestial sphere according to a direction of view determined from its TLE orbital parameters and the observation location. The DRE device further comprises a module M80 for recording in a star catalog, the coordinates of the satellite projected on the celestial sphere, the coordinates of the stars and of said at least one artificial satellite being expressed in the same geocentric reference frame. Figure 5 represents the functional architecture of a DDL decoy detection device according to the invention.The DDL device comprises a module M90 ​​for aiming and observing an object recorded in a star catalog comprising objects consisting of stars and artificial satellites. The DDL device comprises a module M110 for triggering an alert if the targeted object is not observed at the position recorded in the star catalog. Figure 6 represents the hardware architecture of a DREF referencing device according to the invention. In the embodiment described here, the DREF referencing device has the hardware architecture of a computer. It comprises a processor 10, a ROM type read-only memory 11, a random access memory 12, a rewritable non-volatile memory 13 and communication means 14. The ROM type read-only memory 11 constitutes a recording medium within the meaning of the invention.It comprises a computer program PGREF comprising instructions for executing the steps of a referencing method according to the invention when this program is executed by the processor 10. Figure 7 represents the hardware architecture of a DDL decoy detection device according to the invention. In the embodiment described here, the DDL decoy detection device has the hardware architecture of a computer. It comprises a processor 20, a ROM-type read-only memory 21, a random access memory 22, a rewritable non-volatile memory 23 and communication means 24. The ROM-type read-only memory 21 constitutes a recording medium within the meaning of the invention. It comprises a computer program PGDL comprising instructions for executing the steps of a decoy detection method according to the invention when this program is executed by the processor 20.

Claims

CLAIMS

1. Method (PREF) for referencing at least one artificial satellite (SAT) in a star catalogue (CTG) comprising the position of at least one star projected onto a celestial sphere (SC), this method comprising: - a step (E10) of obtaining coordinates ^Φ $%, &^ of an observation location of said at least one artificial satellite (SAT) and orbital parameters (TLE) of said at least one artificial satellite (SAT); - a step (E50) of projecting the satellite (SAT) onto said celestial sphere (SC) in a direction of view determined from said orbital parameters (TLE) and the observation location; - a step (E80) of recording, in said catalog (CTG), coordinates of the satellite (SAT) projected onto the celestial sphere (CS), the coordinates of the stars and of said at least one artificial satellite (SAT) being expressed in the same geocentric reference frame, called the star catalog reference frame.

2. Referencing method (PREF) according to claim 1, characterized in that said geocentric reference frame of the star catalog is the J2000.0, ICRS or GCRS reference frame.

3. Method (PREF) of referencing according to claim 1 or 2, characterized in that it comprises: - a step (E20) of determining coordinates ^2. )343 ^ of said artificial satellite (SAT) in the TEME reference system from said orbital parameters (TLE) and a date ^' ()* ^ of said observation; - a step (E30) of determining coordinates (2 M)NK ^ of said artificial satellite (SAT) in the ITRF reference frame from coordinates ^2 )343 ^ of the artificial satellite in the TEME reference system, and the position (. / , 0 / ) of the Earth's poles; - a step (E40) of determination, from the coordinates (2 M)NK ^ of said artificial satellite (SAT) in the ITRF reference system, with coordinates (2 :3T^ of the artificial satellite (SAT) in a topocentric reference frame centered on said observation location; - a step (E50) of projection of the artificial satellite (SAT) onto a projection point of the celestial sphere (SC) according to a direction of sight defined from said coordinates (2 :3T ^ of the artificial satellite (SAT) in the topocentric reference frame; - a step (E60) of determining coordinates ^2 M)NKXYWZ ^ of said projection point in the ITRF geocentric reference frame; and - une étape (E70) de détermination de coordonnées 2 ^9*N:XYWZ ^ du satellite artificiel (SAT) dans le geocentric reference of the catalog (CTG) from said coordinates ^2 M)NKXYWZ ^ of said projection point in the ITRF reference frame.

4. Star catalog (CTG) comprising: - for at least one object (OBJi) consisting of a star; and - for at least one object (OBJi) consisting of an artificial satellite (SAT); the position of said objects (OBJi) projected onto a celestial sphere (SC), the coordinates of the positions of said objects (OBJi) being expressed in the same geocentric reference frame.

5. Method (PDL) for detecting decoying comprising: - at least one step (E90) of targeting an object (OBJi) recorded in a catalog according to claim 4, said object (OBJi) being targeted using the coordinates of the position of said object (OBJi) as recorded in said catalog (CTG); and - if the targeted object (OBJi) is not observed at said position, a step (E100) of triggering a decoy alert.

6. Device (DREF) for referencing at least one artificial satellite (SAT) in a star catalogue (CTG) comprising the position of at least one star projected onto a celestial sphere (SC), this device comprising: - a module (M10) for obtaining coordinates ^Φ. $%, &^ of an observation location of said at least one artificial satellite (SAT) and orbital parameters (TLE) of said at least one artificial satellite (SAT); - a module (M50) for projecting the satellite (SAT) onto said celestial sphere (SC) according to a direction of view determined from said orbital parameters (TLE) and the observation location; - a module (M80) for recording, in said catalog (CTG), coordinates of the satellite (SAT) projected onto the celestial sphere (CS), the coordinates of the stars and of said at least one artificial satellite (SAT) being expressed in the same geocentric reference frame, called the star catalog reference frame.

7. Device (DDL) for detecting decoy comprising: - a module (M90) for aiming and observing an object (OBJi) recorded in a catalog according to claim 4, said object (OBJi) being aimed using the coordinates of the position of said object (OBJi) as recorded in said catalog (CTG); and - a module (M110) for triggering an alert if the object (OBJi) aimed at is not observed at said position.

8. Computer program (PGREF, PGDL) comprising instructions for executing the steps of the referencing method according to any one of claims 1 to 3 and / or instructions for executing the steps of the decoy detection method according to claim 5 when said program is executed by a computer.

9. Computer-readable recording medium (11, 21) on which a computer program (PGREF, PGDL) according to claim 8 is recorded.

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