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CN-122029456-A - Method and apparatus for referencing satellites in fixed star ephemeris for detecting GNSS fraud

CN122029456ACN 122029456 ACN122029456 ACN 122029456ACN-122029456-A

Abstract

The invention relates to a method (PREF) for referencing at least one Satellite (SAT) in a star table (CTG), comprising the step of locating at least one star projected onto a celestial Sphere (SC). Comprising a step (E10) of obtaining coordinates (Oqd,) of an observation position of at least one artificial Satellite (SAT) and orbit parameters (TLE) of 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 orbit parameters (TLE) and the observation position, a step (E80) of recording the coordinates of the Satellite (SAT) projected onto the Celestial Sphere (CS) into a star table (CTG), wherein the coordinates of the star and of the at least one artificial Satellite (SAT) are expressed in a same geocentric reference system, called the star table reference system.

Inventors

  • Philip Ellie
  • Ji Yaomu Pierre Lens
  • Jean Luc De Mang Re
  • Mary Kapitana

Assignees

  • 赛峰集团电子与防御

Dates

Publication Date
20260512
Application Date
20240821
Priority Date
20230828

Claims (9)

  1. 1. A method (PREF) for referencing at least one artificial Satellite (SAT) in a star-table (CTG) comprising the position of at least one star projected onto a celestial Sphere (SC), the method comprising: -a step E10 of obtaining the coordinates of an observation station of said at least one Satellite (SAT) And the orbit number (TLE) of the at least one satellite vehicle (SAT); -a step E50 of projecting the Satellite (SAT) onto the Celestial Sphere (CS) according to a viewing direction determined by the orbit number (TLE) and the observation station; -a step E80 of recording the coordinates of the Satellites (SAT) projected onto the Celestial Sphere (CS) into the star table (CTG), the coordinates of the stars and the at least one artificial Satellite (SAT) being expressed in the same geocentric reference system, called the stars star table reference system.
  2. 2. The reference method (PREF) according to claim 1, wherein the geocentric reference frame of the star-star table is the J2000.0, ICRS or GCRS reference frame.
  3. 3. The reference method (PREF) according to claim 1 or 2, characterized in that it comprises: -a step E20 of determining, based on the number of Tracks (TLE) and the date of the observation Determining coordinates of said satellite vehicle (SAT) in said tee reference frame ; -Step E30, based on the coordinates of the satellites in the tee reference frame And the position (xp, yp) of the earth's pole, determining the coordinates of said satellite vehicle (SAT) in said ITRF reference frame ; -Step E40, according to the coordinates of the satellite vehicle (SAT) in the ITRF reference frame Determining coordinates of said Satellite (SAT) in a station-core reference system centred on said observation station ; -A step E50 of determining, from said coordinates in said station-core reference system by said Satellite (SAT) -Projecting said satellite vehicles (SAT) onto the projection points of said celestial Sphere (SC) in a defined viewing direction; -step E60, determining coordinates of the projection point in the geocentric ITRF reference frame And (C) sum -Step E70, based on the coordinates of the projection points in the ITRF reference frame Determining coordinates of said satellite vehicle (SAT) in said geocentric reference frame of said star table (CTG) 。
  4. 4. A star-table (CTG) comprising: -for at least one object (OBJ i ) consisting of stars, and -For at least one object (OBJ i ) consisting of Satellites (SAT); The position of said object (OBJ i ) projected onto the Celestial Sphere (CS), The coordinates of the position of the object (OBJ i ) are expressed in the same geocentric reference system.
  5. 5. A fraud detection method (PDL), comprising: -at least one step (E90) of targeting an object (OBJ i ) recorded in a star table (CTG) according to claim 4, said object (OBJ i ) being targeted by using the coordinates of the position of said object (OBJ i ) recorded in said star table (CTG), and -A step (E100) of triggering a fraud alert if no targeted object (OBJ i ) is observed at said location.
  6. 6. An apparatus (DREF) for referencing at least one artificial Satellite (SAT) in a star-table (CTG) comprising the position of at least one star projected onto a celestial Sphere (SC), the apparatus comprising: -a module M10 for obtaining the coordinates of the observation station of said at least one Satellite (SAT) Λ) and the number of orbits (TLE) of said at least one Satellite (SAT); -a module M50 for projecting said Satellites (SAT) onto said celestial Sphere (SC) according to a viewing direction determined by said number of orbits (TLE) and said observation station; -a module M80 for recording the coordinates of the Satellites (SAT) projected onto the Celestial Sphere (CS) into the star table (CTG), the coordinates of the stars and the at least one artificial Satellite (SAT) being expressed in the same geocentric reference system, called the stars star table reference system.
  7. 7. A fraud detection apparatus (DDL), comprising: -a module M90 for aiming and observing an object (OBJ i ) recorded in a star table according to claim 4, said object (OBJ i ) being aimed by using the coordinates of the position of said object (OBJ i ) recorded in said star table (CTG), and -A module M110 for triggering an alarm when no aimed object (OBJ i ) is observed at said location.
  8. 8. Computer program (PGREF, PGDL) comprising instructions for performing the reference method steps according to any of claims 1 to 3 and/or instructions for performing the spoofing detection method steps according to claim 5 when the program is executed by a computer.
  9. 9. A computer-readable recording medium (11, 21) having recorded thereon the computer program (PGREF, PGDL) according to claim 8.

Description

Method and apparatus for referencing satellites in fixed star ephemeris for detecting GNSS fraud The present invention relates to a method and a device for detecting GNSS (global navigation satellite system) fraud, such a system allowing to determine the position and the velocity of an object equipped with a GNSS receiver by using signals emitted by earth orbiting satellites. The invention can be used in particular to detect fraud, i.e. attacks that spoof such positioning systems by sending spurious signals to the receiver. Fraud detection systems have been developed that use fixed star ephemeris to detect the presence of spurious GNSS signals, for example, by comparing received GNSS signals to expected positions of these fixed stars calculated from fixed star ephemeris. If the received signal does not correspond to the expected location, then for example, the rogue equipment may be detected. Unfortunately, the star trackers and other observation devices used to observe stars have optoelectronic capabilities, often limited by the detector (CMOS) technology used, and only the brightest stars, e.g., stars less than 4, can be observed. Thus, current detection systems can only utilize a limited number of stars, which negatively impacts the availability and accuracy of their measurements. The present invention is directed to a method for improving detection of fraud or, more broadly, to improving detection of faults in a global positioning system. Disclosure of Invention Fig. 1 shows a geocentric or station-centric reference system known to those skilled in the art of stars or satellite observations, and which will be used in some embodiments of the present invention. The international earth reference system (ITRF) is an earth-connected reference mark that is identical to the WGS84 reference mark, with errors within a few centimeters. The [ WGS84] reference is created from the coordinates of a number of measuring stations, similar to the [ ICRF ] reference, but in a reference frame connected to the earth. The earth reference is used to define the geographic longitude and latitude used in GPS. The origin of which is located at the centroid of the earth. Its x ITRF axis is oriented along the reference meridian of the international earth rotation and reference system services (ies), which is a meridian almost equal to the greenwich meridian, with an error of within 5.3 arcseconds. The z ITRF axis of which is collinear with the axis of rotation of the ellipsoid. The y ITRF axis is defined such that a right-hand orthogonal reference mark is defined. The earth intermediate reference system (TIRS) or pseudo-earth fixed (PEF) reference frame is defined at date t by the equator of the celestial sphere intermediate pole (CIP), i.e., the true celestial pole, and the longitude origin, designated pi, called the earth intermediate origin (TIO). It is a reference mark that rotates with the earth. The PEF reference frame is a geocentric reference frame whose z PEF axis follows the movement of poles on the earth's crust. The reference frame is obtained by rotating the ITRF reference frame about the x ITRF axis and the y ITRF axis such that the z PEF axis follows the movement of the pole. Its principal plane P PEF is defined as the true equator at date t, and its x PEF axis defines the earth's intermediate origin (TIO). The TEME (true equatorial mean spring point) reference frame, the geocentric mean celestial reference frame, is used to follow the trajectory of the satellite around the earth. Its principal plane P TEME is the true equator at date t, and its x TEME axis points to the average spring point (spring point without regard to nutation). The z TEME axis of which is aligned with the average spin axis of the earth in the direction of the north pole. SEZ (south-east-zenith) station center reference frame-reference frame connected to the observation station with its axes pointing to the south, east and zenith, respectively. Its origin O SEZ corresponds to the position of the observer. Its z SEZ axis is aligned with the local vertical line in the WGS84 model, which points to the zenith of the observer. e SEZ are aligned axially east and point to the observer in the east horizon direction. s SEZ are aligned axially south and point to the observer in the south horizon direction. Its principal plane P SEZ is tangential to the reference ellipsoid. J2000.0 reference frame, geocentric reference frame, average equator/average spring point, 1 month, 1 day, 2000 earth time 12:00. The star-star table is expressed in this reference frame. The x J2000 axis is defined as the vector pointing from the center of the earth to the average spring point at J2000.0 (the specific date corresponding to earth time 12:00 at 1/2000). The z J2000 axis is the average zenith of J2000.0. It is aligned with the earth's spin axis at J2000.0 and is directed generally toward the polar star. The ICRF reference frame (international celestial reference frame) is