• 专利附录
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    • 专利摘要:
    The system comprises: - on board a first gear (10), said host craft, an antenna triplet consisting of a transmitting and receiving antenna (11) and two transmitting antennas (12, 13 ), a transmission chain (16) being successively coupled to each antenna (11, 12, 13) of the antenna triplet by a radio frequency switch (19), a reception chain (17) which can be coupled to the antenna transmit and receive antenna (11), and a processing device (14) for determining a relative angular position between the host craft (10) and a plurality of spacecraft (20) on the one hand, said companion gear, based on measurements of differences in travel achieved and transmitted by the companion gear (20), - on the companion gear (20), a transmitting and receiving antenna (21), a transmission chain (23) and a receiving chain (24) coupled to the transmitting and receiving antenna (21) and a measuring device (2). 2) for measuring differences in the path between three signals from the three antennas (11, 12, 13) of the antenna triplet of the host vehicle.
    公开号:FR3017213A1
    申请号:FR1400257
    申请日:2014-01-31
    公开日:2015-08-07
    发明作者:Jean Baptiste Thevenet；Christian Mehlen
    申请人:Thales SA；
    IPC主号:
    专利说明:

    [0001] FIELD OF THE INVENTION The present invention relates to a method and a radiofrequency system for determining, by a pair of spacecraft, the relative angular position between the spacecraft and the spacecraft. several spacecraft. It applies to any navigation mission that requires a precise determination, in real time, of the relative position between several spacecraft, and in particular to the field of satellites in formation flight, or gear in docking maneuver or in appointment maneuver. Each spacecraft can be of any type such as for example a satellite, a space station, a space shuttle or an orbiter machine.
    [0002] It is known from document EP 1 813 957 to control the relative position between two spacecraft by analyzing two-frequency navigation signals received by each vehicle, the use of bi-frequency signals to obtain unambiguous angular measurements. This document describes carrying out measurements simultaneously on the two spacecraft, for example two satellites, the measurements made by each machine being obtained from the reception of bi-frequency signals emitted by the other vehicle. However, this measurement method requires that the satellites are pre-aligned and that each satellite is equipped with several different reception chains working simultaneously, which poses calibration problems. Indeed, the different measurement chains are not perfectly identical with each other and the signal propagation times may vary due to the power and temperature variations between the different measurement chains, which leads to measurement errors and imprecise positioning. To compensate for inter-channel biases and to limit measurement errors, a dynamic calibration chain with an internal measurement loop, called self-calibration, has been introduced, which increases the complexity and the size of the measurement system. . Furthermore, in order to eliminate the carrier phase ambiguity on the difference of the received signals, this method requires a prior alignment of the satellites via a two-frequency signal, a first rotation of the spacecraft around the spacecraft. antenna axis to reduce carrier cycle ambiguity by using a star sensor and reverse rotation of the vehicle to return to the initial position. The complexity of the corresponding global architecture leads to mass, power consumption and volume that are difficult to match with the resources of certain operational platforms. The object of the invention is to overcome the drawbacks of known solutions and to provide a method and a system for determining the relative position between two remote spacecraft which is simpler and does not require a dual-frequency measurement system and which makes it possible to to obtain a better angular measurement precision while avoiding the problems of ambiguity of the measurement. For this purpose, the invention relates to a method for determining, by a pair of spacecraft, the relative angular position between a plurality of spacecraft, consisting of: - sequentially transmitting at least three radiofrequency signals from a triplet of antennas mounted on a first face of a first spacecraft said host vehicle, the antenna triplet consisting of a main transmitting and receiving antenna and two secondary transmitting antennas, - to receive the three signals radiofrequency on a transmitting and receiving antenna of one or more second spacecraft said companion gear, to be measured on board each companion gear, differences in the path between the signal from the main antenna and the signals from of each of the two secondary antennas, then to transmit by each engine companion to the host machine a radiofrequency signal containing the measurements taken, 30 - to receive and to processing on board the host craft, the radiofrequency signal containing the measurements transmitted by each companion gear and to deduce the relative angular position of each companion gear in a frame linked to the host craft. Advantageously, all the radiofrequency signals are transmitted or received sequentially by the different spacecraft antennas, via a bidirectional radiofrequency link for location and inter-gear communication, according to a TDMA frame consisting of several successive temporal windows respectively. allocated to each antenna of the host craft and to each antenna companion gear for transmitting or receiving radiofrequency signals. Advantageously, all radiofrequency signals transmitted or received are modulated by a carrier having an identical frequency F1. Advantageously, the method further comprises an additional step intended to reduce a phase ambiguity of the carrier, consisting of: without prior alignment of the two spacecraft, to perform a first rotation of the host machine around an axis Z parallel to a pointing axis of the antennas of the triplet, the first rotation being carried out in a first direction and having a rotation angle of any predetermined value, and then acquiring step difference measurements, at different successive measurement times, during the entire duration of the rotation and to calculate variations in the gait between successive measurement instants, at the same successive measurement instants, to measure variations in the inertial attitude of the host vehicle, based on the variations in the differences in gait and measured inertial attitude variations, derive for each pair of spacecraft an estimate of the relative angular position 30 between the spacecraft, then to align, in pairs, the spacecraft host and companion and to perform a second rotation of the host machine around the Z axis, the second rotation being performed in a second opposite direction in the first direction and having a rotation angle of substantially identical value to the first rotation and to achieve for each pair of spacecraft a new unambiguous measurement of the relative angular position between the spacecraft. The invention also relates to a system for determining, by a pair of spacecraft, the relative angular position between two spacecraft spacecraft for the implementation of the method, the system comprising at least a first spacecraft said host craft and a second spacecraft says gear companion. The host vehicle comprises at least one antenna triplet mounted on a first face, the antenna triplet consisting of a main transmitting and receiving antenna and two transmitting secondary antennas, a transmitting channel. which can be successively coupled to the transmission, to each antenna of the antenna triplet and a reception channel which can be coupled to the reception, at the main antenna, a radio frequency switch able to sequentially select the different antennas of the triplet and a device process for determining a relative angular position between the host vehicle and the companion gear based on measurements of differences in travel transmitted by the companion gear. The companion device comprises at least one transmitting and receiving antenna placed on a first face, a transmission chain and a reception channel respectively coupled to the transmitting and receiving antenna and a measuring device intended for measuring differences in the path between a radiofrequency signal received from the main antenna and radio frequency signals received from each of the two secondary antennas of the antenna triplet of the host vehicle.
    [0003] Advantageously, the host vehicle further comprises a device for measuring the attitude variations of the host vehicle. Advantageously, each host and companion spacecraft further comprises a second transmitting and receiving antenna placed on a second face opposite the first face of the corresponding spacecraft.
    [0004] Advantageously, each host and companion spacecraft comprises an antenna triplet, a processing device and a difference of gait measuring device.
    [0005] Advantageously, the system further comprises, on board each host and companion spacecraft, means for measuring the power level of the signals received by each receiving antenna and means for selecting the receiving antenna having the highest level. power.
    [0006] Other features and advantages of the invention will become clear in the following description given by way of purely illustrative and non-limiting example, with reference to the attached schematic drawings which represent: FIG. 1: a diagram of a set of two spacecraft spacecraft, respectively called host and companion gear, according to the invention; FIG. 2 is a block diagram of an exemplary architecture of a radiofrequency terminal on board a host vehicle, according to the invention; FIG. 3: an example of positioning of three antennas of a triplet, on a face of a host machine, according to the invention; FIG. 4 is a block diagram of an exemplary architecture of a radiofrequency terminal on board a companion machine, according to the invention; FIGS. 5a and 5b are two diagrams illustrating the difference between two signals emitted by two main and secondary antennas of an antenna triplet of a host vehicle and the relative angular positions of two corresponding host and companion machines, according to FIGS. the invention; FIG. 5c: a block diagram illustrating the method of measuring the relative angular position between two spacecraft, host and companion, according to the invention; FIG. 6 is a diagram illustrating the elevation and azimuth angles defining the relative angular position of a companion machine in an X, Y, Z coordinate system linked to the host vehicle, according to the invention; FIG. 7a: an example illustrating a rotation of a host vehicle intended to make it possible to reduce a carrier phase ambiguity on the difference in gait measurements, according to the invention; FIG. 7b: a block diagram illustrating the phases of ambiguity reduction of the phase of the carrier, according to the invention; FIG. 8: an example illustrating two spacecraft spaced apart, respectively host and companion, each spacecraft comprising two transmitting and receiving antennas on two opposite faces, according to an embodiment of the invention; FIG. 9a: an example configuration of two spacecraft spacecraft equipped with an antenna triplet on a first face and a transmitting and receiving antenna Rx / Tx on a second opposite face, in another mode particular embodiment of the invention; FIG. 9b: an exemplary TDMA frame applicable to the case of FIG. 9a, for two remote spacecraft equipped with an antenna triplet on a first face and an Rx / Tx antenna on a second opposite face, according to a particular embodiment of the invention. According to the invention, the measurement of the relative position between two spacecraft 10, 20 is carried out aboard one of the two spacecraft, called host craft 10, the other spacecraft being called companion gear 20. On By "relative angular position" is meant the two estimates of the azimuth and elevation angles of each companion gear in a reference frame related to the host craft, the mark being defined by a triplet of antennas mounted on a face of the host craft. In the case where there are several companion gear in the formation, the method of the invention applies to each pair of spacecraft consisting of a host craft and a companion gear. As shown in the schematic example of FIG. 1, the host machine 10 and the companion machine 20 each comprise a radiofrequency terminal 15, 25 connected to antennas. To estimate the angular position of one or more distant companion gear in a frame linked to the host craft, as shown in the diagram of FIG. 2, the radiofrequency terminal 15 of the host craft must include a processing device. 14, a transmission channel 16, a reception chain 17 and at least one set of three antennas consisting of a main antenna Rx / Tx 11 operating on transmission and reception and two secondary antennas Rx 12, 13 operating on the show. The three antennas 11, 12, 13 are positioned in three selected locations on one of the faces of the host vehicle 10, the distances d1, d2, separating the main antenna Rx / Tx 11 from the two secondary antennas Rx 12, 13 being predetermined. The three antennas thus form a triplet of antennas, the bases of the antennas 11 and 12 being aligned in a first direction X and the bases of the antennas 11 and 13 being aligned in a second direction Y. The transmission chain and the transmission chain reception operate at the same predetermined frequency F1. FIG. 3 illustrates a nonlimiting example of positioning the three antennas of an antenna triplet. In this example, the base of the main antenna 11 and the bases of the antennas 12 and 13 are respectively aligned in two directions X, Y of the face of the host machine and their pointing direction is oriented along an axis Z normal to the face. The two directions X and Y can be orthogonal to each other but it is not essential. However, it is preferable to approach the orthogonality of the bases of the antennas, for example to 20 °, to obtain a better homogeneity of the performances in the three dimensions of the space. On the other hand, it is imperative that the three antennas of the triplet are oriented towards an identical pointing direction. The host vehicle 10 may further comprise an additional transmitting and receiving antenna placed on a second face of the host craft, opposite to the first face where the antenna triplet is located. The three antennas of the triplet of the host vehicle, and possibly the additional transmit / receive antenna, are sequentially connected, one after the other, to transmission, to the transmission channel 16. The antenna transmission / reception of the antenna triplet and / or the additional transmitting / receiving antenna of the host vehicle are sequentially connected, on reception, to the reception chain 17. The host vehicle comprises a device for transmitting and receiving switching 18 including a radiofrequency switching means 19 ensuring the sequential selection of the triplet antennas by respecting a TDMA frame defining the succession of transmission and reception periods of the signals by each of the antennas and a radio frequency filter 26 ensuring the routing of the signals transmission signals and reception signals to the transmission channel or to the reception chain. The radiofrequency switching means 19 makes it possible to multiplex the radiofrequency signals between the transmission system and the reception system and between the different antennas. The radiofrequency switching means 19 is connected to the transmission chain and to the reception chain via an input / output filter 28 connected to the switching filter 26 of the transmission signals and the transmission signals. reception. In addition, an attenuator 27 is connected between the switching filter 26 of the transmit and receive signals and the receive chain 17. As shown in FIG. 4, the radiofrequency terminal of each companion machine 20 must comprise a signaling device. measurement 22, a transmission channel 23, a reception channel 24 and an antenna 21 operating on Tx transmission and Rx reception. The transmission chain and the reception chain operate at the same frequency F1 as the transmitting and receiving chains of the host vehicle. The companion machine further comprises an input / output filter 29 connected to a switching filter 30 of the transmission signals and reception signals and an attenuator 31 connected between the switching filter 30 of the transmission signals. and reception channel 15 and the reception chain 24. According to the invention, the host vehicle 10 transmits radio frequency signals towards the companion machine 20 over a bidirectional radiofrequency link for location and inter-gear communication 33. The signals transmitted by each host vehicle or by each companion gear, are constituted by a carrier of frequency F1 modulated firstly by a pseudo-random code making it possible to obtain a pseudo-distance measurement and secondly by data . The radiofrequency terminals 15, 25 of the host craft and of each companion gear comprise unrepresented internal clocks used to generate the carrier frequency F1 and to sequence the pseudo-random code. The clocks also provide clock signals necessary for controlling the transmission and reception of radio frequency signals. The pseudo-random code and a specific field containing local time information added to the data transmitted by one of the spacecraft, host or companion, and received by another spacecraft, allow all spacecraft to synchronize with each other and synchronize the transmission and reception periods between the different spacecraft. According to the invention, the radiofrequency signals are transmitted sequentially in the form of a frame, according to a transmission mode TDMA (in English: time division multiplex access). Each antenna of the host vehicle and 35 of the companion machine is assigned a specific time window in the frame, the time window being dedicated to the transmission of radio frequency signals and, for the antennas also operating at the reception, is allocated also a specific time window dedicated to the reception of radiofrequency signals. The isolation between the transmitted signals and the received signals is achieved by the different time windows allocated to transmission and reception in the TDMA frame. This makes it possible to use a single transmission and reception frequency F1 to be able to carry out the position measurements and to implant a single transmission and reception chain on board each craft.
    [0007] As shown in FIG. 5c, in a first step, radiofrequency signals are transmitted 50, sequentially in dedicated time windows of the TDMA frame, by each of the three antennas 11, 12, 13 of the host machine 10. The apparatus companion 20 receives successively on its antenna 21, in a specific time window dedicated to reception, the different signals emitted by each of the three antennas of the host machine 10. The received signals are transmitted to the measuring device 22 which measures 52 the propagation time of each received signal coming from each of the three antennas 11, 12, 13 of the host machine 10 and deduces therefrom ddml, ddm2 differences between the path traversed by the signal 20 coming from the main antenna Rx / Tx 11 and the path traveled by the signals from each of the two secondary antennas Tx 12 and Tx 13 of the host vehicle. FIGS. 5a and 5b show the principle of measuring the difference of the current ddm1, respectively ddm2, between the signal coming from the main antenna 11 and the signal coming from a secondary antenna 12, respectively 13, the two antennas , main and secondary, being spaced by a distance dl, respectively d2. When the host and companion machines are sufficiently far apart from each other with respect to the distance between the main antenna and each secondary antenna, the signals transmitted by the different antennas of the host machine appear to be parallel as shown by FIG. enlarged partial diagram of Figure 5b. The ddml path difference is the path difference D1-D2 that exists between signals from the two main antennas 11 and secondary 12 of the host craft and received by the companion gear. Likewise, the difference in path ddm2 is the path difference D1-D3 which exists between signals coming from the two main and secondary antennas 11 and 13. Each path difference ddml, ddm2, expressed in meters, is directly proportional to the difference in propagation time between the signals transmitted by the main antenna and the signals emitted by each of the two secondary antennas of the host vehicle and received by the companion gear, the proportionality factor being the speed of propagation of the light in the vacuum . Each difference ddml step, ddm2 depends on the distance dl, separating the two antennas 11, 12, respectively of the distance d2 between the two antennas 11, 13 of the host vehicle. Each difference in operation is determined by the measuring device 22 and corresponds to the difference between the measurements of pseudo-distances on the phase of the carrier between the signals emanating from the two antennas 11 and 12, and respectively 11 and 13. All the signals measurement being obtained by a single receiving chain aboard the companion craft 20, they all follow the same electrical path. This makes it possible to dispense with the use of calibration means and to eliminate measurement errors related to the use of several different measurement chains. In addition, the subtraction performed to obtain the difference of course measurements cancels out any possible errors related to the measurement chain, with the exception of errors related to antennas and switching means which are considered stable and calibrated on the ground beforehand. the mission. In a second step, the antenna 21 retransmits, via the radiofrequency link of location and inter-gear communication 33, the ddml, ddm2 path differences measured by the companion gear 20 in a message, towards the host vehicle 10, the message being transmitted in the time window allocated to the transmission of the companion machine 20. The message comprises, in addition to the transmission of the measurements of differences in operation of other data in the form of a global navigation signal. In practice, the message must include the TDMA specific synchronization field, and data concerning the selection of the antenna in reception, when there are several reception antennas, on the basis of power measurements for example. In addition, additional measurements, such as pseudo-distance measurements, can be exchanged between the transmit / receive antennas of two spacecraft, for example for calculating the inter-gear distance and the inter-clock time bias. . Finally, status and validity data of the measurements can complete the message. In a third step, the measurements of the differences of operation transmitted by the companion machine 20 are received 53 by the main antenna Rx / Tx 11 of the host machine 10 and then processed 54 by the processing device 14. The processing 54 consists of from measurements of gait differences and from the knowledge of the position of the antennas of the host vehicle in a reference frame linked to the triplet of antennas 11, 12, 13, to estimate in near real time, two angles of elevation and azimuth defining the angular position of the companion gear in a reference frame linked to the antenna triplet 11, 12, 13 of the host craft. Each difference of step ddml, ddm2 is equal to the product of the distance d1 separating the two antennas 11, 12, respectively from the distance d2 separating the two antennas 11, 13, and the cosine of the angle a1, respectively a2, between the direction of arrival of the signals called Line-of-Sight line of sight (LoS) and the alignment direction of the two antennas 11, 12, respectively 11, 13, on the face of the host vehicle. The two ddm1 difference of path measurements, ddm2 thus make it possible to obtain two angles a1, a2 of arrival of the signals with respect to the reference linked to the antennas and to deduce from it the angular position 55 of the companion machine 20 with respect to the host vehicle 10. FIG. 6 illustrates the elevation and azimuth angles defining the angular position of a spacecraft in an X, Y, Z coordinate system linked to the host vehicle, the line axis vector LoS is the vector unitary parallel to the vector connecting the landmarks of the two engines host and companion whose relative position must be determined. In the case where the reference X, Y, Z corresponds to the reference linked to the antennas, the components of the vector LoS according to the directions X and Y are first calculated by a simple division of the differences of step ddml, ddm2 by the length of the base antenna dl or d2 corresponding. The last component in the Z direction is obtained using the fact that the LoS vector is unitary. The azimuth angle cp is then obtained by a four-quadrant arc-tangent operation on the pair of directions Y, X. The elevation angle θ is obtained by an arc-cosine-type operation on the component according to the Z direction. Finally, if the clocks are a priori not synchronized between the 35 engines host and companion, it may be necessary to perform a transfer of time between the two spacecraft. For this, one can use a well-known technique of "two-way" type, consisting of combining the measurements of pseudo-distances go and return between a pair of transmit / receive antennas to know the time difference between them. clocks of the two spacecraft in order to be able to restore the angular measurement in the local time of the host vehicle, instead of that of the companion gear in which the raw measurements are made. In addition, the processing device 14 can also determine the inter-vehicle distance from the same measurements of pseudo-distances.
    [0008] The angular position obtained can then be supplied to a navigation filter 61 integrated in a guidance, navigation and control module CNG 62 of a central computer of the host machine, not shown, so that it can calculate in time. real, navigational maneuvers to perform to correct its position or orientation relative to the craft companion if necessary. Both host and companion gear are considered aligned when the azimuth angles cp and elevation 0 are zero. Due to the need for exchanging data between spacecraft, asynchrony of spacecraft clocks, and low-speed software spotting, typically 1 Hz, there is a lag time of one to two seconds between spacecraft clocks. the moment when the difference in operation measurement is made by the companion machine, and the instant when the angular position is available by the host vehicle for transmission to the CNG 62. In other words, CNG 62 is provided with a very high position. accurate but applicable to a past date. This is not a problem since the angular measurements are precisely dated and accompanied by angular velocity measurements, obtained by measuring the variation of the inter-antenna carrier phase differences, which allows precise re-synchronization of the measurements made, at the current time. Independently of the latency time, the measured differences in operation are a priori ambiguous when the distance separating the main antenna from each of the two secondary antennas is greater than the half-wavelength of the transmitted signal, which may correspond to a typical case, in S-band in particular, because the angular accuracy is better when the distance between the antennas increases. The measurements 35 therefore contain an unknown whole number of carrier phase cycles which may be different for each of the principal and secondary antenna pairs 12, 13 of the host vehicle, according to the relative angular position of the gears and the length of the gears. , d2, antenna bases. In the absence of a specific treatment, the calculations of the azimuth and elevation angles are therefore erroneous. In order to reduce the phase ambiguity of the carrier on the difference of gait measurements, the invention furthermore comprises a preliminary step consisting, before producing any nonambiguous difference in running measurement, of making a first rotation 40 of the machine. host around the Z axis parallel to the pointing axis of the antennas as shown in the example of Figure 7a. The first rotation 40 is carried out in a first direction, for example in the direction of clockwise, and has a rotation angle whose amplitude has been fixed in advance on the basis of criteria specific to the mission: the amplitude must be large enough to be able to make the first unambiguous visual axis measurement, but must remain compatible with the rotational capacity of the host vehicle and any constraints on its payload. No pre-alignment condition of the two host and companion gear is necessary, it is only necessary that the antenna triplet of the host craft is in radiofrequency visibility of an antenna Rx / Tx of the companion gear. The first rotation 40 is performed autonomously or by remote control from the ground according to the constraints of the mission, but in any case as a result of a process of acquisition and tracking signals allowing the two spacecraft to synchronize . In other words, the rotation begins when the bidirectional link 33 between two spacecraft is established and that measures of difference of course, then ambiguous, are available. As shown in the block diagram of FIG. 7b, during the rotation of the host vehicle, the host engages a signal on its different transmit antennas in the time slots assigned to it by the TDMA frame. The companion machine 20 acquires the signals in the time slots allocated to it and realizes 52 measurements of differences in operation, at different times t of successive measurements, the measurement instants succeeding each other as a function of the elementary period. of the terminal, typically 1 second between two successive measurement instants t and t + 1, and then transmits the measurements made on the bidirectional link between engines 33, to the host machine 10. Receiving 53 measurements, for the duration of the the rotation, the processing device 14 of the host machine calculates the variations 56 of the measured differences in travel between the successive measurement instants and combines these variations in walking differences with measurements 58 of inertial attitude variations of the machine performed at the same times t measurement by an inertial attitude sensor 59, for example by a stellar sensor or any other device for measuring inertial attitude to high precision, placed on board the host craft. This therefore corresponds to a particular mode of operation of the device of the host vehicle which must be informed by the CNG 62 via a specific means, for example a remote control, starting the rotation. The combination of radiofrequency measurements and inertial measurements makes it possible to obtain, unambiguously, the coordinates of the line axis vector LoS in the X, Y, Z coordinate formed by the two antenna pairs, main and secondary. , 12 and 11, 13, of the host machine: - Addmi - sin. Addm2 X LOS - 2.d1 2. (1 - cos v) .d2 sin Addm, - Addm2 YLOS - cos v) .di 2.d2 20 Noting XL0S and YLos the coordinates of the line-of-sight vector LoS at an initial time of the first rotation 40, y the angle of the rotation effected between the initial moment and the final moment of the first rotation and measured by the inertial attitude sensor 59, Addmi and Addm2 the measured differences in path differences on the two antenna bases of lengths dl and d2 between the two initial and final instants. These coordinates of the LOS axis vector correspond to an estimate 60 of the relative angular position between the host vehicle and the companion gear. Note that the above equations are given for an antenna triplet forming two orthogonal antenna bases, and for a very large inter-gear distance in front of the lengths d1 and d2 of the antenna bases. The person skilled in the art knows how to adapt these equations in the case where the two antenna bases are not perpendicular, or to take into account the effect of parallax when the inter-gear distance is not very great in front of them. dl and d2 lengths of the antenna bases. Once a first unambiguous measurement of the XLos and YLOS coordinates has been obtained, the radiofrequency system maintains the current measurement of the XLos and YLos coordinates by measuring the variation of the inter-antenna carrier phase differences in a continuous, unambiguous manner. and precise. Finally, the accuracy of the current measurement is essentially that of the initial measurement. The error on the initial measurement thus obtained contains several types of error components including error components specific to the radio frequency instrumentation relating to the multipaths caused by the reflection of the signals and to the calibration residuals of the electronics. transmission and reception, error components specific to the combination of radiofrequency and inertial measurements due to harmonization errors between the antenna triplet 11, 12, 13 and the reference trier of the inertial sensor 59 and measurement errors of the inertial sensor 59, and an error component related to the lateral movement of the companion machine 20 during the rotation. The first two types of error components can be reduced by implantation techniques and precautions well known to those skilled in the art. The error component related to the lateral movement of the companion machine 20, that is to say its displacement in a direction orthogonal to the LOS axis vector, can not be completely reduced at this stage of the operations. This component can nevertheless be significant, especially if the rotational actuators of the host machine have a moderate power, which causes a long duration of the first rotation maneuver and the possibility of a significant displacement of 30 companion gear during this time. The difficulty of reducing this error component is due to the fact that the two host 10 and companion gear 20 are not aligned, which leads to a misalignment of the lateral speed, as explained below. The vector V representing the relative speed of the companion gear 35 with respect to the host gear is the derivative with respect to the time t of the product D.
    [0009] LOS between the distance D between the two host and companion gear and the unit vector LOS, and is given by the equation: T7 = d (D.LOS) I dt = D .d LOS I dt + dD I dt "OS La lateral velocity (or orthoradial) is the first term of this sum: T71, = D .d LOS I dt The measurement of the variation of the carrier phase differences of antennas 11, 12, 13 of the triplet provides, in a precise manner and not ambiguous, the quantities derived from the components of the vector LOS in the reference frame X, Y, Z linked to the bases of the antennas 11, 12, 13 of the triplet, dXL0s / dt and dYLos / dt, but there is no direct measurement of dZLos / The knowledge of this third component is obtained from the norm of the unit vector LOS whose square is equal to 1 according to the expression below: X LOS 2 + YLOS 2 + DOS 2 = 1 Deriving this equality, the following equations are obtained: 2X Los dX Los I dt + 2Y Los dY Los I dt + 2.Zlos - dZ Los I dt = o dZ Los / dt = Xlos .dX Los / dt Y This equation shows that the error on the XLIDS and YLOS coordinates induced by the lack of knowledge of the lateral speed of the companion machine, 30 in turn causes the lack of knowledge of the lateral speed. This misunderstanding is weaker as XLos and YLos are small, that is to say that the two spacecraft are aligned. To solve this problem without performing a prior alignment of the spacecraft via dual-frequency measurement signals, the invention consists in carrying out the first rotation 40 despite the misalignment of the spacecraft 10, 20. The invention then consists in using the measurement of approximate angular position obtained at the end of this first rotation to achieve 63 an approximate alignment of the two spacecraft and then perform a second rotation of the host machine around the Z axis. The second rotation is performed in a second direction, opposite to that of the first rotation, for example in the opposite direction of clockwise, the angle of the second rotation having approximately the same value as the angle of the first rotation. The invention then consists in renewing the preceding operations, which makes it possible to perform a new unambiguous measurement of the angular position. The approximate alignment of the two host and companion gear made before the second rotation of the host gear makes it possible to obtain a more accurate measurement of the lateral velocity between the two spacecraft and thus a more accurate measurement of the relative angular position between the two spacecraft. two spacecraft host and companion because it is then corrected lateral movement undergone during this second rotation. It is possible to envisage a third phase of using the new angular position estimation to refine the alignment of the two machines and to perform a third rotation to further refine the knowledge of the angular position. But this third phase will prove useless most of the time. Moreover, the impact of the lack of knowledge of the lateral displacement on the process of identification of the ambiguities of measurement of axis at sight exposed above arises in term of angular uncertainty and not of absolute displacement. This impact can therefore be significantly reduced or canceled by sufficiently moving the companion vehicle away from the host vehicle, if it is compatible with the constraints related to the mission.
    [0010] The invention is not limited to a configuration with two spacecraft but applies to configurations having a number of spacecraft greater than two. Indeed, from the moment when N companion craft are in visibility of the triplet of antennas of the host craft, ie they are located in the half-space defined by the triplet of antennas, then the steps of the process Relative angular position determination can be performed for all these companion units by considering the host gear and each companion gear in pairs. In this case a first, single rotation of the host vehicle leads to a rough estimate of the relative position of the N companion craft in the reference frame related to the host vehicle. A strategy optimizing the number of rotations and / or intermediate alignments with each companion gear completes the process of unambiguous determination of the position of each companion gear. With regard to this last point, depending on the relative distance of the different spacecraft, the desired accuracy specifications or the specifications of the frequency of the chosen signal, it is possible to omit the maneuvers concerning the alignment of the host and companion gear and the second rotation of the host craft. For example, in K-band, an angular solution that is even biased by a few carrier wavelengths can generally provide a sufficiently precise positioning, unlike the S-band. The number of antennas placed on each host or companion machine may be greater to that which is explicitly represented in FIG. 1. In particular, so that the reception can be possible whatever the orientation of the spacecraft and to avoid the situations of blindness for which no antenna of a spacecraft is able to receive the signal, it is possible for each host and companion gear, to use two transmitting and receiving antennas 11a, 11b, 21a, 21b per machine instead of one. In this case, the two transmitting and receiving antennas 25 may preferably be placed on two opposite faces of each machine, as represented for example in the embodiment of FIG. 8. The presence of a single host vehicle 10 comprising a triplet of antennas 11, 12, 13 is sufficient to ensure the positioning of all the spacecraft of a formation in the frame linked to the host vehicle. However, to obtain a redundancy of the measurements or to improve the autonomy of the spacecraft, it is possible to equip each machine with the formation of a triplet of antennas similar to that of the host machine as represented for example in the figure 9a where the two spacecraft are equipped with an antenna triplet 35 on a first face and an antenna Rx / Tx on a second opposite face, according to another particular embodiment of the invention. In this case, the architecture of all the machines is identical to that of a host machine and the processing device 14 further includes a measurement module, allowing each machine to be able to assume the role of the host vehicle or the companion gear as needed. The two spacecraft are then interchangeable and can become the machine carrying the benchmark of the formation. When the formation is complex, that is to say when the number of spacecraft is greater than or equal to three, the different antennas of the training gear then make it possible to maintain the radiofrequency link 33 of location and communication between the different machines regardless of their relative positioning. FIG. 9b shows a graph illustrating an example of a TDMA frame that can be used to transmit and receive signals between two identical machines each comprising an antenna triplet on a first face and a transmitting and receiving antenna on a second face opposite the first face, according to an alternative embodiment of the invention. The antenna triplet mounted on the first face 71 of the first gear 10 consists of a Rx / Tx antenna 11 operating on transmission and reception and two antennas Tx 12, 13 operating on transmission only. In addition, the first machine 10 comprises a transmitting and receiving antenna 73 mounted on the second face 72 opposite to the first face 71. The antenna triplet mounted on the first face 74 of the second vehicle 20 consists of a Rx / Tx 75 antenna operating on transmission and reception and two Tx antennas 76, 77 operating on transmission only. In addition, the second machine 20 comprises a transmitting and receiving antenna 21 mounted on the second face 78 opposite to the first face 74. Only the antennas pointed towards the antennae of another machine can communicate with each other. In FIG. 7, only the antennas Rx / Tx 21 mounted on the face 78 of the second machine 20 and the antenna triplet Rx / Tx 11, Tx 12, Tx 13 mounted on the face 71 of the first machine 10 are capable of communicating. through the inter-gear communication link 33. In addition, each gear has an architecture corresponding to that of a host gear and is capable of processing measurements made and transmitted by the other gear to extract an estimate of the relative angular position between the two machines. The two machines can therefore function as a host vehicle when the orientation of their antenna triplet is pointed to the inter-gear communication link 33 or as a companion device. The signals emitted by antennas pointed in opposite directions to the inter-gear communication link 33 can not be received by another craft. In the example of FIG. 9a, the operational antenna triplet is the triplet 11, 12, 13 placed on the first machine 10. It is therefore the first machine that is capable of processing measurements made by the second machine 20. and to estimate the relative angular position between the two gears. However, in the case of a formation flight for example, the antenna triplet of the second craft 20 may be operational with respect to a third craft, not shown, of the formation and be a host craft with respect to this third craft. . The TDMA frame consists of several successive time windows, each time window being dedicated to the transmission or reception of signals on a particular antenna of the first gear 10 or on an antenna of the second gear 20. The signals emitted by each gear to In turn, there are measurements and data modulated by a carrier. These emitted signals make it possible to transmit data between the machines and to make measurements of angles and relative distances between the machines. The first line of the graph of FIG. 9b indicates the measurements that can be performed during the different time windows of the TDMA frame. The second line of the graph shows the active antennas of the first gear during each time window. The third line of the graph indicates the active antennas of the second gear 20 during each time window. When a machine transmits a signal, all the other machines are in reception mode and listen to the transmitted signal. In order for the reception power level to be sufficient, it is necessary for the receiving antennas of the machines that are listening to be correctly oriented with respect to the antennas of the transmitting machine. It therefore depends on the relative orientation of the different gear. A power measurement device can be placed on board each craft to select, in real time, the best receiving antenna according to the estimated power levels on each antenna.
    [0011] The power measurements necessary for the dynamic selection of the receiving antenna are carried out continuously, following the TDMA frame, in parallel with the other measurements. The first half of the TDMA frame corresponds to the time period allocated to the first gear 10 for transmission. This period of time comprises four time slots respectively allocated to the four antennas Rx / Tx 11, Tx 12, Tx 13, Rx / Tx 73 of the first machine 10 which in turn transmit in a predetermined order and a priori non-modifiable. During this period, the Rx / Tx 21 or Rx / Tx antennas 75 of the second gear 20 listen and the Rx / Tx 21 or Rx / Tx 75 antenna whose power is the strongest makes measurements. The determination of the antenna of the second machine 20 having the highest power is carried out by the first machine 10. For this, in reception, the first machine 10 realizes the power measurement on the signals emitted by the antennas of the second machine 20, and then retransmits the power measurements made on the bidirectional link 33 for transmitting the data. In reception the second gear 20 selects the antenna Rx / Tx which generated the greatest power when it was in transmission. In FIG. 7, it is the Rx / Tx antenna 21 of the second machine 20 which will have the highest power level and whose measurements will be used. In addition, during the emission period of the first gear, the first gear exploits the 20 measurements transmitted to it by the second gear during a previous time window during which he listened and determines his angular position relative to the second gear and the distance that separates it from this second craft. The second half of the TDMA frame corresponds to the time period allocated to the second gear 20 for transmission. This period of time comprises four time slots respectively allocated to the four antennas Rx / Tx 21, Tx 74, Tx 76, Rx / Tx 75 of the second machine 20 which emit in turn in a predetermined order and a priori non-modifiable. During this period, the antennas Rx / Tx 11 and Rx / Tx 73 of the first gear 30 10 listen and the antenna Rx / Tx 11 or Rx / Tx 73 whose power of reception is the strongest measures. In FIG. 7, only the Rx / Tx antenna 21 is correctly oriented so that the signal it emits is received by the first gear 10. Consequently, the first gear can not make any gait difference measurements from the first gear. However, with the reception of a single signal, it is possible to produce measurements of relative distance (in English: ranging) between the two machines from the half-sum of the pseudo-signals. distances exchanged on the bidirectional link 33 of data transmission. The half-difference of the same relative distance measurements generates the inter-clocks bias, necessary for the local time dating of the host vehicle, of the difference in gait measurements made by the companion gear. By way of non-limiting example, for a TDMA frame duration of 80 ms, it is possible to allocate 10 ms to each transmission time window for each of the two devices.
    [0012] The invention can be applied to any set comprising at least two spacecraft whose relative position must be determined. Both spacecraft may be part of a plurality of spacecraft, such as satellites, in formation flight. In this case, the relative positioning between the formation machines can be performed identically for all the spacecraft spacecraft taken twice by two, the TDMA frame then having additional time slots allocated to the antennas. other gear of the formation. For N spacecraft equipped with M antennas each, the frame will have NxM transmission time windows. For example, for a formation of three machines each having four antennas, the TDMA frame must have 12 transmit time windows. If 10 ms is allocated to each antenna, then the overall duration of the frame is 120 ms. Spacecraft may also consist of a cargo vehicle and a space station, the cargo vehicle wishing to dock at the space station. In this case, the cargo vehicle must be equipped with at least one antenna triplet and the space station must have at least one receiver equipped with a transmitting and receiving antenna associated with transmitting and receiving means and measurement means for taking measurements of the relative position of the approaching cargo vehicle and distance measurements between the cargo vehicle and the space station from the signals transmitted by the antenna triplet of the cargo vehicle and retransmitting measurements to the approaching cargo vehicle. Depending on the number of antenna triplets existing on the different gears, the position and the initial orientation of the different gears, there may be 35 cases where no triplet is in visibility of one or more other gears.
    [0013] Thanks to the additional transmit and receive antenna disposed on a face opposite to the triplet of antennas or to previous measurements of the GNC navigation module 62, it is then possible to modify the orientation of the gear (s) concerned in order to quickly replace the corresponding antenna triplet in a favorable configuration. Although the invention has been described in connection with particular embodiments, it is obvious that it is not limited thereto and that it includes all the technical equivalents of the means described and their combinations if they are within the scope of the invention.
    权利要求:
    Claims (9)
    [0001]
    REVENDICATIONS1. A method for determining, by pair of spacecraft, the relative angular position between a plurality of spacecraft (10, 20), characterized in that it consists: - in transmitting (50) sequentially at least three radio frequency signals from an antenna triplet (11, 12, 13) mounted on a first face of a first spacecraft said host vehicle (10), the antenna triplet consisting of a main transmitting and receiving antenna ( 11) and two secondary transmitting antennas (12, 13), - to receive (51) the three radiofrequency signals on a transmitting and receiving antenna (21) of one or more second spacecraft called companion gear (20), to measure (52) onboard each companion gear (20), differences in the path between the signal coming from the main antenna (11) and the signals coming from each of the two secondary antennas (12, 13). , then to transmit by each companion gear (20) to the host craft (10) a signa l radiofrequency containing the measurements made, - to receive (53) and to treat (54) on board the host vehicle (10), the radiofrequency signal containing the measurements transmitted by each companion gear (20) and to deduce the position therefrom relative angular (55) of each companion gear (20) in a frame linked to the host craft (10).
    [0002]
    A method for determining, by a pair of spacecraft, the relative angular position between a plurality of spacecraft according to claim 1, characterized in that all radiofrequency signals are transmitted or received sequentially by the different spacecraft antennas (10, 20), by means of a bidirectional radiofrequency link (33) for locating and inter-gear communication, according to a TDMA frame consisting of several successive time windows respectively allocated to each antenna (11, 12, 13) of the host (10) and at each antenna (21) companion gear (20) for transmitting or receiving radiofrequency signals.
    [0003]
    3. A method for determining, by pair of spacecraft, the relative angular position between several spacecraft according to claim 2, characterized in that all radiofrequency signals transmitted or received are modulated by a carrier having an identical frequency F1.
    [0004]
    4. A method for determining, by pair of spacecraft, the relative angular position between several spacecraft according to claim 3, characterized in that it further comprises an additional step for reducing a phase ambiguity of the carrier, consisting: without prior alignment of the two spacecraft, to perform a first rotation (40) of the host vehicle (10) about an axis Z parallel to a pointing axis of the antennas (11, 12, 13) of the triplet, the first rotation (40) being carried out in a first direction and having a rotation angle of any predetermined value, and then acquiring (52) step difference measurements, at different successive measurement times, throughout the duration of the rotation and calculating (56) variations in gait differences between the successive measurement instants, at the same successive measurement instants, to measure (59) variations in inertial attitude (58) of the host engine, from the variations of the differences in the market and the measured variations of inertial attitude, deduce therefrom (60), for each pair of spacecraft, an estimate of the relative angular position between the spacecraft, then to aligning (63), in pairs, the host and companion spacecraft and performing a second rotation of the host craft (10) about the Z axis, the second rotation being performed in a second direction opposite to the first direction and having a rotation angle of almost identical value to the first rotation and to realize (55) for each pair of spacecraft, a new unambiguous measurement of the relative angular position between the spacecraft.
    [0005]
    5. System for determining, by pair of spacecraft, the relative angular position between several spacecraft for carrying out the method according to one of the preceding claims, the system comprising at least a first spacecraft (10) said host vehicle and a second spacecraft (20) said companion gear, characterized in that: the host craft (10) comprises at least one antenna triplet (11, 12, 13) mounted on a first face, the triplet of antennas consisting of a main transmitting and receiving antenna (11) and two secondary transmitting antennas (12, 13), a transmission channel (16) being successively coupled to the transmission, each antenna of the antenna triplet (11, 12, 13) and a reception channel (17) which can be coupled to the reception, at the main antenna (11), a radiofrequency switch (19) able to sequentially select the different antennas of the triplet and a disposi processing unit (14) for determining a relative angular position between the host machine and the companion machine from measurements of gait differences transmitted by the companion gear (20), the companion gear (20) includes least one transmitting and receiving antenna (21) placed on a first face, a transmitting channel (23) and a receiving chain (24) respectively coupled to the transmitting and receiving antenna (21) and a measuring device (22) for measuring differences in operation between a radiofrequency signal received from the main antenna (11) and radio frequency signals received from each of the two secondary antennas (12, 13) of the antenna triplet of the antenna; host craft (10).
    [0006]
    6. Determination system according to claim 5, characterized in that the host vehicle (10) further comprises a device (59) for measuring the attitude variations of the host vehicle.
    [0007]
    7. Determination system according to claim 5, characterized in that each host and companion spacecraft (10, 20) further comprises a second transmitting and receiving antenna (11b, 21b) placed on a second face (72, 74) opposite the first face (71, 78) of the corresponding spacecraft.
    [0008]
    8. Determination system according to claim 7, characterized in that each host and companion spacecraft (10, 20) comprises a triplet of antennas (11, 12, 13), (75, 76, 77), a processing (14) and a difference measuring device (22).
    [0009]
    9. Determination system according to claim 7, characterized in that it further comprises, on board each host spacecraft and companion (10, 20), means for measuring the power level of the signals received by each antenna of reception and means for selecting the receiving antenna having the highest power level.
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    同族专利:
    公开号 | 公开日
    JP2015155897A|2015-08-27|
    EP2902797A1|2015-08-05|
    FR3017213B1|2016-02-05|
    JP6563204B2|2019-08-21|
    US20150219747A1|2015-08-06|
    EP2902797B1|2021-07-21|
    US10126405B2|2018-11-13|
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    法律状态:
    2015-01-08| PLFP| Fee payment|Year of fee payment: 2 |
    2015-12-23| PLFP| Fee payment|Year of fee payment: 3 |
    2016-12-29| PLFP| Fee payment|Year of fee payment: 4 |
    2017-12-21| PLFP| Fee payment|Year of fee payment: 5 |
    2019-12-30| PLFP| Fee payment|Year of fee payment: 7 |
    2020-12-22| PLFP| Fee payment|Year of fee payment: 8 |
    2021-12-24| PLFP| Fee payment|Year of fee payment: 9 |
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    JP2015016947A| JP6563204B2|2014-01-31|2015-01-30|Radio frequency method and system for determining relative angular position between multiple remote spacecraft by a pair of spacecraft|
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