RU2849445C1 - Method for determining location of satellite communication ground station by retransmitted signal - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: method relates to methods for determining the location (OM) of radio emission sources and can be used to determine the location of a ground station (GS) for satellite communication (SS) by receiving and processing their signals, retransmitted from spacecraft (KA), at a ground station for determining the location (ZCOM). The method uses Q≥ 3 M-channel spatially separated quantum optical stations (COS), the control and synchronisation of which is carried out by ZCOM by setting the parameters of the spacecraft orbit KA_2,…, KA_M+1, and their predicted availability in the controlled area. Based on these parameters, the Q quantum optical stations calculate the angles of inclination of the QOS laser channels for each NKA at the nth point, n=1, 2, …, N, at t_n time points, where N is the number of NCA coordinate measurement points, channels from the 1st to the Mth of each of the Q quantum-optical stations are oriented in the direction of the corresponding NKAs and automatically track their movement, measure the distance of the NKAs at each nth point from the corresponding KOS at time t_n, and transmit the results to the ZCOM, where the signal of the 1st ZS, retransmitted by KA₁ with a positive signal-to-noise ratio, is used at each of the N time points t(n) as a reference, the refined coordinates of all M NKAs are calculated at the ZCOM, and the measurement of delays Δτ_1,m in the reception of signals from the 1st ZS at each of the N points are performed using a correlation method based on the use of refined NCA coordinates and the signals retransmitted by them, the coordinates of the ZS are determined by a differential range-finding method, and the NCA function additionally includes the reflection of laser radiation generated by the COS using corner reflectors.

EFFECT: increased accuracy of the OM ZS due to a significant reduction in the error of determining the coordinates of the NKA and compensation for the error of the OM KA in geostationary orbit by using the differential differential range-finding method for the OM.

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Description

The method relates to radio engineering, namely to methods for determining the location (LO) of radio emission sources, and can be used to determine the location of an earth station (ES) of satellite communications (SC) by receiving and processing their signals, relayed from spacecraft (SC), at an earth station for determining the location (ES).

A method for determining the location of a satellite earth station is known (see Russian Patent No. 2653866, IPC G01S 5/06 (2006.01), published on 16.05.2018, Bulletin No. 14). The analogue assumes the simultaneous recording of a sequence of readings of the levels of useful ES signals y _s (n) and spurious emissions x(n), received over the observation interval T _n 3COM, where n=1,2,…, N, N is the reading number with a step Δt, s=1,2,…, s is the number of the spacecraft with known coordinates. Based on the comparison of y _s (n) and x(n), one-dimensional arrays are formed: A _s with elements A _s (k)=-1 if y _sk <y _S,k-1, A _s (k)=1 if y _s,k >y _S,k+1 , A _s (k)=0 if y _S,k =y _s+1 and B with elements B(k)=1 if x _k <x _k+1 , B(k)=-1 if x _k >x _k+1 , B(k)=0 if x _k =x _k+1 , where k=1, 2,…,N - 1. For each pair of arrays A _s and B, the obtained feature values are summed up and the number of matches of elements with the same indices W _s is determined. The location of the source of spurious emissions (SSE) is determined by referencing the coordinates of the SS operating through the spacecraft exposed to the SSE.

The analogue provides for simplified implementation with the elimination of limitations of functionality in areas with a high density of land use sites when determining the location of the individual data sources.

The analog method has inherent shortcomings that limit its application. Implementation of the analog requires the availability of information on the precise locations of legitimate satellites operating through a single satellite. Low measurement efficiency is due to the need to perform Q measurements to obtain a single coordinate. The analog is characterized by low noise immunity under various types of interference and low accuracy of the satellite's OM.

A method for determining the location of a satellite communication earth station using a retransmitted signal is known (see Russian Federation Patent No. 2663193, IPC H04K 3/00 (2003.01), published on 02.08.2018, Bulletin No. 22). The analogous method uses an earth station for determining location consisting of three antennas Ant. 1, Ant. 2 and Ant. 3, a multi-channel coherent radio receiver (RPU) and a radio transmitter (RTD), with the help of which a test radio signal (TRS) is formed and emitted in the entire band of the operating frequencies of the spacecraft, coherently received over a time interval ΔT using the RPU and its retransmitted copies are stored from at least three spacecraft KA _l, KA ₂ and KA ₃ with known coordinates located in the electromagnetic availability zone 3COM and 3S. The signals from the spacecraft are fed to the corresponding inputs of the multi-channel coherent radio receiver via their corresponding antennas Ant. 1, Ant. 2 and Ant. 3. The frequency instability of each of the coherent channels of the multi-channel radio receiver is compensated for. The slant range from 3COM to spacecraft _1, spacecraft ₂ and spacecraft ₃ is calculated, based on which the coordinates of the spacecraft KA _l, KA ₂ and KA ₃ are adjusted. Coherent reception of retransmitted copies of signals from a given ES is performed. The delays in receiving ES signals Δτ- _1,2 and Δτ _1,3 are measured using the correlation method from the directions to the spacecraft KA ₁ , KA ₂ and KA _l, KA ₃ , respectively. The obtained values Δτ _1,2 and Δτ _1,3 are stored. The location of the ground control station is determined using the differential range finding method (DRF).

The analogue ensures a reduction in the measurement error of the coordinates of the ground station by eliminating the procedures for measuring the values of the Doppler frequency shift of the signal and the associated procedures for measuring the angle between the direction-finding bases (DFB) in the selected pairs of DFBs.

However, the analogue has inherent disadvantages that limit its application. The main ones are low noise immunity and the resulting unsatisfactory accuracy of the ES OM in many cases. A situation arises when the ES signal arrives at the "main" satellite along the main lobe of the radiation pattern (RP) under conditions of a low signal-to-noise ratio (SNR). One of the reasons may be intentional jamming (see Russian Patent No. 2707878, H04K 3/00, GO IS 5/00, published 02.12.2019, Bulletin 34). Another reason is the suboptimal placement of the 3COM relative to the ES location for various reasons. Moreover, the appearance of a legitimate signal in a given part of the spectrum of a "mirror" satellite dramatically worsens the signal-to-noise situation. The ground station's signal arrives at the satellite via a side lobe of the radiation pattern (RP) and is significantly weaker in power than the satellite's legitimate signal. Therefore, when these side lobes occur, the analog signal loses functionality. This, in turn, leads to errors in determining the ground station's coordinates.

A method for determining the location of a satellite communications earth station using a retransmitted signal is known (see Russian Patent No. 2755058, IPC H04 K 3/00 (2008.01), published on September 14, 2021, Bulletin No. 26). The analogue uses an earth station for determining location consisting of three antennas Ant. 1, Ant. 2 and Ant. 3, a multi-channel coherent radio receiver and radio transmitter, form and emit a test radio signal in the entire operating frequency band KAΔF using a radio-frequency transmitter, carry out coherent reception of the radio-frequency transmitter over a time interval ΔT and store its retransmitted copies from at least three spacecraft KA ₁ , KA ₂ and KA ₃ , with known coordinates located in the electromagnetic availability zone of the ZSMO and ZS, the signals of the spacecraft through the corresponding antennas Ant.1, Ant.2 and Ant.3 are fed to the corresponding inputs of the multi-channel coherent radio-frequency transmitter and are used to compensate for the frequency instability of each of the coherent channels of the multi-channel radio-frequency transmitter based on the results of TRS reception, calculate the slant range from 3COM to KA _l, KA ₂ and KA ₃ , correct the coordinates of the spacecraft KA _1, KA ₂ and KA ₃ on their basis, carry out coherent reception of retransmitted copies of the signals from a given ES, the delays in receiving ES signals Δτ _1,2 and Δτ _1,3 are measured using the correlation method from the directions to the spacecraft KA _l, KA ₂ and KA _l, KA ₃ , respectively, the obtained values Δτ _1,2 and Δτ _1,3 are stored, and the locations of the ES are determined using the difference-ranging method. Before each measurement of the ES coordinates, a TRS is formed and emitted in a given frequency band ΔF _j . The frequency instability of each of the coherent channels is eliminated. The measured and stored sets of levels are compared signal of the ground station W _j (.ΔF _i ) and noise W _jш (ΔF _i ) of each j-th spacecraft, j=2.3, =W _j (ΔF _i )+W _jШ (ΔF _i ), in the frequency band ΔF _i, with a set of levels signal W ₁ (ΔF _i ) and noise W _1Ш (ΔF _i ) in the first, main spacecraft. In case of exceeding the threshold level W _min ,

at least for one j-th spacecraft, the signal of the ground state S ₁ (ΔF _i ) is isolated in the first spacecraft from the set =S ₁ (ΔF _i )+S _1Ш (ΔF _i ), S _1Ш (ΔF _i ) - the noise signal distributed in ΔF _t and possible concentrated emissions form its copy with an accuracy of phase with a high level, and noise-free S _1Ш (ΔF _i ), and the measurement of the delay Δτ _1;j is performed by the correlation method using the main signal

In this case, the selection of the ES signal in the first spacecraft S ₁ (ΔF _i ) is carried out using adaptive filtering and subsequent evaluation of its main characteristics at the first stage: the operating frequency band, the value of the carrier frequency, the type of modulation and manipulation, the speed of manipulation, and on their basis the demodulation of the signal, with subsequent restoration of the signal at the second stage with an accuracy of up to the phase and its amplification to a value that ensures the determination of the coordinates of the ground station.

The analogue ensures increased noise immunity in the measurement of the coordinates of the ground station by isolating the ground station signal from the noise, mainly from the spacecraft, analyzing it, creating a copy of it with phase accuracy at a high level and free from noise and interference, with subsequent use in the RDS.

However, the analog has inherent drawbacks that limit its use. In practice, situations are not uncommon where auxiliary satellites are absent, or there is only one. As a result, the analog loses its functionality. Furthermore, reconstructing the _S1 (ΔF _i ) signal with phase accuracy presents a technical challenge. The main drawback of the analog is the low accuracy of the S1 signal.

A known method for determining the coordinates of a satellite communication earth station using a retransmitted signal (see Russian Patent No. 2749456, IPC H04KZ/00 (2006.01), published on 11.06.2021, Bulletin No. 17) consists in using an earth station for determining location consisting of three antennas Ant. 1, Ant. 2 and Ant. 3, a multi-channel coherent radio receiver and radio transmitter (RPD), the formation and emission by the RPD of a test radio signal in the entire operating frequency band of the spacecraft ΔF and coherent reception by the RPU over the interval ΔT and storing its retransmitted copies from at least three spacecraft KA _1? KA ₂ and KA ₃ with known coordinates located in the electromagnetic availability zone 3COM and ES, the signals of which through the corresponding antennas Ant. 1, Ant. 2 and Ant. 3 are fed to the corresponding inputs of the multi-channel coherent radio receiver, compensation for the frequency instability of each of the coherent channels of the multi-channel radio receiver based on the results of receiving the TRS, calculating the slant range from 3COM to KA _1, KA ₂ and KA ₃ with subsequent correlation on their basis of the coordinates of KA _l, KA ₂ and KA ₃ , before each successive measurement of the coordinates of the ES, the TRS is formed and emitted in a given frequency band ΔF _i , the current frequency instability of each of the coherent receiving channels is eliminated, the previously measured and stored noise levels P _j (ΔF _i ), j = 2,3, of the selected j-th KA in the frequency band ΔF _t are compared with their current level P _jcurrent (ΔF _i ), in case of exceeding the noise level increment in the j-th KA Pj(ΔF _i ) the threshold level Δd, ΔP _j >Δd, ΔP _j (ΔF _i )=P _jтек (ΔF _i )-P _j (ΔF _i ), make a decision on the appearance in the frequency band ΔF _i of signals of the 1st ES, retransmitted by the j-th spacecraft, select the detected signals of the 1st ES S _l (ΔF _£ ) of the j-th spacecraft by subtracting from the set signals of the j-th spacecraft: - S _j (ΔF _i )=S _j (ΔF _i )+ -S _j (ΔF _i )= - a set of signals from the 1st earth station, the coordinates of which are subject to determination, and noise, measure the delays in receiving the ES signals Δτ _1,2 and Δτ _1,3 using the correlation method from the directions of KS 1, KS 2 and KS 1, KS 3, respectively, store the obtained values Δτ ₁₂ and Δτ ₁₃ , and determine the location of the ES using the difference-range method.

The analogue ensures increased noise immunity in the measurement of ground station coordinates by using the procedure of isolating the interference signal and subtracting it from the group signal.

However, the analog has a drawback that limits its application. In many practical situations, auxiliary satellites suitable for measurements may be absent, or their number may be limited to one. As a result, the prototype loses its functionality. Furthermore, the low SNR of adjacent satellites leads to low accuracy in determining the ground station's location.

The closest in its technical essence is the method of determining the location of a satellite communications earth station using a retransmitted signal (see Patent of the Russian Federation No. 2837386, IPC H04K 3/00, published 31.03.2025, Bulletin No. 10).

The prototype consists of using a ground station for determining the location in the use of a ground station for determining the location as part of an antenna system, a multi-channel coherent radio receiver with a unit for calculating coordinates and a radio transmitter, M, M≥2 low-orbit spacecraft KA ₂ , KA ₃ , ..., KA _M+1 , a control post for the NKA; automatic tracking of the direction of the antennas Ant.2, ..., Ant.M+1 to the corresponding NKA, orientation of the Ant. 1 in the direction of the "main" KA _1, located in a geostationary orbit and providing retransmission of signals of the 1st ES along the main lobe of the directional aperture, detection of signals of the l -th ES in the coordinate calculation unit 3COM on the basis of the downlink of KA _{1 signals,} technical analysis, determination of the central frequency F _i and the spectrum width ΔF _i , determination on the basis of the frequency plan of KA ₁ of the frequency parameters F _bi and ΔF _bj of the uplink of the l -th ES, transmission of the values of F _bi and ΔF _bj obtained in 3COM to the NSC control unit, the results of the forecast of the date and time of the location of the NSC KA ₂ ,…, KA _M+1 in the electromagnetic availability zone (EMA) of the l -th ES, 3COM and control unit, assignment from the NSC control unit to all M NSC via a low-speed communication channel of the switching on time and turning off repeaters located on board them, the parameters of the relayed signal F _i , ΔF _£ and F _Bi , ΔF _bi , the time of transmitting messages to the control unit about the current coordinates of the corresponding m-th NS (x, y, z, t _n ) _m , n=1,2,…,N,N is the number of messages during the flight over the search area, t _n is the time of measuring the NS coordinates at the n-th point, m=2,3,…, M+1, m is the NS number, coordinate-time data from all M NS, sequential transmission to the control unit and then to 3COM of coordinate-time data from all M NS, timely orientation of Ant.2,…, Ant. M+1 to the corresponding NS based on the TLE parameters of their orbits, elimination of the current instability of all M+1 receiving channels of the RN in the frequency band ΔF _i at times t _n based on the results of receiving the test radio signal emitted by the RPD, determination of the coordinates of the l -th ES M NSC by receiving signals from the l-th ES in the frequency band ΔF _bi and retransmitting them to 3COM in the band ΔF _i , which are fed to the corresponding inputs of the radio receiver through Ant.2,…, Ant. M+1, simultaneously the signals from the l-th ES, retransmitted by KA ₁ , are fed to the first input of the radio receiver through Ant.1, determining M delays in receiving signals Δτ _1,M at each of the N points of the spatial position of the NSC based on the coordinates of KA ₁ and M NSC and the signals from the l-th ES retransmitted by them, determining the location of the l-th ES using the difference-ranging method.

The prototype improves the accuracy of the OM ZS compared to similar devices due to the increased signal strength from the navigation satellites compared to auxiliary satellites in geostationary orbit. However, the prototype shares a common drawback with its analogs: insufficient OM ZS accuracy and the inability to operate in conditions of radio jamming or navigation field distortion.

The purpose of the claimed technical solution is to develop a method for determining the location of a mobile earth station for satellite communications based on a retransmitted signal using differential radar, which ensures an increase in the accuracy of the OM ES by significantly reducing the error in determining the coordinates of the NSC and compensating for the error of the OM SS in geostationary orbit.

The stated objective is achieved by the fact that in the known method of determining the location of satellite communications using a retransmitted signal, which consists of using an earth station for determining the location as part of an antenna system, a multi-channel coherent radio receiver with a coordinate calculation unit and a radio transmitter, M, M≥2 low-orbit spacecraft SC₂, KA₃,…, KA_M+1, the control point of the spacecraft; automatic tracking of the direction of the antennas Ant.2, …, Ant. M+1 to the corresponding spacecraft, orientation of Ant. 1 in the direction of the “main” spacecraft_1,located in geostationary orbit and providing retransmission of signals of the 1st ES along the main lobe of the directional aperture, detection of signals of the l -th ES in the coordinate calculation unit of the 3COM RPU based on the downlink of KA signals_l,technical analysis, determining the central frequency F_£and the spectral width ΔF_i, determined on the basis of the spacecraft frequency plan₁frequency parameters F_biand ΔF_bjascending line of the l -th ZS, transmission of the values of F received in ZSOM_bjand ΔF_bjat the NSC launch site, the results of the forecast of the date and time of the NSC's location₂,., KA_M+1in the electromagnetic availability zone of the l-th ZS, 3COM and PU, the task from the PU of the NSC to all M NSC via a low-speed communication channel of the turn-on timeand turning off repeaters on board, parameters of the retransmitted signal F_i, ΔF_iand F_Bi, ΔF_Bi, the time of transmission of messages to the control unit about the current coordinates of the corresponding m-th NSC (x, y, z, t_n)_m, n=1,2,…,N, N - the number of messages during the flight over the search area, t_n- time of measurement of the coordinates of the navigation spacecraft at the n-th point, m=2,3,…, M+1, m is the number of the navigation spacecraft, coordinate-time data from all M navigation spacecraft, sequential transmission to the control unit and then to 3COM of coordinate-time data from all M navigation spacecraft, timely orientation of Ant. 2,…, Ant. M+1 to the corresponding navigation spacecraft based on the TLE parameters of their orbits, elimination of the current instability of all M+1 receiving channels of the control unit in the frequency band ΔF_iat times t_nbased on the results of receiving a test radio signal emitted by a radio-frequency device, determining the coordinates of the l-th ES of the M NKA by receiving signals from the l-th ES in the frequency band ΔF_Biand their retransmission to 3COM in the ΔF band_i, which through Ant.2,…, Ant. M+1 are sent to the corresponding inputs of the radio receiver, simultaneously the signals of the l -th ground station, retransmitted by the satellite_1,through Δnt. 1 are fed to the first input of the RPU, determining M delays in receiving signals Δτ_1,Mat each of the N points of the spacecraft's spatial position based on the spacecraft's coordinates₁and M NSC and the signals of the l-th ES relayed by them, determining the location of the l-th ES using the difference-ranging method, while additionally using Q≥3 M-channel spatially separated quantum-optical stations (QOS), the control and synchronization of the operation of which is carried out by 3COM by setting the orbital parameters of the NSC KA₂, …, KA_M+1, forecast of their availability in the controlled area, on their basis at Q quantum-optical stations the angles of inclination of laser channels for each NCA at the n-th point, n=1,2,…, N, are calculated in t_n-th moments of time, where N is the number of measurement points of the coordinates of the NSC, channels 1 through M of each of the Q quantum-optical stations are oriented in the direction of the corresponding NSC and their movement is automatically tracked, the distance of the NSC is measured at each n-th point from the corresponding QOS at moments of time t_n,the obtained results are transmitted to 3COM, where the signal of the l-th station, retransmitted by the satellite₁with a positive signal-to-noise ratio, used at each of the N time points t_nas reference, the refined coordinates of all M NKA are calculated on 3COM, and the measurement of delays Δτ_1,Min the reception of signals from the 1st ES in each of the Trays, a correlation method is used based on the use of refined coordinates of the NSC and the signals retransmitted by them; the coordinates of the ES of the differential RDS are determined based on measurements of the signal delays Δτ_m,m+1,and the functions of the NCA additionally include the reflection of laser radiation generated by the COS using corner reflectors.

The claimed method is illustrated by drawings:

Fig. 1 shows the conditions when in the zone of electromagnetic availability of the Earth station there are 3 satellites, 3 COM, a launcher for a spacecraft, a spacecraft KA ₁ in a geostationary orbit and two (KA ₂ and KA ₃ ) in a low-orbit orbit;

Fig. 2 shows a generalized algorithm for determining the location of a satellite earth station using a retransmitted signal;

Fig. 3 shows the external appearance of the U12 CubeSat-based NSC with a corner reflector installed on it;

Fig. 4 shows a generalized structural diagram of the NCA;

Fig. 5 shows a generalized algorithm for the operation of the NCA;

Fig. 6 shows the results of modeling the proposed method:

a) dependence of the root mean square error (RMS) of the positioning of the NSC on the value of the “worst” (maximum difference from 90°) angle of the three possible angles formed by the laser beams of the KOS:

b) dependence of the standard deviation of the position of the ground station on the SNR for different values of the “worst” angle of the probing beams;

c) the dependence of the maximum error of the differential RDS OM on the accuracy of the NCA OM for different SNR at the input of the RPU.

The essence of the proposed method is as follows. Geolocation systems using three or more satellites in geostationary orbit to determine the location of an earth station are currently widely used. A number of requirements must be met for these systems to function. These include the presence of at least two additional relay satellites ("mirror" or adjacent satellites) that have identical uplink frequencies, antenna system polarization, and coverage areas. The accuracy of the EOSS is significantly impacted by the location error of the satellites involved in the measurements and their velocity vectors.

The multi-satellite architecture for determining the location of ground stations involves the use of differential-range, differential-Doppler methods, or their combinations (see Char M. Application of a dual satellite geolocation system on locating sweeping interference // World Academy of Science, Engineering Technology. -2012. V. 6, #9, p.1029-1034).

Repeater satellite KA ₁ is the "primary" one, as it relays the signal from the first ES along the main beam pattern. In analogs, the second and third KA are adjacent, located at some distance from KA ₁ , and capable of transmitting the same radiation received along the side lobes of the ES pattern, but with greater attenuation. Their level typically fluctuates between -70 dB and -40 dB. If 3COM is located within the EMD zone formed by the antenna systems of these KA, its multi-channel radio receiver will be able to receive signals from these KA, process them, and determine the ES coordinates. However, situations are not uncommon where auxiliary spacecraft KA ₂ and KA ₃ are absent, or there is only one. This problem is solved in the prototype using M,M≥2 low-orbit spacecraft with signal repeaters onboard. In this case, the level of the retransmitted signals from the ES is +5…-25 dB for microwave frequencies (taking into account the smaller diameter antenna and the shorter distance to the NS). As a result of the increase in the signal level (by 45 dB) in relation to the auxiliary NS in GEO, the signal-to-noise ratio increases. The latter entails an increase in the accuracy characteristics of the proposed method. Fig. 1 shows a variant of such a solution, when the source signals are retransmitted by NS ₁ in geostationary orbit and two NS. The use of one NS makes it possible to determine the coordinates of a stationary ES. The movement of the NS in space makes it possible to carry out successive measurements of Δτ _{1,n ,} n=1,2,…,N, over time, obtaining not only the position lines but also the coordinates of the ES over the time interval. However, to measure the coordinates of a moving ES, the simultaneous use of two or more NS is necessary. As a result, it becomes possible to determine the current coordinates of a moving ES by obtaining two or more position lines at moments in time t _n . It is proposed to use CubeSat (CubeSat←cube+satellite) as a satellite - a format of small (ultra-small) artificial Earth satellites with dimensions of 30×10×10 cm and a mass of 1.33 kg (see Electronic resource https://www.webcitation.org/6ABSpR8qR?url=http://www.cubesat.org/images/developers/cds_r ev12.pdf. Rev. 03/17/2025).

It is known that the accuracy characteristics of the implementation of the differential ranging method of EOTS are determined, among other things, by the accuracy of determining the coordinates of the repeaters (in this case, KA _1, KA ₂ , KA ₃ ). The permissible error of the OM of the spacecraft in GSO according to TLE is determined by the requirements for tracking the spacecraft with communication antennas and ranges from a few kilometers to 10 km (see Electronic resource

https://cyberleninka.m/article/.n/raschyot-dvizhemya-kosmichtskogo-apparata-na-okolo-krugovoy-orbite-po-dannym-tle-po-uproschyonnoy-modeli-sgp.Obr. 20.03.2025 g.).

The use of spatially distributed synchronous transmitting reference stations and receivers of spacecraft signals makes it possible to increase the accuracy of the spacecraft OM in GSO to subkilometer (see R.D. Gall. Determining the location of ground-based radio sources operating via geostationary repeater satellites. Dissertation for the degree of Candidate of Technical Sciences. - St. Petersburg: ETU named after V.I. Ulyanov (Lenin), 2021; R.V. Volkov, V.V. Svidov, A.O. Chemarov. Accuracy of geolocation by the difference-ranging method using repeater satellites in geostationary orbit // Radioelectronics and Telecommunications. Bulletin of ETU "LETI", No. 9/2014, pp. 12-19).

Further improvement of the accuracy of the spacecraft's OM in geostationary orbit is possible by predicting the spacecraft's ballistic trajectory based on an array of measurements of refined coordinates, taking into account the influence of disturbing factors (see Russian Patent No. 2550814, IPC G01S 19/27 (2010.01), published on May 20, 2015, Bulletin No. 14). However, the execution of any spacecraft maneuver leads to the need to accumulate a new array for prediction.

The accuracy of the navigation satellite system is limited by the characteristics of the navigation receivers ( ^~ 100 nanoseconds), which leads to a root mean square deviation (RMS) of coordinate determination of at least 30 m (see Russian Patent No. 2550814, IPC G01S 19/27 (2010.01), published on 20.05.2015, Bulletin No. 14). It is possible to reduce the RMS of the navigation satellite coordinates to units of meters. However, this is possible under conditions of the absence of maneuvers of the navigation satellite and the installation on board of multimedia receivers of satellite navigation signals of the GLONASS, GPS, Galileo and BeiDou systems with support for network and autonomous assistance modes in terms of ephemeris information (see ibid.).

A significant increase in the accuracy of determining the coordinates of the navigation spacecraft can be achieved through the use of solutions in geolocation that have found application in radio navigation. It is assumed that the time scales of all the navigation spacecraft coordinate systems and control units used in the system must be synchronized with high accuracy. The required mutual distance between the coordinate systems is determined by the flight altitude of the navigation spacecraft and can, for example, be 500 km with the latter flying at an altitude of 500 km. Currently, the best accuracy in synchronizing the time scales of remote objects at distances of several hundred kilometers is provided by systems using fiber-optic communication lines (FOCL) between the objects (see Donchenko SS, Kolmogorov OV, Prokhorov DV et al. System for Comparison and Synchronization of Time Scales of Frequency and Time Standards of Remote Objects // "Radioinfocom-2017". Collection of scientific papers of the international scientific and practical conference. SZ17-321).

In turn, the use of modern new-generation radio-laser stations of the "Tochka" type and their modifications as a COS allows for precision (millimeter accuracy) laser measurements of the two-way slant range to the NSC (see Borisov BA, Donchenko SI, Zhabin AS, et al. On the creation of "Tochka" radio-laser complexes for solving problems of space geodesy and navigation // Radiophotonics, Vol. 16, No. 5, 2022, pp. 370-379). Moreover, the average accuracy of measuring the slant range to an object is 1 mm, and the error of a single measurement does not exceed 10 mm.

High-precision determination of the coordinates of the NS requires the placement of a panel of corner reflectors (the so-called retroreflectors) on board. The purpose of the latter is to reflect the laser rangefinder beam from the NS back to the KOS receiver for precise range measurement. To achieve the required energy and accuracy characteristics, the design of the corner reflectors (CR) must ensure an optimal directivity pattern of the reflected radiation. A compact retroreflector system called "Pyramid" is known, designed for low-orbit spacecraft (see Akentyev A.S., Sokolov A.L. Compact retroreflector system for the Lomonosov spacecraft // Photonics, No. 5/59/2016, pp. 50-53.). The measurement error when using it is small due to the small size of the CR and the connection of their vertices. In general, the calculated value of the target error when measuring the range to the NS does not exceed 0.5 mm.

By improving the accuracy of M satellite coordinate determination, it becomes possible to determine the coordinates of ground stations with greater precision. Using data from the satellite alone to solve the problem of ground station detection is difficult. This is due to the fact that the width of the main lobe of the microwave ray beam ranges from fractions to units of a degree. As a result, the signal transmitted by the satellite is generally below the noise level, making it difficult to detect.

During the preparatory phase, the satellite communications stations are deployed in a circle, with the 3COM and the satellite launcher at the center. It is advisable to use the "Tochka" product from JSC Scientific and Production Corporation "Precision Instrument Systems" (Moscow) as the satellite communications station. Multi-channel satellite communications station capability is achieved by using them simultaneously in each positional area. The distance between the satellite communications stations depends on the satellite's flight altitude to ensure the geometric factor during measurements and can be, for example, 500 km.

The operation of the KOS (including synchronization) is controlled by 3COM.

Next (see Figs. 1, 2), a noise-like test radio signal is emitted using the radio frequency transmitter (RPT) in the satellite's operating frequency band AF and received by the first channel of the radio receiver (RTU) over a time interval of ΔГ. The frequency instability of the first channel of the RTU is compensated for based on the results of TRS reception. The low TRS power used in this case does not have a destructive effect on the operation of the satellite communication system. Using this reference signal, the satellite's frequency plan (uplink frequencies based on the observed frequencies of the downlink signal) is determined or refined. The implementation of these procedures is known (see Russian Federation Patent No. 2172495, IPC G01S 5/00 (2000.01), G01S 5/06 (2000.01), published on August 20, 2001, Bulletin No. 23; Volkov R.V. et al. Fundamentals of the Design and Operation of Difference-Range Measuring Systems for Radio Emission Sources. St. Petersburg: VAS, 2003. — 116 p.). In turn, the definition of EMD zones formed by spacecraft antenna systems is known (see Chelyshev V.D., Yakimovets V.V. Radioelectronic Systems of Administrative and Military Control. Part One. Radio Interfaces of Mobile Radio Service Systems: Textbook. St. Petersburg: VAS, 2006 — 576 p.). The slant range D ₁ = c⋅Δr ₁ /2 from 3COM to KA _l, located in geostationary orbit, is calculated, followed by correction of the coordinates of KA ₁ based on this range. Here Δτ ₁ is the measured value of the delay received after retransmission of the TRS through KS 1, c is the speed of light. Next, the signals of the 1st ES are detected by comparing the previously measured and stored noise levels P ₁ (ΔF _i ) in the frequency band ΔF _j ,ΔF _j ∈ .ΔF, with their current level P _1,current (ΔF _j ). If the noise level in KA ₁ ΔP1(ΔF _i ) exceeds the threshold level Δd ₁ ΔP ₁ (ΔF _i )=P _1,tek (ΔF _i )-P _1, (ΔF _i ), a decision is made about the appearance in the frequency band ΔF _i of signals of the 1st ES, retransmitted by KA ₁ .

After this, the detected signal of the 1st ZS KA 1 is selected:

Where - a set of signals from the first station, the coordinates of which are to be determined, and noise. Based on this, the characteristics S _l (ΔF _i ) are assessed: the operating frequency band F _i , the carrier frequency F _i , the type of modulation and manipulation, and the manipulation speed.

Based on the obtained values of ΔF _i and F _{i ,} the characteristics of the signals of the uplink of the 1st ES F _Bi and ΔF _Bi are determined according to the frequency plan, which is necessary for setting the task of geolocation of the NSC.

Planning a geolocation session includes the following. Based on the TLE parameters of the satellite orbit, the date and time of each m-th satellite's presence in the EMD zone of the 1st ES are determined, as well as the time of activation. and turning off repeater of the m-th navigation satellite, parameters of the relayed signals F _i , ΔF _i and F _bi , ΔF _bi , the time of transmission of messages to the control unit about the current coordinates of the navigation satellite (x, y, z, t _n ) _m , n=1,2,…,N, N is the number of messages during the flight over the search area, t _n is the time of measuring the coordinates of the navigation satellite. The named values from 3COM are sent to the control unit and then via a low-speed communication channel to each navigation satellite. The parameters of the navigation satellite (x, y, z, t _n ) _m are also used for timely orientation of Ant.2,…, Ant.M+1.

When planning a geolocation session, the measurement times t _n and the TLE orbital parameters of the satellites involved are transmitted from the satellite control unit to the satellite communication station. The satellite communication station calculates the slant range D _Qm from their location to each of the M satellites at time t _{n ,} D _Qm = с⋅Δτ _Qm /2. The obtained results D _Qm are transmitted via fiber-optic communication lines to 3COM for correction of the satellite coordinates.

During the time interval ΔT, signals of the 1st ES retransmitted from KA ₁ and M NKA are received and the signal delays are determined at the time t _n using the correlation method M To find the latter, the refined coordinates of the NSC using the laser corner reflector are used. However, it is impossible to refine the coordinates of SC ₁ in a GSO in this way (there is no laser corner reflector). This entails significant measurement errors. To eliminate the latter, it is proposed to use the differential RDS OM ZS (see Kisin Yu.K. Determining the coordinates of aircraft from differential range measurements in the presence of individual systematic errors. - Severodvinsk, 2013. Electronic resource https://elibrary.ru/item.asp?id=20299533. accessed 10.04.2025). The latter involves finding signal delays without using "toxic" measurements obtained from SC _1. For this, signal delays are determined

At the next t _n+1 moment in time, the procedures for testing the receiving paths, refining the coordinates of the satellite ₁ and the satellite and measuring delays repeat. As a result of the spacecraft's flight over the search area, N signal delay values are obtained N>3, which allows one to determine the trajectory of movement (for M>2) and the current location (for M=2) of the l-th ES. The determination of the ES location by differential radar is performed by two independent measurements of the difference in range differences. For this purpose, a well-known method of coordinate measurement is used (see Dvornikov SV, Sayapin VN, Simonov AN Theoretical Foundations of Coordinate Measurement of Radio Emission Sources. - St. Petersburg: VAS, 2007). The latter includes the following stages:

measurement of one of the coordinate-information parameters (CIP) of radio signals of the earth, retransmitted by the spacecraft;

determination of the position parameters corresponding to each control and measuring instrument;

construction of lines (surfaces) of position based on its parameters;

determination of the location of the ground station on the surface of the position lines (surfaces).

The physical coordinates of the ES are found from the system of equations given in Patent of the Russian Federation No. 2663193, p. 6, the solution of which is known (see Sevidov V.V. Implementation options for the difference-range method for determining the coordinates of earth stations using signals from repeater satellites // Radio engineering, electronics and communications (RE i S - 2015). International scientific and technical conference. - St. Petersburg: VAS, 2015. pp. 303-308).

Fig. 3 shows the external appearance of the 12U NSC with a laser corner reflector installed. The latter contains an antenna system consisting of: UHF antenna 1, global navigation satellite system antenna 2, 6-18 GHz range antenna 3, 0.8-6 GHz range antenna 4, X-band antenna 5, solar panel 6, spatial orientation sensor unit 7, repeater module 8, NSC control unit (on-board computer) 9, radio modem 10, power supply 11, batteries 12, flywheel and magnetic coil control unit 13, flywheel unit 14, magnetic coil unit 15, magnetometer 16, laser corner reflector 17 and propulsion system 18. The latter is intended for forming a ballistic linked cluster from several independent NSC. Fig. 4 shows a generalized structural diagram of the NSC. The operating procedure of the NCA is known and is discussed in the description of the prototype method (see Russian Patent No. 2837386). Fig. 5 shows a generalized algorithm for the functioning of the NCA.

Evaluation of the efficiency of the proposed method of implementation based on modeling in the MATLAB environment (see Fig. 6a, b, c). The following were used as initial data: frequency range of 12.75-14.5 GHz, bandwidth of the RES signal of 1 MHz, diameter of the transmitting antenna of 1.2 m, signal/noise ratio in the spacecraft of ₁ 10 dB, synchronization error of the time scale between the COS and the NSC PU of no more than 100 ns, topology of the relative placement of the COS and the NSC flight path, providing angles of arrival of the COS signals to the NSC from 1 to 179 degrees.

The topology of the movement of a ballistically linked cluster of spacecraft relative to a microwave station: there are 2 spacecraft in the cluster, the distance between them is 200 km, the flight altitude of the spacecraft is 500 km, the flight path passes no further than 50 km from the beam connecting the station and spacecraft 1.

It is known that with the signal registration (synchronization) error value not exceeding 0.1 ns and the absence of an error in the OM of the NKA, the maximum error in the OM of the ZS in the specified topology will not exceed one meter (see Dvornikov SV, Sayapin VN, Simonov AN, Theoretical foundations of coordinate measurement of radio emission sources. - St. Petersburg; VAS, 2007.)

To date, the technologically achievable average accuracy of measuring the slant range by existing COS does not exceed 1 mm, and the error of a single measurement is 10 mm (see Borisov B.A., Donchenko S.I., Zhabin A.S., et al. On the creation of Tochka radio laser complexes for solving problems of space geodesy and navigation//Radiophotonics, Vol. 16, No. 5, 2022, pp. 370-379).

In turn, the currently technologically achievable error in synchronization of remote objects located on the Earth’s surface does not exceed 100 ns (see Donchenko S.S., Kolmogorov O.V., Prokhorov D.V. et al. // System for comparison and synchronization of time scales of frequency and time standards of remote objects // Radioinfocom-2017. Collection of scientific papers of the international scientific and practical conference, pp. 317-321).

The values of the results of the OM KA with the optimal geometry of the arrival of the measuring laser beams (the angle between each of them is 90 degrees) do not go beyond the boundaries of a cube with edges d'=2⋅10 mm, and the actual measurement error does not exceed half the length of the cube diagonal 17.32 mm for the named initial data.

Fig. 6a illustrates the influence of the geometric factor of the COS placement relative to the NS flight path on the accuracy of the latter's coordinate determination. It shows the dependence of the NS RMSE β, in km, on the value of the "worst" (maximum deviation from 90°) angle α, of the three formed by the COS laser beams. This angle was chosen because its presence is the main contributor to the total error in determining the NS's coordinates. From this analysis, it follows that the NS RMSE error increases unacceptably at angles from 1 to 17 and from 163 to 179 degrees.

Fig. 6b shows the dependence of the standard deviation of the OM ES γ by the difference-ranging method on the signal-to-noise ratio with a synchronization accuracy of 3COM and a 0.1 ns SNR for the case when the "worst" angle between all probing beams is optimal (equal to 90°), is 60° or 120°, 30° or 150°, 10° or 170°, and 5° or 175°. The presented results indicate a significant influence of the SNR in the signal at the input of the NSC repeater on the accuracy characteristics of the proposed method. Moreover, under measurement conditions with a low SNR, achieving the required accuracy characteristics is possible through the use of a geometric factor: optimization of the NSC flight path.

Fig. 6c shows the dependence of the maximum error of the EO γ,m differential RDS on the accuracy of the NSC EO , m with a synchronization accuracy of 3COM and a 0.1 ns COS. The geometry of the COS placement provides a "worst" angle between all pairs of probing beams from 30 to 150 degrees, the SNR in the signal retransmitted by the NSC from 0 to -20 dB. The presented results indicate the need to take measures to improve the accuracy of EO location determination. While ensuring the 30 m standard deviation of the EO γ, achieved in analogs and the prototype, for various SNRs, the EO RMSD is achieved in the range of 500-700 m, which often does not satisfy consumers. Increasing the accuracy of the EO γ using the proposed method to at least 1 m makes it possible to determine the EO location with an accuracy of 10-50 m.

Thus, the maximum total error of the OM ES when implementing the claimed method is significantly lower than that of known analogs and the prototype. Increasing the number of M NSCs, M>2, simultaneously with those in the EMD zone of the ES, PU, and 3COM, and the corresponding increase in the channel number of the COS allows for an increase in the accuracy of the OM ES by increasing the simultaneously obtained spatially uncorrelated measurements of its signal delays Δτ _1,M . Increasing the number of COSs, Q>3, allows for an increase in the accuracy of the OM ES by increasing the spatial accuracy of the OM ES.

Claims (1)

A method for determining the location of a satellite communication (SC) earth station (ES) based on a retransmitted signal from spacecraft (SC), which consists of using an ES as part of an antenna system, a multi-channel coherent radio receiver (RRU) with a coordinate calculation unit and a radio transmitter (RTD), M, M≥2 low-orbit spacecraft (LOS) KA ₂ , KA ₃ , …, KA _M+1 , a control post (CP) of the LOS; automatic tracking of the direction of the antennas of Ant. 2, …, Ant. M+1 to the corresponding LOS, and orientation of the Ant. 1 in the direction of the "main" SC ₁ located in geostationary orbit and providing retransmission of signals of the 1st ES along the main lobe of the radiation pattern, detection of signals of the 1st ES in the block for calculating coordinates of the RPU ZCOM based on the downlink of signals of SC _1, technical analysis, determination of the central frequency F _i and the spectrum width ΔF _t , determination based on the frequency plan of SC ₁ of the frequency parameters F _bi and ΔF _bj of the uplink of the 1st ES, transmission of the values of F _bi and ΔF _bj obtained in ZCOM to the control unit of the NSC, the results of the forecast of the date and time of the location of the NSC SC ₂ , ..., SC _m+1 in the zone of electromagnetic availability (EMA) of the 1st ES, ZCOM and control unit, assignment from the control unit of the NSC to all M NSC via a low-speed communication channel of the time of switching on and turning off repeaters located on board them, the parameters of the retransmitted signal F _t , ΔF _t and F _Bi , ΔF _Bi , the time of transmission of messages to the control unit about the current coordinates of the corresponding m-th navigational spacecraft [x, y, z, t _n ) _m , n=1, 2, …, N, N is the number of messages during the flight over the search area, t _n is the time of measuring the coordinates of the navigational spacecraft at the n-th point, m=2, 3, …, M+1, m is the number of the navigational spacecraft, the coordinate-time data from all M navigational spacecraft are sequentially transmitted to the control unit and then to the ZCOM of the coordinate-time data from all M navigational spacecraft, timely orientation of the Ant. 2, …, Ant. M+1 to the corresponding NS based on the TLE parameters of their orbits, eliminating the current instability of all M+1 receiving channels of the RPU in the frequency band ΔF _f at times t _n based on the results of receiving a test radio signal emitted by the RPD, determining the coordinates of the 1st ES M of the NS by receiving signals from the 1st ES in the frequency band ΔF _Bi and retransmitting them to the ES in the band ΔF _i , which through Ant. 2, …, Ant. M+1 arrive at the corresponding inputs of the RPU, while the signals of the 1st ES, retransmitted by NS ₁ , through Ant. 1 are received at the first input of the radio receiver, determining M delays in the reception of signals Δτ _{1, M} at each of the N points of the spatial position of the navigation spacecraft based on the coordinates of KA ₁ and M of the navigation spacecraft and the signals of the 1st ES relayed by them, determining the location of the 1st ES using the difference-ranging method, characterized in that they additionally use Q≥3 M-channel spatially separated quantum-optical stations (QOS), control and synchronization, the operation of which is carried out by the 3COM by setting the orbital parameters of the navigation spacecraft KA ₂ , ..., KA _M+1 , forecasting their availability in the controlled area, on their basis, at Q quantum-optical stations, the inclination angles of the laser channels of the QOS for each navigation spacecraft at the n-th point, n=1, 2, ..., N, are calculated at t _n -th moments of time, where N is the number of points of measurement of the coordinates of the navigation spacecraft, channels from the 1st to the M-th of each of the Q quantum-optical stations are oriented in direction of the corresponding navigation satellites and automatically track their movement, measure the distance of the navigation satellites at each n-th point from the corresponding COS at times t _n , the obtained results are transmitted to the ZCOM, where the signal of the 1st ES, retransmitted by satellite ₁ with a positive signal-to-noise ratio, is used at each of the N times t _n as reference, the refined coordinates of all M navigation satellites are calculated at the ZCOM, and the measurement of delays Δτ ₁ , _M in the reception of signals from the 1st ES at each of the N points is performed by the correlation method based on the use of the refined coordinates of the navigation satellites and the signals retransmitted by them, the coordinates of the ES are determined by the differential difference-ranging method based on the measured delays Δτ _m,m+1 , and the functions of the NCA additionally include the reflection of laser radiation generated by the COS using corner reflectors.