CN109283557B - Double-pass pseudo code auxiliary carrier high-precision inter-satellite ranging system and method - Google Patents
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Abstract
The invention discloses a double-pass pseudo code assisted carrier high-precision inter-satellite distance measurement system and a method, which are used for obtaining the absolute distance between two satellites with high precision.
Description
Technical Field
The invention relates to the technical field of inter-satellite distance measurement, in particular to a high-precision inter-satellite distance measurement system and method combining a pseudo code distance measurement technology and a carrier distance measurement technology.
Background
With the continuous development of the aerospace technology, the functions of a space system are stronger and stronger, and the task of a large satellite can be completed by the cooperation of a plurality of small satellites with relatively single functions. Small satellites play an increasingly important role in the aerospace field due to their low cost, small size, light weight, short development cycle, and high technology content. In the field of formation of artificial satellites, measurement of relative distances of satellite formation units is the basis of formation cooperative work, and the inter-satellite distance measurement accuracy directly determines the application level of formation technology. At present, the inter-satellite distance measurement means of satellite formation is mainly GPS (Global Positioning System) measurement, but the method has certain limitations, such as incapability of using in deep space, unpublished high-precision distance measurement code and the like; in addition, the technology of obtaining the distance phase difference by using different methods is developed and applied to a certain extent, and the applications have certain precision and stability.
For example, patent document CN 102778678A discloses a high-precision carrier ranging system with high measurement precision and stability. However, the method has limitations, the carrier ranging has a problem of cycle ambiguity, and only the relative distance between two stars can be obtained. The pseudo code ranging method capable of obtaining the absolute distance of the two stars has the problem of low measurement accuracy, and the measurement accuracy is only in centimeter level.
Disclosure of Invention
The invention provides a double-pass pseudo code assisted carrier high-precision inter-satellite distance measurement system and a method, wherein the distance measurement system utilizes the thought of double-pass pseudo code regeneration (or forwarding) technology to assist carrier coherent forwarding, does not depend on precise time synchronization, realizes the autonomous acquisition of the absolute distance between double satellites, and can reach the sub-millimeter level in precision after verification.
A two-way pseudo code auxiliary carrier high-precision inter-satellite ranging system comprises hardware design and ranging algorithm design and is used for measuring the absolute distance between a master satellite and a slave satellite, and the hardware design of the master satellite comprises the following steps: the transmitting antenna is used for transmitting a carrier ranging signal and a pseudo code ranging signal generated by the main satellite; the transmitting radio frequency link is used for up-mixing the ranging signals generated by the baseband to a transmitting frequency and transmitting the ranging signals through a transmitting antenna; a receiving antenna for receiving a carrier ranging signal forwarded from a satellite and a pseudo code ranging signal regenerated (or forwarded) from the satellite; a receiving radio frequency link for down-mixing the ranging signal received by the receiving antenna to a baseband processing signal; the ultra-stable crystal oscillator module is used for providing signals with different frequencies and simultaneously providing a unified reference time standard for pseudo code ranging and carrier wave forwarding ranging; a digital part for implementing a ranging algorithm;
the hardware design of the slave star is the same as that of the master star except that the transmitting frequency and the receiving frequency are interchanged.
Particularly, the hardware design of the master satellite and the slave satellite adopts the medium-frequency undersampling technology of software radio idea, the structure of a full digital modulation transmitter and the modularized design idea to meet the requirements of miniaturization, low power consumption and flexibility;
particularly, the hardware design of the master satellite and the slave satellite is adopted, and the receiving radio frequency link only adopts a once intermediate frequency scheme, so that compared with the traditional design idea, the structure greatly simplifies the structure of the radio frequency front end, thereby realizing miniaturization and low power consumption;
the main satellite ranging algorithm comprises the following steps: the carrier generating module is used for generating a carrier ranging signal; the pseudo code generating module is used for generating a pseudo code ranging signal; the modulation module is used for modulating the pseudo code ranging signal to a carrier wave; the carrier recovery and tracking module is used for recovering the carrier signals forwarded by the satellite coherence, obtaining a phase difference with the reference signal of the main satellite in a phase comparison manner and further obtaining a carrier ranging value; the pseudo code signal demodulation module is used for recovering a pseudo code signal regenerated (or forwarded) from the satellite; the pseudo code phase delay measurement module is used for comparing a pseudo code ranging signal of the pseudo code generation module with a pseudo code ranging signal to obtain a pseudo code rough measurement value and a pseudo code accurate measurement value; the distance calculating module is used for calculating the absolute distance between the master satellite and the slave satellite;
the range finding algorithm from the satellite comprises the following steps: the carrier coherent forwarding module is used for carrying out coherent transformation on the received main satellite carrier ranging signals; the pseudo code regeneration (or forwarding) module is used for regenerating (or forwarding) the received main satellite pseudo code ranging signal; and the modulation module is used for modulating the regenerated (or forwarded) pseudo code ranging signal to a carrier after coherent conversion and transmitting the signal through a transmitting radio frequency link and a transmitting antenna.
Particularly, the master satellite ranging algorithm and the slave satellite ranging algorithm can be realized on the same satellite except for different coherent forwarding ratios in the carrier coherent forwarding modules, and the satellite can be switched between the master satellite and the slave satellite through a ground instruction;
the invention mainly emphasizes the idea of using a two-way pseudo code regeneration (or forwarding) technology to assist carrier coherent forwarding, and obtains the absolute distance between a master satellite and a slave satellite with high precision, wherein:
the key technology of the invention is that the carrier coherent forwarding is assisted by the double-pass pseudo code regeneration (or forwarding) technology, the absolute distance between a master satellite and a slave satellite is acquired with high precision, and the measuring steps are as follows:
1) the carrier generation module of the master satellite generates a local carrier ranging signal and sends the local carrier ranging signal to the slave satellite through the master satellite transmitting radio frequency link and the transmitting antenna;
2) after the slave satellite receives the carrier ranging signal of the master satellite, the carrier coherent forwarding module firstly carries out carrier locking judgment on the received signal, and the judgment is used for eliminating a noise signal;
3) after the carrier ranging signals are received from the satellite and locked, the carrier coherent forwarding module recovers the received carrier ranging signals and carries out conversion according to a corresponding coherent forwarding ratio; wherein the coherent forwarding ratio is determined by the ratio of the transmitting frequency and the receiving frequency of the slave satellite, and the value can be selected from 240/221 in general.
4) The slave satellite transmits the carrier ranging signal after the coherent conversion to the master satellite through a slave satellite transmitting radio frequency link and a transmitting antenna;
5) after the master satellite receives the carrier ranging signals coherently forwarded by the slave satellite, a carrier recovery and tracking module of the master satellite performs carrier locking judgment on the received signals, wherein the judgment is used for eliminating noise signals;
6) after the carrier signals of the master satellite and the slave satellite are locked, the carrier recovery and tracking module recovers the carrier ranging signals coherently forwarded by the slave satellite, and meanwhile, the pseudo code generation module of the master satellite starts to continuously generate local pseudo code ranging signals;
7) the modulation module of the master satellite modulates the pseudo code ranging signal to a carrier ranging signal in a phase modulation mode and sends the pseudo code ranging signal to the slave satellite through a master satellite transmitting radio frequency link and a transmitting antenna;
8) receiving ranging signals modulated with pseudo codes from a satellite, and performing pseudo code ranging signal locking judgment through a pseudo code regeneration (or forwarding) module;
9) after the pseudo code ranging signals are received from the satellite and locked, a pseudo code regeneration (or forwarding) module regenerates (or forwards) the pseudo code ranging signals; the processing mode of the satellite-to-pseudo code ranging signals can be selected by a specific ranging task: for inter-satellite measurement with a short baseline (high signal-to-noise ratio), because a transmission path is short, the signal power of a receiver is generally strong, and at this time, a slave satellite can select a forwarding mode with higher precision; when the inter-satellite baseline is longer (low signal-to-noise ratio), it is more appropriate to select a regenerative treatment from the satellites due to limited signal-to-noise ratio. In a specific application, factors such as a pseudo code rate, a ranging accuracy, a system resource quantity and the like need to be considered in a comprehensive manner from the selection of a forwarding mode and a regeneration mode by a satellite, and generally, when a signal-to-noise ratio reaches more than 70dB (namely, a high signal-to-noise ratio, otherwise, a low signal-to-noise ratio), the forwarding mode is adopted, otherwise, the regeneration mode is adopted.
10) Modulating the regenerated (or forwarded) pseudo code ranging signal to the carrier ranging signal obtained in the step 3) by a modulation module of the slave satellite in a phase modulation mode, and transmitting the signal to the master satellite through a slave satellite transmitting radio frequency link and a transmitting antenna;
11) the main satellite receives the ranging signal modulated with a regenerated (or forwarded) pseudo code, and a pseudo code signal demodulation module firstly locks and judges the pseudo code ranging signal;
12) after the master satellite receives and locks the pseudo code ranging signals regenerated (or forwarded) by the slave satellite, the pseudo code ranging signals regenerated (or forwarded) by the slave satellite are recovered by the demodulation mode of the pseudo code signals;
13) comparing the carrier ranging signal recovered in the step 6) with the local carrier ranging signal generated in the step 1) by a carrier recovery and tracking module of the main satellite to obtain a phase difference delta theta; the pseudo code phase delay measurement module compares the pseudo code ranging signal recovered in the step 12) with the local pseudo code ranging signal generated in the step 6) to obtain the integral chip delay N of coarse pseudo code measurement; acquiring pseudo code phase delay time tau of pseudo code accurate measurement;
14) the distance resolving module of the master satellite obtains the absolute distance between the master satellite and the slave satellite after carrier ambiguity resolution and filtering processing, and the calculation formula is as follows:
end of single measurement, wherein TcIs the pseudo code chip period, c is the vacuum speed of light, and λ is the carrier wavelength.
In addition, multiple measurements can be adopted and post-processing can be carried out to further improve the ranging precision.
The principle of the pseudo code regeneration (or forwarding) technique and the carrier coherent forwarding technique does not belong to the scope of the present invention.
In the method, a closed loop structure is adopted as a method for acquiring a main satellite end pseudo code accurate measurement value, and after a recovered pseudo code signal is locked by a code tracking loop, a phase of a loop NCO (Numerically Controlled Oscillator) is compared with a phase of a local code clock NCO (local code clock) and is subjected to integral jitter filtering to obtain a chip accurate measurement value. The method has little difference on the ranging precision of various pseudo code waveforms, almost has no influence on the absolute distance, and does not need the assistance of carrier Doppler information, thereby reducing the influence of carrier tracking on the ranging precision of the pseudo codes, effectively eliminating the influence of parameters such as ranging signal waveforms, speed and the like, and when the loop parameters are reasonably selected, the precision is the same as or even higher than that of an open loop mode. One specific implementation of this approach is shown in fig. 6.
Under the condition of adopting a closed-loop mode to obtain a pseudo code measured value, the bandwidth of the loop of the master satellite and the bandwidth of the slave satellite are selected to be smaller than the bandwidth of the slave satellite. When the bandwidth of the master satellite is larger than that of the slave satellite, the noise jitter of the slave satellite is completely transmitted back to the master satellite end, so that the system end-to-end measurement jitter is the sum of the jitter of the master satellite loop and the jitter of the slave satellite loop; when the bandwidth of the master satellite is smaller than that of the slave satellite, the jitter value is obviously smaller than that of the former case, especially when the signal-to-noise ratio is low.
Drawings
FIG. 1 is a schematic diagram of a two-pass pseudo code assisted high-precision inter-satellite ranging system measurement according to the present invention;
FIG. 2 is a block diagram of a hardware implementation of a two-way pseudo-code assisted carrier high-precision inter-satellite ranging system of the present invention;
FIG. 3 is a block diagram of an algorithm implementation of a two-way pseudo-code assisted carrier high-precision inter-satellite ranging system of the present invention;
FIG. 4 is a view showing a structure of a satellite pseudo code regeneration process;
FIG. 5 is a schematic diagram of a primary satellite pseudo code phase delay measurement;
FIG. 6 is a block diagram of the implementation of the method for extracting pseudo code accurate measurement value of the main satellite terminal in a closed loop manner;
FIG. 7 is a diagram illustrating the effect of different loop bandwidths of the master satellite and the slave satellite on the total measurement jitter between the master satellite and the slave satellite according to the present invention;
FIG. 8 is a ground test result of the two-pass pseudo code assisted carrier high-precision inter-satellite ranging system of the present invention.
Detailed Description
The system and the method for measuring the distance between two satellites with the double-pass pseudo-code auxiliary carrier have been applied to the distance measurement between two satellites of A/B No. 2 of Zhejiang Pisa and formation flight tasks.
As shown in fig. 1, the inter-satellite distance measurement system of the present embodiment adopts a completely new measurement system: the double-pass pseudo code regeneration (or forwarding) technology acquires the absolute distance between the two satellites and is used for assisting the double-pass carrier coherent forwarding technology, so that the absolute distance between the master satellite and the slave satellite can be acquired with high precision.
As shown in fig. 2, the hardware design of the present embodiment adopts a compatible idea, and the hardware designs of the master satellite and the slave satellite are all the same except that the transmit and receive frequency points are opposite. The hardware design of the main star comprises: the transmitting antenna is used for transmitting a carrier ranging signal and a pseudo code ranging signal generated by the main satellite; the transmitting radio frequency link is used for up-mixing the ranging signals generated by the baseband to a transmitting frequency and transmitting the ranging signals through a transmitting antenna; a receiving antenna for receiving a carrier ranging signal forwarded from a satellite and a pseudo code ranging signal regenerated (or forwarded) from the satellite; a receiving radio frequency link for down-mixing the ranging signal received by the receiving antenna to a baseband processing signal; the ultra-stable crystal oscillator module is used for providing signals with different frequencies and simultaneously providing a unified reference time standard for pseudo code ranging and carrier wave forwarding ranging; a digital part for implementing a ranging algorithm;
particularly, the hardware design of the master satellite and the slave satellite adopts the medium-frequency undersampling technology of software radio idea, the structure of a full digital modulation transmitter and the modularized design idea to meet the requirements of miniaturization, low power consumption and flexibility;
particularly, the hardware design of the master satellite and the slave satellite is adopted, and the receiving radio frequency link only adopts a once intermediate frequency scheme, so that compared with the traditional design idea, the structure greatly simplifies the structure of the radio frequency front end, thereby realizing miniaturization and low power consumption;
as shown in fig. 3, the algorithm of the two-way pseudo code assisted carrier high-precision inter-satellite ranging system of the present embodiment includes a master-satellite ranging algorithm and a slave-satellite ranging algorithm.
The main satellite ranging algorithm comprises the following steps: the carrier generating module is used for generating a carrier ranging signal; the pseudo code generating module is used for generating a pseudo code ranging signal; the modulation module is used for modulating the pseudo code ranging signal to a carrier wave; the carrier recovery and tracking module is used for recovering the carrier signals forwarded by the satellite coherence, obtaining a phase difference with the reference signal of the main satellite in a phase comparison manner and further obtaining a carrier ranging value; the pseudo code signal demodulation module is used for recovering a pseudo code signal regenerated (or forwarded) from the satellite; the pseudo code phase delay measurement module is used for comparing a pseudo code ranging signal of the pseudo code generation module with a pseudo code ranging signal to obtain a pseudo code rough measurement value and a pseudo code accurate measurement value; the distance calculating module is used for calculating the absolute distance between the master satellite and the slave satellite;
the range finding algorithm from the satellite comprises the following steps: the carrier coherent forwarding module is used for carrying out coherent transformation on the received main satellite carrier ranging signals; the pseudo code regeneration (or forwarding) module is used for regenerating (or forwarding) the received main satellite pseudo code ranging signal; and the modulation module is used for modulating the regenerated (or forwarded) pseudo code ranging signal to a carrier after coherent conversion and transmitting the signal through a transmitting radio frequency link and a transmitting antenna.
The carrier coherent forwarding ranging algorithm and the corresponding module are not the inventive content of the present invention, and the implementation manner thereof can refer to the patent document with publication number CN 102778678A, and the phase difference Δ θ calculation formula obtained after phase comparison is as follows: Δ θ (t) ═ θl(t)-θt(t)
θl(t) is the reference phase of the primary satellite carrier at time t; thetat(t) the phase of the signal received by the primary satellite at time t; here Δ θ does not include a full-circle blur.
The two-way pseudo code regeneration (or forwarding) ranging algorithm adopts a composite code form consisting of a plurality of subcodes, and the code patterns recommended by CCSDS (refrigerated Committee for Space Data Systems, International Committee for spatial Data System consultation) are mainly JPL1999, T2B and T4B. According to the CCSDS proposal, the chip rate of the ranging pseudo code must be carrier coherent, for example in the S-band:
wherein f iscThe code rate of the ranging pseudo code is in unit Mcps; f. ofRCIs the ranging clock frequency in MHz; f. ofS-bandIs an S waveSegment uplink carrier frequency in MHz. Meanwhile, in the design of the ranging system hardware, the transceiving frequency works in a coherent mode, so that the downlink pseudo code rate is coherent with the downlink carrier.
As shown in fig. 4, the satellite pseudo Code regeneration processing structure is composed of three parts, i.e., a Code Tracking Loop (CTL), a correlator bank (Code Correlators), and a downlink pseudo Code Generator (Down-Link Code Generator). The code tracking loop has the function of recovering the frequency and the phase of a ranging pseudo code clock, 6 groups of correlators parallelly search the positions of all received subcodes in a pseudo code sequence, and a downlink pseudo code generator generates a downlink ranging pseudo code according to the correlation result of the correlators under the driving of the recovered ranging pseudo code clock and sends the downlink ranging pseudo code to a modulator. The input signal Qc of the whole structure is the Q output Q (k) of the carrier recovery loop, and the structure starts to operate only after the carrier recovery loop is locked. Q (k) is calculated as:
where P is the signal power, θrR (k) is a pseudo code signal.
Fig. 5 shows a primary satellite pseudo code phase delay measurement process, which compares a received signal returned from a secondary satellite and a demodulated ranging signal with a locally transmitted pseudo code sequence to obtain a two-way signal delay, thereby calculating a distance between the two satellites. The measuring method comprises the following steps: carrying out correlation operation on the received ranging signal and a local subcode to obtain the delay of the whole chip, wherein the delay is rough measurement; and meanwhile, correlating the received ranging code with the local clock code to obtain the time delay in the chip, which is the accurate measurement. The accuracy of the measurement depends on the fine measurement, while the coarse measurement provides a settlement of the ambiguity distance for the measurement.
Wherein the rough measurement is calculated by using the Chinese remainder theorem, and the obtained whole chip delay is as follows: n ═ a1s1+a2s2+a3s3+a4s4+a5s5+a6s6)modLr
Wherein a1-a6 is a fixed constant determined by the corresponding pseudo-code system, and s1-s6 are eachCorresponding to the amount of delay of the subcode. L isrIs the product of the length of the composite pseudo code subcode.
The formula of the measured value is as follows:
wherein T isRC＝2TCFor ranging pseudo code clock period, Tc＝1/fcX is the in-phase correlation result of the local clock code, and y is the quadrature correlation result of the local clock code.
The key technology of the invention is that the carrier coherent forwarding is assisted by the double-pass pseudo code regeneration (or forwarding) technology, the absolute distance between a master satellite and a slave satellite is acquired with high precision, and the measuring steps are as follows:
1) the carrier generation module of the master satellite generates a local carrier ranging signal and sends the local carrier ranging signal to the slave satellite through the master satellite transmitting radio frequency link and the transmitting antenna;
2) after the slave satellite receives the carrier ranging signal of the master satellite, the carrier coherent forwarding module firstly carries out carrier locking judgment on the received signal, and the judgment is used for eliminating a noise signal;
3) after the carrier ranging signals are received from the satellite and locked, the carrier coherent forwarding module recovers the received carrier ranging signals and carries out conversion according to a corresponding coherent forwarding ratio; wherein the coherent forwarding ratio is determined by the ratio of the transmitting frequency and the receiving frequency of the slave satellite, and the value can be selected from 240/221 in general.
4) The slave satellite transmits the carrier ranging signal after the coherent conversion to the master satellite through a slave satellite transmitting radio frequency link and a transmitting antenna;
5) after the master satellite receives the carrier ranging signals coherently forwarded by the slave satellite, a carrier recovery and tracking module of the master satellite performs carrier locking judgment on the received signals, wherein the judgment is used for eliminating noise signals;
6) after the carrier signals of the master satellite and the slave satellite are locked, the carrier recovery and tracking module recovers the carrier ranging signals coherently forwarded by the slave satellite, and meanwhile, the pseudo code generation module of the master satellite starts to continuously generate local pseudo code ranging signals;
7) the modulation module of the master satellite modulates the pseudo code ranging signal to a carrier ranging signal in a phase modulation mode and sends the pseudo code ranging signal to the slave satellite through a master satellite transmitting radio frequency link and a transmitting antenna;
8) receiving ranging signals modulated with pseudo codes from a satellite, and performing pseudo code ranging signal locking judgment through a pseudo code regeneration (or forwarding) module;
9) after the pseudo code ranging signals are received from the satellite and locked, a pseudo code regeneration (or forwarding) module regenerates (or forwards) the pseudo code ranging signals; the processing mode of the satellite-to-pseudo code ranging signals can be selected by a specific ranging task: for the inter-satellite measurement with the short baseline, the signal power of the receiver is generally stronger due to the shorter transmission path, and the slave satellite can select a forwarding mode with higher precision; when the inter-satellite baseline is longer, the treatment of regeneration is more appropriate to select from the satellite due to limited signal-to-noise ratio.
10) Modulating the regenerated (or forwarded) pseudo code ranging signal to the carrier ranging signal obtained in the step 3) by a modulation module of the slave satellite in a phase modulation mode, and transmitting the signal to the master satellite through a slave satellite transmitting radio frequency link and a transmitting antenna;
11) the main satellite receives the ranging signal modulated with a regenerated (or forwarded) pseudo code, and a pseudo code signal demodulation module firstly locks and judges the pseudo code ranging signal;
12) after the master satellite receives and locks the pseudo code ranging signals regenerated (or forwarded) by the slave satellite, the pseudo code ranging signals regenerated (or forwarded) by the slave satellite are recovered by the demodulation mode of the pseudo code signals;
13) comparing the carrier ranging signal recovered in the step 6) with the local carrier ranging signal generated in the step 1) by a carrier recovery and tracking module of the main satellite to obtain a phase difference delta theta; the pseudo code phase delay measurement module compares the pseudo code ranging signal recovered in the step 12) with the local pseudo code ranging signal generated in the step 6) to obtain the integral chip delay N of coarse pseudo code measurement; pseudo code phase delay time tau of pseudo code accurate measurement;
14) the distance resolving module of the master satellite obtains the absolute distance between the master satellite and the slave satellite after carrier ambiguity resolution and filtering processing, and the calculation formula is as follows:
end of single measurement, wherein TcIs the pseudo code chip period, c is the vacuum light speed, and lambda is the carrier wavelength;
15) multiple measurements are adopted and post-processing is carried out to improve the ranging precision.
The method is characterized in that a closed loop structure is adopted for obtaining a main satellite end pseudo code accurate measurement value, after a recovered pseudo code signal is locked by a code tracking loop, the phase of a loop NCO and the phase of a local code clock NCO are compared and subjected to integral jitter filtering to obtain a chip accurate measurement value. The method has little difference on the ranging precision of various pseudo code waveforms, almost has no influence on the absolute distance, and does not need the assistance of carrier Doppler information, thereby reducing the influence of carrier tracking on the ranging precision of the pseudo codes, effectively eliminating the influence of parameters such as ranging signal waveforms, speed and the like, and when the loop parameters are reasonably selected, the precision is the same as or even higher than that of an open loop mode. The structure of this mode is shown in fig. 6.
The invention is characterized in that under the condition of acquiring the pseudo code accurate measurement value by adopting a closed loop mode, the loop bandwidths of a master satellite and a slave satellite are selected. When the bandwidth of the master satellite is larger than that of the slave satellite, the noise jitter of the slave satellite is completely transmitted back to the master satellite end, so that the system end-to-end measurement jitter is the sum of the jitter of the master satellite loop and the jitter of the slave satellite loop; when the bandwidth of the master satellite is smaller than that of the slave satellite, the jitter value is significantly smaller than that of the former case, which is particularly significant at low snr, and the comparison effect is shown in fig. 7.
As shown in fig. 8, it is a ground test result of the dual-pass pseudo code assisted carrier high-precision inter-satellite ranging system. In a test environment with an actual distance of 60 meters, the mean value of the solution results is 60.00m, and the uncertainty is 0.18mm (2 sigma).
Claims (2)
1. A high-precision inter-satellite ranging method of a double-pass pseudo code auxiliary carrier is characterized in that a double-pass pseudo code regeneration or forwarding technology is adopted to assist carrier coherent forwarding, and the absolute distance between a master satellite and a slave satellite is obtained, wherein the method comprises the following steps:
1) the carrier generation module of the master satellite generates a local carrier ranging signal and sends the local carrier ranging signal to the slave satellite through the master satellite transmitting radio frequency link and the transmitting antenna;
2) after the slave satellite receives the carrier ranging signal of the master satellite, the carrier coherent forwarding module firstly carries out carrier locking judgment on the received signal, and the judgment is used for eliminating a noise signal;
3) after the carrier ranging signals are received from the satellite and locked, the carrier coherent forwarding module recovers the received carrier ranging signals and carries out conversion according to a corresponding coherent forwarding ratio;
4) the slave satellite transmits the carrier ranging signal after the coherent conversion to the master satellite through a slave satellite transmitting radio frequency link and a transmitting antenna;
5) after the master satellite receives the carrier ranging signals coherently forwarded by the slave satellite, a carrier recovery and tracking module of the master satellite performs carrier locking judgment on the received signals, wherein the judgment is used for eliminating noise signals;
6) after the carrier signals of the master satellite and the slave satellite are locked, the carrier recovery and tracking module recovers the carrier ranging signals coherently forwarded by the slave satellite, and meanwhile, the pseudo code generation module of the master satellite starts to continuously generate local pseudo code ranging signals;
7) the modulation module of the master satellite modulates the pseudo code ranging signal to a carrier ranging signal in a phase modulation mode and sends the pseudo code ranging signal to the slave satellite through a master satellite transmitting radio frequency link and a transmitting antenna;
8) receiving ranging signals modulated with pseudo codes from a satellite, and performing pseudo code ranging signal locking judgment through a pseudo code regeneration or forwarding module;
9) after the pseudo code ranging signals are received from the satellite and locked, the pseudo code regeneration or forwarding module regenerates or forwards the pseudo code ranging signals; for inter-satellite measurements with short baselines (high signal-to-noise ratio), selecting a forwarding mode from a satellite; when the inter-satellite baseline is long (low signal-to-noise ratio), selecting a regenerative treatment from the satellites;
10) modulating the regenerated or forwarded pseudo code ranging signal to the carrier ranging signal obtained in the step 3) by a modulation module of the slave satellite in a phase modulation mode, and sending the signal to the master satellite through a slave satellite transmitting radio frequency link and a transmitting antenna;
11) the main satellite receives the ranging signal modulated with a regeneration or forwarding pseudo code, and a pseudo code signal demodulation module firstly locks and judges the pseudo code ranging signal;
12) after the master satellite receives and locks the pseudo code ranging signals regenerated or forwarded by the slave satellites, the pseudo code signal demodulation module of the master satellite recovers the pseudo code ranging signals regenerated or forwarded by the slave satellites;
13) comparing the carrier ranging signal recovered in the step 6) with the local carrier ranging signal generated in the step 1) by a carrier recovery and tracking module of the main satellite to obtain a phase difference; the pseudo code phase delay measurement module compares the pseudo code ranging signal recovered in the step 12) with the local pseudo code ranging signal generated in the step 6) to obtain the integral chip delay N of coarse pseudo code measurement; acquiring pseudo code phase delay time tau of pseudo code accurate measurement; the method comprises the steps that a closed loop structure is adopted for obtaining a pseudo code accurate measurement value of a main satellite end, after a recovered pseudo code signal is locked through a code tracking loop, phase comparison is carried out between a loop NCO phase and a local code clock NCO phase, and chip accurate measurement values are obtained after integral jitter filtering, wherein the loop bandwidth of the main satellite is smaller than that of a slave satellite;
14) the distance resolving module of the master satellite obtains the absolute distance between the master satellite and the slave satellite after carrier ambiguity resolution and filtering processing, and the calculation formula is as follows:
end of single measurement, wherein TcIs the pseudo code chip period, c is the vacuum speed of light, and λ is the carrier wavelength.
2. The method as claimed in claim 1, wherein the coherent forwarding ratio of step 3) is determined by the ratio of the transmitting frequency and the receiving frequency of the slave satellite, and 240/221 is selected.
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