Device and method for measuring deep space ultra-long distance

Abstract

The invention discloses a deep space ultra-long distance measuring device and method, and the method comprises the following steps: constructing a simulation scene and a data set, and preparing a related parameter set; establishing a measurement system and acquiring data, and defining hardware and equipment requirements; processing a frequency difference sequence correlation problem to obtain data necessary for incoherent Doppler measurement; carrying out orbit calculation and measurement result evaluation, error measurement and precision evaluation; according to the measurement method, through a series of operations such as construction of a simulation scene and a data set based on an improved incoherent Doppler measurement model, establishment of a measurement system, processing of a frequency difference sequence and orbit calculation and evaluation, many technical problems in deep space ultra-long distance measurement are solved, the orbit measurement precision is improved, and the measurement efficiency is improved. Especially in complex deep space environments such as solar system boundary detection, challenges such as weak signals and many interference factors are effectively handled, and the accuracy and reliability of measurement are ensured.

Description

Technical Field

[0001] The present invention relates to the field of aerospace exploration and orbit measurement technology, and in particular to a deep space ultra-long distance measurement device and a measurement method, and in particular to a deep space ultra-long distance measurement method based on an improved incoherent Doppler measurement model. Background Art

[0002] In the field of deep space ultra-long-distance measurement, especially for solar system boundary exploration missions, accurate measurement of spacecraft orbits is crucial. It is a key link to ensure the smooth implementation of missions and obtain scientific data. At present, mainstream deep space ultra-long-distance measurement methods and devices face many challenges when dealing with extreme distances and complex environments. In the early days, one-way Doppler measurement was one of the commonly used orbit measurement methods. It was based on the instantaneous measurement model under the classical Newtonian framework. However, in the deep space environment, the satellite platform environment is unstable, and the output frequency of the onboard crystal oscillator has random walk noise and aging. These deviations are difficult to completely eliminate through the model in the orbit solution, resulting in low orbit solution accuracy in the one-way Doppler measurement mode, which cannot meet the high-precision measurement requirements.

[0003] In order to solve the problem of one-way Doppler measurement, two-way closed-loop Doppler measurement technology came into being. In this technology, the ground station transmits the signal, the spacecraft receives it and then forwards it back to the ground station, and the speed and orbit information of the spacecraft are calculated by comparing the difference between the transmit and receive frequencies. This method effectively solves the problem of unstable frequency of the onboard crystal oscillator and significantly improves the measurement accuracy. However, in very long-distance measurement (over 70AU), since the signal delay reaches the order of days, it is impossible to transmit and receive signals at the same station, and the traditional closed-loop measurement mode fails. The three-way open-loop measurement can theoretically meet the measurement requirements in terms of geometric configuration. It forwards the signal through an intermediate station to achieve the measurement of the spacecraft. However, the environment where the spacecraft is located at the edge of the solar system is extreme, such as low temperature and low light. It is difficult to use traditional methods to provide enough energy through solar panels to ensure the normal operation of the onboard transponder, so it cannot be widely used in very long-distance measurement and control.

[0004] In addition to the above-mentioned Doppler measurement technology, optical-based measurement methods are also used in deep space exploration. For example, the orbit of the spacecraft is determined by observing the relative position changes between the spacecraft and the background stars through a telescope. However, this method is greatly affected by weather, atmospheric interference, and the distance between the spacecraft and the earth. At the boundary of the solar system, due to the long distance, the optical signal of the spacecraft is extremely weak, and it is difficult to accurately distinguish its position, and the measurement accuracy is difficult to guarantee. With the development of the aerospace industry, the task of exploring the boundary of the solar system is on the agenda, and the demand for deep space ultra-long-distance measurement technology is more urgent. The limitations of existing mainstream measurement methods and devices in terms of signal strength, measurement accuracy, equipment power consumption, and environmental adaptability have become bottlenecks restricting the development of deep space exploration. Therefore, the development of a new deep space ultra-long-distance measurement method and device that can overcome these problems is of great significance to promoting the smooth implementation of the solar system boundary exploration mission. Summary of the invention

[0005] The purpose of the present invention is to provide a deep space ultra-long distance measurement device and measurement method in view of the problems existing in the prior art.

[0006] To achieve the above object, the technical solution adopted by the present invention is: In the first aspect, a deep space ultra-long distance measurement device is provided, comprising: A simulation scenario construction and data generation unit, used to construct simulation data sets and provide simulation data; A measurement system construction unit, including a measurement system of an uplink station, an aircraft and a downlink station, wherein the uplink station is equipped with a high-precision frequency source for transmitting an uplink frequency, the aircraft is equipped with a signal transceiver and a frequency differentiator for receiving the uplink frequency, transmitting a downlink frequency, acquiring and transmitting frequency differential information, and the downlink station is used to receive the downlink frequency and the frequency differential information; A frequency difference information processing unit, used to evaluate the accuracy of the frequency difference information, select and control the error of the frequency differentiator, and optimize the sampling rate; The orbit solution and evaluation unit uses a mechanical model to perform orbit integration, performs orbit solution on simulation data under different measurement modes, compares and evaluates measurement results, and analyzes the advantages of different measurement modes.

[0007] Furthermore, the high-precision frequency source is a high-precision hydrogen clock, and the quantization error and random error of the frequency differentiator are controlled within 0.5mHz.

[0008] In a second aspect, a measurement method of a deep space ultra-long distance measurement device is provided, the measurement method comprising the following steps: Step 1: construct a simulation scenario, set scenario parameters, obtain simulation data, accurately annotate the simulation data, and construct a simulation data set for subsequent measurement and verification; Step 2: Building a measurement system, which transmits the acquired data to a data processing module to provide raw data for orbit solution; Step 3: Processing frequency differential information related issues, including at least precision analysis and control of the frequency differential information, time scale precision determination, and sampling rate optimization, to obtain the necessary data for incoherent Doppler measurement; Step 4: Perform orbit solution and measurement result evaluation. Perform orbit solution on the simulation data under the one-way Doppler and incoherent Doppler measurement modes respectively, compare the solution results under these two measurement modes, and evaluate the advantages of the incoherent Doppler measurement mode in deep space and ultra-long-distance orbit measurement.

[0009] Furthermore, in step one, with the aircraft flying past a celestial body as a reference, the set scene parameters include at least the distance between the celestial body and the earth, the one-way light travel time and the downlink signal power; the simulation data are various types of data in the simulation measurement process, including at least the orbital parameters of the aircraft, signal frequency information and Doppler observation noise data.

[0010] Furthermore, in the step 2, a measurement system including an uplink station, an aircraft and a downlink station is built, the uplink station is equipped with a high-precision hydrogen clock, and transmits a stable uplink frequency; the aircraft is equipped with a signal transceiver and a frequency differentiator, the signal transceiver receives the uplink frequency and transmits the downlink frequency at the same time; the frequency differentiator records the frequency differential information of the same satellite time, and sends it back to the downlink station through a telemetry link; the downlink station receives the downlink frequency and the frequency differential information transmitted by the aircraft, and prepares for subsequent orbit solution.

[0011] Furthermore, in terms of the accuracy analysis and control, the random walk noise of the frequency differential information is controlled within 0.5mHz; in terms of time scale accuracy determination, the time scale is determined by utilizing the homologous nature of the frequency differential information and the downlink frequency, and the time scale accuracy is better than 1µs.

[0012] Furthermore, in the aspect of the sampling rate optimization, the components of the frequency difference information are analyzed and expressed by the following formula: ,in Characterizes the relative motion between the uplink station and the satellite (aircraft), Characterize the linear drift of the onboard crystal oscillator, is a random walk model, Characterize crystal thermal noise; , and Improve interpolation accuracy by increasing the sampling rate or reducing the sampling step size.

[0013] Furthermore, gravitational redshift is considered in the orbit solution process and incorporated into the orbit solution model. The gravitational redshift is calculated as follows: , In the formula, is the downlink reference frequency, is the Newtonian gravitational potential of the celestial body on the spacecraft or station, Represents the celestial bodies, The speed of light.

[0014] Furthermore, during the orbit solution process, a mechanical model is selected for orbit integration according to the distance between the spacecraft and each celestial body.

[0015] Furthermore, after completing the orbit solution, the measurement result evaluation, error measurement and accuracy assessment stage is entered. The statistical analysis method is used to process multiple measurement results. When evaluating the measurement accuracy, error source analysis is required. By comparing the solution results under the one-way Doppler and incoherent Doppler measurement modes, the advantages of the incoherent Doppler measurement mode can be intuitively evaluated.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The measuring device realizes high-precision measurement of the orbit of very long-distance spacecraft in the solar system by combining the incoherent Doppler measurement principle with data processing algorithms and onboard equipment design; its application range not only covers the solar system boundary detection mission, such as the detection of Kuiper belt objects and heliosphere boundary areas, but can also be extended to the orbit monitoring and control of spacecraft in future interstellar voyages, providing key technical support for mankind to explore the universe in depth and expand the scope of space activities; 2. The measuring device fully considers the problems of weak signals that are difficult to capture, large measurement delays, and insufficient accuracy caused by crystal oscillator errors when measuring very long distances, constructs a high-fidelity simulation data set, builds a more reasonable measurement system, and uses a frequency differential information processing unit to improve the orbit measurement accuracy, reduce errors and optimize data processing, so that the measurement system can work more stably and accurately under complex conditions, enhancing the adaptability of the device and method to various actual measurement scenarios; 3. The measurement method is based on Improve the measurement model of incoherent Doppler, construct simulation scenarios and data sets, build measurement systems, process frequency difference sequences, and perform orbit solution and evaluation, etc., in order to solve many technical problems in deep space ultra-long-distance measurements and improve the accuracy of orbit measurements, especially in complex deep space environments such as solar system boundary detection, effectively deal with challenges such as weak signals and multiple interference factors, and ensure the accuracy and reliability of measurements; 4. Based on a high-fidelity simulation data set, this measurement method trains a measurement model that is still highly robust in similar scenarios for deep space ultra-long-distance measurements; it can improve the accuracy of orbit measurements. Compared with traditional one-way Doppler measurements, the position uncertainty in the incoherent mode is reduced from 5Km to 300m, and the velocity uncertainty is reduced from 0.01m / s to 0.001m / s, which greatly improves the measurement accuracy and meets the needs of the solar system boundary detection mission for high-precision orbit measurements; it can adapt to measurements in extreme environments, optimize data processing and system adaptability, and enhance the expansibility of system functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of a measurement process of a deep space ultra-long distance measurement method of the present invention; Figure 2 This is the distribution diagram of the incoherent Doppler link in the present invention.

[0018] Figure 3 This is the gravitational redshift diagram used in the test of the present invention.

[0019] Figure 4 This is a comparison diagram between the residual effect achieved by the present invention and the residual effect of the traditional method. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Example 1

[0022] A deep space ultra-long distance measurement device, comprising: A simulation scenario construction and data generation unit, used to construct simulation data sets and provide simulation data; A measurement system construction unit, including a measurement system of an uplink station, an aircraft and a downlink station, wherein the uplink station is equipped with a high-precision frequency source for transmitting an uplink frequency, the aircraft is equipped with a signal transceiver and a frequency differentiator for receiving the uplink frequency, transmitting a downlink frequency, acquiring and transmitting frequency differential information, and the downlink station is used to receive the downlink frequency and the frequency differential information; A frequency difference information processing unit, used to evaluate the accuracy of the frequency difference information, select and control the error of the frequency differentiator, and optimize the sampling rate; The orbit solution and evaluation unit uses a mechanical model to perform orbit integration, performs orbit solution on simulation data under different measurement modes, compares and evaluates measurement results, and analyzes the advantages of different measurement modes.

[0023] This measurement device achieves high-precision measurement of the orbits of very distant spacecraft in the solar system by combining the incoherent Doppler measurement principle with data processing algorithms and satellite-borne equipment design. Its application range not only covers solar system boundary detection tasks, such as the detection of Kuiper belt objects and the heliosphere boundary area, but can also be extended to the orbit monitoring and control of spacecraft in future interstellar voyages, providing key technical support for humans to explore the universe in depth and expand the scope of space activities.

[0024] This measurement device fully considers the problems exposed in long-distance measurements, such as weak signals that are difficult to capture, large measurement delays, and insufficient accuracy due to crystal oscillator errors. It constructs a high-fidelity simulation data set and builds a more reasonable measurement system. It uses a frequency differential information processing unit to improve orbit measurement accuracy, reduce errors and optimize data processing, so that the measurement system can work more stably and accurately in complex situations, enhancing the adaptability of the device to various actual measurement scenarios.

[0025] Furthermore, the high-precision frequency source is a high-precision hydrogen clock, and the quantization error and random error of the frequency differentiator are controlled within 0.5mHz. Example 2

[0026] A measurement method for a deep space ultra-long distance measurement device, combined with Figure 1 to Figure 4 As shown, the measuring method comprises the following steps: Step 1: construct a simulation scenario, set scenario parameters, obtain simulation data, accurately annotate the simulation data, and construct a simulation data set for subsequent measurement and verification; Step 2: Building a measurement system, which transmits the acquired data to a data processing module to provide raw data for orbit solution; Step 3: Processing frequency differential information related issues, including at least precision analysis and control of the frequency differential information, time scale precision determination, and sampling rate optimization, to obtain the necessary data for incoherent Doppler measurement; Step 4: Perform orbit solution and measurement result evaluation. Perform orbit solution on the simulation data under the one-way Doppler and incoherent Doppler measurement modes respectively, compare the solution results under these two measurement modes, and evaluate the advantages of the incoherent Doppler measurement mode in deep space and ultra-long-distance orbit measurement.

[0027] This measurement method aims to solve many technical problems in deep space and ultra-long-distance measurements and improve orbit measurement accuracy, especially in complex deep space environments such as solar system boundary detection, by constructing simulation scenarios and data sets, setting up measurement systems, processing frequency difference sequences, and performing orbit solution and evaluation. It aims to effectively deal with challenges such as weak signals and multiple interference factors to ensure measurement accuracy and reliability.

[0028] The purpose of constructing the simulation scenario and data set in step 1 is to create a measurement scenario that highly simulates the real situation and generate a corresponding simulation data set to provide basic data support for subsequent research.

[0029] In setting the key parameters of the simulation scenario, the scenario parameters set with the aircraft flying over a celestial body as a reference include at least the distance between the celestial body and the earth, the one-way light travel time and the downlink signal power; the simulation data are various types of data in the simulation measurement process, including at least the orbital parameters of the aircraft (considering the orbital changes under the gravitational effect of surrounding celestial bodies), signal frequency information (long-term drift, random walk and white noise components of the aircraft's transmission frequency, as well as uplink frequency and downlink frequency) and Doppler observation noise data (the magnitude of each error term is determined in combination with the actual noise level measured at the relevant stations). The simulation data are accurately annotated, including information such as the measurement time, aircraft position, observation station and observation mode, to construct a simulation data set for subsequent measurement method research and verification.

[0030] Specifically, the New Horizons spacecraft's flyby of Pluto in 2015 is used as a model, because this system is representative in the field of deep space exploration and provides us with an excellent reference example. First, it is necessary to accurately determine the distance between Pluto and the Earth during the flyby, which is about 4.7 billion kilometers. The determination of this distance is crucial for various subsequent calculations and simulations. It will affect the calculation of signal transmission delays and gravity and other factors. Secondly, the calculation of the one-way light travel time is about 4.5 hours. The calculation of this time parameter needs to take into account the propagation speed of light in a vacuum, which is the basis for the subsequent accurate marking of data timestamps and the evaluation of signal delay effects. For the downlink signal power, it is clearly about -145dBm (65-meter antenna aperture power), which is determined based on the actual antenna performance and the expected signal reception. The setting of this power level will affect the sensitivity and noise analysis of the signal receiving end.

[0031] When simulating measurement data, not only these basic scene parameters should be considered, but also a variety of physical effects and environmental factors. For example, in the simulation of orbital parameters, the gravitational effects of various celestial bodies in the solar system should be fully considered, including the strong gravitational force of the sun and the gravitational perturbations of massive planets such as Jupiter, and the orbital motion trajectory of the spacecraft in this complex gravitational environment should be simulated through accurate mechanical models. For signal frequency information, the characteristics of the spacecraft's own crystal oscillator should be considered, including long-term drift of the transmission frequency, random walk, and white noise components. These factors will have a complex impact on the final received signal frequency. At the same time, the uplink frequency needs to be considered from the uplink station equipped with a high-precision hydrogen clock to ensure the stability and accuracy of the transmission frequency, and the uplink frequency received by the spacecraft will be calculated based on its relative motion with the uplink station.

[0032] In addition, in the simulation of Doppler observation noise data, it is necessary to combine the actual station conditions, conduct a detailed analysis of multiple noise sources such as ground equipment thermal noise, interstellar medium, and earth medium, and accurately determine the magnitude of each error term, so as to provide a basis for adding noise to the data to simulate the actual observation situation. Finally, all simulated data are accurately labeled, including the measurement time (accurate to UTC time), the position information of the spacecraft, the observation station information, and the observation mode, etc., to ensure the integrity and availability of the data set, and provide sufficient and reliable data support for the subsequent measurement system construction, data processing, and orbit solution.

[0033] In step 2, a measurement system is built and data is acquired. This step is one of the core links of the entire measurement method. The accuracy and stability of its design and implementation are directly related to the reliability of the final measurement results. In step 2, a measurement system including an uplink station, an aircraft, and a downlink station is built. The uplink station is equipped with a high-precision hydrogen clock and transmits a stable uplink frequency; the aircraft is equipped with a signal transceiver and a frequency differentiator. The signal transceiver receives the uplink frequency and transmits the downlink frequency at the same time; the frequency differentiator records the frequency differential information of the same satellite time and sends it back to the downlink station through a telemetry link; the downlink station receives the downlink frequency and the frequency differential information transmitted by the aircraft to prepare for subsequent orbit solution.

[0034] Specifically, when building a measurement system, a complete architecture including the uplink station, the aircraft, and the downlink station must be carefully constructed. The uplink station, as the transmitter of the signal, is equipped with a high-precision hydrogen clock, which has extremely high frequency stability and accuracy and can provide a stable and accurate frequency reference signal for the entire measurement process. The stability of this reference frequency signal is crucial to the accuracy of subsequent measurements. Slight frequency fluctuations may be amplified in the subsequent signal processing and solution process, resulting in increased measurement errors. For example, in deep space ultra-long-distance measurements, the signal propagates over extremely long distances. Any slight deviation in frequency will cause a significant change in the frequency of the received signal after long-distance transmission, thus affecting the accurate measurement of the spacecraft's orbital parameters.

[0035] The equipment carried by the aircraft is the key node to realize the measurement function. The signal transceiver is responsible for receiving the signal (uplink frequency) from the uplink station and calculating the uplink frequency based on the relative motion relationship. ,in is the projection of the relative speed of the uplink station to the aircraft in the visual direction, and c is the speed of the electromagnetic signal in a vacuum; at the same time, it also transmits the downlink frequency , and this frequency is affected by the satellite-borne crystal oscillator, and there will be frequency deviation. In order to eliminate the influence of this deviation on the measurement, the spacecraft is also equipped with a frequency (phase) differentiator, which can record the difference between the downlink frequency transmitted by the same satellite and the uplink frequency received at the same time. , that is, frequency differential information (or frequency differential sequence). This frequency differential information is the key data for the subsequent correction of the frequency deviation of the satellite-borne crystal oscillator. Its accuracy directly determines the degree of improvement in measurement accuracy. Send back to the downlink station.

[0036] The downlink station is responsible for receiving the downlink frequency transmitted by the aircraft And frequency difference information The receiving equipment of the downlink station needs to have high sensitivity and anti-interference ability to ensure that weak signals can be accurately received even when the signal is transmitted over long distances and its intensity is greatly attenuated. The received data will be transmitted to the subsequent data processing module in a timely manner to provide raw data for orbit solution. These data are like the "cornerstone" of the measurement system, and all subsequent analysis, calculations and orbit determination are based on this. Only by ensuring the accuracy and completeness of data acquisition can accurate and reliable results be obtained in the subsequent orbit solution, realizing high-precision measurement of the orbits of deep space and ultra-long-distance aircraft, and meeting the stringent requirements of tasks such as solar system boundary detection.

[0037] The problem of processing frequency differential information in step three is key to improving measurement accuracy and ensuring the reliability of the measurement system.

[0038] In terms of the accuracy analysis and control, the random walk noise of the frequency differential information is controlled within 0.5mHz; in terms of time scale accuracy determination, the time scale is determined by utilizing the homology between the frequency differential information and the downlink frequency, and the time scale accuracy is better than 1µs.

[0039] Specifically, frequency difference information The accuracy will directly affect the measurement results. According to the formula It can be seen that The random walk noise is composed of the quantization error and thermal noise error of the differentiator. In order to control the error to a very small range, a suitable differentiator needs to be selected. In practical applications, differentiators of different models and specifications have significant differences in quantization error and thermal noise performance. By performing performance tests and comparative analysis on a variety of differentiators, we can select products that can control the combined impact of quantization error and random walk noise to the 0.5mHz level, which can effectively reduce the interference of errors on measurements and ensure the stability of measurement accuracy.

[0040] Time scale accuracy determination is an important step in frequency differential information (sequence) processing. Directly using the satellite atomic clock time system, its conventional accuracy is only sub-millisecond level, which is difficult to meet the needs of high-precision measurement; if it is to meet the requirements, additional satellite time calibration is required, which not only increases the complexity and cost of the measurement task, but also may introduce new error sources. Therefore, this method has great limitations in practical applications. Considering the light travel time model Although it is theoretically feasible to use time-stamping, in practice, the introduction of additional dynamic processes in the observed quantity can easily cause the solution matrix to be singular; moreover, its accuracy will be affected by both orbit accuracy and link effect. In deep space, slight deviations in orbit accuracy and various interference factors in the link will greatly reduce the accuracy of the time-stamping based on the light-travel time model, making it impossible to meet the requirements of accurate measurement. and The homologous nature of the time scale has obvious advantages. This method does not need to consider The absolute time scale can effectively overcome the interference of link effect and is not affected by orbit accuracy. and The alignment accuracy is better than 1µs, which provides a strong guarantee for accurate measurement. Therefore, this method is also used in the present invention to determine and Corresponding value.

[0041] Furthermore, in the aspect of the sampling rate optimization, the components of the frequency difference information are analyzed and expressed by the following formula: ,in Characterizes the relative motion between the uplink station and the satellite (aircraft), Characterize the linear drift of the onboard crystal oscillator, is a random walk model, Characterize crystal thermal noise; , and Improve interpolation accuracy by increasing the sampling rate or reducing the sampling step size.

[0042] Characterize the relative motion between the uplink station and the satellite. Since the celestial motion function is relatively smooth, a high interpolation accuracy can still be guaranteed at a larger sampling interval; Characterizing the linear drift of the onboard crystal oscillator, high sampling accuracy can be maintained at a larger sampling interval. As a random walk model, its parameters are random and can be improved by reducing the sampling step size. However, the model parameters of different crystal oscillators are different, which requires comprehensive testing of the crystal oscillator to obtain its detailed model parameters, so as to reasonably limit the sampling step size. Characterizing the thermal noise of the crystal oscillator has no direct correlation with the sampling rate and cannot be eliminated by increasing the sampling rate. In actual operation, a sampling rate that is too high will put tremendous pressure on the data channel, which may cause data transmission congestion or even loss; a sampling rate that is too low will affect the interpolation accuracy, thereby reducing the measurement accuracy. Therefore, it is necessary to fully consider the carrying capacity of the data channel while ensuring the interpolation accuracy, find a balance point through a large number of experiments and data analysis, and determine the most appropriate sampling rate to ensure that the measurement system can obtain high-precision data while running stably and efficiently.

[0043] The orbit solution and measurement result evaluation, error measurement and accuracy assessment in step 4 are key links in the entire measurement process, which are directly related to the reliability and effectiveness of the measurement method and are of great significance for achieving the goals of deep space ultra-long-distance measurement missions such as solar system boundary detection.

[0044] In the process of orbit solution, the influence of various complex factors on the measurement frequency should be fully considered. Among them, gravitational redshift is an important factor that cannot be ignored. It is necessary to incorporate gravitational redshift into the orbit solution model. The calculation method of gravitational redshift is: , where is the downlink reference frequency, is the Newtonian gravitational potential of the celestial body on the spacecraft or station, Represents the celestial bodies, The speed of light.

[0045] In the scenario of solar system boundary detection, the distance between the spacecraft and the ground station from the sun is very different, making the gravitational redshift effect very significant. For example, in the measurement of the New Horizons spacecraft, the influence of the sun's gravitational redshift is dominant, and the gravitational redshift of celestial bodies such as the Earth and Jupiter cannot be underestimated. Accurately calculating the gravitational redshift and incorporating it into the orbit solution model can effectively improve the accuracy of the orbit solution and avoid orbit parameter deviations caused by ignoring this factor.

[0046] Furthermore, in the process of orbit solution, the mechanical model is selected for orbit integration according to the distance between the spacecraft and each celestial body. In the simulation of the New Horizons spacecraft flying over Pluto, the gravity truncation error is taken as Under the condition of , a simple point mass gravity model can simplify the calculation and meet the accuracy requirements, while the light pressure and relativistic effects can be ignored. However, in other more complex detection scenarios, a more accurate mechanical model may be needed to describe the interaction between celestial bodies to ensure the accuracy of the orbital integration results.

[0047] Furthermore, after completing the orbit solution, the measurement result evaluation, error measurement and accuracy assessment stage is entered. The statistical analysis method is used to process multiple measurement results. When evaluating the measurement accuracy, error source analysis is required. By comparing the solution results under the one-way Doppler and incoherent Doppler measurement modes, the advantages of the incoherent Doppler measurement mode can be intuitively evaluated.

[0048] The orbits of the simulation data in the one-way Doppler and incoherent Doppler measurement modes are solved respectively. During the solution, the positions of Pluto and Charon during the flyby are read from the BSP ephemeris published by SPICE / NAIF, and the quality adopts the reference value published by IAU. By comparing the solution results in the one-way Doppler and incoherent Doppler measurement modes, such as key parameters such as position uncertainty and velocity uncertainty, the advantages of the incoherent Doppler measurement mode can be intuitively evaluated. Taking the actual simulation results as an example, the position uncertainty in the one-way mode is 5Km, and the velocity uncertainty is 0.01m / s; the position uncertainty in the incoherent mode is 300m, and the velocity uncertainty is 0.001m / s, which clearly shows the excellent performance of the incoherent Doppler measurement mode in reducing measurement errors and improving measurement accuracy.

[0049] In order to more comprehensively evaluate the measurement accuracy, error source analysis is also required. Measurement errors may come from many aspects, such as the frequency deviation of the onboard crystal oscillator, thermal noise of ground equipment, interference of the interstellar medium and the earth medium on the signal, station coordinate error, and the accuracy of the ground clock. By analyzing each error source in detail and quantifying its impact on the measurement results, the key direction for improving measurement accuracy can be identified. For example, if it is found that the frequency deviation of the onboard crystal oscillator is the main factor causing the measurement error, then further optimizing the crystal oscillator performance or improving the frequency calibration method will become the key work to improve the measurement accuracy.

[0050] At the same time, the statistical analysis method is used to process the multiple measurement results, and the statistical indicators such as the standard deviation and root mean square error of the measurement results are calculated, which can more accurately evaluate the stability and reliability of the measurement accuracy. For example, if the standard deviation of multiple measurement results is small, it means that the measurement method has good repeatability and stability, and the measurement accuracy is relatively reliable; otherwise, it is necessary to further check whether there are unstable factors in the measurement process and make corresponding improvements.

[0051] Through rigorous orbit solutions, comprehensive measurement results evaluation, in-depth error measurement and accuracy assessment, we can continuously optimize measurement methods and systems, improve the accuracy and reliability of deep space and ultra-long-distance measurements, provide solid technical support for aerospace missions such as solar system boundary detection, and help mankind's exploration of the universe move deeper and farther.

[0052] The main innovations and advantages of this method are combined in the following aspects: Improve orbit measurement accuracy: This invention adopts the principle of incoherent Doppler measurement and effectively eliminates the influence of long-term drift and random walk noise of the satellite crystal oscillator on orbit measurement by introducing frequency (phase) differential information. When equipped with an ordinary precision satellite crystal oscillator and ignoring the influence of the earth medium and link, the orbit measurement accuracy can reach 0.2mm / s (1 second integration). Compared with the traditional one-way Doppler measurement, the position uncertainty in the incoherent mode is reduced from 5Km to 300m, and the velocity uncertainty is reduced from 0.01m / s to 0.001m / s, which greatly improves the measurement accuracy and meets the needs of the solar system boundary detection mission for high-precision orbit measurement.

[0053] Adapt to extreme environment measurement: Incoherent Doppler measurement adopts open-loop receiving mode and uses a transceiver with much lower power consumption than traditional transponders. This design feature makes the measurement system more adaptable to the extreme environment of the spacecraft at the edge of the solar system, such as low temperature and low light, ensuring the smooth progress of measurement work in very long-distance measurement and control, and overcoming the limitation that the traditional three-pass measurement mode cannot be applied due to spacecraft environmental problems.

[0054] Optimize data processing and system adaptability: In-depth research and reasonable handling of issues such as the time scale accuracy and sampling rate of frequency difference sequences have improved the accuracy of data processing and the adaptability of the system. By selecting appropriate time scale determination methods, such as using the homology of the sequence and the observed value to determine the corresponding value, and reasonably selecting the sampling rate to balance the interpolation accuracy and data transmission rate, the measurement system can work more stably and accurately in complex situations, and enhance the system's adaptability to various actual measurement scenarios.

[0055] Enhanced system functional expandability: Incoherent Doppler measurement technology can not only be used for high-precision orbit measurement, but also has the potential to correct the frequency offset of the onboard crystal oscillator, and can provide a high-precision frequency source for the aircraft. This makes it possible to achieve onboard ultra-stable frequency reference maintenance in the core technology of space VLBI in the future, expands the application scope of the technology, and improves the functional diversity and practicality of the entire aerospace measurement system.

[0056] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A deep space ultra-long distance measurement device, characterized in that: include: A simulation scenario construction and data generation unit, used to construct simulation data sets and provide simulation data; A measurement system construction unit, including a measurement system of an uplink station, an aircraft and a downlink station, wherein the uplink station is equipped with a high-precision frequency source for transmitting an uplink frequency, the aircraft is equipped with a signal transceiver and a frequency differentiator for receiving the uplink frequency, transmitting a downlink frequency, acquiring and transmitting frequency differential information, and the downlink station is used to receive the downlink frequency and the frequency differential information; A frequency difference information processing unit, used to evaluate the accuracy of the frequency difference information, select and control the error of the frequency differentiator, and optimize the sampling rate; The orbit solution and evaluation unit uses a mechanical model to perform orbit integration, performs orbit solution on simulation data under different measurement modes, compares and evaluates measurement results, and analyzes the advantages of different measurement modes.

2. The deep space ultra-long distance measurement device according to claim 1, characterized in that: The high-precision frequency source is a high-precision hydrogen clock, and the quantization error and random error of the frequency differentiator are controlled within 0.5mHz.

3. A measurement method for a deep space ultra-long distance measurement device according to claim 1 or 2, characterized in that: The measuring method comprises the following steps: Step 1: construct a simulation scenario, set scenario parameters, obtain simulation data, accurately annotate the simulation data, and construct a simulation data set for subsequent measurement and verification; Step 2: Building a measurement system, which transmits the acquired data to a data processing module to provide raw data for orbit solution; Step 3: Processing frequency differential information related issues, including at least precision analysis and control of the frequency differential information, time scale precision determination, and sampling rate optimization, to obtain the necessary data for incoherent Doppler measurement; Step 4: Perform orbit solution and measurement result evaluation. Perform orbit solution on the simulation data under the one-way Doppler and incoherent Doppler measurement modes respectively, compare the solution results under these two measurement modes, and evaluate the advantages of the incoherent Doppler measurement mode in deep space and ultra-long-distance orbit measurement.

4. The measurement method of the deep space ultra-long distance measurement device according to claim 3, characterized in that: In step one, with the aircraft flying past a celestial body as a reference, the set scene parameters include at least the distance between the celestial body and the earth, the one-way light travel time and the downlink signal power; the simulation data are various types of data in the simulation measurement process, including at least the orbital parameters of the aircraft, signal frequency information and Doppler observation noise data.

5. The measurement method of the deep space ultra-long distance measurement device according to claim 3, characterized in that: In the step 2, a measurement system including an uplink station, an aircraft and a downlink station is built. The uplink station is equipped with a high-precision hydrogen clock and transmits a stable uplink frequency. The aircraft is equipped with a signal transceiver and a frequency differentiator. The signal transceiver receives the uplink frequency and transmits the downlink frequency at the same time. The frequency differentiator records the frequency differential information of the same satellite time and sends it back to the downlink station through a telemetry link. The downlink station receives the downlink frequency and the frequency differential information transmitted by the aircraft to prepare for subsequent orbit solution.

6. The measurement method of the deep space ultra-long distance measurement device according to claim 3, characterized in that: In terms of the accuracy analysis and control, the random walk noise of the frequency differential information is controlled within 0.5mHz; in terms of time scale accuracy determination, the time scale is determined by utilizing the homology between the frequency differential information and the downlink frequency, and the time scale accuracy is better than 1µs.

7. The measurement method of the deep space ultra-long distance measurement device according to claim 3, characterized in that: In terms of the sampling rate optimization, the components of the frequency difference information are analyzed and expressed by the following formula: ,in Characterizes the relative motion between the uplink station and the aircraft, Characterize the linear drift of the onboard crystal oscillator, is a random walk model, Characterize crystal thermal noise; , and Improve interpolation accuracy by increasing the sampling rate or reducing the sampling step size.

8. The measurement method of the deep space ultra-long distance measurement device according to claim 3, characterized in that: The gravitational redshift is considered in the orbit solution process and incorporated into the orbit solution model. The gravitational redshift is calculated as follows: , In the formula, is the downlink reference frequency, is the Newtonian gravitational potential of the celestial body on the spacecraft or station, Represents the celestial bodies, The speed of light.

9. The measurement method of the deep space ultra-long distance measurement device according to claim 3, characterized in that: In the process of orbit solution, the mechanical model is selected for orbit integration according to the distance between the spacecraft and each celestial body.

10. The measurement method of the deep space ultra-long distance measurement device according to claim 3, characterized in that: After completing the orbit solution, the measurement result evaluation, error measurement and accuracy assessment stage begins. Statistical analysis methods are used to process multiple measurement results. When evaluating the measurement accuracy, error source analysis is required. By comparing the solution results under the one-way Doppler and incoherent Doppler measurement modes, the advantages of the incoherent Doppler measurement mode can be intuitively evaluated.

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