Method for improving long-term stability of atomic time by using pulsar time

Abstract

The invention discloses a method for improving long-term stability of atomic time by using pulsar time, which comprises the following steps: acquiring timing observation data of a pulsar in a preset time period, and fitting timing model parameters of the pulsar; forecasting the time of arrival (TOA) data of the pulsar on the basis of the timing model parameters, meanwhile, continuing to carry out pulsar timing observation by using local atomic time, and comparing the observed TOA sequence with the forecasted TOA data to obtain timing residual data; wiener filtering and classical weighting processing are carried out on timing residual data of multiple pulsar to obtain a clock error sequence of local atomic time and comprehensive pulsar time, a result of smoothing processing of the clock error sequence is negated and then added to the local atomic time, and a new fusion time scale is obtained. According to the method, the paper local atomic time with higher long-term stability can be established, and a powerful guarantee is provided for generating national standard time with higher long-term autonomous retention capability by using a local atomic time control main clock system subsequently.

Description

Technical Field

[0001] The present invention relates to the technical field of pulsar timing applications, and relates to but is not limited to a method for improving the long-term stability of atomic time by using pulsar time. Background Art

[0002] At present, time laboratories in various countries in the world use various types of atomic clocks for timekeeping, such as hydrogen atomic clocks, cesium atomic clocks and other timekeeping atomic clocks. Some laboratories also have reference clocks that provide frequency references, such as cesium fountain clocks and optical clocks. Multiple atomic clocks of different types can be used together to keep time and establish a more stable atomic time. Due to the various noises in atomic clocks, their long-term stability is difficult to guarantee. Moreover, due to the short service life of atomic clocks, atomic clocks need to be replaced irregularly during the long-term maintenance of atomic time, which makes the long-term stability of atomic time not high. Therefore, time laboratory timekeeping usually requires regular calibration of International Atomic Time (TAI) or Coordinated Universal Time (UTC). These international cooperation products may be difficult to obtain in extraordinary times, resulting in poor autonomy of my country's standard time. It is necessary to establish high-precision, long-term stable local atomic time to ensure the independence, autonomy, safety and controllability of my country's standard time. Therefore, improving the long-term stability of local atomic time is an effective means to achieve long-term high-level maintenance of my country's standard time.

[0003] Pulsars are a type of compact celestial body in the universe, and their rotation is very stable. Millisecond pulsars in particular are known as natural clocks in the universe. People can observe highly stable periodic signals from pulsars on the ground through radio telescopes. This stable periodic pulse signal forms a natural frequency source. The atomic clock at the station can record TOA, and the measurement accuracy of TOA is very high, reaching the order of hundreds of nanoseconds or even smaller. After long-term timing observations, people can fit a series of timing model parameters such as the rotation frequency, rotation frequency change rate, position, proper motion, and parallax of millisecond pulsars through TOA data. Based on these model parameters, the TOA of pulsar pulses can be accurately predicted. Therefore, a pulsar is similar to a distant clock, and multiple millisecond pulsars can be used to establish a comprehensive pulsar time through appropriate algorithms. After long-term research, people have found that the long-term stability of the comprehensive pulsar time is better than that of the atomic time, and compared with the atomic clock, the pulsar time has good continuity and can be continuously observed. This is because pulsars are natural celestial bodies with advantages such as long life, high reliability, and no influence from environmental and human factors. The established comprehensive pulsar time can detect the long-term systematic fluctuations of atomic time, that is, the instability caused by low-frequency noise. Therefore, eliminating or weakening the fluctuations in the atomic time system detected by pulsar time can improve the long-term stability of the autonomously maintained local atomic time, which is of great significance to improving the long-term high-level maintenance of our country's standard time. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a method for improving the long-term stability of atomic time by using pulsar time, which at least solves the problem that the long-term autonomous maintenance capability and stability of local atomic time are poor.

[0005] The technical solutions of the embodiments of the present invention are as follows: An embodiment of the present invention provides a method for improving the long-term stability of atomic time by using pulsar time, the method comprising: Acquire the timing observation data of the pulsar within a preset time period and fit the timing model parameters of the pulsar; predict the TOA data of the pulsar based on the timing model parameters, and continue to perform pulsar timing observation using local atomic time at the same time, and compare the observed TOA sequence with the predicted TOA data to obtain timing residual data; perform Wiener filtering and classical weighting processing on the timing residual data of multiple pulsars to obtain the clock difference sequence between the local atomic time and the integrated pulsar time, and add the inverse result of the smoothing of the clock difference sequence to the local atomic time to obtain a new fusion time scale.

[0006] Furthermore, the obtaining of timing observation data of a pulsar within a preset time period and fitting of timing model parameters of the pulsar include: obtaining TOA observation data of the pulsar within a preset time period using the Earth time TT published by BIPM as a reference; and fitting the timing model parameters of the pulsar using a least squares fitting method based on the TOA observation data.

[0007] Furthermore, the timing model parameters include at least the pulsar's rotation frequency and its first-order derivative, position, proper motion, parallax, interstellar medium dispersion and binary orbit model parameters.

[0008] Furthermore, the local atomic time is TA (NTSC), and the method also includes: taking the earth time TT as a reference, simulating the TOA data of multiple pulsars to obtain the clock difference TT-PTi between TT and the pulsar time constructed by each pulsar; constructing TT-EPT by a classical weighted algorithm for the TT-PTi corresponding to each of the multiple pulsars, wherein EPT is the integrated pulsar time; combining the collected clock difference sequence of TA (NTSC) and TT to obtain the clock difference sequence TA (NTSC)-EPT between TA (NTSC) and the integrated pulsar time.

[0009] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least: In an embodiment of the present invention, a method of using pulsar time to improve the long-term stability of atomic time is proposed, and pulsar time is integrated into the timekeeping work to achieve joint timekeeping using atomic time and pulsar time, while giving full play to the advantages of short-term stability of atomic time and long-term stability of pulsar time. Compared with the original single means of using atomic clocks to construct atomic time, after the participation of pulsar time, the long-term stability of the fusion time scale is improved, and there is no loss of short-term stability. According to this method, a paper local atomic time with higher long-term stability can be established, which provides a strong guarantee for the subsequent use of local atomic time to control the main clock system to produce a national standard time with stronger long-term autonomous maintenance capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 A schematic diagram of the process steps of a method for improving the long-term stability of atomic time by using pulsar time provided by an embodiment of the present invention; Figure 2 A logic flow chart of a method for improving the long-term stability of atomic time by using pulsar time provided by an embodiment of the present invention; Figure 3 Improvement of the fusion time scale provided by the embodiment of the present invention Lun deviation; Figure 4 An improved Hadamard deviation of the fusion time scale provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0012] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0013] Those skilled in the art will appreciate that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the field to which the embodiments of the present invention belong. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as here.

[0014] Figure 1 A schematic diagram of the process steps of a method for improving the long-term stability of atomic time by using pulsar time provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method comprises at least the following steps: Step S110, obtaining the timing observation data of the pulsar within a preset period of time, and fitting the timing model parameters of the pulsar.

[0015] Here, the timing observation data is the pulse arrival time TOA, and the preset period is a fixed period of time, such as one year, three years, etc. For millisecond pulsars, the measurement accuracy of TOA is very high, which can reach the order of hundreds of nanoseconds or even smaller. After long-term timing observations, people can fit a series of timing model parameters such as the pulsar's rotation frequency, rotation frequency change rate, position, proper motion, parallax, etc. through TOA data fitting. Among them, the pulsar's rotation frequency and its change rate are actually the clock model parameters of the pulsar clock.

[0016] Using the long-term timing observation data of pulsars (i.e. TOA data) and combining it with the existing fitting algorithm for multiple iterations, the parameters of the pulsar timing model can be accurately determined. The precise measurement of these parameters is the basis for pulsar timing applications, such as detecting low-frequency gravitational waves, establishing pulsar time scales, and measuring the mass of solar system planets.

[0017] In the implementation, the TOA is first predicted at the solar system center of mass (SSB) based on the initial timing model parameters. The TOA actually measured by the reference atomic time is subtracted from the TOA predicted by the model to obtain the pulsar timing residual before fitting. Then, the least squares method is used to iterate the fitting multiple times until convergence, and the timing residual after fitting and the updated pulsar timing model parameters are obtained. Therefore, when new observation data is obtained, the above process will be repeated to update the pulsar timing model parameters again.

[0018] Step S120, predicting the TOA data of the pulsar based on the timing model parameters, while continuing to perform pulsar timing observations using local atomic time, and comparing the observed TOA sequence with the predicted TOA data to obtain timing residual data.

[0019] Here, the pulsar timing process is actually the process of comparing the time of the local atomic clock and the pulsar clock, so the timing residual actually represents the clock difference between the local atomic clock and the pulsar clock. Local atomic time is the atomic time established by the atomic clock used in the time laboratories in various places, and is used as the object to be adjusted in the present invention.

[0020] During implementation, on the one hand, TOA is predicted using the determined timing model parameters, and on the other hand, pulsar timing observations are continued using local atomic time as a reference to obtain the TOA sequence measured by the local atomic clock. The difference between the observed TOA sequence and the predicted TOA data is used as the timing residual data to characterize the clock difference between the local atomic time and pulsar time.

[0021] Step S130, the timing residual data of multiple pulsars are subjected to Wiener filtering and classical weighting processing to obtain a clock difference sequence between the local atomic time and the integrated pulsar time, the result of the smoothing processing of the clock difference sequence is inverted and added to the local atomic time to obtain a new fusion time scale.

[0022] Here, the calculation of the Wiener filter method is relatively simple and easy to implement quickly. Its principle is to perform correlation operations on the timing residual data of different pulsars to obtain an estimate of the statistical characteristics of the detected signal, and then use it to filter the timing residual of each pulsar, and finally perform a weighted average on the filtering results. The problem with the Wiener filter method is that when several pulsars have high noise levels, the synthetic pulsar established will also have high noise, which will directly drown out the detected signal. Improving the signal energy estimation method and taking reasonable weights are the key to using the Wiener filter method to construct a synthetic pulsar.

[0023] Assuming that the local atomic time is TA (NTSC), and using the Earth Time TT (BIPM) (hereinafter referred to as TT) published by BIPM as the reference time, the timing residual data of the local atomic time and pulsar time (PTi) before fitting is first calculated as TA (NTSC)-PTi, and then the TA (NTSC)-PTi corresponding to multiple pulsars are processed comprehensively to obtain the clock difference sequence between the local atomic time and the comprehensive pulsar time as TA (NTSC)-EPT, where EPT is the comprehensive pulsar time. The result of the smoothing of the clock difference sequence is (TA (NTSC)-EPT)s.

[0024] Finally, add the minus sign of the smoothed result to the atomic time to obtain TA(NTSC)-TT+(EPT-TA(NTSC))s, and define the new fusion time scale as APT, that is, APT-TT=TA(NTSC)-TT+[EPT-TA(NTSC)]s.

[0025] It should be noted that pulsar time is affected by measurement noise and its short-term stability is not as good as atomic time, but as observation data accumulates, its long-term stability will be better than atomic time. Therefore, to establish a time scale with excellent short-term and long-term stability, it is necessary to give full play to the advantages of short-term and medium-term stability of atomic time and the advantages of long-term stability of pulsars.

[0026] The low-frequency random walk noise of the atomic clock will cause the low-frequency red noise of the atomic time to be more significant, so the long-term stability is not high. Some pulsars with small red noise are mainly affected by high-frequency noise. Therefore, if the clock difference between the pulsar time and the atomic time is smoothed (high-frequency noise is removed), the remaining low-frequency noise is mainly contributed by the atomic time. Compensating the smoothed pulsar time and the atomic clock difference into the atomic time will eliminate or weaken the low-frequency noise of the atomic time, and the long-term stability of the atomic time will be improved. At the same time, since the pulsar time has been smoothed, no additional high-frequency noise will be introduced.

[0027] Therefore, after the method proposed in the present invention combines pulsar time and atomic time, the fusion time scale not only maintains the short stability of atomic time but also inherits the long stability of pulsar time.

[0028] In the embodiment of the present invention, a method of using pulsar time to improve the long-term stability of atomic time is proposed, and pulsar time is integrated into the timekeeping work to achieve joint timekeeping using atomic time and pulsar time, while giving full play to the advantages of short-term stability of atomic time and long-term stability of pulsar time. Compared with the original single means of using atomic clocks to construct atomic time, after the participation of pulsar time, the long-term stability of the fusion time scale is improved, and there is no loss of short-term stability. According to this method, a paper local atomic time with higher long-term stability can be established, which provides a strong guarantee for the subsequent use of local atomic time to control the main clock system to produce a national standard time with stronger long-term autonomous maintenance capability.

[0029] In some embodiments of the present invention, the above-mentioned step S110 "obtaining timing observation data of the pulsar within a preset time period and fitting the timing model parameters of the pulsar" is further implemented through the following process: using the Earth time TT published by BIPM as a reference, obtaining the TOA observation data of the pulsar within a preset time period; based on the TOA observation data, fitting the timing model parameters of the pulsar through the least squares fitting method.

[0030] Here, first, one or more millisecond pulsars of interest are selected for observation. Then TOA data are collected: timing observations of the selected pulsars are made using a radio telescope over a preset period (e.g., months to years), and the arrival time (TOA) of each observed pulse is recorded. These TOA data are usually expressed in a time standard such as Modified Julian Day (MJD) or GPS time, and need to be converted to the Terrestrial Time (TT) time standard. This usually involves converting the observation time to International Atomic Time (TAI) and then back to TT.

[0031] The observed TOA data are fitted to the preset timing model using the least squares fitting method. Least squares fitting is an optimization technique that estimates the model parameters by minimizing the sum of squares of the differences between the observed data and the model predictions. The fitting process may require iterative optimization to find the best model parameters. This usually involves continually adjusting the model parameters until the difference between the observed data and the model predictions is minimized.

[0032] Therefore, the timing model parameters of pulsars can be obtained through the least squares fitting method, and these parameters can be used for subsequent pulsar timing array (PTA) research, gravitational wave detection and other applications. At the same time, these parameters can also be used to calibrate and verify other time standards to improve the accuracy and stability of time measurement.

[0033] In some embodiments of the present invention, the timing model parameters include at least the pulsar's rotation frequency and its first-order derivative, position, proper motion, parallax, interstellar medium dispersion, and binary orbit model parameters.

[0034] Here, the fitted parameters include the pulsar's rotation frequency and its first-order derivative (describing the change in the pulsar's rotation speed), position (coordinates on the celestial sphere), proper motion (the change in the pulsar's position on the celestial sphere due to space motion), parallax (the change in apparent velocity due to the relative motion between the Earth and the pulsar), interstellar medium dispersion (DM, describing the delay caused by electron scattering when the pulsar signal propagates in interstellar space), and possible binary orbit model parameters (if the pulsar is in a binary system). The precise measurement of these parameters is the basis for pulsar timing applications, such as detecting low-frequency gravitational waves, establishing pulsar time scales, and measuring the mass of solar system planets.

[0035] In some embodiments of the present invention, the local atomic time is TA (NTSC), and the method further includes: taking the earth time TT as a reference, simulating the TOA data of multiple pulsars to obtain the clock difference TT-PTi between TT and the pulsar time constructed by each pulsar; constructing TT-EPT by a classical weighted algorithm for the TT-PTi corresponding to each of the multiple pulsars, wherein EPT is the integrated pulsar time; combining the collected clock difference sequence of TA (NTSC) and TT to obtain the clock difference sequence TA (NTSC)-EPT between TA (NTSC) and the integrated pulsar time.

[0036] Here, local atomic time TA (NTSC) is the local time standard of the National Time Service Center (NTSC).

[0037] First, use simulation software or algorithms to generate TOA data for multiple pulsars. These data should be based on the actual rotation period, rotation deceleration rate, position, and apparent velocity relative to the Earth of each pulsar. At the same time, ensure that the simulation process takes into account the influence of factors such as the Earth's rotation, the Earth's orbital motion, and the effects of general relativity on the arrival time of the pulses.

[0038] Then, for each pulsar, the clock difference TT-PTi between TT and the pulsar time PTi is calculated by comparing its simulated TOA data with the expected arrival time (based on known pulsar parameters and Earth time TT). This step requires precise time measurement and data processing technology to ensure the accuracy of the clock difference.

[0039] The TT-PTi data of multiple pulsars are integrated, and the clock difference TT-EPT between the Earth time TT and the Ensemble Pulsar Time (EPT) is constructed using a classical weighted algorithm (such as the least squares method). The purpose of the weighted algorithm is to assign different weights according to the stability and accuracy of each pulsar, so as to obtain a more reliable TT-EPT clock difference.

[0040] Collect the clock difference sequence between the time standard TA (such as NTSC, National Time Service Center) and the Earth time TT from actual observations or data. Ensure that the collected clock difference sequence has sufficient accuracy and density to reflect the actual difference between TA and TT.

[0041] Using the TT-EPT clock difference obtained above, the clock difference sequence between TA and TT is converted into the clock difference sequence between TA and EPT, TA (NTSC) -EPT. This step involves mathematical transformation and data processing to ensure the accuracy and consistency of the clock difference sequence.

[0042] Through the above steps, the clock difference sequence between TA (NTSC) and the integrated pulsar time EPT can be finally obtained, and the result of smoothing the clock difference sequence is inverted and added to the local atomic time to obtain a new fusion time scale. This is of great significance for studying the stability and accuracy of time standards, improving navigation and time synchronization systems, etc.

[0043] The method for improving the long-term stability of atoms when using pulsars is described below in conjunction with a specific embodiment. However, it should be noted that this specific embodiment is only for better illustrating the present invention and does not constitute an improper limitation to the present invention.

[0044] At present, among the paper time realized based on atomic clocks, the Earth Time, TT (BIPM), issued by the International Bureau of Weights and Measures BIPM, is considered to have the highest accuracy. TT (BIPM) is obtained by processing the Earth Time TT (TAI) realized by TAI one year later by BIPM after considering the weighting of the reference clock, and is issued once a year. Some time laboratories will establish and maintain their own local atomic time. For example, the local atomic time maintained by the National Time Service Center of the Chinese Academy of Sciences is TA (NTSC), which is a comprehensive atomic time jointly established by dozens of atomic clocks, while TT (BIPM) is established by more than 500 atomic clocks in laboratories around the world. Therefore, TA (NTSC) still has deviations relative to TT (BIPM), and its accuracy and stability are not as good as TT (BIPM). This specific embodiment takes the local atomic time TA (NTSC) of the National Time Service Center as an example, and uses the simulation data of three millisecond pulsars for illustration. Figure 2 The pulsar time and atomic time fusion flow chart provided in the embodiment of the present invention is as follows: Figure 2 As shown, the process is implemented through the following process: S1, first simulate the TOA data of three millisecond pulsars, respectively using the model parameters of J0437-4715, J1909-3744 and J1713+0747 released by the International Pulsar Timing Array, with the reference time being Earth Time TT (BIPM) (hereinafter referred to as TT), and simulate to generate equidistant TOA data with a total length of 15 years and one data point every 10 days, with white noise levels (RMS errors) of 50ns (nanometers), 100ns and 200ns, respectively. Then the clock difference between TT and the pulsar time constructed by each pulsar is obtained: TT-PTi.

[0045] S2, based on the TT-PTi of each pulsar, construct the comprehensive pulsar time EPT through the classical weighted algorithm to obtain TT-EPT.

[0046] S3, based on S2, combines the clock difference sequence between NTSC atomic time, i.e. TA (NTSC) and earth time TT: TA (NTSC)-TT, and obtains the clock difference sequence between TA (NTSC) and integrated pulsar time: TA (NTSC)-EPT.

[0047] S4, smooth the TA (NTSC) -EPT data, remove the high-frequency noise, and obtain the smoothed clock difference sequence: [TA (NTSC) -EPT]s.

[0048] S5, take the negative sign of [TA(NTSC)-EPT]s in the previous step, and then add it to the clock difference sequence of TA(NTSC)-TT to obtain the fusion time scale APT of atomic time and pulsar time, which can be called "atomic-pulsar time": APT-TT=TA(NTSC)-TT + [EPT-TA(NTSC)]s.

[0049] This completes the construction of the fusion time scale.

[0050] S6, evaluate the stability of APT-TT and compare it with the stability of TA (NTSC)-TT.

[0051] Figure 3 and Figure 4 The stability evaluation of the modified Allan deviation and modified Hadamard deviation of three time scales (with TT as reference) of APT-TT, EPT-TT and TA (NTSC)-TT is given respectively, where the horizontal axis is time τ, in seconds, and the vertical axis is the modified Allan deviation and the modified Hadamard deviation respectively. It can be clearly seen that the fusion time scale APT-TT proposed in the present invention not only maintains the short-term stability of TA (NTSC) but also inherits the long-term stability of EPT, and has the characteristics of both short-term and long-term stability, that is, the short-term stability of APT-TT is maintained by TA (NTSC) and the long-term stability is maintained by EPT. Therefore, after the pulse time star is added to the timekeeping, the long-term stability of the paper time achieved by the single means of the atomic clock is improved.

[0052] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present invention, the size of the serial number of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention. The serial numbers of the above-mentioned embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

[0053] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0054] In the several embodiments provided by the present invention, it should be understood that the disclosed methods can be implemented in other ways. The methods disclosed in the several method embodiments provided by the present invention can be arbitrarily combined without conflict to obtain new method embodiments. The features disclosed in the several method embodiments provided by the present invention can be arbitrarily combined without conflict to obtain new method embodiments.

[0055] The above is only an embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for improving the long-term stability of atomic time using pulsar time, characterized in that: include: Obtaining the timing observation data of the pulsar within a preset period of time and fitting the timing model parameters of the pulsar; Predicting the TOA data of the pulsar based on the timing model parameters, while continuing to perform pulsar timing observations using local atomic time, and comparing the observed TOA sequence with the predicted TOA data to obtain timing residual data; The timing residual data of multiple pulsars are subjected to Wiener filtering and classical weighting processing to obtain a clock difference sequence between the local atomic time and the integrated pulsar time. The result of smoothing the clock difference sequence is inverted and added to the local atomic time to obtain a new fusion time scale.

2. The method according to claim 1, characterized in that: The step of obtaining the timing observation data of the pulsar within a preset period of time and fitting the timing model parameters of the pulsar includes: Using the Earth Time TT published by BIPM as the reference time, the TOA observation data of the pulsar within the preset period is obtained; Based on the TOA observation data, the timing model parameters of the pulsar are fitted by a least squares fitting method.

3. The method according to claim 1, characterized in that The timing model parameters include at least the pulsar's rotation frequency and its first-order derivative, position, proper motion, parallax, interstellar medium dispersion and binary orbit model parameters.

4. The method according to claim 1, characterized in that: The local atomic time is TA (NTSC), and the method further comprises: Taking the Earth time TT as the reference, simulate the TOA data of multiple pulsars to obtain the clock difference TT-PTi between TT and the pulsar time constructed by each pulsar; The TT-EPT is constructed by using a classical weighted algorithm for the TT-PTi corresponding to each of the plurality of pulsars, wherein EPT is the integrated pulsar time; Combining the collected clock difference sequences of TA (NTSC) and TT, the clock difference sequence of TA (NTSC) and integrated pulsar time TA (NTSC)-EPT is obtained.

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