A method for improving the long-term stability of atomic time using pulsar time

Abstract

This invention discloses a method for improving the long-term stability of atomic time using pulsar time. The method includes: obtaining pulsar timing observation data within a preset period and fitting the pulsar timing model parameters; predicting the pulsar's pulse time of arrival (TOA) data based on the timing model parameters; simultaneously continuing pulsar timing observations using local atomic time; comparing the observed TOA sequence with the predicted TOA data to obtain timing residual data; and applying Wiener filtering and classical weighting to the timing residual data of multiple pulsars to obtain a clock difference sequence between local atomic time and integrated pulsar time. The result of smoothing this clock difference sequence is then inverted and added to the local atomic time to obtain a new fused time scale. This method can establish a paper local atomic time with higher long-term stability, providing a strong guarantee for the subsequent use of local atomic time to control the master clock system to produce a national standard time with stronger long-term autonomous maintenance capabilities.

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 utilizing pulsar time. Background Art

[0002] Currently, time laboratories around the world use various types of atomic clocks for timekeeping, such as hydrogen and cesium 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 maintain time, creating a more stable atomic time. Due to the various noises inherent in atomic clocks, their long-term stability is difficult to guarantee. Furthermore, due to the short lifespan of atomic clocks, they require periodic replacement during the long-term maintenance of atomic time, resulting in low long-term stability. Therefore, timekeeping in time laboratories typically requires regular calibration with International Atomic Time (TAI) or Coordinated Universal Time (UTC). These internationally coordinated products can be difficult to obtain during emergencies, resulting in a lack of autonomy in my country's standard time. Therefore, establishing a highly accurate, long-term stable local atomic time is crucial to ensure the independence, autonomy, security, and control of my country's standard time. Therefore, improving the long-term stability of local atomic time is an effective means of maintaining a high level of standard time over the long term in my country.

[0003] Pulsars are a class of compact celestial objects in the universe with extremely stable rotation. Millisecond pulsars, in particular, are known as natural clocks of the universe. Pulsars' highly stable periodic signals can be observed on the ground using radio telescopes. These stable periodic pulses form a natural frequency source. Atomic clocks at observation stations can record the time of arrival (TOA) with high precision, reaching hundreds of nanoseconds or even less. Through long-term timing observations, TOA data can be fitted to derive a series of timing model parameters, including the millisecond pulsar's rotation frequency, rate of change of rotation frequency, position, proper motion, and parallax. Based on these model parameters, the TOA of the pulsar pulses can be accurately predicted. Thus, a pulsar is like a distant clock, and a composite pulsar time can be constructed from multiple millisecond pulsars using appropriate algorithms. Long-term research has shown that the long-term stability of composite pulsar time is superior to that of atomic time. Furthermore, compared to atomic clocks, pulsar time offers superior continuity and can be observed continuously. This is because pulsars are natural objects with advantages such as long lifespans, high reliability, and immunity to environmental and human influences. The resulting composite pulsar time can detect long-term systematic fluctuations in atomic time, namely instabilities 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 my 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 of poor long-term autonomous maintenance capability and low stability of local atomic time.

[0005] The technical solutions of the embodiments of the present invention are as follows:

[0006] 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:

[0007] Acquire timing observation data of a 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 observations using local atomic time. Compare the observed TOA sequence with the predicted TOA data to obtain timing residual data; perform Wiener filtering and classical weighting on the timing residual data of multiple pulsars to obtain a clock difference sequence between the local atomic time and the integrated pulsar time, and invert the result of smoothing the clock difference sequence and add it to the local atomic time to obtain a new fusion time scale.

[0008] 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.

[0009] 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.

[0010] Furthermore, the local atomic time is TA (NTSC), and the method also includes: taking the earth time TT as the reference time, 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.

[0011] The beneficial effects of the technical solutions provided in the embodiments of the present application include at least:

[0012] In an embodiment of the present invention, a method for utilizing pulsar time to improve the long-term stability of atomic time is proposed. This method integrates pulsar time into timekeeping, achieving joint timekeeping using atomic and pulsar time, leveraging the advantages of both the short-term stability of atomic time and the long-term stability of pulsar time. Compared to conventional atomic time construction using atomic clocks alone, the inclusion of pulsar time improves the long-term stability of the fused time scale without sacrificing short-term stability. This method can establish a local atomic time with enhanced long-term stability, providing strong support for the subsequent use of local atomic time to control the master clock system to generate a national standard time with greater long-term autonomy. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] 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. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0014] Figure 1 A schematic diagram of the process steps of a method for improving the long-term stability of atomic time using pulsar time provided by an embodiment of the present invention;

[0015] Figure 2 A logic flow chart of a method for improving the long-term stability of atomic time using pulsar time provided by an embodiment of the present invention;

[0016] Figure 3 The improvement of the fusion time scale provided by the embodiment of the present invention is Lun deviation;

[0017] Figure 4 An improved Hadamard deviation of the fusion time scale provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions 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 of 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.

[0019] In the following description, reference is made to “some embodiments”, which describes 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.

[0020] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art in the art to which the embodiments of the present invention pertain. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless specifically defined as herein, should not be interpreted in an idealized or overly formal sense.

[0021] 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:

[0022] Step S110 , obtaining timing observation data of the pulsar within a preset time period, and fitting timing model parameters of the pulsar.

[0023] Here, the timing observation data refers to the pulse time of arrival (TOA), and the preset period is a fixed period of time, such as one year or three years. For millisecond pulsars, TOA measurement accuracy is very high, reaching hundreds of nanoseconds or even less. After long-term timing observations, TOA data can be used to fit a series of timing model parameters, including the pulsar's rotation frequency, rotation frequency change rate, position, proper motion, and parallax. The pulsar's rotation frequency and its rate of change are, in fact, the clock model parameters of the pulsar clock.

[0024] Using long-term pulsar timing observations (i.e., TOA data) combined with established fitting algorithms and multiple iterations of fitting, the parameters of the pulsar timing model can be accurately determined. The precise measurement of these parameters is fundamental to pulsar timing applications, such as detecting low-frequency gravitational waves, establishing pulsar timescales, and measuring the masses of planets in the solar system.

[0025] In implementation, the TOA is first predicted at the Solar System Center of Mass (SSB) based on the initial timing model parameters. The pre-fitted pulsar timing residual is then obtained by subtracting the model-predicted TOA from the actual TOA measured using the reference atomic clock. Then, a least-squares fit is performed repeatedly until convergence, yielding the post-fit timing residual and updated pulsar timing model parameters. This process is repeated as new observational data becomes available to further update the pulsar timing model parameters.

[0026] 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.

[0027] Here, pulsar timing is actually the process of comparing the time of local atomic clocks with pulsar clocks. Therefore, the timing residual actually represents the clock difference between local atomic clocks and pulsar clocks. Local atomic time is the atomic time established by atomic clocks used in local time laboratories, and is the object of stability adjustment in this invention.

[0028] During implementation, on the one hand, the determined timing model parameters are used to predict TOA, and on the other hand, pulsar timing observations are continued using local atomic time as a reference time 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 local atomic time and pulsar time.

[0029] In 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.

[0030] The Wiener filter method is computationally relatively simple and quick to implement. It works by correlating the timing residuals of different pulsars to estimate the statistical characteristics of the detected signal. This is then used to filter the timing residuals of each pulsar, and finally a weighted average of the filtered results is taken. However, a problem with the Wiener filter method is that when several pulsars have high noise levels, the resulting composite pulsar will also be highly noisy, drowning out the detected signal. Improving the signal energy estimation method and appropriately weighting the signal are key to constructing a composite pulsar using the Wiener filter method.

[0031] Assuming local atomic time is TA(NTSC) and using Terrestrial Time (TT(BIPM)) published by the International Bureau of Prediction and Measurement (BIPM) as a reference, we first calculate the timing residual between local atomic time and pulsar time (PTi) before fitting, as TA(NTSC)-PTi. Then, by synthesizing the TA(NTSC)-PTi values ​​corresponding to multiple pulsars, we obtain the clock difference sequence between local atomic time and synthesized pulsar time, as TA(NTSC)-EPT, where EPT is synthesized pulsar time. The smoothed result of this clock difference sequence is (TA(NTSC)-EPT)s.

[0032] Finally, the smoothed result is minus-added to the atomic time to obtain TA(NTSC)-TT+(EPT-TA(NTSC))s, and the new fusion time scale is defined as APT, that is, APT-TT=TA(NTSC)-TT+[EPT-TA(NTSC)]s.

[0033] It should be noted that pulsar time, affected by measurement noise, has a lower short-term stability than atomic time. However, as observational data accumulates, its long-term stability will surpass that of atomic time. Therefore, to establish a time scale with excellent short- and long-term stability, it is necessary to leverage both the short- and medium-term stability of atomic time and the long-term stability of pulsar time.

[0034] The low-frequency random walk noise of atomic clocks causes significant low-frequency red noise in atomic time, resulting in poor long-term stability. However, some pulsars with low red noise are primarily affected by high-frequency noise. Therefore, if the clock difference between pulsar time and atomic time is smoothed (removing high-frequency noise), the remaining low-frequency noise is primarily contributed by atomic time. Compensating the smoothed pulsar time difference with the atomic clock into atomic time eliminates or reduces the low-frequency noise in atomic time, improving its long-term stability. Furthermore, since pulsar time has already been smoothed, it does not introduce additional high-frequency noise.

[0035] 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.

[0036] In one embodiment of the present invention, a method for utilizing pulsar time to improve the long-term stability of atomic time is proposed. This method integrates pulsar time into timekeeping, achieving joint timekeeping using atomic and pulsar time, leveraging the advantages of both the short-term stability of atomic time and the long-term stability of pulsar time. Compared to conventional atomic time construction using atomic clocks alone, the inclusion of pulsar time improves the long-term stability of the fused time scale without sacrificing short-term stability. This method enables the establishment of a local atomic time with enhanced long-term stability, providing strong support for the subsequent use of local atomic time to control the master clock system to generate a national standard time with enhanced long-term autonomy.

[0037] In some embodiments of the present invention, the above-mentioned step S110 "obtaining the 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, the timing model parameters of the pulsar are fitted by the least squares fitting method.

[0038] First, one or more millisecond pulsars of interest are selected for observation. Time-of-arrival (TOA) data are then collected: over a predetermined period (e.g., several months to several years), a radio telescope is used to perform timing observations of the selected pulsars and record the time of arrival (TOA) of each observed pulse. This TOA data is typically expressed in a time standard such as Modified Julian Day (MJD) or GPS time and needs to be converted to Terrestrial Time (TT). This typically involves converting the observation time to International Atomic Time (TAI) and then back to TT.

[0039] The observed TOA data are fitted to a pre-defined timing model using a least-squares fitting method. Least-squares fitting is an optimization technique that estimates model parameters by minimizing the sum of the squares of the differences between the observed data and the model predictions. The fitting process may require iterative optimization to find the optimal model parameters. This typically involves repeatedly adjusting the model parameters until the difference between the observed data and the model predictions is minimized.

[0040] The pulsar timing model parameters can then be obtained through least-squares fitting methods. These parameters can be used in subsequent Pulsar Timing Array (PTA) research, gravitational wave detection, and other applications. Furthermore, these parameters can be used to calibrate and verify other time standards, improving the accuracy and stability of time measurements.

[0041] 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.

[0042] The parameters fitted here include the pulsar's rotation frequency and its first-order derivative (describing the variation in the pulsar's rotation speed), its position (its coordinates on the celestial sphere), its proper motion (the variation in the pulsar's position on the celestial sphere due to its motion), its parallax (the variation in its radial velocity due to the relative motion between the Earth and the pulsar), the interstellar medium dispersion (DM), which describes the delay in the pulsar signal due to electron scattering as it propagates through interstellar space, and possible binary orbit model parameters (if the pulsar is in a binary system). Accurate measurements of these parameters are fundamental to pulsar timing applications, such as detecting low-frequency gravitational waves, establishing pulsar timescales, and measuring the masses of planets in the Solar System.

[0043] In some embodiments of the present invention, the local atomic time is TA (NTSC), and the method further includes: simulating TOA data of multiple pulsars with the earth time TT as a reference time 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.

[0044] Here, local atomic time TA (NTSC) is the local time standard of the National Time Service Center (NTSC).

[0045] First, use simulation software or algorithms to generate TOA data for multiple pulsars. This data should be based on parameters such as each pulsar's actual rotation period, spin deceleration rate, position, and radial velocity relative to Earth. Simulations should also take into account the effects of Earth's rotation, orbital motion, and general relativity on the arrival times of the pulses.

[0046] Then, for each pulsar, the simulated TOA data is compared with the expected arrival time (based on known pulsar parameters and Earth time TT) to calculate the clock difference TT-PTi between TT and the pulsar time PTi. This step requires precise time measurement and data processing techniques to ensure the accuracy of the clock difference.

[0047] By combining TT-PTi data from multiple pulsars, a classical weighting algorithm (such as the least squares method) is used to construct the clock difference between Earth time (TT) and Ensemble Pulsar Time (EPT), TT-EPT. The goal of this weighting algorithm is to assign different weights to each pulsar based on its stability and accuracy, resulting in a more reliable TT-EPT clock difference.

[0048] Collect the clock difference series between the time standard TA (such as NTSC, National Time Service Center) and Earth time TT from actual observations or data. Ensure that the collected clock difference series has sufficient accuracy and density to reflect the actual difference between TA and TT.

[0049] Using the previously obtained TT-EPT clock difference, 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.

[0050] Through the above steps, the clock difference sequence between TA (NTSC) and the integrated pulsar time (EPT) is finally obtained. The smoothed result of this clock difference sequence is then inverted and added to the local atomic time to obtain a new converged time scale. This is of great significance for studying the stability and accuracy of time standards and improving navigation and time synchronization systems.

[0051] The method for improving the long-term stability of atomic time using pulsars is described below with reference to 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.

[0052] Currently, among the paper-based timekeeping methods based on atomic clocks, Terrestrial Time (TT(BIPM)) published by the International Bureau of Weights and Measures (BIPM) is considered the most accurate. TT(BIPM) is derived from Terrestrial Time (TT(TAI)) achieved by TAI, and then processed by BIPM one year later, taking into account the weighting of the reference clock. It is published annually. Some time laboratories 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), a composite atomic time established by dozens of atomic clocks. TT(BIPM) is, however, established by over 500 atomic clocks from laboratories worldwide. Therefore, TA(NTSC) still exhibits deviations compared to TT(BIPM), and its accuracy and stability are inferior to TT(BIPM). This specific example uses the local atomic time TA(NTSC) of the National Time Service Center as an example, and utilizes simulated data from three millisecond pulsars for illustration. Figure 2 The flow chart of fusion of pulsar time and atomic time provided by the embodiment of the present invention is as follows: Figure 2 As shown, the process is implemented through the following procedures:

[0053] S1. First, we simulated TOA data for three millisecond pulsars using the model parameters published by the International Pulsar Timing Array for J0437-4715, J1909-3744, and J1713+0747, respectively. The reference time was Terrestrial Time (BIPM) (hereinafter abbreviated as TT). The simulation generated 15 years of equally spaced TOA data, with one data point every 10 days. The white noise level (RMS error) was 50 nanometers (nanometers), 100 nanometers, and 200 nanometers, respectively. The resulting clock difference between TT and the pulsar time constructed for each pulsar was calculated: TT-PTi.

[0054] S2, based on the TT-PTi of each pulsar, construct the comprehensive pulsar time EPT through the classical weighted algorithm to obtain TT-EPT.

[0055] S3, based on S2, combines the clock difference sequence between NTSC atomic time, i.e., TA (NTSC), and Earth time TT: TA (NTSC)-TT, to obtain the clock difference sequence between TA (NTSC) and integrated pulsar time: TA (NTSC)-EPT.

[0056] S4, smooth the TA (NTSC) -EPT data and remove high-frequency noise to obtain the smoothed clock error sequence: [TA (NTSC) -EPT]s.

[0057] S5. Take the negative sign of [TA(NTSC)-EPT]s from the previous step and 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.

[0058] This completes the construction of the fusion time scale.

[0059] S6, evaluate the stability of APT-TT and compare it with the stability of TA (NTSC)-TT.

[0060] Figure 3 and Figure 4 The stability assessments of the modified Allan deviation and modified Hadamard deviation are presented for three time scales (APT-TT, EPT-TT, and TA(NTSC)-TT) (with TT as the reference). The horizontal axis represents time τ in seconds, while the vertical axis represents the modified Allan deviation and modified Hadamard deviation, respectively. It is clear that the proposed fused time scale, APT-TT, maintains both the short-term stability of TA(NTSC) and the long-term stability of EPT, achieving both short-term and long-term stability. The short-term stability of APT-TT is maintained by TA(NTSC), while the long-term stability is maintained by EPT. Therefore, the addition of a pulsed time satellite to timekeeping improves the long-term stability of paper time achieved solely by atomic clocks.

[0061] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that the 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 numbers 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 for description only and do not represent the advantages and disadvantages of the embodiments.

[0062] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0063] In the several embodiments provided herein, it should be understood that the disclosed methods can be implemented in other ways. The methods disclosed in the several method embodiments provided herein can be combined arbitrarily, unless they conflict, to produce new method embodiments. The features disclosed in the several method embodiments provided herein can be combined arbitrarily, unless they conflict, to produce new method embodiments.

[0064] The above description is merely an embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for improving the long-term stability of atomic time using pulsar time, characterized in that: include: Obtaining pulsar timing observation data within a preset period and fitting the pulsar timing model parameters; Predicting pulsar TOA data based on the timing model parameters, while continuing pulsar timing observations using local atomic time (TA), and comparing the observed TOA sequence with the predicted TOA data to obtain pre-fit timing residual data (TA-PTi); TA is an independent local atomic time scale generated and maintained by the National Time Service Center (NTSC) of the Chinese Academy of Sciences. The TA-PTi of multiple pulsars are subjected to Wiener filtering and classical weighting to obtain the clock difference sequence TA-EPT between the local atomic time and the integrated pulsar time; wherein EPT is the integrated pulsar time; The result of smoothing the clock difference sequence TA-EPT is inverted and added to the clock difference data TA-TT between local atomic time and Earth time TT to obtain the new fusion time scale and the clock difference data APT-TT of Earth time; among them, APT is the fusion time scale of atomic time and pulsar time.

2. The method according to claim 1, characterized in that The step of obtaining the timing observation data of the pulsar within a preset time period and fitting the timing model parameters of the pulsar includes: Using the Earth Time (TT) published by BIPM as a reference, the TOA observation data of the pulsar within a preset period is obtained; Based on the TOA observation data, the timing model parameters of the pulsar are obtained by fitting using 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, wherein The method further comprises: Taking the Earth time TT as the reference time, simulate the TOA data of multiple pulsars and 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; Combining TT-EPT and the collected clock difference sequence TA-TT between TA and TT, the clock difference sequence TA-EPT between TA and the synthetic pulsar time is obtained.

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