CN113985719B - Sliding window-based pulsar time taming cesium atomic clock method - Google Patents
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Abstract
A sliding window based pulsar time taming cesium atomic clock method comprises the following steps: pulsar timing observation; processing pulsar timing data; calculating the frequency deviation of the cesium atomic clock by using the movable window; cesium atomic clock frequency calibration. The invention solves the problem that the pulsar pulse arrival time measurement error is large and influences the measurement precision of the frequency drift of the atomic clock, increases the size of the sliding window under the condition that the sliding step length of the window is not changed, and effectively improves the measurement precision of the frequency deviation. The invention provides support for realizing high-precision frequency tracing of the atomic clock based on pulsar, and has the advantages of short forecasting time, small measuring error, high identification precision and high speed.
Description
Technical Field
The invention belongs to the technical field of applied atomic clocks, and particularly relates to a sliding window-based pulsar time taming method for a cesium atomic clock.
Background
The traditional atomic clock frequency calibration is to compare and measure signals of a local atomic clock with a reference atomic clock, calculate the frequency deviation of the local atomic clock relative to the reference atomic clock according to comparison and measurement clock difference data, use the current frequency deviation value as a frequency deviation estimation value in the next period of time, and calibrate the atomic clock frequency through a frequency control system, so that the frequency of the local atomic clock is consistent with that of the reference atomic clock.
Pulsar is a compact celestial body, has the characteristics of strong magnetic field and strong electric field, radiates stable periodic pulse signals, and is known as the most stable 'natural clock' in the nature. The accurate measurement of the rotation parameters of the pulsar can be realized by utilizing an astronomical observation technology, and the uncertainty of the measurement of the rotation frequency of the pulsar reaches 10 at present -15 Magnitude, which can be used as a reference frequency source. When there is no atomic time reference frequency reference signal, the ground pulsar observation device is used to observe the pulsar signal by taking the atomic clock as time reference, the clock difference sequence of the atomic clock and the pulsar time can be obtained by the timing data processing technology, and if there is an error in the reference atomic clock frequency, the phase of the measured pulse peak value has an error accumulation effect with time relative to the phase of the intrinsic forecast pulse peak value, as shown in fig. 1. And obtaining the frequency drift value of the atomic clock by using clock difference sequence fitting, thereby realizing the frequency calibration of the atomic clock. The most important characteristics of the domesticated atomic clock are that the short-term stability is good, and the predictability of the atomic time trend is strong, which is beneficial to establishing an accurate atomic time forecasting model. By combining the performances of various atomic clocks and the characteristics of pulsar time, the medium-and-long-term stability (lunar stability) of the cesium atomic clock is superior to that of a hydrogen clock, and the frequency drift is mainly shown. Is most suitable for being acclimated by the pulsar-time signal.
Pulsar hour is characterized by good long-term stability (stable year), and long-term self-maintenance of production time. However, at present, the Time of arrival (TOA) of a pulse signal is low in measurement accuracy, which is hundreds of nanoseconds or even microseconds, and the measurement accuracy of an atomic clock is better than that of a nanosecond. The cesium atomic clock is controlled by measuring pulsar time with large noise, and the pulsar time and atomic clock comparison data of at least more than 3 months are required to calculate the frequency drift amount of the atomic clock. At present, the atomic clock control adopts a strategy that modeling data of the atomic clock is consistent with clock forecast data span, and the national time standard keeps the atomic clock control strategy of a laboratory that the modeling data span and the forecast duration are both 30 days. If the traditional atomic clock control strategy is directly utilized, when the atomic clock is modeled based on 30-day-span pulsar observation data, because the pulsar TOA measurement error is large, and the pulsar time and the atomic clock comparison data have large errors, the atomic clock frequency deviation value calculated by utilizing clock difference comparison data has large measurement errors, so that the accuracy of the time-frequency signal of the controlled atomic clock is low. If the characteristics of good pulse satellite time stability are utilized, the atomic clock is modeled by time span data of more than 6 months, and the forecasting time based on the clock model is also more than 6 months, the final time-frequency signal accuracy is influenced due to too long forecasting time. The key of pulsar time application is how to effectively utilize the characteristic of high time stability of pulsar time and reduce the influence of large TOA measurement error on the atomic clock frequency drift amount resolving precision.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a sliding window-based pulsar time taming cesium atomic clock method which is short in forecasting time, small in measurement error, high in identification precision and high in speed.
The technical scheme for solving the technical problems is as follows: a sliding window based pulsar time cesium atom clock discipline method comprises the following steps:
s1, pulsar timing observation
Timing observation is carried out on one millisecond pulsar by taking a cesium atomic clock as reference, observation data are collected, observation is carried out for 1 time every day, and the observation time is 30-60 minutes each time;
s2, pulsar timing data processing
When the time span of the observation data reaches the size of a movable window, processing the observation data by using pulsar professional data processing software psrchive to obtain a series of pulse arrival time data sequences, and then performing timing analysis on the pulse arrival time data sequences by using timing professional data processing software Tempo2 in combination with a latest pulsar ephemeris to obtain a clock difference sequence of pulsar time and an atomic clock;
s3, calculating the frequency deviation of the cesium atomic clock by utilizing the movable window
Performing least square fitting according to a cesium atomic clock model formula (1) by using a clock difference sequence of a pulse star clock and a cesium atomic clock in a sliding window to obtain a cesium atomic clock frequency deviation k;
the cesium atomic clock model established based on the pulsar-hour observation data is as follows:
x(t)＝x 0 +(t-t 0 )·k+δ AT +δ PT (1)
wherein x (t) is the difference between the cesium atomic clock and the pulsar clock, x 0 Is t 0 The initial clock difference of the time cesium atomic clock relative to the pulsar time, k is the frequency deviation of the cesium atomic clock, delta AT Is cesium atomic clock random noise, delta PT Is the pulse satellite-time noise;
s4, frequency calibration of cesium atomic clock
Using a phase trimmer to steer the frequency of the cesium atomic clock, wherein the frequency of steering is 1 time/window sliding step, namely when the sliding step of each window is added to the observation data, taking the current moment as a terminal point, extracting the observation data according to the size of the sliding window, calculating and updating the frequency deviation k of the cesium atomic clock, and using the phase trimmer to steer the frequency of the cesium atomic clock; the window sliding step is 1/4-1/3 times of the sliding window.
As a preferred technical solution, the size of the active window in step S2 is 90 days to 180 days.
As a preferred technical solution, the impulsive star time noise δ in step S3 PT A source of white noise is selected.
The invention has the following beneficial effects:
the invention provides a method for measuring frequency deviation of a cesium atomic clock relative to a pulsar clock based on a sliding window technology, which solves the problems that the pulsar pulse arrival time measurement error is large and the influence on the frequency drift measurement precision of the atomic clock is caused, increases the size of a sliding window under the condition that the sliding step length of the window is not changed, and effectively improves the frequency deviation measurement precision. The invention provides support for realizing high-precision frequency tracing of the atomic clock based on pulsar, and has the advantages of short forecasting time, small measuring error, high identification precision and high speed.
Drawings
FIG. 1 is a schematic diagram of atomic clock error measurement using pulsar.
FIG. 2 is a flow chart of the sliding window based pulsar-hour cesium atom clock disciplining method of the present invention.
Fig. 3 is a schematic view of a sliding window.
Detailed Description
The present invention will be described in further detail below with reference to the drawings and examples, but the present invention is not limited to the embodiments described below.
In this embodiment, a method for disciplining a cesium atomic clock based on a sliding window by using pulsar J0437-4715 to observe data is taken as an example, and a method for disciplining a cesium atomic clock based on a sliding window pulsar time is described, as shown in fig. 2 and 3, the specific steps are as follows:
s1, pulsar timing observation
The pulsar observation system of the ground radio telescope is utilized, a cesium atomic clock is used as a reference to perform timing observation on pulsars J0437-4715, observation data are collected, observation is performed for 1 time every day, and the observation time is 60 minutes each time;
s2, pulsar timing data processing
When the time span of the observation data reaches the size of an active window, wherein the size of the active window is 90 days or 180 days, processing the observation data by using a pulsar professional data processing software psrchive to obtain a series of pulse arrival time data sequences, and then performing timing analysis on the pulse arrival time data sequences by using a timing professional data processing software Tempo2 in combination with a latest pulsar ephemeris to obtain a clock difference sequence of pulsar time and cesium atomic clock time;
during the timing analysis, the parameters of the pulse ephemeris are not fitted;
s3, calculating the frequency deviation of the cesium atomic clock by utilizing the movable window
Performing least square fitting according to a cesium atomic clock model formula (1) by using a clock difference sequence of a pulsar time and a cesium atomic clock time in a sliding window to obtain a cesium atomic clock frequency deviation k;
the cesium atomic clock model established based on the pulsar hour observation data is as follows:
x(t)＝x 0 +(t-t 0 )·k+δ AT +δ PT (1)
wherein x (t) is the difference between the cesium atomic clock and the pulsar clock, x 0 Is t 0 The initial clock difference of the time cesium atomic clock relative to the pulsar time, k is the frequency deviation of the cesium atomic clock, delta AT Is cesium atomic clock random noise, delta PT For pulsar timing noise, a preference delta is given to candidate observed pulsar times PT The method is a white noise source, and is beneficial to reducing the influence of the pulsar-hour noise on the frequency deviation k fitting of the cesium atomic clock;
s4, frequency calibration of cesium atomic clock
And (3) utilizing a phase trimmer to drive the frequency of the cesium atomic clock, wherein the driving frequency is 1 time/window sliding step length, namely when every window sliding step length is added to the observation data, taking the current moment as a terminal point, extracting the observation data according to the size of a sliding window, calculating and updating the frequency deviation k of the cesium atomic clock, and utilizing the phase trimmer to drive the frequency of the cesium atomic clock, wherein the window sliding step length is 30 days.
The effect of driving the cesium atomic clock by using pulsar hours based on a sliding window technology is analyzed by using cesium atomic clock Cs2147 which runs freely by a national time service center of the Chinese academy of sciences and actually measured clock difference data of national standard time UTC (NTSC) as reference. Firstly, analyzing the precision of utilizing UTC (NTSC) to drive Cs2147 clocks, wherein the modeling data span and the forecast duration of the atomic clock are both 30 days. The handling strategy and results are shown in table 1, with handling Cs2147 being 18.86ns relative to utc (ntsc) clock error RMS, and the difference value, i.e., the difference between the maximum and minimum values of the clock error data, being 107.58 ns.
TABLE 1 results of using UTC (NTSC) to harness Cs2147
Next, a sliding window based pulsar time driving cesium atomic clock Cs2147 precision simulation analysis is performed with reference to pulsar J0437-4715, which is the highest timing precision at present. The timing data of the J0437-4715 are observed by simulating a Haoheing 40-meter antenna by using professional pulse timing software Tempo2, an observation reference clock is Cs2147, and the parameters of the simulation data are set as follows: the observation frequency is 1 time/day, and the measurement error of the time of arrival TOA of the pulse is 0.1 microsecond. The simulated observation span is the cesium atomic clock Cs2147 versus utc (ntsc) clock alignment data span.
To compare the effect of manipulating cesium atomic clocks based on the sliding window technique, Cs2147 was manipulated using simulated pulsar data, analyzed in the following two ways:
1) consistent with the utc (ntsc) harness Cs2147 strategy above;
2) the sliding window technology is adopted, the size of the sliding window is set to be 90 days, and the window sliding step length is set to be 30 days. The following table shows the results of using pulsar J0437-4715 to drive cesium atomic clock Cs 2147.
TABLE 2 results of utilizing pulsar-time steering Cs2147 based on sliding window technique
As can be seen from the above table, with the conventional atomic clock handling technology, when the clock modeling data span is consistent with the forecast duration, i.e., 1 month, the handled Cs2147 relative to utc (ntsc) pole difference value with pulsar is 246.93ns, and the clock difference RMS is 44.72 ns. Using the sliding window technique, post-harness Cs2147 has a polarization difference value of 103.5ns relative to utc (ntsc) and an RMS of 17.58 ns. According to the results, the traditional driving strategy is utilized, and the accuracy of the atomic clock driven based on pulsar time is obviously lower than that of the atomic clock driven by UTC (NTSC) as a reference. When the sliding window technology is adopted, the driving result is slightly better than the precision of the traditional atomic clock driving method.
Claims (3)
1. A sliding window based pulsar time taming cesium atomic clock method is characterized by comprising the following steps:
s1, pulsar timing observation
Timing observation is carried out on one millisecond pulsar by taking a cesium atomic clock as reference, observation data are collected, observation is carried out for 1 time every day, and the observation time is 30-60 minutes each time;
s2, pulsar timing data processing
When the time span of the observation data reaches the size of a movable window, processing the observation data by using pulsar professional data processing software psrchive to obtain a series of pulse arrival time data sequences, and then performing timing analysis on the pulse arrival time data sequences by using timing professional data processing software Tempo2 in combination with a latest pulsar ephemeris to obtain a clock difference sequence of pulsar time and an atomic clock;
s3, calculating the frequency deviation of the cesium atomic clock by utilizing the movable window
Performing least square fitting according to a cesium atomic clock model formula (1) by using a clock difference sequence of a pulsar time and a cesium atomic clock time in a sliding window to obtain a cesium atomic clock frequency deviation k;
the cesium atomic clock model established based on the pulsar hour observation data is as follows:
x(t)＝x 0 +(t-t 0 )·k+δ AT +δ PT (1)
wherein x (t) is the difference between the cesium atomic clock and the pulsar clock, x 0 Is t 0 The initial clock difference of the time cesium atomic clock relative to the pulsar time, k is the frequency deviation of the cesium atomic clock, delta AT Is cesium atomic clock random noise, delta PT Is the pulse satellite-time noise;
s4, frequency calibration of cesium atomic clock
Using a phase trimmer to steer the frequency of the cesium atomic clock, wherein the frequency of steering is 1 time/window sliding step, namely when the sliding step of each window is added to the observation data, taking the current moment as a terminal point, extracting the observation data according to the size of the sliding window, calculating and updating the frequency deviation k of the cesium atomic clock, and using the phase trimmer to steer the frequency of the cesium atomic clock; the window sliding step is 1/4-1/3 times of the sliding window.
2. The sliding-window based pulsar-hour taming cesium atomic clock method of claim 1, wherein: the size of the active window in the step S2 is 90 days to 180 days.
3. The sliding-window based pulsar-hour taming cesium atomic clock method of claim 1, wherein: the impulsive star time noise δ in step S3 PT A source of white noise is selected.
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