CN114002933B - Method for measuring atomic clock frequency drift based on pulsar search technology - Google Patents
Method for measuring atomic clock frequency drift based on pulsar search technology Download PDFInfo
- Publication number
- CN114002933B CN114002933B CN202111280913.XA CN202111280913A CN114002933B CN 114002933 B CN114002933 B CN 114002933B CN 202111280913 A CN202111280913 A CN 202111280913A CN 114002933 B CN114002933 B CN 114002933B
- Authority
- CN
- China
- Prior art keywords
- frequency
- pulsar
- atomic clock
- time
- autorotation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G04—HOROLOGY
- G04F—TIME-INTERVAL MEASURING
- G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
- G04F5/14—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks
-
- G—PHYSICS
- G04—HOROLOGY
- G04D—APPARATUS OR TOOLS SPECIALLY DESIGNED FOR MAKING OR MAINTAINING CLOCKS OR WATCHES
- G04D7/00—Measuring, counting, calibrating, testing or regulating apparatus
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Frequencies, Analyzing Spectra (AREA)
Abstract
The invention provides a method for measuring frequency drift of an atomic clock based on a pulsar searching technology, which searches and observes pulsars by taking a time-frequency signal provided by the atomic clock as a reference; processing the observed data, searching for the optimal pulsar autorotation frequency value by using frequency domain Fourier transform or time domain period folding technology, obtaining the autorotation frequency value at the observation time, and calculating the corresponding value t of the intermediate time of the observed data under the TCB time scale TCB (ii) a Calculating t by using pulsar autorotation parameters provided by pulsar ephemeris TCB The predicted value of the autorotation frequency corresponding to the moment; and calculating to obtain the frequency relative deviation amount of the atomic clock, and controlling the atomic clock by using a time-frequency servo system to realize frequency calibration. The method can measure the frequency deviation of the atomic clock by utilizing single pulsar observation data, and realizes the calibration of the frequency deviation of the atomic clock.
Description
Technical Field
The invention belongs to the field of time-frequency technology application, and relates to a method for measuring frequency drift of an atomic clock.
Background
The pulsar is a compact celestial body, has the characteristics of strong magnetic field and strong electric field, radiates stable periodic pulse signals, particularly has very stable autorotation, and the periodic derivative of the autorotation of part of the millisecond pulsars is-10 -22 . In 1991, taylor proposes that the millisecond pulsar is the most stable clock in the nature, and researches show that the long-term stability of the millisecond pulsar can be comparable to that of an atomic clock, and the millisecond pulsar can be applied to the time-frequency field. The pulsar rotation frequency can be measured very accurately by astronomical observation techniques, e.g. J0437-4715, by utilizing a timing observation technology, measuring to obtain a rotation frequency value as follows: 173.68794581218460089Hz, the error is 8.0E-14Hz, the uncertainty of the rotation frequency is 4.6E-16, and the frequency accuracy of a reference clock-cesium fountain clock is achieved at present. The stable and accurate autorotation frequency signal of the pulsar can be used as a natural reference frequency source to calibrate the atomic clock. With the advancement of observation technology and the construction of large observation devices, such as the conventional operation of FAST radio telescopes and the construction of Square kilometer radio arrays (SKAs) in the future, the measurement accuracy of the intrinsic autorotation frequency of pulsar is further improved, and the application of pulsar in the time-frequency field is accelerated.
The pulsar clock has the advantages of long service life, high reliability, difficult attack and the like. The pulsar time application is not limited by regions, and can be used as a time reference in a range from the ground, the near ground to a deep space as long as a pulsar observation device receives a pulse signal. The traditional pulsar time establishment and application is based on pulsar timing observation data to carry out related research and realize the accurate measurement of the pulsar rotation frequency. The pulsar timing data processing technology is used for carrying out related research by analyzing the Time of arrival (TOA) obtained by observation and the Time of arrival (TOA) predicted by a pulsar rotation model. By performing timing analysis on the multiple observation data, a clock difference sequence of Pulsar Time (PT) and observation reference Atomic Time (AT), namely PT-AT, can be obtained. The pulse satellite time has the characteristics of high long-term stability, and can obtain the frequency deviation of the atomic clock by fitting by using the PT-AT clock difference time sequence obtained by observation by taking PT as a reference frequency signal. At present, the accuracy of the pulsar time PT is in hundred nanosecond level, the atomic clock frequency drift is accurately calculated by utilizing pulsar time and atomic clock difference time comparison data, and the data is observed in a time span of at least more than 3 months, so that the scheme is used for measuring the frequency deviation of an atomic clock, an observation data sequence is required to be accumulated for a period of time, and the atomic clock frequency deviation cannot be measured through real-time pulsar observation.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for measuring the frequency drift of an atomic clock based on a pulsar search technology, which can measure the frequency deviation of the atomic clock by utilizing single pulsar observation data and realize the calibration of the frequency deviation of the atomic clock.
The technical scheme adopted by the invention for solving the technical problem comprises the following steps:
(1) Searching and observing the pulsar by taking a time-frequency signal provided by an atomic clock as a reference;
(2) Carrying out data processing on observation data, wherein the data processing comprises interference elimination and chromatic dispersion elimination;
(3) Searching for the optimal pulsar autorotation frequency value by using frequency domain Fourier transform or time domain period folding technology to obtain the autorotation frequency value v of the observation moment Measuring And calculating the corresponding value t of the intermediate time of the observation data under the TCB time scale TCB ；
(4) Using pulsar autorotation parameters provided by a pulsar calendar table and forecasting formula according to autorotation frequency
Calculating t TCB Autorotation frequency predicted value v corresponding to time Intrinsic Wherein v (t) is the pulsar rotation frequency forecasted at the moment t, v 0 Is a reference epoch t 0 The rotation frequency of the moment of time is,
is a reference epoch t 0 The first derivative and the second derivative of the rotation frequency of the pulsar are measured at the moment, and the related parameters in the formula are measured values under the TCB time scale;
(5) Calculating to obtain the frequency relative deviation amount of the atomic clock
Wherein, delta AT Is the relative frequency deviation, Δ f, of the atomic clock AT The absolute deviation value of the frequency of the atomic clock under the TAI scale is shown;
(6) According to the relative deviation delta of atomic clock frequency AT And the frequency calibration is realized by controlling the atomic clock by using a time-frequency servo system.
The observation wave band in the step (1) is an L wave band, the bandwidth is 800MHz, the sampling time is 10 microseconds, and the observation time is 1 hour.
The frequency domain Fourier transform technology performs Fourier transform on the data subjected to the offset dispersion, and further processes the data in the frequency domain to find the autorotation frequency.
The data stream in the frequency domain after Fourier transform of the frequency domain Fourier transform technology has a structure of 2/P,3/P,4/P, \ 8230, with 1/P as fundamental frequency, P represents a period, and the measurement precision of the rotation frequency is improved by utilizing a harmonic wave superposition technology.
The time domain period folding technology takes an intrinsic rotation frequency value as a center, selects a certain range and step values and provides a series of rotation frequency candidate values; and then, carrying out periodic folding on the data stream subjected to dispersion cancellation according to the rotation frequency candidate values respectively to obtain an integral pulse profile to detect signals.
When the time domain period folding technology searches pulse signals, the optimal autorotation frequency is judged by taking the signal-to-noise ratio of the pulse signals as a basis, and the candidate autorotation frequency corresponding to the integral pulse profile with the highest signal-to-noise ratio is the optimal autorotation frequency value.
The invention has the beneficial effects that: the pulsar signal searching technology is used for measuring the frequency deviation of the atomic clock, so that the frequency deviation of the atomic clock is measured based on single pulsar observation, and support is provided for frequency tracing of the atomic clock.
The pulsar has the characteristics of stable rotation and accurate measurement of rotation frequency. The method is similar to two atomic clocks, and utilizes a counter to obtain clock difference comparison data and calculate frequency drift. The invention provides another method for calculating the frequency deviation of an atomic clock based on pulsar observation data, which is characterized in that pulsar search mode observation is carried out by taking the atomic clock as reference, the optimal autorotation frequency value of the observation time is searched and given by utilizing a search technology, and then the autorotation frequency of the pulsar at the observation time is compared with the autorotation frequency of the pulsar at the observation time forecasted by intrinsic frequency parameters, so that the frequency drift of the atomic clock is obtained. The method is similar to two atomic clocks, and frequency deviation is obtained by directly comparing frequencies.
Drawings
FIG. 1 is a basic flow chart of the measurement of the rotation frequency;
fig. 2 is a flow chart for measuring a steering atomic clock based on the rotation frequency of a pulsar.
Detailed Description
The present invention will be further described with reference to the following drawings and examples, which include, but are not limited to, the following examples.
According to the method, through receiving stable pulse signals radiated by pulsar, pulsar rotation frequency is measured based on pulsar searching technology, and is compared with intrinsic pulsar rotation frequency, frequency drift of an observation reference atomic clock is determined, and finally atomic clock frequency deviation calibration is achieved.
By utilizing the long-term timing observation technology of the ground radio telescope, the rotation parameters of the pulsar under the TCB time scale can be accurately measured. Because the long-term stability of the rotation of the pulsar is high, once the rotation parameters are accurately measured, the pulsar can be used for a long time. Based on the measured high-precision autorotation parameter values, the method can accurately forecast the pulsar autorotation frequency value at any time under the TCB time scale, and the autorotation frequency forecasting formula is as follows:
wherein v (t) is pulsar rotation frequency forecasted at t moment, v 0 Is a reference epoch t 0 The rotation frequency of the moment of time is,
is a reference epoch t 0 The first derivative of the rotation frequency of the pulsar and the second derivative of the rotation frequency are measured at the moment, and relevant parameters in the formula are measured values under the TCB time scale.
In pulsar search observation, the atomic clock provides reference frequency for pulsar observation data acquisition, so that pulsar rotation frequency values measured by using a search technology can reflect the frequency characteristics of the atomic clock. At present, the time scale used on the earth is based on the TAI or TT time scale (the TAI and TT seconds are consistent) generated by an atomic clock, and if the pulsar observation is used for calculating the frequency deviation of the observation reference atomic clock relative to the TT, the frequency measurement value and the forecast value of the pulsar are both reduced to be under the TT time scale. The intrinsic frequency values of the pulsar are measured under TCB time scale at present, and the International astronomical society (IAU) gives the relation between TCB and TT of different time scales:
wherein L is B ＝1.55051976772×10 -8 ，x E 、v E The method is characterized in that the method is a position and velocity vector of the earth in a centroid coordinate BCRS, x is a position vector of an observer in the centroid coordinate, P is various periodic variation parts in an expansion containing a gravitational potential function, and a main term of the method is a yearly term generated by variation of solar gravitational potential at the centroid due to earth elliptic motion. The second term at the right end of the above formula is a solar-solar period term caused by the earth rotation motion, and the amplitude is about 2.1 mus.
The above equation (2) is differentiated, and the average velocity relationship between TCB and TT on the time scale is as follows:
<d(TCB)/d(TT)>＝1+L B (3)
the above formula shows that the average second length on TCB time scale is 1+ L of TT time scale B Multiple, i.e. the pulsar rotation frequency measured on the TCB time scale is the rotation frequency measured on the TT time scale
And (4) multiplying.
Because the frequency values measured under different time scales TCB and TT are in a fixed proportional relation, the relative frequency offsets measured under the time scales TCB and TT are the same, namely the autorotation frequencies of the pulsar have the following relation under the time scales TCB and TT:
that is, the same atomic clock, the relative frequency drift amounts measured at the time scales of TT and TCB are the same.
The standard frequency signal provided by a common atomic clock is 10MHz, and if the actual output frequency of the atomic clock deviates from the standard value by Δ f AT Then, the relative frequency deviation value of the atomic clock is:
wherein, delta AT Is the relative frequency deviation, Δ f, of an atomic clock AT Is the absolute deviation value v of the frequency of an atomic clock under the TAI scale Measuring For a value of the pulsar rotation frequency at time t, measured with an atomic clock under the TCB time scale, v Intrinsic The autorotation eigenfrequency of the pulsar at the t moment under the TCB time scale can be calculated according to the formula (1) to obtain the autorotation eigenfrequency value at the t moment. The key for measuring the frequency deviation of the atomic clock based on the method is to accurately measure and give a rotation frequency measured value v Measuring The invention provides a method for providing a rotation frequency measured value v by using a pulsar searching technology Measuring 。
Pulsar searching theoretically finds periodic pulse signals from noisy observations. The traditional pulse signal searching is to search a periodic pulse signal under the condition of not knowing the rotation frequency and the Dispersion (DM), and the processing amount of searching data is large. In the specific data processing: firstly, within a certain dispersion range (for example, DM-0-2000) the data is dispersed in a certain step length to produce a series of data streams correspondent to different DM, then the data stream correspondent to every DM is undergone the process of periodic folding or Fourier change to search self-rotation frequency.
The application of pulsar time is to use the known pulsar, i.e. to perform signal search on the known pulsar, the intrinsic rotation frequency and dispersion are known. However, since the frequency error of the reference atomic clock is observed, the actually measured autorotation frequency value has a certain deviation from the intrinsic frequency value, but the intrinsic autorotation frequency obtained by the previous measurement can be used as an initial value, and the pulsar search technology is utilized to search in a small range near the intrinsic autorotation frequency to obtain the optimal autorotation frequency, so that the processing amount of search data is reduced, and the search efficiency is improved. The basic flow chart of the pulsar rotation frequency measurement is shown in the figure, and the specific searching steps are as follows:
(1) And (3) radio interference elimination: the pulsar radiated signal is weak and is easily polluted by ground radio interference, so that the pulsar signal searching quality is influenced. Interference elimination processing needs to be performed on the observation data first, so that the influence of interference on the pulse signal is eliminated. The main interference cancellation techniques are time domain and intra-frequency interference cancellation techniques.
(2) Eliminating the dispersion influence: pulsar observation is broadband observation, and due to the influence of interplanetary media, the arrival time of pulse signals with different frequencies at an antenna is different, the pulse profile is widened by directly superposing all frequency band channel signals, the signal to noise ratio of the signals is reduced, and even the signals cannot be detected, so that the measurement of the rotation frequency of the pulsar is influenced. According to the dispersion amount of the pulsar, the dispersion influence is eliminated, and signals with different frequencies are superposed to obtain one-dimensional time sequence data. The invention observes a known pulsar, so that the dispersion amount is known, namely, the known DM value is used for carrying out dispersion elimination, and then frequency channel data are superposed to generate a one-dimensional time series data stream.
(3) Pulsar signal search: the method comprises the following steps of detecting periodic pulse signals by using a pulsar searching technology, wherein the pulsar signal searching method mainly comprises two methods; 1) The time domain searching technology takes the intrinsic rotation frequency value as the center, selects a certain range and step value and provides a series of rotation frequency candidate values. And (3) carrying out periodic folding on the data stream subjected to dispersion elimination in the step (2) according to the rotation frequency candidate values respectively to obtain an integral pulse profile to detect signals. 2) And (3) a frequency domain searching technology, namely performing Fourier transformation on the data subjected to dispersion elimination in the step (2), and further processing in a frequency domain to search for the rotation frequency.
(4) And (3) determining the rotation frequency: when the pulse signal is searched by the period folding technology, the optimal autorotation frequency is judged by taking the signal-to-noise ratio of the pulse signal as a basis, and the candidate autorotation frequency corresponding to the integral pulse profile with the highest signal-to-noise ratio is the optimal autorotation frequency value; the frequency domain searching technology searches the frequency of a periodic signal by utilizing a Fourier transform technology, and because a pulsar radiation signal is a pulse signal, a data stream in a frequency domain after the Fourier transform has a structure of taking 1/P (period) as a fundamental frequency and 2/P,3/P,4/P, \8230, wherein the quantity of high-frequency subharmonics depends on the ratio (P/W) of the half width of the pulse to the period, namely the narrower the pulse profile is, the larger the ratio is, and the more the harmonics are. The harmonic superposition technology is utilized to improve the measurement precision of the rotation frequency, and the detailed harmonic superposition technology can refer to pulsar to search relevant documents.
The technology of pulsar searching is well established, and more than 3000 pulsars are found based on the technology. There are many mainstream general pulsar professional search software such as PRESTO software published internationally. The measured value v of the rotation frequency under the TCB time scale and the TAI time scale can be directly given by processing the observation data by using PRESTO software Measuring Finally, the predicted value v of the eigenfrequency is combined Intrinsic The frequency deviation of the observed reference atomic clock can be calculated.
A ground radio telescope pulsar observation system is utilized, a search mode observation is carried out on known pulsars J0437-4715 by taking an atomic clock as reference, the rotation frequency is measured at high precision by utilizing the search mode data, the atomic clock frequency deviation is calculated based on the measured rotation frequency and the predicted intrinsic rotation frequency value, and finally the atomic clock frequency calibration is realized. Scheme for implementation the scheme is shown in figure 2, and the specific implementation is as follows:
a) And (4) establishing an observation scheme such as an observation frequency band, observation time, sampling time and the like according to the characteristics of the observation pulsar and the sensitivity of the telescope. Wherein, the sampling time is less than one hundredth of the pulsar cycle, the observation time is determined according to the pulsar radiation flux intensity, and the observation time is usually set to be 1 hour;
b) Searching and observing J0437-4715 by using a radio telescope and using a time-frequency signal provided by an atomic clock as reference, wherein an observation wave band is an L wave band, the bandwidth is 800MHz, the sampling time is 10 microseconds, and the observation time is 1 hour;
c) And carrying out data processing on the observation data according to a search mode, wherein the specific data processing flow comprises the following steps: 1) Interference elimination, namely eliminating radio interference influence to improve the signal-to-noise ratio of a signal; 2) Eliminating dispersion, eliminating influence of interplanetary medium on pulse signals, observing known pulsar with dispersion amount of known value, such as J0437-4715, dispersion amount of 2.64, calculating dispersion delay according to dispersion amount, and eliminating influence of dispersion; 3) Searching an optimal pulsar rotation frequency value by using a frequency domain Fourier transform or time domain period folding technology;
d) Searching data processing flow according to the step (3) by using professional pulsar searching software PRESTO to obtain a rotation frequency value v at the corresponding moment Measuring And calculating the corresponding value t of the intermediate time of the observation data under the TCB time scale TCB ；
e) Calculating and obtaining observation time t according to formula (1) by using pulsar autorotation parameters provided by a pulsar ephemeris TCB Corresponding autorotation frequency predicted value v Intrinsic ；
f) V measured with search data Measuring And a predicted value v Intrinsic Calculating and obtaining the frequency relative deviation quantity delta of the atomic clock according to the formula (5) AT ；
g) Relative deviation of atomic clock frequency delta AT And the frequency calibration is realized by controlling the atomic clock by using a time-frequency servo system.
Claims (5)
1. A method for measuring atomic clock frequency drift based on pulsar search technology is characterized by comprising the following steps:
(1) Searching and observing the pulsar by taking a time-frequency signal provided by an atomic clock as a reference;
(2) Carrying out data processing on observation data, wherein the data processing comprises interference elimination and chromatic dispersion elimination;
(3) Searching for the optimal pulsar autorotation frequency value by using frequency domain Fourier transform or time domain period folding technology to obtain the autorotation frequency value v of the observation moment Measuring And calculating the corresponding value t of the intermediate time of the observation data under the TCB time scale TCB ；
(4) Using pulsive ephemerisThe provided pulsar rotation parameters are forecast according to a rotation frequency formula
Calculating t TCB Autorotation frequency predicted value v corresponding to time Intrinsic Wherein v (t) is the pulsar rotation frequency forecasted at the moment t, v 0 Is a reference epoch t 0 The rotation frequency of the moment of time is,
is a reference epoch t 0 The first derivative and the second derivative of the rotation frequency of the pulsar are measured at the moment, and the related parameters in the formula are measured values under the TCB time scale;
(5) Calculating to obtain the frequency relative deviation amount of the atomic clock
Wherein, delta AT Is the relative frequency deviation, Δ f, of an atomic clock AT The absolute deviation value of the frequency of the atomic clock under the TAI scale is shown;
(6) According to the relative deviation delta of atomic clock frequency AT And the frequency calibration is realized by controlling the atomic clock by using a time-frequency servo system.
2. The method for measuring atomic clock frequency drift based on pulsar search technology according to claim 1, wherein in said step (1), the observation wavelength band is L-band, the bandwidth is 800MHz, the sampling time is 10 μ s, and the observation time is 1 hour.
3. The method of claim 1, wherein the frequency domain fourier transform technique performs fourier transform on the de-dispersed data and further processes the de-dispersed data in the frequency domain to find the rotation frequency.
4. The method for measuring atomic clock frequency drift based on pulsar search technology of claim 3, wherein the data stream of the frequency domain Fourier transform technology after Fourier transform has a structure of 2/P,3/P,4/P, \8230;, with 1/P as fundamental frequency and P as period, and the autorotation frequency measurement precision is improved by using harmonic superposition technology.
5. The method for measuring atomic clock frequency drift based on pulsar search technology according to claim 1, wherein the time domain period folding technology takes an intrinsic rotation frequency value as a center, selects a certain range and step value, and provides a series of rotation frequency candidate values; and then, carrying out periodic folding on the data stream subjected to dispersion cancellation according to the rotation frequency candidate values respectively to obtain an integral pulse profile to detect signals.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111280913.XA CN114002933B (en) | 2021-11-01 | 2021-11-01 | Method for measuring atomic clock frequency drift based on pulsar search technology |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111280913.XA CN114002933B (en) | 2021-11-01 | 2021-11-01 | Method for measuring atomic clock frequency drift based on pulsar search technology |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114002933A CN114002933A (en) | 2022-02-01 |
| CN114002933B true CN114002933B (en) | 2022-10-21 |
Family
ID=79925925
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111280913.XA Active CN114002933B (en) | 2021-11-01 | 2021-11-01 | Method for measuring atomic clock frequency drift based on pulsar search technology |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114002933B (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111292222A (en) * | 2020-01-22 | 2020-06-16 | 中国科学院新疆天文台 | Pulsar de-dispersion device and method |
| CN113078901A (en) * | 2021-03-30 | 2021-07-06 | 中国科学院国家授时中心 | Method for improving accuracy of atomic clock based on pulsar control |
| CN113219815A (en) * | 2021-05-06 | 2021-08-06 | 中国科学院国家授时中心 | Deep space time service method based on X-ray pulsar |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7197381B2 (en) * | 2003-12-08 | 2007-03-27 | University Of Maryland | Navigational system and method utilizing sources of pulsed celestial radiation |
| US10802036B2 (en) * | 2018-09-14 | 2020-10-13 | Booz Allen Hamilton Inc. | System and methods for updating a reference time from a decaying rotational period of a pulsar |
-
2021
- 2021-11-01 CN CN202111280913.XA patent/CN114002933B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111292222A (en) * | 2020-01-22 | 2020-06-16 | 中国科学院新疆天文台 | Pulsar de-dispersion device and method |
| CN113078901A (en) * | 2021-03-30 | 2021-07-06 | 中国科学院国家授时中心 | Method for improving accuracy of atomic clock based on pulsar control |
| CN113219815A (en) * | 2021-05-06 | 2021-08-06 | 中国科学院国家授时中心 | Deep space time service method based on X-ray pulsar |
Non-Patent Citations (2)
| Title |
|---|
| 毫秒脉冲星计时和原子时;倪广仁等;《计量学报》;20011022;第24卷(第04期);308-313 * |
| 脉冲星钟模型精度分析;赵成仕等;《天文学报》;20170531;第58卷(第03期);23-1-23-9 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114002933A (en) | 2022-02-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109001771B (en) | Navigation satellite and low-orbit satellite real-time clock error determining and forecasting method and system | |
| Wyithe et al. | Baryonic acoustic oscillations in 21-cm emission: a probe of dark energy out to high redshifts | |
| Trott et al. | Spectral calibration requirements of radio interferometers for epoch of reionisation science with the SKA | |
| Gaulme et al. | Detection of Jovian seismic waves: a new probe of its interior structure | |
| Foster et al. | Interstellar propagation effects and the precision of pulsar timing | |
| CN108388720B (en) | Multi-source error calibration method of bionic polarization sensor based on unscented Kalman filtering | |
| CN111665709B (en) | Method for unifying time in wide area space and space time keeping system | |
| Kocsis et al. | Premerger localization of gravitational-wave standard sirens with LISA:<? format?> Harmonic mode decomposition | |
| Dyrud et al. | Ionospheric measurement with GPS: Receiver techniques and methods | |
| CN110046368B (en) | Bionic polarization sensor multisource error calibration method based on self-adaptive UKF | |
| Page et al. | Bayesian time delay interferometry | |
| RU2421753C1 (en) | Method of determining ionosphere characteristics and device for realising said method | |
| Shamohammadi et al. | Searches for Shapiro delay in seven binary pulsars using the MeerKAT telescope | |
| CN114002933B (en) | Method for measuring atomic clock frequency drift based on pulsar search technology | |
| CN115826004B (en) | Three-star cooperative direct positioning method based on two-dimensional angle and time difference combination | |
| CN114624513B (en) | Method and device for detecting phase of periodic signal with anti-harmonic interference | |
| CN103698793B (en) | Based on the GNSS signal simulator emulation angular velocity range measuring method of software receiver | |
| Erdoğan et al. | Identification of vertical total electron content by time series analysis | |
| CN115598650A (en) | Double-frequency self-calibration double-optical-frequency comb distance measurement system and method | |
| Zhan et al. | Mitigation of multipath effects in GPS and BDS positioning using window matching method based sidereal filtering | |
| Gilboy et al. | An intercomparison of current measurements using a vector measuring current meter, an acoustic Doppler current profiler, and a recently developed acoustic current meter | |
| Bignall et al. | New results from an ATCA study of intraday variable radio sources | |
| CN114384539B (en) | Absorption spectrum line phase shift speed measurement method based on background light synchronous difference | |
| Honma et al. | Performance of VERA in the Phase-Referencing Astrometry | |
| Zhang et al. | Celestial spectrum velocimetry with non-linear Fourier phase shift and its CRLB |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |