S.V. Ermak1, V.V. Semenov2, M.V. Sergeeva3

1-3 Higher School of Applied Physics and Space Technologies, Institute of Electronics and Telecommunication,
Peter the Great St. Petersburg Polytechnic University (St. Petersburg, Russia)

1 serge_ermak@mail.ru; 2 vladimir_semenov@mail.ru; 3 sergeeva_mar_vyach21@mail.ru

Correction of the on-board rubidium atomic clock frequency by the on-board quantum magnetometer signal makes it possible to significantly suppress the influence of variations in the magnitude and direction of the geomagnetic field on the clock frequency. The analysis of the time dependences of the orientation error of on-board navigation satellites allows us to determine the following main sources of variations in the frequency of on-board rubidium atomic clock in satellite orbit:

variations of the geomagnetic field caused by artificial interference and the action of magnetic storms during solar activity;

a change in the orientation of the geomagnetic field vector relative to the optical axis of the on-board quantum magnetometer as a result of the orbital motion of the satellite and its rotation around its own axis;

variations in the angle of magnetic declination as a result of the daily rotation of the planet.

The effectiveness of the correction of atomic clock by the quantum magnetometer signal depends on the degree of complexity of the time dependence of the clock positioning error Σ(t), while the orientation error δ(t) of the atomic clock frequency, depending on variations of the geomagnetic field ∆H(t), can be approximated by a superposition of harmonic components with corresponding weighting coefficients Ak and phase shifts φk. Numerical indicators of the correction effectiveness are the correlation coefficient R between the positioning error Σ(t) and the orientation error δ(t), as well as the correction efficiency coefficient kEF, numerically equal to the ratio of variances with the atomic clock frequency correction system turned off and on by the quantum magnetometer signal.

It is advisable to adjust the parameters of the atomic clock correction signal (amplitude and phase of the alternating signal controlling the magnitude of the atomic clock operation magnetic field) with a period equal to the half-period of the satellite's orbital motion, while the criterion for setting the optimal values of the amplitude and phase of this signal is to achieve the maximum values of the coefficients R and kEF. For the selected experimental dependences δ(t) of satellites of various navigation systems, the maximum values of the coefficients R and kEF were, respectively: for GPS satellites – 0.95 and 8.7; for Galileo satellites – 0.99 and 41.

When developing an algorithm for correcting atomic clock in neighboring half-periods of the orbital motion of satellites in the quantum magnetometer correction signal, the input values of the coefficients Ak and phase shifts φk may differ significantly in neighboring half-periods, due to the difference in the longitudinal coefficient of atomic clock shielding in neighboring half-periods of the positioning error Σ(t). As laboratory experiments show, the longitudinal shielding coefficient significantly depends on the orientation of the geomagnetic field vector relative to the direction of the operation magnetic field created by DC coils in the area of the atomic clock gas cell. This difference is due to the different degree of magnetization of the magnetic shield when the orientation of the geomagnetic field vector changes with respect to the direction of the atomic clock axis. In this case, there is a change in the magnitude of the magnetic permeability of the magnetic shield material and, as a result, a change in the shielding factor. The practical use of this phenomenon makes it possible to significantly (almost by an order of magnitude) increase the shielding coefficient of the magnetic shield of on-board rubidium atomic clock and thereby increase the stability of their frequency under conditions of variations in the magnitude and direction of the geomagnetic field.

Ermak S.V., Semenov V.V., Sergeeva M.V. On the possibility of correcting the onboard atomic clock by the signal of a quantum magnetometer. Radiotekhnika. 2025. V. 89. № 1. P. 87−98. DOI: https://doi.org/10.18127/j00338486-202501-08 (In Russian)

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