The paper describes the current state of fiber-optic gyroscope (FOG) development. An overview of the modern gyroscopic market for inertial navigation is made with a special focus on the FOG niche. The principle of operation is briefly described; classification of existing FOGs is presented; their advantages and disadvantages are discussed; and some examples are given. Key Russian and international manufacturers are mentioned in the paper. Finally, trends of FOG development are analyzed, and the future development of the gyroscope market is assessed.

The paper presents the analytical review of an inertial measuring unit (IMU) rotation as a method to improve the accuracy of a strapdown inertial navigation system (SINS). There are two ways to improve the accuracy. One of them is based on the transformation of the error change pattern in the inertial sensors (IS) when using the IMU self-compensation rotation (SCR). The criteria for selecting an efficient SCR law to minimize the accumulated error in the parameters generated by SINS are presented. Along with the advantages of this technology, its weak points that may limit significantly the potentially achievable accuracy are described. The other technique consists in increasing the observability of the IS error model components due to the IMU rotation while filtering the SINS errors. The IS error model is described, and the problem of recursive filtering of the SINS errors is stated to refine these errors, with the reference data on coordinates and motion velocity being available. The methods for quantifying the observability of the IS error model components are presented.

The paper discusses the techniques developed for inspecting inertial measurement units (IMU) with nonorthogonal orientation of their sensitive axes and the results of their application. A methodology was proposed as part of the development of IMUs for a strapdown inertial navigation system (SINS) during the modernization of the Soyuz-family spacecraft transport system under the International Space Station (ISS) program for six-axis units of angular rate sensors (ARS) and accelerometers with nonorthogonal orientation of their sensitive axes. The positive results of the ground and flight tests carried out aboard 86 Soyuz and Progress spacecraft from 2002 to 2023 confirmed the effectiveness of the proposed methodology.

The paper addresses a hemispherical resonator gyroscope (HRG) with flat electrodes applied in the vehicle control and navigation loop. In order to enhance the gyro accuracy, we formulate the problem of constructing a new mathematical model describing the nonlinearities of the electrome chanical system controlling the hemispherical resonator oscillations. The mathematical model of the resonator dynamics is based on Lagrange-Maxwell differential equations. The obtained nonlinear model is studied with the asymptotic Krylov-Bogolyubov averaging method. The reference voltage on flat control electrodes is shown to arouse systematic drift and changes in the resonance frequency. The provided example demonstrates the influence of reference voltage on the gyro drift and reduc tion in the resonator oscillation frequency.

Under the water, the data are transferred for ranges above dozens of meters using the acoustic modems. The acoustic modems are employed, in particular, for data transfer in positioning and navigation of both single and grouped underwater vehicles. Network communication methods are widely used for exchanging the navigation data be tween grouped autonomous underwater vehicles (AUVs). They are applied, for example, to keep the AUV formation geometry and/or to exchange the navigation data with the master vehicles. These methods can be combined, i.e., provide not only the exchange of mutual/rela tive positions (for formation keeping) between the AUVs, but also underwater georeferenced positioning for the group navigation in the geographical frame. However, a number of factors should be taken into account in the coordinated or cooperated AUV group navigation. As the number of interacting AUVs increases, their frequent address ing the acoustic medium is undesirable, because low capacity of the acoustic channel se verely limits the underwater data traffic. Moreover, it is important to minimize the effect pro duced by the AUV acoustic system on the acoustic medium, particularly, to make the AUV less visible when its onboard acoustic communication and positioning system is operating.

To improve the localization accuracy and tracking robustness of monocular feature-based visual SLAM systems in low-texture environments, a visual-inertial odometry method combining line features and point features is proposed, taking advantage of the easy avail ability of line features in real-world environments and the high accuracy of feature-based methods. The combination of point and line features ensures accurate positioning of the SLAM system in low-texture environments, while the inclusion of IMU data provides prior information and scale information. The pose is optimized by minimizing the reprojection error of point and line features and the IMU error using bundle adjustment. An improved EDlines algorithm is introduced, which incorporates a pixel chain length suppression pro cess to enhance the effectiveness of extracted line features and reduce the rate of line fea ture misalignment. Experimental results on the public EuRoC dataset and TUM RGB-D dataset show that the proposed method meets the real-time requirements and has higher localization accuracy and robustness compared with the visual SLAM method based on single point feature or the method adding traditional line features.

The aim of the Uragan space experiment on board the International Space Station (ISS) is to adjust the scientific equipment and improve the methods for monitoring various objects and phenomena on the Earth. Part of this scientific equipment is already operated on board the station, and the other part is planned to be delivered in the orbit soon. In contrast to the Russian orbital stations Salyut and Mir, the ISS was not designed for pointing the installed equipment at the survey targets, because the gyrodines used on the American segment for the ISS attitude control had a too small kinematic momentum. For this reason, special methods and devices had to be developed for pointing the Uragan scientific equipment at the survey targets. This paper considers the methods for pointing the scientific equipment, which would optimize the research program of the Uragan experiment on board the ISS.

Small satellite attitude angles are estimated using measurements of star trackers and rate gyro in this study. The issue related to gyro drifts is overcome by adding the bias terms into the state vector in order to estimate them. As an estimation method, two-stage non-tradi tional filter is used. In the first stage, singular value decomposition (SVD) is used for de termining the attitude measurements. As a second stage, an extended Kalman filter (EKF) is designed based on linear attitude measurements. These two stages are integrated for the whole estimation algorithm in order to have estimations with high accuracy, and it is called SVD-Aided EKF.

The proposed SVD-Aided EKF is used with two attitude models of satellite: only the kine matics model which does not include the dynamics of a satellite, and both kinematics and dynamics relations. Several scales of uncertainties on the principal moment of inertia of the satellite are considered in order to determine the level when estimation error of the kinemat ics and dynamics-based filter exceeds the error of the case using only kinematics relations.

The article compares the test results for gimballess electrostatic gyroscopes containing rotors with a light-contrast pattern applied to titanium nitride (TiN) coating or to beryllium. The criteria for comparing the de-vices with different types of rotors are proposed and jus tified. The need to modify the rotor manufacturing technology in order to improve the rotor design and mature some technological operations is analyzed. It has been shown that at a certain stage it is rational to mark the raster pattern on the titanium nitride coating, and currently the pattern can be again applied directly to the rotor beryllium surface.

This article is a review of publications on maritime cybersecurity with the focus made on navigation support. Cyber threats to ECDIS, automatic identification system (AIS), voy age data recorder, and integrated navigation system as a whole are considered. The specif ic features of cybersecurity of maritime autonomous surface ships (MASS) as well as the impact of the human factor on cybersecurity are discussed, and the regulatory framework for preventing cyber threats is analyzed.

The proposed approach to identifying the parameters of the motion model for a surface ship subject to external disturbances uses the measurements of heading, yaw rate, speed through the water, and global satellite navigation system (GNSS) data. The model struc ture is set in the state space.

We use the criterion of how close is the real vehicle response to a given control input to its motion model response under the same disturbances. It is proposed to apply the Kalman filter with the state vector including the disturbances, and an iterated procedure for estimating pa rameters by minimizing the criterion. It is shown that this ensures stable identification of mod el parameters under different disturbances. Simulation results are presented to evaluate the quality of identification. The approach was validated in full-scale tests of a high-speed boat.

The paper studies the temperature dependency of h-parameter of the fiber-optic gyro scope (FOG) coil. It has been shown that the thermal dependency of h-parameter behaves differently in positive and negative temperature ranges. It is noted that the polarization effect can severely limit the FOG accuracy in a broad temperature range. Ways to elimi nate the polarization effect are proposed.