Introduction: Magnetocardiography (MCG) based on optical atomic magnetometers has shown promise for detecting heart diseases accurately. Different methods were introduced to improve the sensitivity of detecting magnetic fields during cardiac activity. Methods: In this paper, an optical pump-probe magnetometer operated on the ground-state Hanle effect based on the zero-field level crossing technique was developed and the laser output signal was optimized in an unshielded environment. Then, the optical magnetometer was utilized to record the simulated MCG trace of different stages of myocardial ischemia. Results: The probe output light intensity followed the variation of cardiac magnetic field (MCG trace) generated by Helmholtz coil accurately. Conclusion: Based on the results, the feasibility of our highly sensitive optical magnetometer in tracing showed no change in the P-QRS-T waveform associated with ischemic heart disease (IHD), where P indicates atrial depolarization, QRS is responsible for ventricular depolarization, and T represents ventricular repolarization.

Optically pumped helium magnetometers are important instruments which have many applications in military, mass spectroscopy and space applications. In this paper, the working principles of helium magnetometers have been explained. There is also an introduction of a new method for finding the resonant frequency, which has advantages to the typical method such as more sample rate possibility and realizing with cheaper prices.

Magnetometer is one of the main sensors in satellite attitude determination and control subsystems and its data calibration plays an important role in mission’s success. In this paper, the subject of magnetometer calibration using two optimal approaches is analyzed and their robustness in the presence of measurement disturbances is investigated. In this regard, firstly, a measurement model which contains main magnetometer parameters, namely, biases, scale factors and non-orthogonality corrections is presented. Then, two approaches for magnetometer calibration are proposed. In the first approach which is a centered method, nonlinear magnetometer calibration problem is transferred to a linear problem and calibration parameters are derived. However, in the second method which is based on maximum likelihood approach, magnetometer calibration problem is considered as a nonlinear problem and calibration parameters are estimated. Two kinds of magnetic field profiles are considered to evaluate the performance of calibration methods for a LEO satellite. According to the results, accuracy of the maximum likelihood approach is much better than centered method. Finally, in order to assess the robustness of the two presented methods, 100 Monte Carlo simulations are performed. Based on the Monte Carlo simulations results, estimation of calibration parameters using maximum likelihood approach is much smoother and calibration parameters are estimated more accurately.

Magnetometer is one of the main sensors in Attitude Determination and Control Subsystem (ADCS) of Low Earth Orbit (LEO) satellites and since it is operable in all times during an orbital period, it can be utilized in almost all functional modes like detumbling, nadir pointing and orbit transfer. Therefore, the accuracy of magnetometer data and its calibration is essential in the success of the missions. In this paper, regarding to the importance of real-time approaches in practical applications, an Extended Kalman Filter (EKF) is used for magnetometer calibration. Then, in order to study the role of magnetometer calibration in attitude estimation (AE) results, calibrated data is employed in the structure of a Multiplicative Quaternion EKF (MQEKF). Finally, a Hardware in the Loop (HIL) test bed equipped with a three axis Helmholtz coil and a three degree of freedom platform is utilized to measure the performance of developed algorithms experimentally. In the calibration process, magnetometer parameters are estimated and used in the AE filter. The results show that the attitude error gradually decreases and the final accuracy increases.

Three-axis-magnetometers (TAMs) are widely utilized as a key component of attitude determination subsystems and as such are considered the corner stone of navigation for low Earth orbiting (LEO) space systems. Precise geomagnetic-based navigation demands accurate calibration of the magnetometers. In this regard, a complete online calibration process of TAM is developed in the current research that considers the combined effects of environmental and instrumental errors including biases, non-orthogonally parameters, and the scale factors, without the need for clean room facilities. The sensor characteristics are estimated utilizing Kalman filter for a micro electro-mechanical sensor(MEMS)-based TAM standing on the experimental measured outputs in a noisy laboratory environment. Moreover, the stochastic TAM behavior is identified using the method of Allan variance analysis (AVA) through a six-hour static test. Subsequently, the nonlinear/non-Gaussian problem of attitude estimation, using a set of calibrated strap-down magnetometers is addressed utilizing the unscented particle filter (UPF), developed for the removal of colored-noise. Comparison of the estimated attitude, represented by quaternion parameters, with the true orientations demonstrates an acceptable level of accuracy of the developed calibration technique for small LEO space systems. Analysis of the root mean square error of the estimated attitude illustrates an accuracy of less than one degree for all axes. This is an ideal result, given the fact that MEMS-based magnetometers have been utilized.

In recent years, according to progress of aerospace industries particularly satellites it has been paying much attention to attitude determination of satellite. Attitude determination of satellite in various ways, such as: radio, radar, optical methods and using GPS, q and kalman filter is done, that each of these methods has advantages and disadvantages. Due to disturbance in space, high accuracy in attitude determination, various algorithms to obtain properly accurately attitude, desirable access to position, velocity and time of satellite to achieve desired attitude determination satellite are considered a top priority. However in this Paper, first we review the various methods for attitude determination satellite and then examine of operation and relations of algorithms discussed. This Paper focus on the advantages and disadvantages of qEKF algorithm in compare to other methods are available.

Evaluation of the satellite attitude determination system is very complicate because of need to simulate space environment on the ground. In this paper a laboratory Implementation of attitude estimation using sun sensor and magnetometer is reported.The test setup includes a sun simulator installed in a dark room. The magnetometer measures the local magnetic field. Sensors are rotated using a 2 DOF table. The reference models are adapted with the test setup. Attitude determination using classic and extended kalman filter methods is implemented by sensors data fusion. The test results verify the controlled motion of sensors in the limits of setup accuracy order.

Miniaturized atomic vapor cells are useful devices that would trace activity of electrical signals of ‎‎brain, Nitrogen vacancy center magnetometry, electric and magnetic fields' sensors and some other ‎applications. High ‎signal to noise ratio in these miniaturized systems is one of the main bottlenecks ‎which must be ‎managed by selective spectroscopy methods. Here we introduce novel type of atomic ‎vapor cell based on Rubidium hot atomic vapor suitable to ‎increase spatial resolution of ‎magnetometers and advantages of frequency modulation spectroscopy ‎method to increase spectral ‎resolution. These cells fabricate in 10-3 mbarr base pressure and under nitrogen Gas filling in clean ‎vacuum system. Combination of these cells and spectroscopy method would ‎be used in feedback ‎loops of laser system of atomic sensors to lock on desired atomic transition. ‎These ideas for new ‎miniaturized cell can open new insight in quantum based devices in new generation of quantum ‎sensor's, atomic clock or quantum computation applications.‎