The Macao Science Satellite-1(known as MSS-1)is the first scientific exploration satellite that was designed to measure the Earth's low latitude magnetic field at high resolution and with high precision by collect...The Macao Science Satellite-1(known as MSS-1)is the first scientific exploration satellite that was designed to measure the Earth's low latitude magnetic field at high resolution and with high precision by collecting data in a near-equatorial orbit.Magnetic field data from MSS-1's onboard Vector Fluxgate Magnetometer(VFM),collected at a sample rate of 50 Hz,allows us to detect and investigate sources of magnetic data contamination,from DC to relevant Nyquist frequency.Here we report two types of artificial disturbances in the VFM data.One is V-shaped events concentrated at night,with frequencies sweeping from the Nyquist frequency down to zero and back up.The other is 5-Hz events(ones that exhibit a distinct 5 Hz spectrum peak);these events are always accompanied by intervals of spiky signals,and are clearly related to the attitude control of the satellite.Our analyses show that VFM noise levels in daytime are systematically lower than in nighttime.The daily average noise levels exhibit a period of about 52 days.The V-shaped events are strongly correlated with higher VFM noise levels.展开更多
High-precision magnetic field measurements are crucial for understanding Earth’s internal structure,space environment,and dynamic geomagnetic variations.Data from the Fluxgate Magnetometer (FGM) on the Macao Science ...High-precision magnetic field measurements are crucial for understanding Earth’s internal structure,space environment,and dynamic geomagnetic variations.Data from the Fluxgate Magnetometer (FGM) on the Macao Science Satellite-1A (MSS-1A),added to data from other space-based magnetometers,should increase significantly the ability of scientists to observe changes in Earth’s magnetic field over time and space.Additionally,the MSS-1A’s FGM is intended to help identify magnetic disturbances affecting the spacecraft itself.This report focuses on the in-flight calibration of the MSS-1 FGM.A scalar calibration,independent of geomagnetic field models,was performed to correct offsets,sensitivities,and misalignment angles of the FGM.Using seven months of data,we find that the in-flight calibration parameters show good stability.We determined Euler angles describing the rotational relationship between the FGM and the Advanced Stellar Compass (ASC) coordinate system using two approaches:calibration with the CHAOS-7 geomagnetic field model,and simultaneous estimation of Euler angles and Gaussian spherical harmonic coefficients through self-consistent modeling.The accuracy of Euler angles describing the rotation was better than 18 arcsec.The calibrated FGM data exhibit good agreement with the calibrated data of the Vector Field Magnetometer (VFM),which is the primary vector magnetometer of the satellite.These calibration efforts have significantly improved the accuracy of the FGM measurements,which are now providing reliable data for geomagnetic field studies that promise to advance our understanding of the Earth’s magnetic environment.展开更多
Zero-and ultralow-field nuclear magnetic resonance(ZULF NMR)has experienced rapid development and provides an excellent tool for diverse research fields ranging from materials science and quantum information processin...Zero-and ultralow-field nuclear magnetic resonance(ZULF NMR)has experienced rapid development and provides an excellent tool for diverse research fields ranging from materials science and quantum information processing to fundamental physics.The detection of ZULF NMR signals in samples with natural abundance remains a challenging endeavor,due to the limited sensitivity of NMR detectors and thermal polarization.In this work,we demonstrate a femtotesla(fT)Potassium spin-exchange relaxation-free(SERF)magnetometer designed for ZULF NMR detection.A Potassium vapor cell with high buffer gas pressure and high atomic number density is used in the magnetometer.With absorption spectroscopy and SERF effect,the key parameters of the vapor cell are characterized and applied to optimize the magnetometer sensitivity.To combine our SERF magnetometer and ZULF NMR detection,a custom-made vacuum chamber is employed to keep NMR sample close to the magnetometer cell and protect the sample from undesired heating effects.Gradiometric measurement is performed to greatly reduce the magnetic noise.With the phase calibration applied,the gradiometric measurement achieves 7-fold enhancement in magnetic-field sensitivity compared to the single channel and has a magnetic noise floor of 1.2 fT/Hz^(1/2).Our SERF magnetometer exhibits high sensitivity and is promising to realize ZULF NMR detection of samples with natural abundance.展开更多
A miniature quad-channel optically pumped atomic magnetometer(OPM) has been developed based on the spinexchange relaxation-free(SERF) mechanism. With a vapor cell of size 8 mm×8 mm×8 mm, we have incorporated...A miniature quad-channel optically pumped atomic magnetometer(OPM) has been developed based on the spinexchange relaxation-free(SERF) mechanism. With a vapor cell of size 8 mm×8 mm×8 mm, we have incorporated four SERF magnetometer channels, which provides sufficient spatial resolution for magnetoencephalography(MEG). The four channels share the same laser beam for the best cancellation of common mode noise due to laser fluctuations. With gradient measurement, the sensitivities of the four sensors are better than 6 fT/Hz^(1/2), which is also good enough for MEG measurement. The vapor cell is heated to 160℃ by a novel nonmagnetic current-heating structure. Our sensor with high spatial resolution and compact size is particularly suitable for MEG systems.展开更多
This article presents a near-Earth satellite orbit estimation method for pico-satellite applications with light-weight and low-power requirements. The method provides orbit information autonomously from magnetometer a...This article presents a near-Earth satellite orbit estimation method for pico-satellite applications with light-weight and low-power requirements. The method provides orbit information autonomously from magnetometer and sun sensor, with an extended Kalman filter （EKF）. Real-time position/velocity parameters are estimated with attitude independently from two quantities： the measured magnitude of the Earth’s magnetic field, and the measured dot product of the magnetic field vector and the sun vector. To guarantee the filter’s effectiveness, it is recommended that the sun sensor should at least have the same level of accuracy as magnetometer. Furthermore, to reduce filter’s computation expense, simplification methods in EKF’s Jacobian calculations are introduced and testified, and a polynomial model for fast magnetic field calculation is developed. With these methods, 50% of the computation expense in dynamic model propagation and 80% of the computation burden in measurement model calculation can be reduced. Tested with simulation data and compared with original magnetometer-only methods, filter achieves faster convergence and higher accuracy by 75% and 30% respectively, and the suggested simplification methods are proved to be harmless to filter’s estimation performance.展开更多
For the vector attitude determination, the traditional optimal algorithms which are based on quaternion estimator（QUEST） measurement noise model are complicated for just two observations. In our application, the mag...For the vector attitude determination, the traditional optimal algorithms which are based on quaternion estimator（QUEST） measurement noise model are complicated for just two observations. In our application, the magnetometer and accelerometer are not two comparable kinds of sensors and both are not small field-of-view sensors as well. So in this paper a new unit measurement model is derived. According to the Wahba problem, the optimal weights for each measurement are obtained by the error variance researches. Then an improved quaternion Gauss–Newton method is presented and adopted to acquire attitude. Eventually, simulation results and experimental validation employed to test the proposed method demonstrate the usefulness of the improved algorithm.展开更多
As one of the seven scientific payloads on board the Tianwen-1 orbiter,the Mars Orbiter Magnetometer(MOMAG)will measure the magnetic fields of and surrounding Mars to study its space environment and the interaction wi...As one of the seven scientific payloads on board the Tianwen-1 orbiter,the Mars Orbiter Magnetometer(MOMAG)will measure the magnetic fields of and surrounding Mars to study its space environment and the interaction with the solar wind.The instrument consists of two identical triaxial fluxgate magnetometer sensors,mounted on a 3.19 meter-long boom with a seperation of about 90 cm.The dual-magnetometers configuration will help eliminate the magnetic field interference generated by the spacecraft platform and payloads.The sensors are controlled by an electric box mounted inside the orbiter.Each magnetometer measures the ambient vector magnetic field over a wide dynamic range(to 10,000 nT per axis)with a resolution of 1.19 pT.Both magnetometers sample the ambient magnetic field at an intrinsic frequency of 128 Hz,but will operate in a model with alternating frequency between 1 and 32 Hz to meet telemetry allocations.展开更多
We observed the steady-state visually evoked potential(SSVEP) from a healthy subject using a compact quad-channel potassium spin exchange relaxation-free(SERF) optically pumped magnetometer(OPM). To this end, 30 s of ...We observed the steady-state visually evoked potential(SSVEP) from a healthy subject using a compact quad-channel potassium spin exchange relaxation-free(SERF) optically pumped magnetometer(OPM). To this end, 30 s of data were collected, and SSVEP-related magnetic responses with signal intensity ranging from 150 fT to 300 f T were observed for all four channels. The corresponding signal to noise ratio(SNR) was in the range of 3.5–5.5. We then used different channels to operate the sensor as a gradiometer. In the specific case of detecting SSVEP, we noticed that the short channel separation distance led to a strongly diminished gradiometer signal. Although not optimal for the case of SSVEP detection, this set-up can prove to be highly useful for other magnetoencephalography(MEG) paradigms that require good noise cancellation.Considering its compactness, low cost, and good performance, the K-SERF sensor has great potential for biomagnetic field measurements and brain-computer interfaces(BCI).展开更多
Satellite attitude information is essential for pico-satellite applications requiring light-weight,low-power,and fast-computation characteristics.The objective of this study is to provide a magnetometer-only attitude ...Satellite attitude information is essential for pico-satellite applications requiring light-weight,low-power,and fast-computation characteristics.The objective of this study is to provide a magnetometer-only attitude estimation method for a low-altitude Earth orbit,bias momentum pico-satellite.Based on two assumptions,the spacecraft spherical symmetry and damping of body rates,a linear kinematics model of a bias momentum satellite's pitch axis is derived,and the linear estimation algorithm is developed.The algorithm combines the linear Kalman filter(KF) with the classic three-axis attitude determination method(TRIAD).KF is used to estimate satellite's pitch axis orientation,while TRIAD is used to obtain information concerning the satellite's three-axis attitude.Simulation tests confirmed that the algorithm is suited to the time-varying model errors resulting from both assumptions.The estimate result keeps tracking satellite attitude motion during all damping,stable,and free rotating control stages.Compared with nonlinear algorithms,such as extended Kalman filer(EKF) and square root unscented Kalman filer(SRUKF),the algorithm presented here has an almost equal performance in terms of convergence time and estimation accuracy,while the consumption of computing resources is much lower.展开更多
Exploration of deep mineralization,particularly where the mineralization of interest is covered by a conductive overburden,is still a challenge for the conventional transient electromagnetic(TEM)method,which measures ...Exploration of deep mineralization,particularly where the mineralization of interest is covered by a conductive overburden,is still a challenge for the conventional transient electromagnetic(TEM)method,which measures TEM response using induction coils as the sensor.However,sensors such as fluxgate and superconductive quantum interfere device(SQUID)magnetometers can measure the B-field directly,which can provide more reliable deep information for mineralization exploration.In this paper,we report on the research and development of our newly developed high-temperature su-perconductor(HTS)SQUID magnetometer,which is cooled by liquid nitrogen at 77 K,and its applica-tion in TEM measurement for deep exploration in a gold deposit in China.This improved SQUID magnetometer version has a good performance with noise(60 fT/√Hz),slew rate(0.8 mT/S),dynamic range(100 dB),sensitivity(6.25 mV/nT),and bandwidth(DC-20 kHz).To find deep and peripheral ore in the Baiyun gold deposit located in Liaoning Province,NE China,both the SQUID magnetometer and induction coil were used for TEM data acquisition.Results show that TEM can detect the distribution of local strata and the faults contained within them.Results also indicate that the SQUID magnetome-ter has superior response performance for response over geological targets with slower decay time when compared to the induction coil signals.The SQUID magnetometer is more sensitive at observing the induced-polarization effect which is closely related to the ore-controlling faults.展开更多
The space-borne fluxgate magnetometer(FGM)requires regular in-flight calibration to obtain its zero offset.Recently,Wang GQ and Pan ZH(2021a)developed a new method for the zero offset calibration based on the properti...The space-borne fluxgate magnetometer(FGM)requires regular in-flight calibration to obtain its zero offset.Recently,Wang GQ and Pan ZH(2021a)developed a new method for the zero offset calibration based on the properties of Alfvén waves.They found that an optimal offset line(OOL)exists in the offset cube for a pure Alfvén wave and that the zero offset can be determined by the intersection of at least two nonparallel OOLs.Because no pure Alfvén waves exist in the interplanetary magnetic field,calculation of the zero offset relies on the selection of highly Alfvénic fluctuation events.Here,we propose an automatic procedure to find highly Alfvénic fluctuations in the solar wind and calculate the zero offset.This procedure includes three parts:(1)selecting potential Alfvénic fluctuation events,(2)obtaining the OOL,and(3)determining the zero offset.We tested our automatic procedure by applying it to the magnetic field data measured by the FGM onboard the Venus Express.The tests revealed that our automatic procedure was able to achieve results as good as those determined by the Davis-Smith method.One advantage of our procedure is that the selection criteria and the process for selecting the highly Alfvénic fluctuation events are simpler.Our automatic procedure could also be applied to find fluctuation events for the Davis-Smith method.展开更多
A transverse relaxation determination of spin-exchange relaxation free （SERF） magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency （RF） excitation and light intens...A transverse relaxation determination of spin-exchange relaxation free （SERF） magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency （RF） excitation and light intensity excitation meth- ods used in SERF magnetometer, the light polarization modulation method has a high stability in low-frequency range, which indicates a more accurate transverse relaxation measurement.展开更多
Four levels of the data from the search coil magnetometer(SCM) onboard the China Seismo-Electromagnetic Satellite(CSES)are defined and described. The data in different levels all contain three components of the wavefo...Four levels of the data from the search coil magnetometer(SCM) onboard the China Seismo-Electromagnetic Satellite(CSES)are defined and described. The data in different levels all contain three components of the waveform and/or spectrum of the induced magnetic field around the orbit in the frequency range of 10 Hz to 20 kHz; these are divided into an ultra-low-frequency band(ULF,10–200 Hz), an extremely low frequency band(ELF, 200–2200 Hz), and a very low frequency band(VLF, 1.8–20 kHz). Examples of data products for Level-2, Level-3, and Level-4 are presented. The initial results obtained in the commission test phase demonstrated that the SCM was in a normal operational status and that the data are of high enough quality to reliably capture most space weather events related to low-frequency geomagnetic disturbances.展开更多
In a pico-satellite with small volume, measurements from on-board three-axis magnetometer （TAM） are not accurate, as it can be easily disturbed by other electronic systems. To improve its accuracy, a scheme of compe...In a pico-satellite with small volume, measurements from on-board three-axis magnetometer （TAM） are not accurate, as it can be easily disturbed by other electronic systems. To improve its accuracy, a scheme of compensation methods is introduced in this article. The scheme is based on an improved meast, rement model of pico-satellite TAM, and it mainly consists of three steps. First, in satellite design stage, several techniques are recommended to simplify the afterwards compensations. Then after satellite assembly, TAM ground tests and pre-launch calibration with least-square batch filter are introduced to improve magnetometer performance. At the end, a post-launch calibration with unscented Kalman filter （UKF） is implemented with in-orbit data. The compensation scheme is used in the development of Chinese pico-satellite ZDPS-1A made by Zhejiang University. Results show that with the introduced compensation scheme, the maximum error of ZDPS-1A TAM can be reduced from 80 mG to 6 naG （1 G=10^-4T）.展开更多
The laser-pumped potassium spin-exchange relaxation free （SERF） magnetometer is the most sensitive detector of magnetic field and has many important applications. We present the experimental results of our potassium...The laser-pumped potassium spin-exchange relaxation free （SERF） magnetometer is the most sensitive detector of magnetic field and has many important applications. We present the experimental results of our potassium SERF magne- tometer. A pump-probe approach is used to identify the unique spin dynamics of the atomic ensemble in the SERF regime. A single channel sensitivity of 8 f.THz-1/2 is achieved with our SERF magnetometer.展开更多
This Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer technologies have been widely used in a variety of positioning and navigation applications. In this paper, a low cost so...This Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer technologies have been widely used in a variety of positioning and navigation applications. In this paper, a low cost solid state INS/GPS/Magnetometer integrated navigation system has been developed that incorporates measurements from an Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer (Mag.) to provide a reliable complete navigation solution at a high output rate. The body attitude estimates, especially the heading angle, are fundamental challenges in a navigation system. Therefore targeting accurate attitude estimation is considered a significant contribution to the overall navigation error. A better estimation of the body attitude estimates leads to more accurate position and velocity estimation. For that end, the aim of this research is to exploit the magnetometer and accelerometer data in the attitude estimation technique. In this paper, a Scaled Unscented Kalman Filter (SUKF) based on the quaternion concept is designed for the INS/GPS/Mag integrated navigation system under large attitude error conditions. Simulation and experimental results indicate a satisfactory performance of the newly developed model.展开更多
An all-optical cesium magnetometer with high sensitivity based on absorptive detection is reported.The experiment achieves a polarized rotational spectrum of the probe light which is induced by circular dichroism and ...An all-optical cesium magnetometer with high sensitivity based on absorptive detection is reported.The experiment achieves a polarized rotational spectrum of the probe light which is induced by circular dichroism and a quarter wave plate together.The frequency response of the rotational spectrum is 1.8mrad/Hz at Larmor precession resonance.Analyzing the signal-to-noise ratio from the experimentally observed spectrum,we predict that the magnetic measurement sensitivity of 0.3pT/Hz^(1/2) would be obtained in the responsive range from 20nT to 2000nT.展开更多
The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to ...The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.展开更多
基金supported by the National Key R&D Program of China(Grant2022YFF0503700)the National Natural Science Foundation of China(42474200 and 42174186)。
文摘The Macao Science Satellite-1(known as MSS-1)is the first scientific exploration satellite that was designed to measure the Earth's low latitude magnetic field at high resolution and with high precision by collecting data in a near-equatorial orbit.Magnetic field data from MSS-1's onboard Vector Fluxgate Magnetometer(VFM),collected at a sample rate of 50 Hz,allows us to detect and investigate sources of magnetic data contamination,from DC to relevant Nyquist frequency.Here we report two types of artificial disturbances in the VFM data.One is V-shaped events concentrated at night,with frequencies sweeping from the Nyquist frequency down to zero and back up.The other is 5-Hz events(ones that exhibit a distinct 5 Hz spectrum peak);these events are always accompanied by intervals of spiky signals,and are clearly related to the attitude control of the satellite.Our analyses show that VFM noise levels in daytime are systematically lower than in nighttime.The daily average noise levels exhibit a period of about 52 days.The V-shaped events are strongly correlated with higher VFM noise levels.
文摘High-precision magnetic field measurements are crucial for understanding Earth’s internal structure,space environment,and dynamic geomagnetic variations.Data from the Fluxgate Magnetometer (FGM) on the Macao Science Satellite-1A (MSS-1A),added to data from other space-based magnetometers,should increase significantly the ability of scientists to observe changes in Earth’s magnetic field over time and space.Additionally,the MSS-1A’s FGM is intended to help identify magnetic disturbances affecting the spacecraft itself.This report focuses on the in-flight calibration of the MSS-1 FGM.A scalar calibration,independent of geomagnetic field models,was performed to correct offsets,sensitivities,and misalignment angles of the FGM.Using seven months of data,we find that the in-flight calibration parameters show good stability.We determined Euler angles describing the rotational relationship between the FGM and the Advanced Stellar Compass (ASC) coordinate system using two approaches:calibration with the CHAOS-7 geomagnetic field model,and simultaneous estimation of Euler angles and Gaussian spherical harmonic coefficients through self-consistent modeling.The accuracy of Euler angles describing the rotation was better than 18 arcsec.The calibrated FGM data exhibit good agreement with the calibrated data of the Vector Field Magnetometer (VFM),which is the primary vector magnetometer of the satellite.These calibration efforts have significantly improved the accuracy of the FGM measurements,which are now providing reliable data for geomagnetic field studies that promise to advance our understanding of the Earth’s magnetic environment.
基金supported by National Science Foundation of China(Grant Nos.T2388102,11927811,92476204,12150014,12205296,12274395,and 12261160569)Innovation Program for Quantum Science and Technology(Grant No.2021ZD0303205)+1 种基金Youth Innovation Promotion Association(Grant No.2023474)Chinese Academy of Sciences Magnetic Resonance Technology Alliance Research Instrument and Equipment Development/Functional Development(Grant No.2022GZL003).
文摘Zero-and ultralow-field nuclear magnetic resonance(ZULF NMR)has experienced rapid development and provides an excellent tool for diverse research fields ranging from materials science and quantum information processing to fundamental physics.The detection of ZULF NMR signals in samples with natural abundance remains a challenging endeavor,due to the limited sensitivity of NMR detectors and thermal polarization.In this work,we demonstrate a femtotesla(fT)Potassium spin-exchange relaxation-free(SERF)magnetometer designed for ZULF NMR detection.A Potassium vapor cell with high buffer gas pressure and high atomic number density is used in the magnetometer.With absorption spectroscopy and SERF effect,the key parameters of the vapor cell are characterized and applied to optimize the magnetometer sensitivity.To combine our SERF magnetometer and ZULF NMR detection,a custom-made vacuum chamber is employed to keep NMR sample close to the magnetometer cell and protect the sample from undesired heating effects.Gradiometric measurement is performed to greatly reduce the magnetic noise.With the phase calibration applied,the gradiometric measurement achieves 7-fold enhancement in magnetic-field sensitivity compared to the single channel and has a magnetic noise floor of 1.2 fT/Hz^(1/2).Our SERF magnetometer exhibits high sensitivity and is promising to realize ZULF NMR detection of samples with natural abundance.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2016YFA0300600 and 2016YFA0301500)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07030000)the National Natural Science Foundation of China(Grant No.11474347)
文摘A miniature quad-channel optically pumped atomic magnetometer(OPM) has been developed based on the spinexchange relaxation-free(SERF) mechanism. With a vapor cell of size 8 mm×8 mm×8 mm, we have incorporated four SERF magnetometer channels, which provides sufficient spatial resolution for magnetoencephalography(MEG). The four channels share the same laser beam for the best cancellation of common mode noise due to laser fluctuations. With gradient measurement, the sensitivities of the four sensors are better than 6 fT/Hz^(1/2), which is also good enough for MEG measurement. The vapor cell is heated to 160℃ by a novel nonmagnetic current-heating structure. Our sensor with high spatial resolution and compact size is particularly suitable for MEG systems.
基金New Century Program for Excellent Talents of Minis-try of Education of China (NCET-06-0514)China Postdoctoral Science Foundation (20081458, 20080431306)
文摘This article presents a near-Earth satellite orbit estimation method for pico-satellite applications with light-weight and low-power requirements. The method provides orbit information autonomously from magnetometer and sun sensor, with an extended Kalman filter （EKF）. Real-time position/velocity parameters are estimated with attitude independently from two quantities： the measured magnitude of the Earth’s magnetic field, and the measured dot product of the magnetic field vector and the sun vector. To guarantee the filter’s effectiveness, it is recommended that the sun sensor should at least have the same level of accuracy as magnetometer. Furthermore, to reduce filter’s computation expense, simplification methods in EKF’s Jacobian calculations are introduced and testified, and a polynomial model for fast magnetic field calculation is developed. With these methods, 50% of the computation expense in dynamic model propagation and 80% of the computation burden in measurement model calculation can be reduced. Tested with simulation data and compared with original magnetometer-only methods, filter achieves faster convergence and higher accuracy by 75% and 30% respectively, and the suggested simplification methods are proved to be harmless to filter’s estimation performance.
文摘For the vector attitude determination, the traditional optimal algorithms which are based on quaternion estimator（QUEST） measurement noise model are complicated for just two observations. In our application, the magnetometer and accelerometer are not two comparable kinds of sensors and both are not small field-of-view sensors as well. So in this paper a new unit measurement model is derived. According to the Wahba problem, the optimal weights for each measurement are obtained by the error variance researches. Then an improved quaternion Gauss–Newton method is presented and adopted to acquire attitude. Eventually, simulation results and experimental validation employed to test the proposed method demonstrate the usefulness of the improved algorithm.
基金supported by the Chinese National Space Administration,and the science team of MOMAG is supported by the Strategic Priority Program(Grant No.XDB41000000)the key Research Program of Frontier Sciences(No.QYZDB-SSW-DQC015)of the Chinese Academy of Sciences.
文摘As one of the seven scientific payloads on board the Tianwen-1 orbiter,the Mars Orbiter Magnetometer(MOMAG)will measure the magnetic fields of and surrounding Mars to study its space environment and the interaction with the solar wind.The instrument consists of two identical triaxial fluxgate magnetometer sensors,mounted on a 3.19 meter-long boom with a seperation of about 90 cm.The dual-magnetometers configuration will help eliminate the magnetic field interference generated by the spacecraft platform and payloads.The sensors are controlled by an electric box mounted inside the orbiter.Each magnetometer measures the ambient vector magnetic field over a wide dynamic range(to 10,000 nT per axis)with a resolution of 1.19 pT.Both magnetometers sample the ambient magnetic field at an intrinsic frequency of 128 Hz,but will operate in a model with alternating frequency between 1 and 32 Hz to meet telemetry allocations.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2016YFA0300600 and 2016YFA0301500)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB07030000 and XDBS32000000)+1 种基金the National Natural Science Foundation of China(Grant Nos.11474347 and 31730039)the Fund from the Ministry of Science and Technology of China(Grant No.2015CB351701)
文摘We observed the steady-state visually evoked potential(SSVEP) from a healthy subject using a compact quad-channel potassium spin exchange relaxation-free(SERF) optically pumped magnetometer(OPM). To this end, 30 s of data were collected, and SSVEP-related magnetic responses with signal intensity ranging from 150 fT to 300 f T were observed for all four channels. The corresponding signal to noise ratio(SNR) was in the range of 3.5–5.5. We then used different channels to operate the sensor as a gradiometer. In the specific case of detecting SSVEP, we noticed that the short channel separation distance led to a strongly diminished gradiometer signal. Although not optimal for the case of SSVEP detection, this set-up can prove to be highly useful for other magnetoencephalography(MEG) paradigms that require good noise cancellation.Considering its compactness, low cost, and good performance, the K-SERF sensor has great potential for biomagnetic field measurements and brain-computer interfaces(BCI).
基金supported by the Program for New Century Excellent Talents in University (No. NCET-06-0514),Chinathe Postdoctoral Science Foundation of China (Nos. 20081458 and 20080431306)
文摘Satellite attitude information is essential for pico-satellite applications requiring light-weight,low-power,and fast-computation characteristics.The objective of this study is to provide a magnetometer-only attitude estimation method for a low-altitude Earth orbit,bias momentum pico-satellite.Based on two assumptions,the spacecraft spherical symmetry and damping of body rates,a linear kinematics model of a bias momentum satellite's pitch axis is derived,and the linear estimation algorithm is developed.The algorithm combines the linear Kalman filter(KF) with the classic three-axis attitude determination method(TRIAD).KF is used to estimate satellite's pitch axis orientation,while TRIAD is used to obtain information concerning the satellite's three-axis attitude.Simulation tests confirmed that the algorithm is suited to the time-varying model errors resulting from both assumptions.The estimate result keeps tracking satellite attitude motion during all damping,stable,and free rotating control stages.Compared with nonlinear algorithms,such as extended Kalman filer(EKF) and square root unscented Kalman filer(SRUKF),the algorithm presented here has an almost equal performance in terms of convergence time and estimation accuracy,while the consumption of computing resources is much lower.
基金This study was supported by the National Key Research and Development Project of China(No.2018YFC0603803)Fundamental Research Funds of Chinese Academy of Geological Sciences(Nos.AS2020Y01,AS2020P01).
文摘Exploration of deep mineralization,particularly where the mineralization of interest is covered by a conductive overburden,is still a challenge for the conventional transient electromagnetic(TEM)method,which measures TEM response using induction coils as the sensor.However,sensors such as fluxgate and superconductive quantum interfere device(SQUID)magnetometers can measure the B-field directly,which can provide more reliable deep information for mineralization exploration.In this paper,we report on the research and development of our newly developed high-temperature su-perconductor(HTS)SQUID magnetometer,which is cooled by liquid nitrogen at 77 K,and its applica-tion in TEM measurement for deep exploration in a gold deposit in China.This improved SQUID magnetometer version has a good performance with noise(60 fT/√Hz),slew rate(0.8 mT/S),dynamic range(100 dB),sensitivity(6.25 mV/nT),and bandwidth(DC-20 kHz).To find deep and peripheral ore in the Baiyun gold deposit located in Liaoning Province,NE China,both the SQUID magnetometer and induction coil were used for TEM data acquisition.Results show that TEM can detect the distribution of local strata and the faults contained within them.Results also indicate that the SQUID magnetome-ter has superior response performance for response over geological targets with slower decay time when compared to the induction coil signals.The SQUID magnetometer is more sensitive at observing the induced-polarization effect which is closely related to the ore-controlling faults.
基金financially supported by the Shenzhen Science and Technology Research Program(grant no.JCYJ2021032412141-2034)the National Natural Science Foundation of China(grant nos.41804157,41774171,41774167,41974205,41804157,and 41904156)+3 种基金financial support from the pre-research Project on Civil Aerospace Technologies(grant no.D020103)funded by the China National Space Administrationthe 111 Project(grant no.B18017)the Chinese Academy of Sciences Center for Excellence in Comparative Planetologythe Macao Foundation.
文摘The space-borne fluxgate magnetometer(FGM)requires regular in-flight calibration to obtain its zero offset.Recently,Wang GQ and Pan ZH(2021a)developed a new method for the zero offset calibration based on the properties of Alfvén waves.They found that an optimal offset line(OOL)exists in the offset cube for a pure Alfvén wave and that the zero offset can be determined by the intersection of at least two nonparallel OOLs.Because no pure Alfvén waves exist in the interplanetary magnetic field,calculation of the zero offset relies on the selection of highly Alfvénic fluctuation events.Here,we propose an automatic procedure to find highly Alfvénic fluctuations in the solar wind and calculate the zero offset.This procedure includes three parts:(1)selecting potential Alfvénic fluctuation events,(2)obtaining the OOL,and(3)determining the zero offset.We tested our automatic procedure by applying it to the magnetic field data measured by the FGM onboard the Venus Express.The tests revealed that our automatic procedure was able to achieve results as good as those determined by the Davis-Smith method.One advantage of our procedure is that the selection criteria and the process for selecting the highly Alfvénic fluctuation events are simpler.Our automatic procedure could also be applied to find fluctuation events for the Davis-Smith method.
基金Project supported by the National Natural Science Foundation of China(Grant No.61227902)the National Key R&D Program of China(Grant No.2017YFB0503100)the Natural Science Foundation of Beijing Municipality,China(Grant No.4162038)
文摘A transverse relaxation determination of spin-exchange relaxation free （SERF） magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency （RF） excitation and light intensity excitation meth- ods used in SERF magnetometer, the light polarization modulation method has a high stability in low-frequency range, which indicates a more accurate transverse relaxation measurement.
基金supported by the State Key R&D Project (Grant No. 2016YFE0122200)the Civil Aerospace Scientific Research Project “Data calibration and validation for CSES, ”the Central-Level Public Welfare Research Projects of the Institute of Crustal Dynamics Institute, China Earthquake Administration (Grant No. ZDJ2017-21)
文摘Four levels of the data from the search coil magnetometer(SCM) onboard the China Seismo-Electromagnetic Satellite(CSES)are defined and described. The data in different levels all contain three components of the waveform and/or spectrum of the induced magnetic field around the orbit in the frequency range of 10 Hz to 20 kHz; these are divided into an ultra-low-frequency band(ULF,10–200 Hz), an extremely low frequency band(ELF, 200–2200 Hz), and a very low frequency band(VLF, 1.8–20 kHz). Examples of data products for Level-2, Level-3, and Level-4 are presented. The initial results obtained in the commission test phase demonstrated that the SCM was in a normal operational status and that the data are of high enough quality to reliably capture most space weather events related to low-frequency geomagnetic disturbances.
基金Program for New Century Excellent Talents in University (NCET-06-0514)China Postdoctoral Science Foundation (20081458, 20080431306)
文摘In a pico-satellite with small volume, measurements from on-board three-axis magnetometer （TAM） are not accurate, as it can be easily disturbed by other electronic systems. To improve its accuracy, a scheme of compensation methods is introduced in this article. The scheme is based on an improved meast, rement model of pico-satellite TAM, and it mainly consists of three steps. First, in satellite design stage, several techniques are recommended to simplify the afterwards compensations. Then after satellite assembly, TAM ground tests and pre-launch calibration with least-square batch filter are introduced to improve magnetometer performance. At the end, a post-launch calibration with unscented Kalman filter （UKF） is implemented with in-orbit data. The compensation scheme is used in the development of Chinese pico-satellite ZDPS-1A made by Zhejiang University. Results show that with the introduced compensation scheme, the maximum error of ZDPS-1A TAM can be reduced from 80 mG to 6 naG （1 G=10^-4T）.
基金supported by the National Natural Science Foundation of China(Grant No.61227902)
文摘The laser-pumped potassium spin-exchange relaxation free （SERF） magnetometer is the most sensitive detector of magnetic field and has many important applications. We present the experimental results of our potassium SERF magne- tometer. A pump-probe approach is used to identify the unique spin dynamics of the atomic ensemble in the SERF regime. A single channel sensitivity of 8 f.THz-1/2 is achieved with our SERF magnetometer.
文摘This Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer technologies have been widely used in a variety of positioning and navigation applications. In this paper, a low cost solid state INS/GPS/Magnetometer integrated navigation system has been developed that incorporates measurements from an Inertial Navigation System (INS), Global Positioning System (GPS) and fluxgate magnetometer (Mag.) to provide a reliable complete navigation solution at a high output rate. The body attitude estimates, especially the heading angle, are fundamental challenges in a navigation system. Therefore targeting accurate attitude estimation is considered a significant contribution to the overall navigation error. A better estimation of the body attitude estimates leads to more accurate position and velocity estimation. For that end, the aim of this research is to exploit the magnetometer and accelerometer data in the attitude estimation technique. In this paper, a Scaled Unscented Kalman Filter (SUKF) based on the quaternion concept is designed for the INS/GPS/Mag integrated navigation system under large attitude error conditions. Simulation and experimental results indicate a satisfactory performance of the newly developed model.
基金Supported by the International Cooperation Project of Ministry Science and Technology of China(2008DFR20420)the Fundamental Research Funds of Central Universities(HEUCF20111111).
文摘An all-optical cesium magnetometer with high sensitivity based on absorptive detection is reported.The experiment achieves a polarized rotational spectrum of the probe light which is induced by circular dichroism and a quarter wave plate together.The frequency response of the rotational spectrum is 1.8mrad/Hz at Larmor precession resonance.Analyzing the signal-to-noise ratio from the experimentally observed spectrum,we predict that the magnetic measurement sensitivity of 0.3pT/Hz^(1/2) would be obtained in the responsive range from 20nT to 2000nT.
基金supported by the NSFC(Grant Nos 42130204 and 42188101)the Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the support of the Tencent Foundation.
文摘The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.
