CubeSats have evolved from purely educational tools to a standard platform for technology demonstration,scientific instrumentation and application in less than a decade.They open the door to new challenges and interpl...CubeSats have evolved from purely educational tools to a standard platform for technology demonstration,scientific instrumentation and application in less than a decade.They open the door to new challenges and interplanetary missions which lead to the direct realization of autonomous orbit determination(AOD)which has been investigated before with different integrated sensors combined with various filters.Mostly these studies were carried out for larger satellites with more accurate sensors.Magnetometer and sun sensor combined with extended Kalman filter(EKF)are chosen to complete AOD task considering their light weight.For the purpose of AOD and the computational cost requirements imposed on CubeSats,it is important to develop and apply low cost on-board models.In this perspective,a magnetic model based on a table look up is proposed to generate the reference magnetic field with a low computational burden.In current article the simulations through Matlab and Satellites Tool Kit(STK)especially focus on the accuracy of the AOD system provided by this model.For analysis three EKFs are carried out with different calculation models and data types.The system based on the proposed model is fully autonomous,low-cost and has moderate-accuracy required by most CubeSats missions.The AOD system can be applied as main or backup system depending on the space missions′demands.展开更多
Stringent attitude determination accuracy is required for the development of the advanced space technologies and thus the accuracy improvement of digital sun sensors is necessary.In this paper,we presented a proposal ...Stringent attitude determination accuracy is required for the development of the advanced space technologies and thus the accuracy improvement of digital sun sensors is necessary.In this paper,we presented a proposal for measurement error analysis of a digital sun sensor.A system modeling including three different error sources was built and employed for system error analysis.Numerical simulations were also conducted to study the measurement error introduced by different sources of error.Based on our model and study,the system errors from different error sources are coupled and the system calibration should be elaborately designed to realize a digital sun sensor with extra-high accuracy.展开更多
Digital sun sensor is one of the most important sensors used in the Attitude Determination System(ADS)of the satellite.Due to the harsh environmental conditions that exist in the space,various distortions may occur in...Digital sun sensor is one of the most important sensors used in the Attitude Determination System(ADS)of the satellite.Due to the harsh environmental conditions that exist in the space,various distortions may occur in the sun sensor optical system that lead to the reduced accuracy of this equipment.So,it is necessary to recalibrate the optical parameters of the aforementioned sensors.For this purpose,first a novel attitude independent error model is proposed for the SS-411 sun sensor that includes the central point of the CCD array,installation error,filter thickness and sensor misalignment.So,the mutual interfaces between the sensor parameters are considered in the developed model.In order to extract the sensor parameters,a nonlinear optimization technique called the Levenberg–Marquardt is applied to the developed model as a batch algorithm.In addition,the Extended Kalman Filter(EKF)and the Unscented Kalman Filter(UKF)have been utilized as sequential strategies.It will be shown that by considering a worst case of variation amount for sensor parameters,an accuracy improvement of about 17°is achieved by the developed calibration algorithms.Comparison between the developed algorithms represents that UKF has higher accuracy,shorter time convergence but higher computational load.展开更多
基金supported by the Research Fund for the Doctoral Program of Higher Education of China(No.20113219110025)
文摘CubeSats have evolved from purely educational tools to a standard platform for technology demonstration,scientific instrumentation and application in less than a decade.They open the door to new challenges and interplanetary missions which lead to the direct realization of autonomous orbit determination(AOD)which has been investigated before with different integrated sensors combined with various filters.Mostly these studies were carried out for larger satellites with more accurate sensors.Magnetometer and sun sensor combined with extended Kalman filter(EKF)are chosen to complete AOD task considering their light weight.For the purpose of AOD and the computational cost requirements imposed on CubeSats,it is important to develop and apply low cost on-board models.In this perspective,a magnetic model based on a table look up is proposed to generate the reference magnetic field with a low computational burden.In current article the simulations through Matlab and Satellites Tool Kit(STK)especially focus on the accuracy of the AOD system provided by this model.For analysis three EKFs are carried out with different calculation models and data types.The system based on the proposed model is fully autonomous,low-cost and has moderate-accuracy required by most CubeSats missions.The AOD system can be applied as main or backup system depending on the space missions′demands.
基金the financial support by the National 863 Project ( No. 2012AA121503 )the China NSF projects ( No. 61377012 , No. 61505094 )China Postdoctoral Science Foundation funded project ( 2015M571034 )
文摘Stringent attitude determination accuracy is required for the development of the advanced space technologies and thus the accuracy improvement of digital sun sensors is necessary.In this paper,we presented a proposal for measurement error analysis of a digital sun sensor.A system modeling including three different error sources was built and employed for system error analysis.Numerical simulations were also conducted to study the measurement error introduced by different sources of error.Based on our model and study,the system errors from different error sources are coupled and the system calibration should be elaborately designed to realize a digital sun sensor with extra-high accuracy.
文摘Digital sun sensor is one of the most important sensors used in the Attitude Determination System(ADS)of the satellite.Due to the harsh environmental conditions that exist in the space,various distortions may occur in the sun sensor optical system that lead to the reduced accuracy of this equipment.So,it is necessary to recalibrate the optical parameters of the aforementioned sensors.For this purpose,first a novel attitude independent error model is proposed for the SS-411 sun sensor that includes the central point of the CCD array,installation error,filter thickness and sensor misalignment.So,the mutual interfaces between the sensor parameters are considered in the developed model.In order to extract the sensor parameters,a nonlinear optimization technique called the Levenberg–Marquardt is applied to the developed model as a batch algorithm.In addition,the Extended Kalman Filter(EKF)and the Unscented Kalman Filter(UKF)have been utilized as sequential strategies.It will be shown that by considering a worst case of variation amount for sensor parameters,an accuracy improvement of about 17°is achieved by the developed calibration algorithms.Comparison between the developed algorithms represents that UKF has higher accuracy,shorter time convergence but higher computational load.
