GPS and navigation GPS)، GLONASS، GALILEO
Mona Zahednamazi; Alireza Toloui
Volume 16, Issue 4 , December 2023, , Pages 57-70
Abstract
One of the attitude sensors for the spacecraft is the star sensor. The attitude calculation by the star sensor includes several steps: image processing, star identification, database search, and implementation of the attitude determination algorithm. This paper presents analysis and improvements on the ...
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One of the attitude sensors for the spacecraft is the star sensor. The attitude calculation by the star sensor includes several steps: image processing, star identification, database search, and implementation of the attitude determination algorithm. This paper presents analysis and improvements on the star identification algorithm based on singular value decomposition. To improve the identification results, modifications have been made to the algorithm. Also, analysis and simulation are presented to investigate the effect of field of view dimensions and the number of stars used on the identification results, and the rate of duplicate sets in the database. In addition, identification has been considered a two-step process based on singular values and vectors. The results show the superiority of the improved algorithm in increasing the identification rate and reducing the rate of duplicate sets in the database. The identification rate of the improved algorithm in 〖10〗^°×〖10〗^° and 〖12〗^°×〖12〗^° fields of view dimension is always more the %97. The simulations were performed based on the Hipparcos star catalog for stars brighter than magnitude 6.5 and using MATLAB software.
space sciences and exploration
Farshad Somayehee; Amir Ali Nikkhah; Jafar Roshanian
Volume 14, Issue 2 , June 2021, , Pages 103-110
Abstract
In this paper, a new algorithm for determining the density of scattered data at the surface of the sphere is presented and then the proposed algorithm along with Geodesic Weighted K-Means clustering and Deluany triangulation are used to make uniform star catalogs. Comparison of the results with the results ...
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In this paper, a new algorithm for determining the density of scattered data at the surface of the sphere is presented and then the proposed algorithm along with Geodesic Weighted K-Means clustering and Deluany triangulation are used to make uniform star catalogs. Comparison of the results with the results of other related articles shows that the proposed algorithm resulted in a significant decrease in the probability of observing a large number of stars in all simulated star sensor fields of view. This improvement is due to the uniformity of the star catalog, especially in the celestial sphere poles due to the proposed density determination algorithm. On the other hand, the use of a proper data density algorithm has increased the likelihood of observing a few stars (such as 3 or 5) in all fields of view used in the Monte Carlo simulation.
Amie ali Nikkhah; farsahd somayehee; Jafar Roshanian
Volume 11, Issue 3 , December 2018, , Pages 21-32
Abstract
In this paper, the aim is to simulate night-sky images for use in star-sensor designing software. For this purpose, a comprehensive and precise algorithm was developed to simulate night sky images based on the ideal pinhole method and the use of Gaussian distribution functions. Then, in order to create ...
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In this paper, the aim is to simulate night-sky images for use in star-sensor designing software. For this purpose, a comprehensive and precise algorithm was developed to simulate night sky images based on the ideal pinhole method and the use of Gaussian distribution functions. Then, in order to create more realism, sources of random and systematic errors, the elongated images due to the high dynamics of the platform, as well as the asymmetric back-lighting of the moon, the sun, and the planets of the solar system have been simulated. Finally, considering the importance of realism in the problem-solving simulation approach, the use of precision ray tracking method as an alternative to the ideal pinhole method is suggested.
H. Bolandi; F. Fani-Saberi
Volume 2, Issue 2 , July 2009, , Pages 17-26
Abstract
In this paper, a novel and highly accurate attitude estimation method for a LEO satellite is designed. The method is based on multiple model adaptive estimation (MMAE) structure. In this method, the satellite dynamic equation is linearized in a few points in order to increase the computational rate compared ...
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In this paper, a novel and highly accurate attitude estimation method for a LEO satellite is designed. The method is based on multiple model adaptive estimation (MMAE) structure. In this method, the satellite dynamic equation is linearized in a few points in order to increase the computational rate compared with extended Kalman filter (EKF) method. The attitude determination and control system of the satellite is consists of a star sensor, gyroscope and reaction wheels. As known, star sensor is a very power consuming sensor in attitude determination of the satellite; therefore, a lesser power consuming method, using the dynamic model of the satellite along with angular momentum of the reaction wheels, is proposed to estimate the satellite attitude. This method assures the proper operation and the attitude estimation of the satellite in eclipse mode as well. By applying this method, the star sensor is used for a short period of time which reduces power consumption considerably. The performance and effectiveness of the proposed algorithm are investigated through numerical simulations and is compared with extended Kalman filter.
