Malihe Hashemi; Seyed Kamaleddin Mosavi Mashhadi; Seyed Majid Esmaeilzadeh; Mohammad Fiuzy
Volume 9, Issue 2 , September 2016, , Pages 85-90
Abstract
Attitude Determining is one of the major and critical satellites space missions. In this study, a new method to Attitude determination of satellites is presented. Such that, based on the proposed method search space will be more limited then accuracy and speed of attitude determination in the proposed ...
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Attitude Determining is one of the major and critical satellites space missions. In this study, a new method to Attitude determination of satellites is presented. Such that, based on the proposed method search space will be more limited then accuracy and speed of attitude determination in the proposed method has risen. At first in this method, implementation and the test algorithms will be discussed, after these some algorithms, such as navigation, pattern recognition and ultimately attitude determination will be reviewed. In order to implement these algorithm. High quality images of stars which must provided by the star tracker camera requires to implement. Really these images to perform the necessary processing sent to the processor so the processor based on designed algorithms, determines the attitude of camera and satellite in all three axes. This means that some features considered for star tracker and based on them begins the designing process. The range of accurately determination for star tracker is one of these features. In this article, the ranges of two axes of Yao and Pitch less than 20 seconds on the scale of degree are considered and in the roll axis less than 100 seconds is intended. Can show in the results, much better accuracy and less than initial assumptions have been achieved. It also carried out by an adaptive identified algorithm so that the brighter stars are identified and based on their attitude determination, the sensor accuracy have increased. Because of according research, the clearer stars, have more accurate in calculation. The other important feature is the speed of attitude detection which performed by 1 GHz processor, and correct identification of pyramidal algorithm where have reached less than 15 milliseconds. Due to the duration, the desire update rate gained. Other important parameters which influence the accuracy of the attitude determination is knowing the exact coordinates of the intersection point vector of focal length lens with image sensors. By Land calibration for camera with a good accuracy, these parameters were estimated.
H. Bolandi; M. H. Ashtari; M. Esmaeilzadeh; M. Haghparast
Volume 6, Issue 3 , October 2013, , Pages 27-37
Abstract
In this paper predicting of position of satellite based on extended kalman filter with considering hardware implementation consideration and simultaneously maintaining desired accuracy is investigated. For this purpose, first, effective forces on orbital dynamic and nonlinear equation of orbital motion ...
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In this paper predicting of position of satellite based on extended kalman filter with considering hardware implementation consideration and simultaneously maintaining desired accuracy is investigated. For this purpose, first, effective forces on orbital dynamic and nonlinear equation of orbital motion are presented. In order to increasing accuracy of prediction in position of satellite, J2, J3 and J4 harmonics of potentialfunction of the earth are considered and future position of satellite is predicted using linearized dynamic model and applying EKF on this model. Here Measurement data are position and velocity vector of satellite which are extracted by GPS receivers. Since in this paper systematic satellite design is considered, scenario of “ON TIME” of GPS receivers based on power consumption considerations is discussed. Finally simulation results for a LEO satellite and comparing these results with STK results, shows accuracy of presented modeling and equations.
H. Bolandi; M. H. Ashtari; M. Nadi; M. Esmaeelzade
Volume 6, Issue 2 , July 2013, , Pages 29-42
Abstract
In this article by analyzing the TLE data of Navid satellite from IranUniversityofScienceand Technology the effects of these data on tracking operation of ground station has been studied. Then the prediction accuracy of satellite position, the error rate of antenna ground station, the error rate of satellite ...
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In this article by analyzing the TLE data of Navid satellite from IranUniversityofScienceand Technology the effects of these data on tracking operation of ground station has been studied. Then the prediction accuracy of satellite position, the error rate of antenna ground station, the error rate of satellite rise time and the sensitivity survey of these toward the variation of drag term () of TLE data has been investigated. The results show that the accuracy of TLE data, the intervals of updating them and the time elapsed the epoch related to TLE data directly effected on accuracy prediction of thesatellite position and atracking operation. In some cases such as the limitation of ground antenna beam, tracking satellite is not succeeded. Therefore it has been suggested that tracking operation of satellite is done by ground station and independent of the TLE data and using TLE data as a reserve state has been considered. In this case TLE data must be updated daily.
H. Bolandi; A. M. Gheitaghy; B. Ghorbany Vagheii; S. M. Smailzadeh; M. R. Talaee
Volume 5, Issue 1 , April 2012, , Pages 81-90
Abstract
The responsibility of the satellite thermal control system is to maintain equipments temperature in all external environments and under operational modes within an allowable temperature range. The geometric math model of satellite with available relations in references is obtained and certified with ...
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The responsibility of the satellite thermal control system is to maintain equipments temperature in all external environments and under operational modes within an allowable temperature range. The geometric math model of satellite with available relations in references is obtained and certified with Thermal Desktop software. The outputs of geometric math model are external heating rates and radiation interchange factors. In this paper, the electrical simulation method is proposed as a tool for thermal math model of rotating satellite as equipments and structure of satellite are divided into several nodes and each term of thermal balance equation is simulated with equivalent electrical elements (capacitor, resistance, current source and etc.) and obtained circuit is solved fast and easily with HSPICE code. The values of voltage and current in each node are equivalent to temperature and heat flux, respectively. The results are illustrated the low run time with exact temperature responses of electrical simulation method in thermal modeling of satellite. By using the semi active thermal control, the thermal requirements are achieved and the effect of radiator paint is investigated.
