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.
Ahmad Reza Sadeghi; Mohammad Farzan Sabahi; Sayed Mohamad Saberali
Volume 9, Issue 1 , May 2016, , Pages 37-46
Abstract
Automatic control of satellites and spacecrafts, has been extensively paid attention. Attitude determination is one of the most important procedures to control a spacecraft. Star trackers are widely used for attitude determining. A star tracker provides images from the around space and try to identify ...
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Automatic control of satellites and spacecrafts, has been extensively paid attention. Attitude determination is one of the most important procedures to control a spacecraft. Star trackers are widely used for attitude determining. A star tracker provides images from the around space and try to identify the stars in the images. Several algorithms are proposed to this end. However, most of these algorithms use the raw measurements to star identification and attitude determination. As the measurements are often affected by various types of noise, the performance of such algorithms is degraded. Here, we employ tracking algorithms to improve the performance of existing methods for attitude determining. The Kalman filter-based tracking algorithms are shown to have satisfactory results for object tracking. We use the JPDAF to build an algorithm for accurate tracking of stars locations in successive images and, consequently, determining the attitude of spacecraft. The presented algorithm is compared with the well known algorithm for attitude determining called SNA.
Jafar Roshanian; Mehdi Hassani; Shabnam Yazdan; Masoud Ebrahimi
Volume 5, Issue 4 , January 2013, , Pages 1-8
Abstract
Star tracker is an attitude determination device which determines the satellite or spacecraft’s attitude using the star position information in inertial and body references. Star information is collected and stored onboard as a “Star or mission catalog”. There are several star catalogs ...
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Star tracker is an attitude determination device which determines the satellite or spacecraft’s attitude using the star position information in inertial and body references. Star information is collected and stored onboard as a “Star or mission catalog”. There are several star catalogs that contain different kinds of information with different accuracy. In this paper the most used star catalogs are introduced and a few star catalog selection features are recommended. These features are weighted according to the star tracker mission type. For the selected star tracker mission, results demonstrate that Hipparcos star catalog is the best choice. Eventually using Hipparcos star catalog, a mission catalog is developed to be used onboard a typical star tracker.
Jafar Roshanian; Shabnam Yazdani; S. Mehdi Hasani; Masoud Ebrahimi Kachouie
Volume 5, Issue 2 , July 2012, , Pages 15-23
Abstract
Star trackers are one of the most accurate attitude determination devices of a spacecraft. Star trackers are able to determine the spacecraft attitude with the use of recognizing the stars within their field of view. One of the major subsystems of star tracker software is the star pattern recognition ...
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Star trackers are one of the most accurate attitude determination devices of a spacecraft. Star trackers are able to determine the spacecraft attitude with the use of recognizing the stars within their field of view. One of the major subsystems of star tracker software is the star pattern recognition algorithm. In this research a novel star pattern recognition algorithm called Non-Dimensional is considered. This algorithm can recognize the stars within its field of view without using the information of camera calibration. In order to fulfill this goal, the algorithm requires a database which contains the star inertial information. Afterwards a fast search method is used to compare the combinations on the image with database. Eventually there has been a tradeoff between database volume and the update frequency for a better performance.
