An accurate satellite attitude determination system using a chargecoupled device sensor

number: 
26
English
Degree: 
Author: 
Hussein Subhee Fadhel
Supervisor: 
Dr. Fawzi M. Al-Naima
Dr. Rawa A. Said
year: 
1994
Abstract:

A dedicated CCD sensor for satellite attitude determination is designed and implemented which consists of three units : the CCD camera, the sequencing circuits and the microprocessor circuit. The CCD camera is used as a sensing element. The sequencing circuits are designed to process the CCD camera output analog video signals and convert the signals to digital form stored in external RAM memory. The microprocessor circuit is designed to control and operate all sensor parts. Also, it provides a way of applying the required fiucge analysis, such as object image segmentation, edge detection, and object center finding . Three algorithms are suggested to find the object center point coordinates with the required system accuracy. These algorithms are : center finding by averaging process, center of the best circle passing through object edge points, and object center finding from Fourier series coefficients of the object boundary function. An eclipae phenomena effect reduction algorithm is suggested to find the object center point during eclipse period with the required system accuracy. System performance and accuracy limits are measured practically under laboratory conditions by monitoring the Sun through an appropriate optical system proposed for the Sun sensing system. Computer simulation programs are written that simulate each of the suggested object edge detection and center finding algorithms and they are tested by using the binary Sun images obtained from the implemented CCD sensor .The results obtained from simulation programs confirm the algorithms ability to find the object center point with the required accuracy of the system design. A TMS320C25 microprocessor is used In the design of the microprocessor circuit which offers a wide range of digital signal process and system hardware design. A TMS320C25 microprocessor operating program is written that Implements the averaging process algorithm which is suitable for Sun, Earth, and Moon sensing system. Results of Sun center points are obtained from the implemented CCD sensor that is controlled by the TMS320C25 operating program. The results are highly accurate with accuracy of one pixel error value in finding the Sun center points.