H. Bazrafshan; Sh. Baradaran Shokouhi; B. Ghorbani Vagheii
Volume 3, Issue 1 , July 2010, , Pages 45-54
Abstract
In this paper, the complete block diagram of the imaging payload of a spin satellite capable of real time imaging is designed. Because of the satellite spin, the system needs to recognize the suitable camera angle in order to start imaging. The angle is the starting point of the observation of the part ...
Read More
In this paper, the complete block diagram of the imaging payload of a spin satellite capable of real time imaging is designed. Because of the satellite spin, the system needs to recognize the suitable camera angle in order to start imaging. The angle is the starting point of the observation of the part of the earth to be imaged. In this paper, at first the suitable imaging method and detector for this kind of satellite are elected and then the angle and the time of the spin camera imaging and the necessary number of lines and pixels are calculated. If the system is also capable of real time imaging, the captured images should be transmitted to the earth station before the next imaging starts. The completion of the above scenario needs a complete and parallel relationship between the satellite image payload subsystem and other subsystems such as power, communication and specially satellite on-board computer. For imaging and transmission, image payload status information such as temperature, voltage and current should be sampled and transmitted to the on-board computer for processing. Also this information should be attached to the image frames and transmitted to the earth station. All this processing is summarized into time pulses with exact timing between subsystems. Because of resource limitation in a space mission, satellite systems design must have the minimum mass, power and cost. But these shouldn’t cause the efficiency and specially system processing speed to decline. Imaging payload with real time capability needs a high processing speed requiring high resource utilization. In this paper, an imaging system is designed with the mentioned characteristics based on FPGA high parallel processing speed but having low mass, volume and power.
H. Bazrafshan; Sh. Baradaran Shokouhi; B. Ghorbani Vagheii
Volume 2, Issue 3 , December 2009, , Pages 19-26
Abstract
Satellite camera Charged Coupled Device (CCD) read out system needs a high Signal to Noise Ratio (SNR). This is because of the special and inevitable space imaging payload noises. These noises include CCD noises, satellite noises such as lack of complete stability, and environmental noises such as atmospheric ...
Read More
Satellite camera Charged Coupled Device (CCD) read out system needs a high Signal to Noise Ratio (SNR). This is because of the special and inevitable space imaging payload noises. These noises include CCD noises, satellite noises such as lack of complete stability, and environmental noises such as atmospheric interferences, charged particles, relative earth and satellite movement and electromagnetic interferences. CCD noises because of their low output voltage compose the main part of the final read out system noise. Therefore if the CCD read out system is not designed properly, SNR declines significantly. These noises depend on CCD characteristics and design parameters such as temperature and frequency. On the other hand, in a satellite temperature and frequency range is partially controllable. The algorithm presented in this paper, with respect to the applied limitations and dependencies, designs the system parameters so that the optimized SNR is achieved.
