Fuzzy image processing in Sun sensor

Sun sensors are widely used in spacecraft attitude determination subsystems to provide a measurement of the Sun vector in spacecraft coordinates. At the Jet Propulsion Laboratory, California Institute of Technology, there is an ongoing research activity to utilize Micro Electro Mechanical Systems (MEMS) processes to develop a smaller and lighter Sun sensor for space applications. A prototype Sun sensor has been designed and constructed. It consists of a piece of silicon coated with a thin layer of chrome, and a layer of gold with hundreds of small pinholes, placed on top of an image detector at a distance of less than a millimeter. Images of the Sun are formed on the detector when the Sun illuminates the assembly. Software algorithms must be able to identify the individual pinholes on the image detector and calculate the angle to the Sun. Fuzzy image processing is utilized in this process. This paper describes how the fuzzy image processing is implemented in the instrument. Also, a camera pin hole model is constructed and used to evaluate the accuracy of the Sun sensor.