In satellite systems to derive attitude sometime earth sensor is used. This basically outputs two axis information which when combined with orbit knowledge and sun vector from the sun sensor provides inertial fix i.e Inertial Attitude.
I am intrigued with the details of working of such sensor. I understand earth is infrared source and there is some sort of scan happening to determine the horizon of earth which can then be used to determine two axis information.
My question is more detailed working of such sensor. Is it scanning in conical manner or linear manner. If it is conical then does it get some sort of arc length information that is cutting the earth? Or it keeps scanning to get some sort of infrared image? I want to know inner working of such sensor !