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 !


There are a few different ways, but basically they are fixed sensors in a linear array. There are usually two of them, pointed roughly 90 degrees apart. These sensors will have some pointed certainly at space, others pointed at Earth, and one or more pixels at the horizon. The brightness of the pixel on the edge, as well as its location, allows one to tell with a pretty high precision where the Earth is.

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  • $\begingroup$ May I suggest to add the word "optical"? $\endgroup$ – Uwe Nov 16 '19 at 16:04
  • $\begingroup$ I understand the principle as such. I want to understand the mechanism in more detail. Is there a CCD? The link in question says about some sort of conical scanning. How does conical scanning is then processed to angles output ! $\endgroup$ – Prakhar Nov 16 '19 at 16:14
  • $\begingroup$ There are a lot of different ways they can work. The ones that I know of do not really do scanning, they just read the entire array similar to a CCD (Although I'm not sure if that is what they actually use, CCDs don't do well in infrared...) $\endgroup$ – PearsonArtPhoto Nov 16 '19 at 16:18

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