How do star sensor work?

Question

How do star sensor work?

Answer 1

Do you mean the sensors that detect starts for navigation purposes?  They are also called "star trackers".  The hardware is relatively simple: lens with CCD or CMOS matrix.  Signal processing can be more complex, after getting the image of the piece of the sky, it's correlated to a known image.  Ultimately, the elevation and azimuth of the star(s) are obtained and the coordinates of the observer are calculated.