A staring horizon sensor is mounted on an orbiting satellite has one or more linear infrared detector arrays having the horizon being detected imaged thereon. The arrays are each connected in cyclic repetitive alternating polarity patterns for generating at least two output signals which are offset in phase. The output signals are processed to locate the position of the horizon on the arrays. The repetitive pattern interconnection of the elements in the arrays provide a focal plane data compression which reduces the bandwidth as well as the complexity of the processing electronics. In addition, interconnecting the detective elements in repetitive alternating polarity groups having a spatial frequency greater than the spatial frequency of the thermal variation of the horizon minimize any error due to the earth's thermal variations.