ASun sensor is anavigational instrument used byspacecraft to detect the position of theSun.[1][2] Sun sensors are used forattitude control,solar array pointing,gyro updating, andfail-safe recovery.[3][4]
In addition to spacecraft, Sun sensors find use in ground-basedweather stations and Sun-tracking systems, and aerial vehicles includingballoons andUAVs.[2]
There are various types of Sun sensors, which differ in their technology and performance characteristics. Sun presence sensors provide abinary output, indicating when the Sun is within the sensor'sfield of view.Analog anddigital Sun sensors, in contrast, indicate the angle of the Sun by continuous anddiscrete signal outputs, respectively.[2]
In typical Sun sensors, a thin slit at the top of a rectangular chamber allows a line of light to fall on an array ofphotodetector cells at the bottom of the chamber. A voltage is induced in these cells, which is registered electronically. By orienting two sensors perpendicular to each other, the direction of the Sun can be fully determined.[2]
Often, multiple sensors will share processing electronics.[3]
There are a number of design and performance criteria which dictate the selection of a Sun sensor model: