Solar collectors
Attitude sensors and imaging devices for satellites

Of all optical sensors, solar collectors are the most widely used. This is mainly due to the intrinsic characteristics of the Sun, namely :

• its energetic radiation, equivalent to a luminance of 2 · 10⁷ W · m^–2· sr ^–1 or an average illuminance outside the atmosphere of 1,350 W · m^–2, which makes it possible to use simple, reliable equipment without detection problems due to an excessively low signal-to-noise ratio;

• its inertial galactic position and apparent angular diameter ("32' as seen from Earth), which greatly simplify attitude determination algorithms;

• its spectral emission, which is close to that of a black body at 6,000 K (maximum emission around 0.55 µ m), with a broad spectrum in the visible and near infrared.

Solar sensors are frequently used, either in attitude control...