Design and Fabrication of an Albedo Insensitive Analog Sun Sensor

Abstract

A sun sensor is usually included in a satellite for optically measuring the position relative to the sun. The accuracy of a conventional sun sensor is affected by reflected sunlight at the nearby earth atmosphere: the albedo radiation. The part of the spectrum at near IR (1.5 ?m) is not included in the albedo radiation, due to the high water absorption in the earth atmosphere. The feasibility of such a near infrared (IR) analog albedo insensitive sun sensor in terms of the design constraints and fabrication is presented. The proposed sensor system comprises a spectral selective coating layer, a black absorbing coating layer, an anti-reflection layer, an InGaAs quadrant detector and is built on a sapphire substrate. The black absorbing ensures that the position measurement is not affected by back-reflected light from the detector surface. A lift-off process is used for patterning of the coating layer.