Spacecraft Line-of- Sight Stabilization Using LWIR Earth Signature

Until the time of this reporting, when a space vehicle required a reference signal for inertial pointing, the choices were a signal beacon from an Earth location, the Earth radiance in the visible spectrum, or a star tracker. However, limitations can arise from using these techniques. For example, the signal beacon suffers from limited signal power (either in RF or optical) and will constrain the application to limited ranges, errors due to stray-light and centroiding limit the accuracy of a star tracker, and the spatial/temporal variability of the Earth’s albedo and its illumination by the Sun introduces limitations when used in the visible or near infrared light.