This invention, developed at NASA's Goddard Space Flight Center, was originally conceived as a high-accuracy, high-sensitivity, bi-axial Sun angle sensor, but has also been proposed for applications involving the general field of precisely measuring the direction in which light travels toward the sensor. It has applications in spacecraft navigation, formation flying in space, space beacons, and automotive collision avoidance.
The sensor is based on a carefully patterned Cartesian mask, an area array image sensor, and a very robust, proven image processing algorithm, and has dramatic advantages over conventional Sun sensors. In the new sensor, a perforated mask containing a grid of slit segments arranged in a Cartesian fashion is placed just in front of a radiation-hard image sensor having familiar rows and columns of pixels, with some gap between the mask and the image sensor. There are a nearly infinite number of different patterns of slit segments from which advantage can be gained, depending on requirements of a given sensor application. When illuminated by a beam of light, each slit segment creates its own single slit, Fresnel or Fruanhofer diffraction pattern, or simply a shadow of itself on the image sensor. Slit segments are arranged such that the patterns they produce on the image sensor do not influence each other.
The sensor applies, generally, to any light source (not just the Sun). For example, it applies equally well with the Moon. The layout details of mask features, the selection of an image sensor, and the arrangement of the mask with respect to the image sensor are all tailorable to numerous other light direction sensing applications. This would include applications such as measuring the vector direction connecting any two objects, for example from one spacecraft having a beacon light source mounted to it to another having the disclosed sensor mounted to it, or for determining the direction of travel of an automobile whose headlights are turned on traveling toward another which possesses this light direction sensor.